Do-it-yourself gable roof. Roof truss system: elements, types, fastenings, calculation Pitched roof construction with wooden rafters

The roof performs a number of important functions in creating decent living conditions, coupled with providing external attractiveness. It is quite reasonable to consider it a significant constructive component of the building. The truss frame is responsible for the formation of the roof structure. He must steadfastly hold the load, determine the configuration and be combined with the exterior of the house.

Only a well-chosen roof base can cope with the solution of the tasks. Making the right choice is much easier if the owner of a country estate knows all possible types and schemes of roof systems, the specifics of their construction and scope are clear.

The list of responsibilities of a roof is not limited to weather protection. Although the opposition to weather phenomena in a particular area, without a doubt, tops an impressive list of tasks.

The roof, as a final architectural touch, complements the appearance of the building, gives it a stylistic direction or completely deprives it. The truss system as the basis of the roof structure must meet the full range of technical and aesthetic requirements that apply directly to the roof.

Factors for choosing the "backbone" of the roof

The rafter system is an indisputable accessory of pitched roofs, which:

• sets the configuration and steepness;
• holds the topcoat and components of the roofing cake;
• creates the conditions for the perfect operation of the elements of the roofing system.

The choice of a roof ultimately comes down to determining the ideal variant of the truss system, which, in addition to the personal preferences of the owner of the house, is also influenced by such weighty factors as:

• The amount of winter and summer precipitation typical for the area in which the construction is planned.
• Strength and direction with the speed of the winds prevailing in the region.
• The desire of the owner to use the space under the roof to organize utility or residential premises.
• Type of finishing roofing.
• The financial capacity of the owner.

Climatic data to a large extent affect the choice of the roof and the construction of the truss system. In regions with abundant snowfall, it is impractical to build structures with a slight steepness that contributes to the formation of snow deposits. In areas with gusty winds, on the contrary, streamlined and low-slope forms are preferred, which will be difficult to disrupt and carry away with a powerful weather phenomenon.

It is clear that the sloping design is not adapted to the arrangement of useful premises in it. For those who want to equip the space under the roof, there are truss systems designed for construction in regions with varying degrees of wind loads.

If there is no need to use an attic, a roof of a complex or simple configuration can be built without it. There are a lot of options, including a variety of combinations of basic versions, familiarization with which will give an idea of ​​​​the essence of building a truss system of any type.

In order not to suffer in conjectures about the most rational form and angle of inclination of a pitched roof, it is enough to take a closer look at the surrounding low-rise buildings.

A proven configuration can be safely taken as a basic option in order to adjust and refine it in accordance with the requirements of the future owner and the technical characteristics of the roofing. If there is no desire to copy neighbors, you should familiarize yourself with the design and operational specifics of various truss systems.

Basic options for truss systems

A pitched roof can be simplistically represented as a set of slopes - planes along which atmospheric water "rolls down". The slopes are formed by the ribs of the rafter legs - the main elements of the truss system. The classification of pitched roofs and their corresponding truss systems is made depending on the number and configuration of slopes. According to the indicated signs, their ranks include:

• Shed. Roofs with one slope suit mainly over household objects, outbuildings, verandas. rest on two walls or two rows of racks. One of the walls or one row of supports must be higher than the other, so that water can drain without obstacles along the plane formed by the rafters.
• Gable. Roofs with two rectangular slopes are most often found in domestic open spaces. The rafter legs of gable systems rest on two walls of a rectangular box at home. In the classical version, the area of ​​\u200b\u200bboth slopes is equal, as is the height of the supporting walls. True, design solutions with slopes differing in area and supporting walls of different heights have become common.
• Hip. Otherwise they are called four-slope, based on the number of sloped planes. The rafter legs of the hip system form a pair of trapezoidal and a pair of triangular slopes. The rafters of the trapezoidal components rest on the long walls of the box, and the triangular counterparts on the short end ones. In terms of the hip roof, it looks like a postal envelope. Looks great and is used everywhere. The four-slope category includes roofs with shortened triangular slopes, strongly recommended for construction in areas with high wind load.
• Tent . The roof, which consists of triangular slopes converging at one vertex. The minimum number of ramps is 4, the upper limit is not limited. The rafters of the tent system are supported by walls or supports of equal height. Tent structures are preferred to be erected over verandas and gazebos. Variations with the steepness of the hipped roof make it possible to arrange them in regions with any wind load.
• broken lines. They are also called attic, because it is the broken technology that allows you to create the most spacious rooms under the roof. Rafter legs of broken structures are installed by analogy with gable systems, but are built in two tiers. The lower rafters rest on the walls of the equipped box, the upper ones on the supports of the lower tier of the truss frame.

The listed types of roofs and truss structures have numerous variations on the pitched theme. For example, a gable roof can have a regular gable at one end and a hip on the opposite side, or be supplemented with a shed structure above the porch in the middle of the main slope.

With the cruciform combination of two gable systems, a complex composite roof is formed with four wooden gables or stone gables. In the arrangement of boxes of a T-shaped or L-shaped configuration, several types of rafter systems are often involved at the same time. The upper tier of a sloping roof can be built using hip technology.

A truss structure of any complexity can be represented as a set of simple forms. To make it easier to understand the construction intricacies, it is better to conditionally divide the object into separate blocks. It is they who will tell you how to build each of the parts and connect the basic types of truss frames listed above to each other.

Overview of pitched roof structures

In order to understand the abundant variety of structures and the possibilities of their layout, we will consider the main types of truss systems and their corresponding schemes.

View # 1 - single-pitched truss frame

Most shed roofs are classified as non-attic, because, regardless of the steepness, the space under the roof they create is not enough in volume. However, if you want to build a strictly horizontal ceiling, the ceiling that separates the attic from the main premises is still being built.

The scheme depends on the size of the span to be covered with a single slope:

• If the distance between the upper and lower support of the rafter leg is less than or equal to 4.5 m, additional struts and racks are not used.
• If the span is in the range from 4.5 m to 6 m, a bed is laid near the high wall. A strut rests against it - a rafter leg, which ensures the rigidity of the rafter closer to the upper part of the span.
• If the span is to be covered from 6m to 9m, the beds are laid on both sides and the rafter legs rest against both beds.

If necessary, block a larger span, it is divided into sectors with the distances indicated above. At the border of adjacent sectors, racks are installed for runs, and within the sector, beds and struts are installed according to the described rules. For construction in regions with high wind activity, single-pitched truss structures are supplemented from the inside with diagonal wind ties.

In plan, the scheme of a single-pitched truss frame resembles a series of parallel-laid beams. A roof with one slope is not very beautiful, but very economical. The optimal angle of inclination is from 4º to 12º, a larger slope is not prohibited.

It is desirable to equip structures with low slopes with a continuous crate and waterproofing, which is not necessary for steep roofs. As a topcoat, it is better to use for low structures, profiled sheet or roofing metal for arranging structures in a steeper way.

View # 2 - gable roof truss systems

Gable truss frames are built on reinforced concrete floors and wooden beams, mainly with attics. The most common type of roof has a huge number of low and high, insulated and cold modifications.

Depending on the architectural and technical conditions of the object, the rafters used in the construction of gable roofs are divided into:

• Layered. These are rafters that have a strong support under the upper and lower heels. They are made and installed like the rafters of shed roofs. Layered truss systems are built over boxes with an internal load-bearing wall. It is needed as a supporting structure for a ridge run. The role of the wall can be played by a series of support posts or columns. In the simplest layered scheme with a span of up to 5 m, the top of the rafters rests on a run, which rests on a bed through support posts. Rigidity is provided by struts. Schemes for more solid spans are equipped with contractions, grandmas and additional runs.
• Hanging. Hanging type rafters have only a lower support, they rest against each other at the top. The elements of the hanging truss frame are immediately made in the shape of a triangle, so that you can abandon the Mauerlat. The Mauerlat function in such cases is trusted to the base of the triangle - the puff used to compensate for the thrust on the roof from the weight of snow, the roof and the system itself. Hanging technology is used in the arrangement of small boxes that do not have an internal support for a ridge run. If it is necessary to cover large-span structures, the hanging scheme is equipped with hanging headstocks, struts, ties, etc.

Depending on the technical characteristics of the roof, the crate is arranged solid or sparse. Low slopes up to 12º are completely covered with a waterproof carpet, high ones - only in places of possible leaks: along cornices, ridges, valleys, around pipes and other roof passages.

View # 3 - hip and half-hip system

Hip roofs, which are also “envelope” roofs, differ from gable structures in that the place of vertical tongs-pediments in their structures is occupied by inclined triangular slopes - hips. The central part of the roof is occupied by a standard gable truss system, to which those same hips adjoin at an angle.

Diversity in the family of hip structures is achieved through variations with proportions. By changing the ratio of the length of the ridge to the length of the base and the height of the slope, you can get a design that meets any taste and architectural requirements.

In the construction of rafter frames are used for:

• Sloping or hanging truss trusses with appropriate structural elements: beds, ridge runs, puffs, etc.
• Diagonal rafters connecting the tops of the outermost trusses to the corners of the box.
• Skewed shortened rafters, forming inclined slopes of the hips and parts of the main slopes adjacent to the hips.

Hip structures are attic and non-attic. I must admit, they are not very suitable for organizing rooms under the roof. Four sloping slopes seriously limit the space. However, for lovers of attic houses, there is a Danish variety with a shortened hip. Adherents of non-standard architecture will surely like the Dutch type, which belongs to the category called "" along with the Danish version.

Rafter systems for hip roofs and varieties are erected with an angle of inclination from 10-12º to 60º. In unconditional priority, classical proportions with a slope of 25-30º.

In addition to penetrations, ridges and cornice overhangs, all convex and concave corners of the hip structure need reinforced waterproofing. The difficult configuration of the slopes dictates the use of piece materials in the finishing. When cutting metal tiles and profiled sheets, there will be too much waste.

View #4 - hipped roof

A simple four-pitched hipped design is a hip roof, devoid of a ridge part. Its scheme in plan resembles a square with diagonals passing from corner to corner. Triangular slopes are connected at one vertex, which makes the roof look like a tent. They are built over boxes of a clear rectangular or polygonal shape.

In the construction of tent truss systems, standard layered and hanging principles are used:

• A truss structure of a layered variety is erected above a box with a central support or a load-bearing wall.
• Above an object without an internal wall or support, a frame is erected according to a hanging principle.

The steepness and number of slopes depend on the personal preferences of the future owner. The ideal roofing for finishing triangular slopes will be piece material, solely because when cutting large sheets, an impressive amount of waste remains. Regardless of the steepness, tent structures are preferred to be equipped with a continuous crate and a waterproofing carpet.

View # 5 - broken truss system

Rafter frames for broken lines, i.e. specially focused on increasing the attic space in order to create domestic or residential premises in it.

Broken technology is mainly used in the construction of attic roofs, which can be cold in country houses and insulated in permanent residences.

Each slope of a classic sloping roof can be conditionally divided into two rectangular parts, creating an external angle between them. The required shape is obtained by changing the dimensions of the parts of the slopes, the angles between them and the angle in the ridge zone.

The attic-type truss system is one of the most complex types of truss systems: diagrams and drawings of a broken frame introduce the complex structure of the structure. It consists of two tiers perched on top of each other:

• The lower tier of the rafter legs rests through the Mauerlat on the beams of the wooden floor, reinforced concrete slabs or the ceiling beam of a wooden house. To support the top of the rafters, runs are installed, which also serve as a support for the bottom of the rafters of the upper tier. The rafters of the lower part of a sloping roof are only allowed to be layered.
• The upper tier of rafters with its lower heels rests on the runs of the tier located below it. Runs also serve as the basis for laying the ceiling beams of the attic. In the construction of the upper part, both layered and hanging techniques can be used. The task of the top is only to form the ridge part, because the responsibility for the distribution of the roofing cake is assigned to the lower part of the mansard roof.

The owner chooses the angle of inclination of the lower and upper parts of the slopes according to his own preferences. The ideal shape is considered if five corners intersect an imaginary circle. A solid or sparse crate is arranged depending on the type of roofing, and there are no restrictions on its choice at all.

On a flatter upper part, it is better to mount a continuous crate and waterproofing. On the steep lower part of the slopes, precipitation does not linger, but it is threatened by heavy winds.

In order to prevent the breakdown of a broken roof in areas with frequent strong winds, each rafter is attached with a wire bundle to the wall, and not through one, as is customary for fixing conventional pitched roofs.

Video review of types and shapes of roofs

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Photo selection (slideshow):

The presented schemes of different types of truss systems are suitable for arranging a wooden house, brick and foam concrete box. The only difference is the fastening of the Mauerlat on wooden and stone walls. Information about the basic varieties of rafters will help you correctly determine the type and configuration of the roof for suburban property.

The truss system of any object is equivalent to the value of the load-bearing structural elements of the house. The roof plays the role of a node under which the stiffening ribs of the building are assembled. Accordingly, when installing the roof with your own hands, it is required to give the maximum value to all structural units, even when using a simple option - gable.

Advantages of gable roofs

There are a lot of options for pitched truss systems. Among them, simple symmetrical is especially popular. Why? Here are her virtues:

• On the basis of a gable roof, variations are created to reflect the special architecture of the building.
• Simple calculations, easy to understand.
• The one-piece design creates favorable conditions for the dryness of the internal space and the unhindered flow of water, snow and ice.
• The maintainability, strength and durability of a gable roof are much higher than other options.

Depending on the size, homeowners always have the opportunity to equip the under-roof space, make it a full-fledged floor or attic. In a word, a gable roof is the right and profitable solution for any object, whether it is a residential building, a summer house or a bathhouse.

Elements of the truss system

Depending on the type of roof, structural elements vary. Without knowledge of the appointments of each, it is impossible to arrange a reliable coverage at home. Let's analyze in detail:

Mauerlat

The basis of the truss system. It is a beam with a section of at least 150 mm, or an I-beam channel, if the roof structure is metal. It is located on the bearing walls of the object. Its purpose is to distribute the load of the system evenly throughout the structure of the house.

Rafter leg

Structural basic unit of the system. Together with others, it forms a truss system - strengthening the strength of the entire roof. It is made of a wooden beam, which is not inferior in cross section to Mauerlat or profile pipes.

Rafter rack

Vertical bar or pipes. Depending on the variant of the gable roof, the pillars can be located in the center and / or on the sides. They take part of the weight of the entire truss system, which is why the cross section is 150 mm.

Rafter girders

Horizontal beams laid on racks and under the ridge to support the rafter legs. They provide structural rigidity and relieve stress on trusses.

Puffs and braces

Connecting beam for rafters. The action is similar - relieving the stress of a beam or metal and making the structure rigid.

lying down

Mounting support for racks and struts. To securely connect these two elements, you need a large cross-section beam - 150 mm or a thick-walled pipe of impressive diameter.

Lathing beam

Elements laid perpendicular to the rafters. Serve to install the selected roofing and create a multilayer protective cake. The cross section is small - 40–50 mm.

If the conceived roof structure is made of wooden beams, you should carefully consider the quality of the wood upon purchase - the beam should not have interspersed knots, be made of soft woods.

Also, wood must have natural moisture, otherwise it will begin to dry right in the system structure, cracking, deforming the roof model, depriving it of reliability and safety.

Calculation of the truss system

A gable roof is a complex structure. The project takes into account many factors - natural nuances, wind, constant and variable loads. It is extremely difficult to make calculations on your own, without special knowledge about the climate of the area, the characteristics of the material for the manufacture of the system, and the nuances of pressure distribution.

Ideally, the calculations are at the mercy of professionals, you can independently choose only the material for coating - the following parameter depends on its type:

Tilt angle

The minimum angle of inclination of the roof relative to the parallel of the earth is 5 degrees. However, its dependence comes from the chosen roofing material. In this capacity, traditional slate, profiled sheet, flexible and metal tiles are used.

They are guided by the following rule: the steeper the slope, the more textured the roof can be.
From 5 degrees for laying rolled protective insulation of the roof. The number of layers matters - up to 15 degrees three-layer coatings, above - two- and single-layer coatings.

• From 6 - ondulin.
• From 11 - slate.
• From 12 - corrugated board.
• From 14 to 20 - metal tiles.
• From 15 to 45 - soft roof.

Thus, the resulting precipitation - snow, water - will not linger on the surface, although complete cleaning requires one's own efforts or the involvement of specialists for the installation of the Anti-Ice system.

Determining the parameters of the rafters - step, length, section

The rarer the step, the more impressive the cross-section of the beam or the diameter of the pipes should be. As a rule, for load-bearing structures, this parameter is at least 150 mm, 100 mm - for country houses and related construction - gazebos, bathhouses, outbuildings.

Next, you need to set the number of rafters per slope: its length is divided by the installation step, which is from 60 to 100 cm + 1 extreme leg. Multiplying the result by 2 gives the total. Depending on the section of the beam, the amount of rafter legs and the installation step vary.

The length of the rafters is simply calculated if the school knowledge about the right triangle is left in the luggage. The rafter leg is equal to the hypotenuse of the resulting figure. The calculation is as follows: A² + B² = C², where - A is the height of the roof, B is half the length of the pediment, C is the length of the rafter leg. To the resulting value is always added from 30 to 70 cm for cornice overhangs.

Types of truss systems

Before getting down to work, it is important to choose a truss system option for a gable roof. There are few of them, each has its own advantages and disadvantages:

hanging

Suitable only for a standard roof width of 6 m, respectively, this is the length of the rafter leg. Fastening occurs by fixing the ends to the ridge run and the bearing wall. Be sure to install a puff that levels the stress and pressure of the structure.

In addition, they will play the role of load-bearing beams. Without them, the structure will disperse under weight. The advantages of the option are in the absolute dryness of the roof surface during the off-season, and in less deformation at the time of shrinkage.

Layered

The option is suitable for any roof width. Reliability and stability is ensured by fixing the bed to the Mauerlat. Thus, the pressure is leveled by the rack, which reduces the tension in the rafter legs. The advantage of the system is simplicity, but the design requires large investments - additional lumber is required to equip the beds.

hybrid

These systems are typical for multi-pitched roofs, where transitions are accompanied by numerous reinforcements, beams, posts, beds, slopes and other elements for the stability of the entire structure. The device is expensive and complicated, so only a professional should deal with the project and construction. At least curate it.

Do-it-yourself installation of a gable roof

So, when the option of the truss system is selected, lumber is purchased, a roof project is drawn up, you can get to work. You cannot deviate from the sequence of steps. This threatens to delay installation and loss of structural reliability.

Mauerlat mount

If the length of the beam for installing the Mauerlat is insufficient, an extension is made. Using the half-tree cutting method, the ends are connected. Additional fasteners are anchor bolts. Do not use self-tapping screws, dowels or nails - they are unreliable. Mounting to the wall is as follows:

• There must be a margin of at least 5 cm from the edge.
• Holes are drilled along the wall for inserting fasteners. Similar actions are carried out with a bar.
• Mauerlat is attached to the edge with steel studs. The fastening step is more often 2 times than the distance between the rafter legs. Subsequently, before installing the main units, they are guided by metal marks.

Important - before laying the Mauerlat, the edge of the wall is protected with waterproofing. Spread one layer even if the house is made of wood.

Making and fixing rafters

Roof trusses are convenient in that they can be assembled on the ground into a finished structure and moved to the roof. This will reduce installation time, however, the model is heavy and lifting equipment will be required, which, of course, will increase the cost of the project.

For budget construction, another method is suitable:

• At the bottom and top of the rafter legs, a gash is made to attach to the Mauerlat and the ridge run. This must be done separately with each unit, after lifting the wood up.
• Places for fixing are marked on the Mauerlat and a ridge run is installed: racks are installed along the gables, on which a beam is placed. If the length is not enough, it is increased, but in a different way, unlike the Mauerlat - a board is screwed to the junction from both sides.
• Depending on the chosen model of the truss system - layered, hanging - they make cuts in the ridge beam, Mauerlat or drill holes in them for fasteners.
• Next, begin the installation of rafter legs from opposite ends of the roof, gradually moving towards the middle. Between the corners of the extreme trusses, it is not bad to stretch the cord to exactly match the entire horizontal part.
• Between themselves, the rafter legs are connected by puffs and struts. Under the ridge part, at the angle formed by the rafters, wooden linings are stuffed, and the ends themselves are tightened with bolts.

More recently, professional builders have begun to use sliding fasteners for roof installation. Metal plates securely hold the bearing elements and at the same time move due to shrinkage. This cancels out its effects.

The work of fixing the rafters is hard and long. You should calculate the time in advance - you can not leave the roof unfinished during the rainy season, otherwise the rigidity of the structure will be lost in the future due to absorbed moisture.

Gables and framing

The side parts of the roof - gables, are made in the form of ready-made shields from boards and are completely installed at the top. Difficulties should not arise - it is only important to carefully file them at the required angle. It is necessary to fasten the crate only after the final appearance of the roofing is known. For example:

• Under the corrugated board, the step of the crate beam will be 440 mm.
• The metal tile is fastened to the crate in increments of 350 mm.
• A soft roof needs a solid plywood coating.

It is important to note the places for the passage of the chimney - the crate should not come into contact with a brick or metal surface. The distance to the hot unit is at least 15 cm. Before installing the lathing, the finished roof is covered with waterproofing with allowances extending beyond the edges of the walls. Then the beam is mounted.

If it is decided to make an insulation cake from above, then first the vapor barrier is strengthened from the inside, then the selected material is put into the boxes formed by the rafter legs. Next, waterproofing and wind protection.

Then it is required to re-mark the contours of the rafter legs with a bar 20 * 20 and then fill a new layer of the crate, along which the laying of the roofing material will take place - the formation of ventilation ducts. This method will save the capacity of the under-roof space if the owners are going to use it for a specific purpose.

Roofing material flooring

Regardless of the type of roofing raw material, installation starts from the edges of the roof and leads it up, overlaying one unit on another. Thus, rain moisture will not get under the material.

The method of fastening depends on the type of material - soft tiles or tiles with a bitumen or polymer base are fused. Solid profiled sheets - ondulin, metal tiles - are fixed in pre-drilled holes to the crate, using rubber pads to seal and preserve the anti-corrosion layer.

As a result: the description of the installation of the truss system and the roof is easy only on the screen or paper. In reality, the process is complex and multifaceted. Therefore, if knowledge is not enough, it is better to invite professionals to work - their work is always guaranteed.

The erection of the roof is one of the most important stages of construction. The durability of the building itself and the level of comfort of living in it directly depend on the reliability of the "umbrella" from above, on its resistance to precipitation and any external influences.

Of all the variety of roof structures, gable can be attributed to the most popular, simply because of the relative simplicity of its construction. However, behind this “simplicity” lies a lot of different nuances, the need to carry out certain calculations and follow technological rules. However, this publication has the main task: to show that installing the rafters of a gable roof with your own hands is a completely doable task, even for a novice builder.

Let's go through all the steps in the process of installing rafters for such a roof together, from the basics of preliminary design to an example of practical implementation.

General arrangement of a gable roof

Basic concepts

Structural elements of the gable roof truss system

Let's make a reservation right away that this scheme, of course, cannot reflect the entire possible variety of designs, but the main parts and assemblies on it are shown quite clearly.

1 - Mauerlat. This is a board or beam that is rigidly attached to the upper end of the external load-bearing walls of the building. Its purpose is to evenly distribute the load from the entire roof system to the walls of the house, creating conditions for reliable fastening of the rafter legs at their lower fulcrum.

2 - rafter legs installed in pairs. They become the main load-bearing parts of the entire roof system - it is the rafters that set the steepness of the slopes, will be the basis for attaching the batten, roofing, and if the roof is planned to be insulated, then the entire thermal insulation "pie".

For the manufacture of rafter legs, high-quality boards or timber are used, and round timber can also be used. About the section of lumber, which will be sufficient to ensure that all possible loads can be guaranteed, will be discussed below.

The rafters may end on the Mauerlat, but more often they go beyond the perimeter of the walls of the house, forming a cornice overhang. However, lighter parts can also be used for this - the so-called "fillies", with which the rafter legs are increased to the required width of the overhang.

To form a cornice overhang, the rafters are extended with “fillies”

3 - skating run. It can be a beam, a board or even a composite structure. The run runs along the entire line of the ridge and serves to securely connect the upper points of paired rafter legs, connect all rafter pairs in order to impart overall rigidity to the entire roof structure. In various roof options, this run can be rigidly supported by racks, or tied only to the connection node of the rafter legs.

4 - puffs (contractions, crossbars). Horizontal details of the reinforcement of the system, additionally connecting paired rafter legs to each other. Several puffs located at different heights can be used.

5 - floor beams, which will serve as the basis for mounting the floor in the attic and the ceiling from the side of the room.

6 - and this beam simultaneously performs the role of a bed. This is a beam that runs along the entire length of the roof, which is a support for installing additional reinforcement parts for the truss system. The bed can be installed as shown in the figure (like a floor beam), or it can be rigidly laid on a main partition inside the building.

7 - racks (headstock) - additional vertical supports of the rafter legs, preventing their deflection under the influence of external loads. Racks at the top can rest against the rafters themselves, or against an additional run, longitudinally connecting the rafter legs at a certain height.

8 - braces. Often, with a large length of the rafter legs, their bearing capacity is not enough, and reinforcement only with racks does not provide the necessary strength. In these cases, diagonal reinforcing elements are used, resting on the bed from below, creating an additional point of support for the rafters. The number of struts and the place of their installation can vary in roofs of varying degrees of complexity.

Some differences between hanging and sloping gable roof systems

Gable roofs can be divided into two types of structures - with layered and hanging rafters. In addition, combined systems are widely used, in which both principles of construction are combined. What is the fundamental difference?

Laminated rafter system

This design of the truss system is characterized by the presence of support on the internal capital partition in the building. On the upper end of this partition, a bed is mounted, on which drains are supported, supporting the ridge run. Thus, the rafter legs are “leaned” on a vertical support, which makes the entire system as strong as possible.

This scheme is the most popular because of its reliability and relative ease of implementation. If it is possible to create an additional point of support in the center, then why not take advantage of this? True, if it is planned to place a living space in the attic, then vertical racks can sometimes become a hindrance. However, their presence is also sometimes “beaten up”, using, for example, an internal light partition for mounting.

Depending on the number and placement of internal partitions, the design of the layered truss system may vary. Some examples are shown in the illustration below:

Fragment “a” shows the simplest option, which, by the way, on short rafter lengths (up to 5 meters) may not even have struts shown - a row of central racks under the ridge run is enough

With an increase in the width of the building, the system naturally becomes more complicated, and additional reinforcing elements appear - puffs and struts (fragment "b").

Fragment "c" clearly demonstrates that the internal main wall does not have to be located exactly in the center, under the ridge. Such an option as shown in the illustration is also quite possible, but with the condition that the displacement of the lying relative to the ridge does not exceed one meter.

Finally, fragment "d" shows how the rafter system can be supported in a large building, but with two main partitions inside. The distance between such parallel beds can reach up to a third of the width of the building.

Hanging rafter system

Graphically, this roof scheme can be depicted something like this:

It immediately catches the eye that the rafters rest only on the lower part, and then are connected to each other on the ridge. There is no additional support in the center, that is, the rafter legs seem to “hang”, which predetermines the name of such a system. This feature imposes certain restrictions on the use of hanging rafters - usually such a scheme is practiced with a distance between the bearing walls on which the Mauerlat is fixed, no more than 7 meters. Installed puffs only partially relieve the load from the external walls.

The illustration below shows several options for a hanging system. However, some of them already, rather, can be classified as combined.

Fragment "d" - hanging rafters are interconnected by a screed at the level of the Mauerlat or fixed to a powerful floor beam, forming a triangle with it. There are no other reinforcing parts. A similar scheme is permissible with a distance between walls of up to 6 meters.

Option "g" - for the same size house (up to 6 meters). The puff (bolt) in this case is shifted upwards, and is often used for filing the ceiling of the attic.

Options "e" and "h" are designed for a span between walls up to 9 meters. Multiple puffs may be used (or top puff in combination with bottom floor beam). Another approach is to install racks under the ridge run, by analogy with a layered system. Only as a lower point of support, it is not a bed on the main partition that is used, but the racks are supported by a puff or a floor beam. To call such an option purely “hanging” is already difficult, since here is clearly a combination of parts from both designs.

To an even greater extent, such a combination of two schemes is expressed in the "and" variant, which is designed for large spans, from 9 to 14 meters. Here, in addition to the headstock, diagonal struts are also involved. Often, such trusses are generally assembled on the ground, and only then they are lifted and set in place, connected to each other, thereby forming the entire roof frame.

So, in preparation for the construction of a gable roof, it is necessary to study the principles of the device of a particular system, evaluate their advantages and disadvantages, choose the best one for your conditions and draw up a graphic working diagram. It will be needed both when purchasing the necessary material, and for the production of the installation work itself. However, drawing up a drawing should still be preceded by some calculations.

Calculation of the basic parameters of the gable roof truss system

Let's take another look at the concept of a gable roof device to highlight those parameters that need to be calculated.

So, in the process of calculation, we need to decide on the following values.

The initial data is the length of the side of the house along the gable part (highlighted in blue - F), and the length of the house along the ridge (purple - D). It is assumed that the owners have already decided on the type of roofing in advance - since there will be certain restrictions on the steepness of the roof slopes. (angle a).

• The height of the ridge above the plane of the Mauerlat (H - green), or, conversely, determine the angle of the slope, starting from the planned height of the ridge.
• The length of the rafter leg (blue color - L), and, if necessary, the extension of the rafter to form a cornice overhang of the required width (l).
• Calculate the total loads that fall on the truss system in order to determine the optimal section of lumber for the manufacture of rafters, their installation step (red - S) and the allowable span length between the support points. All these parameters are closely interconnected.
• When these calculated values ​​\u200b\u200bare on hand, it is already easy to draw up a graphic diagram, determine the need and optimal arrangement of reinforcement elements, and calculate the amount of material for their manufacture.

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We calculate the steepness of the slope and the height of the ridge

The slope angle of the slopes can be determined by the owners according to various evaluation criteria:

• For purely aesthetic reasons - when the appearance of the building becomes "at the forefront". Many people like roofs with a high ridge, but at the same time, one must not forget that the wind load increases sharply on such a roof. Yes, and materials for the manufacture of a high roof will go immeasurably more. At the same time, on steep slopes, the snow load is reduced to almost zero - it is possible that for the “snowy” regions this assessment parameter may become decisive.
• For reasons of useful use of the attic space. With a gable roof scheme, in order to achieve the maximum attic area, it is necessary to build slopes with a very steep slope, that is, with the same consequences as mentioned above.

• Finally, there may be a completely opposite approach - for reasons of economy, make a roof structure with a minimum height in the ridge. But in this case, you will have to focus on the minimum allowable slope angles for a particular type of roofing. To reduce the steepness below the indicators recommended by the manufacturer is to “plant a bomb” in your roof, both for reasons of its strength and durability, and from the standpoint of the waterproofing qualities of the coating.

It is not difficult to calculate the height of the ridge above the floor plane (Mauerlat). At the heart of the vast majority of nodes of any roofing system is a triangle, which, in turn, obeys strict geometric (more precisely, trigonometric) laws.

So, in our case, the width of the roof along the gable line is known. If the roof is symmetrical, then the ridge will be located exactly in the middle, and for calculations, you can simply divide the width F by two (the base of the triangle f=F/2). With asymmetrical slopes, you will have to project the top of the ridge onto line F, and measure the distances f1 and f2 from it to the edge of the triangle (to the Mauerlat) on each side. Naturally, in this case, the slope of the slopes will be different.

H =f × tga

In order not to force the reader to look for the values ​​​​of tangents and carry out calculations manually, a calculator is placed below, in which the necessary tabular values ​​\u200b\u200bare already entered.

When building one-story houses, a roof with two slopes is very popular. This is due to the speed of construction of the structure. In this parameter, only a single-pitched roof can compete with a gable roof. In the device, a gable rafter roof is not too complicated. And you will successfully master this work on your own.

The design of the gable roof truss system

The gable roof consists of two inclined surfaces that have a rectangular shape. Thanks to this, precipitation, which is represented by rain and melt water, flows off the roof in a natural way. The gable roof has a rather complex structure. It consists of such structural units: Mauerlat, rafter system, filly, ridge, roof overhang, bed, struts, puffs, crate and racks:

1. Mauerlat. This element performs the functions of transferring and distributing the load created by the rafter system on the load-bearing walls of the house. For the manufacture of Mauerlat, a beam is used, which has a square section - from 100 by 100 to 150 by 150 mm. It is better to use softwood. The beam is placed around the perimeter of the building and fixed to the outer walls. For fastening use special rods or anchors.
2. Rafter leg. Rafters form the main frame of any roof. In the case of a gable roof, they form a triangle. The rafters are responsible for the uniform transfer of loads to the Mauerlat. First of all, those that arise from precipitation, wind and the weight of the roof itself. For the manufacture of rafters, boards are used that have a section of 100 by 150 or 50 by 150 mm. Choose a rafter pitch of about 60-120 cm, depending on the type of roofing material. When using a heavy coating, place the rafter legs more often.
3. Skate. This element connects two slopes at the top of the roof. The ridge is formed after connecting all the rafter legs.
4. Filly. They act as a continuation of the rafters and form the overhang of the gable roof. It is customary to install fillies if the rafter legs are very short and do not allow an overhang to form. To make this structural unit, take a board that has a smaller section than the rafter. The use of fillies facilitates the construction of the truss system, as it allows the use of short rafters.
5. Eaves. This part of the design of the gable roof truss system is responsible for draining water from the walls during rain and at the same time preventing them from getting wet and quickly destroyed. The overhang protrudes from the wall, as a rule, by 400 mm.
6. Sill. It is located on the inner wall and serves to evenly distribute the load from the roof racks. For the manufacture of bedding, a beam is used, which has a section of 150 by 150 or 100 by 100 mm.
7. Racks. These vertical elements are responsible for transferring the load from the ridge to the interior walls. To create this element, prepare a beam that has a square section of 150 by 150 or 100 by 100 mm.
8. Struts. They are needed to transfer loads from the rafters to the load-bearing walls. Struts and puffs form a solid structure called a truss. Such a device is designed to withstand loads at large spans.
9. Puff. This structural unit, together with the rafters, forms a triangle. It does not allow the rafters to part in different directions.
10. Crate. This design consists of boards and bars. They are attached perpendicular to the rafters. Sheathing is necessary to evenly distribute the weight of the roof covering and the loads created by weather phenomena on the rafters. In addition, the crate is required to fasten the rafters together. When arranging a soft roof to create a crate, you should not use boards and bars, but moisture-resistant plywood.

Varieties of gable roof truss system

There are gable truss systems with hanging and layered rafters. Ideally, the design contains a combination of them. It is customary to install hanging-type rafters if the outer walls are located at a distance of less than 10 m. Also, there should no longer be walls between them that divide the space of a residential building. The design with hanging rafters creates a bursting force transmitted to the walls. It can be reduced if you arrange a puff made of wood or metal and place it at the base of the rafters.

At the same time, the rafters and tightening form a rigid geometric figure - a triangle. It is not able to deform under loads that are in any direction. The puff will be stronger and more powerful if it is placed higher. The floor beams act as puffs. Thanks to their use, the hanging rafter system of a gable roof acts as the basis for the arrangement of the attic floor.

Laminated rafters in their design have a support beam, which is located in the middle. It is responsible for transferring the weight of the entire roof to the intermediate column or middle wall located between the outer walls. It is recommended to install rafters if the outer walls are placed more than 10 m apart. If there are columns instead of internal walls, you can alternate between rafters and hanging rafters.

Do-it-yourself gable truss system

The roof must be strong to withstand various loads - precipitation, gusts of wind, the weight of a person and the roofing itself, but at the same time light, so as not to put a lot of pressure on the walls of the house. A properly arranged gable rafter roof evenly distributes the load on all load-bearing walls.

Calculation of a gable roof

The choice of a gable roof slope will depend on the material you have chosen for laying on the roof and architectural requirements:

• When building a gable roof, remember that it must slope at an angle of more than 5 degrees. It happens that the slope of the roof reaches 90 °.
• For areas with heavy rainfall, and when the roofing does not fit snugly, steep slopes are made. In this situation, the angle should be 35-40 ° so that precipitation does not linger on the roof. But such an angle does not allow building a living space in the attic. The output will be a broken roof structure. It will have a flat upper part, and on the lower part there will be a sharp slope.
• In regions with strong gusts of wind, sloping roofs are equipped. If constant winds prevail in the area, then make a slope of 15-20 ° for high-quality protection of the roofing.
• It is best to choose the middle option. Equip a gable roof that is not too steep. But also the slope should not be very gentle.
• When choosing a large angle of the roof, its windage increases, and, accordingly, the price of the gable roof truss system and the crate. After all, such a slope entails an increase in the area of ​​\u200b\u200bthe roof and, accordingly, the amount of necessary material - building and roofing.

When buying materials for the construction of a gable roof, it is useful to calculate its area:

1. Find the area of ​​one slope of the structure, and then double the result.
2. Ideally, a slope is an inclined rectangle that is placed along a long load-bearing wall. To determine the area of ​​​​a slope, multiply its length by its width.
3. The length of the slope is equal to the length of the wall. In addition, the length of the ledge of the roof above the gable is added to the length. Remember that the protrusions are present on both sides.
4. The width of the slope is the length of the rafter leg. To it is added the length of the ledge of the roof above the load-bearing wall.

In order to properly design the structure, it is recommended to carry out an accurate calculation of the gable roof truss system, including determining the loads and characteristics of the rafters:

1. When erecting a roof for a standard building that has one floor, the design load on the roof will consist of two values. The first of them is the weight of the roof, the second is the load from external factors: precipitation and wind.
2. Calculate the weight of the roof by adding up the weight of each layer of the "pie" - heat-insulating, vapor barrier and waterproofing materials, truss system, battens and directly roofing material. Calculate the weight per 1 m2.
3. Increase the result by 10%. You can also take into account the correction factor. In our case, K=1.1.
4. If you plan to change the design of the roof over time and increase the angle of its inclination, then include a margin of safety in the calculation. Take immediately higher load indicators than those that you received at the time of the calculation. It is recommended to build on the value, which is 50 kg per 1 m2.
5. When calculating the load exerted by atmospheric phenomena, take into account the climatic features of the area where the building is located. In this calculation, take into account the slope of the slope. If the gable roof forms an angle of 25 degrees, then take the snow load equal to 1.
6. If the roof is equipped with a greater slope - up to 60 degrees, the correction factor reaches 1.25. Snow load for an angle greater than 60 degrees is not taken into account.
7. The rafters transfer the entire load from the created structure to the load-bearing walls. Therefore, their parameters must also be taken appropriately. Select the section and length of the rafter leg, depending on the current load on the roof and the angle of the slope. Increase the values ​​obtained by 50% to ensure a high margin of safety.

Mauerlat installation methods

The construction of any roof begins with the installation of a Mauerlat:

• If logs or timber were used to build the walls, then the upper timber will act as a Mauerlat, as shown in the photo of the gable roof truss system.
• If you used bricks to build walls, then brick the metal rods into the masonry. They must have a cut thread for attaching the Mauerlat. Install rods every 1-1.5 m. Choose rods with a diameter of at least 10 mm. Lay waterproofing between masonry and Mauerlat.
• For walls made of ceramic or foam concrete blocks, pour concrete on top. Be sure to make the layer reinforced. It should have a height of approximately 200-300 mm. Be sure to attach metal rods that are threaded to the reinforcement.
• For Mauerlat, use a beam that has a section of 15 by 15 cm. It will act as a kind of foundation for the truss system.
• Lay the Mauerlat on the top edge of the wall. Depending on its design, the Mauerlat can be laid along the outer and inner edges. Do not place it close to the very edge, as otherwise it may be torn off by the wind.
• Mauerlat is recommended to be placed on top of the waterproofing layer. To connect all the parts into one whole, use bolts and metal plates.
• To avoid sagging, make a lattice of racks, struts and a crossbar. To do this, take boards measuring 25x150 mm. The angle between the strut and the leg of the rafter should be as straight as possible.
• If using a rafter leg that is too long, install another support. She must lean on the bed. Each element is associated with two adjacent ones. As a result, a stable structure is created around the entire perimeter of the roof.

Rafter leg attachment

The best option for a gable roof truss system is a combination of sloping and hanging rafters. This design allows you to create a reliable gable roof and reduce the cost of building materials. Consider the following recommendations when working:

1. Use only the highest quality wood as a material. Beams that have cracks and knots should not be used.
2. Rafters have standard dimensions - 50x150x6000 mm. When the beams are longer than 6 m, it is recommended to increase the width of the board so that the beams do not break under their own weight. Take boards 180 mm wide.
3. First, make a template for the rafter leg. Attach the board to the floor beam and the end of the ridge beam. Having outlined two lines, saw off a board along them. The template is ready.
4. Cut the rafters according to this pattern. After that, do the top washed down on them.
5. Take the resulting workpiece, bring it to the floor beam to mark the lower cut in place.
6. Install all rafters. At the same time, remember that after installing one leg, you must immediately install the opposite one. So you will quickly remove the lateral loads on the ridge beam.
7. If the slope is too long, then standard boards will not be enough to make a rafter leg. In this case, you can splice two boards together. To do this, sew on them a piece of wood of a similar section. It should have a length of 1.5 - 2 meters. According to the diagram of the gable roof truss system, the joint should always be at the bottom. Under it, install an additional rack.
8. Attach the rafter leg to the ridge beam with nails. Use self-tapping screws to fasten the rafters to the floor beam. Metal mounting plates are also suitable. In addition, a few nails are added.
9. If you are building a structure exclusively from hanging rafters, then skip the next step. When erecting a structure with layered rafters, you need to think about the supports that are installed on their floor. To reduce the deflection of the rafters, correctly calculate the location of such supports.
10. If you're building a gabled mansard roof, the intermediate studs will form the frame for the side walls.
11. When performing this work, maintain a certain step of the beams. Set its size at the design stage.
12. After installing the rafters, attach the ridge. It is located on their upper edge. For fastening use metal corners or staples. Bolts are the most popular.

Giving structure rigidity

After installing the gable roof truss system, strengthen it using the technology below:

• For small buildings such as saunas, cottages, utility buildings, and roofs with a simple hanging rafter system, connect each pair of rafters from below with a tightening and from above using a crossbar.
• For large buildings that are light at the same time, provide a lightweight roof. The walls must support it.
• If the house has a width of 6-8 m, then the structure should be tightened. Install in the middle of the support. Such racks are called grandmas. Place them at each pair of rafter legs.
• If the span of the walls reaches 10 meters, then reinforcing beams will be needed. The struts act as an additional support for the rafter legs for tightening. They are attached to each rafter - closer to the ridge or in the middle of the rafter leg. Fasten them to the bottom end of the headstock and to each other as shown in the gable roof truss video.
• In a situation with long roofs, gable beams should be relieved. This is done by installing braces. The upper end should rest against the corner of the gable. The lower one is mounted on the central floor beam. For fasteners, use a beam that has a large cross section. So you can prevent them from breaking if there are strong gusts of wind.
• In areas where winds predominate, the rafters must be resistant to such influences. Strengthen them by installing diagonal ties. Boards are nailed from the bottom of one rafter to the middle of the next.
• For greater rigidity, when creating the most critical fasteners, it is better not to use nails. Use pads and metal fasteners for this. Nails will not be able to provide high-quality fastening, since the wood can dry out after some time.

Lathing of the truss system

The final stage of the construction of the gable roof truss system is the creation of the crate. It is on it that you will lay the roofing. Carry out the work in the following sequence:

1. Select a dry timber for the crate. It should not have cracks or knots. Nail the bars on the bottom. Attach two boards near the ridge so that there are no gaps. The lathing must withstand the weight of the top roofing material and not sag under the weight of the workers.
2. If you will equip a soft roof, make two layers of sheathing. One is sparse, the other is solid. The same applies to roll roofing. To begin with, parallel to the ridge beam, place boards that are 25 mm thick and no more than 140 mm wide. A small gap is allowed - no more than 1 cm. Lay a continuous layer on top. To do this, it is better to use roofing plywood, slats or boards of small thickness. After that, check that there are no errors left on the crate - bumps and knots. Also check that the nail heads are not sticking out.
3. Lay one layer of timber under the metal tile. It should have a section of 50 by 60 mm. Do the same when using slate or steel roofing sheets. Maintain a step between the timber, depending on the roofing you have chosen - from 10 to 50 cm. Hammer nails closer to the edges of the board, and not in the middle. Drive hats deep. So they will not be able to damage the roof later. If you are making a crate for a metal tile, then remember that the connection of the timber at the same level should fall on the rafters.

When you have installed and strengthened the gable roof truss system, you can start installing the roofing pie. Place a thermal insulation material between the rafters, a layer of vapor barrier and waterproofing. When using insulation in slabs, calculate in advance the pitch of the rafters for its installation. At the final stage, fasten the roofing material.

The frame format stands out among a number of types of roofing. It can be done in quite different ways, but in any case, you will need to calculate the rafters and install them according to all the rules. With proper knowledge of the problem, you can solve it on your own without resorting to specialists.

Features and forms of the roof

The frame roof can only be installed with spans no longer than 1220 cm, while the gap from one truss to another is a maximum of 0.6 m. The dimensions of the frame fragments are determined by the span distances and the calculated snow load. Rafters can be either freely installed or accepting loads from attic elements. In the case of a broken roof, it is possible to provide a ceiling height sufficient for a residential attic, and it will look best on a square structure.

The multi-gable roof is considered the most complex and hardly accessible variation for amateur builders. A balanced truss system effectively withstands even very high loads, while having an excellent "appearance". Since the slope is steep, the risk of snow retention will be minimal. But at the same time, all structural elements will have to be calculated very carefully, and a lot of waste will appear in the process. In addition, the valley will have to survive exposure to a significant amount of snow.

Purpose and types of systems

Mauerlat can be used in a variety of rafter systems. The mass of the roof of the house varies depending on the area occupied by the slopes and the materials used. But in any case, the load created is very solid. When there is a ridge on the structures, a truss frame must be provided, with legs resting against the walls. Force is applied along several vectors at once, and in the cold season, the accumulation of snow only exacerbates the problem.

Mauerlat is designed to eliminate this shortcoming and prevent the destruction of the walls. This word means a beam of significant section, which can be both wooden and steel. In most cases, they take the same material that was used to form the rafters, but be sure to achieve the continuity of the strapping or create strong and especially stable joints. The use of Mauerlat is abandoned only in log houses or in buildings built using frame technology - and even there there are parts that perform a similar task. When it is not possible to make a non-breaking block, all fragments must be exactly the same length.

A T-shaped roof is characterized by a tie-in of two wings at a certain angle. Because of this, it is necessary to form a valley. The outer rafters will rest against the support boards. In addition to them, there will also be basic parts that are directly fixed to the wall. In order for everything in the valley to correspond to the task being solved, wooden elements 3.8 cm thick are used. The crate is supposed to be made monolithic, the coating is attached to it with clamps every 50 cm. steel, you can slightly reduce this figure.

A reinforcing belt is often equipped under the Mauerlat. This is especially important if you plan to insulate the roof and provide reliable waterproofing. Such a belt is formed from the same mixture that is used to build the foundation. Completely the entire formwork is poured with concrete in one step, the slightest individual layers are unacceptable. In the aerated concrete wall, intermediate jumpers are cut down at the top line of blocks - and a practical gutter immediately appears. The Mauerlat is attached either with the help of a knitting wire, or with reinforcing bolts (but they will not help in any way without a reinforcing belt), or with building studs.

Having dealt with the support for the rafters, you need to find out what they can be, and what is more correct to use to support the roof. Hanging rafters are used if there is no main wall inside the building, their support points are located exclusively on the outer contours.

Such supports were in demand during the construction of:

• residential buildings with one span;
• production facilities;
• various pavilions;
• attic.

This option should not be underestimated, thanks to engineering developments, suspended rafters are able not to bend, covering spans of 15–17 m. But it is important to understand that they gain all their capabilities only in close interaction with other details. You will have to use puffs, and grandmas, and crossbars. The simplest truss is made of two beams connected in the upper position; in configuration, such a device is close to a triangle. The horizontal connection of the frame parts is provided by a tightening (a beam made of wood or a metal profile).

Due to the tightening, the transfer of thrust to the walls is excluded, while the force applied in the horizontal plane is suppressed. The outer walls experience the action of only those forces whose vector is oriented vertically. Builders do not always place a puff at the very bottom, often it is set at the very ridge. In preparation for the construction of the attic, this element is most often placed higher than the base of the rafter legs. Then it will be possible to make a floor, on the ceiling of which you will not have to beat your head with any careless movement.

Hanging rafters for spans longer than 6 m must be reinforced with hangers and braces. In this case, the monolithic puff is replaced by one assembled from a pair of connected beams. In the classical scheme (triangular hinged), the grassroots bases abut against horizontal parts. For the normal functioning of the system, it is required that the height of the ridge is at least 15% of the span of the trusses. The rafters act on the bend, but tightening does not allow them to move to the sides. In order for the beams to bend less, the ridge knots are cut in with the expectation of eccentricity (the occurrence of a bending force opposite in vector).

Mansard attics are built for the most part with the help of triangular arches on three hinges, and the puffs are assigned the function of floor beams. The components of the tightening are bolted by means of an oblique or direct cut. Raised tightening can also be used in the construction of rafters under the attic. The higher it rises, the more the ceiling can be raised. But it is important to remember that at the same time, the loads on all elements also increase. The transfer of forces is carried out on the Mauerlat with the help of a movable mount, which dampens dimensional changes due to changes in humidity and temperature.

The rafters can be subjected to uneven loading, since it is higher on one side. This leads to a shift in the same direction of the entire system. You can eliminate such an unpleasant effect if you take out the rafters beyond the contour of the walls. The tightening with such a solution ceases to be a support, it transfers either tensile effects (if an attic is being arranged), or stretched-bending ones (when an attic is being built). Hinged arches with the inclusion of a crossbar differ from the previous version by replacing the sliding support with an identical one in function - rigid. Due to the change in the type of supports, the type of stresses generated also becomes different, the rafter system turns into a spacer.

The puff is formed in the upper lobe of the arch. Its purpose is to endure no longer a stretch, but a compressive effect. Additional tightening, reinforcing the crossbar, is needed with a significant load. Arches with suspensions and struts complement the arch systems with headstocks. Such a system is needed for significant spans (from 6 to 14 m). The struts that correct the resulting bend must rest against the headstock. Regardless of the specific type of truss system, it is necessary to carry out all the details and their connections with each other as clearly as possible.

Not always hinged rafters can perform the task. Then the slanting elements come to the rescue. This type of rafters is used under hip roofs and under roofs equipped with a valley. Their length is longer than in the usual case. In addition, they become supports for the shortened rafters of the slopes. That is why the load on the rafters is about 50% more than in other structures.

Thanks to the increased length, it is possible to:

• resist significant impacts;
• form beams without cuts;
• bring the parts to a single size by pairing the boards.

To build a hip roof with many spans, the diagonal legs are provided with supports. Such supports are made in the form of standard struts or racks of timber, or a pair of connected boards. Support through a lining made of wood and a waterproofing layer is made directly on the reinforced concrete floor. The struts are placed at an angle of not less than 45 and not more than 53 degrees, at the bottom such a detail rests on the beds. The angle of installation is less important than the ability to fix parts of the rafters at the point experiencing the strongest load.

Sloping rafters placed in openings up to 750 cm should be held by struts only in the upper lobe. With a length of 750 to 900 cm, a truss truss or rack is additionally mounted below. And if the total span length exceeds 9 m, then for maximum reliability in the middle you need to put a rack, no other support will do. If the selected floor is unable to withstand the load, it will have to be reinforced with a beam. The type of support in the ridge is determined by how many intermediate supports are used, what they are, how the key layered rafters are made.

In addition to the type of rafters, you need to clearly understand their material. Both wooden and metal structures can be good, but only each in its place. Even the high strength of the metal does not allow to push the usual wood. The tree has proven its benefits for thousands of years, and now it is even gaining popularity due to its excellent ecological characteristics. Boards and timber can be bought at an affordable price, and if something has not been taken into account, it is always easy to saw off the desired fragment or build up a part right on the construction site.

Sometimes there are problems associated with the operation of the created structures. Wooden rafters will have to be carefully treated with antiseptics, as well as means that block the development of mold colonies and insects. The combustibility of wood is suppressed due to regular processing, and in addition, it is too difficult to find the necessary components for slopes longer than 7 m. Before installation, the walls are laid with a mauerlat, made from a log frame or based on a block of timber. The thickness of the structures is at least 180 mm, this is the only condition for a uniform distribution of loads.

Metal rafters are inevitably heavier than wood rafters for the same section. Therefore, the walls need to be strengthened, the work on their construction becomes more expensive and longer. It will not be possible to mount metal blocks manually; cranes will be required. It is impossible or very difficult to adjust the dimensions, the geometry of the rafters, so you will immediately have to build the walls as accurately as possible and eliminate errors during their construction. The slightest mistake can make an expensive block almost useless in practice.

Metal rafters are connected by welding, and welded joints are inevitably weakened, as corrosion develops rapidly there. The cost of the work is very high, and when performing them, it is necessary to comply with the requirements of fire and electrical safety. But there is such an indisputable advantage as the ability to support a roof slope from 700 cm and longer. If you use a special anti-corrosion paint, the durability of metal structures is fully guaranteed. All these advantages allow you to quickly and comfortably build industrial buildings with a significant height and length of spans.

How to choose: what to consider?

The truss system should be chosen as correctly and clearly as possible.

When looking for a suitable solution, you need to pay attention to the following points:

• strength;
• the ability to support the slopes and the roof as a whole of a certain size and geometry;
• creating a positive aesthetic image of the building as a whole.

Technical parameters take precedence. Even the most beautiful structures that follow the principles of design will not show their positive qualities if they last too little. Experienced builders always analyze the average annual and seasonal temperatures, the financial capabilities of developers, the maximum possible wind speed and the severity of the overlying roof. The future use of the under-roof space and the scale required for it are also taken into account. Wind, snow and rain should not be underestimated, since these factors can have a very strong effect on the roof, and through it on the rafters.

If it is reliably known that a particular area is characterized by heavy snowfalls, the minimum slope angle is impractical. This point is even more relevant when using flat roofs. Under the pressure of accumulating precipitation, the frame can rapidly deform or water will pour inside. Another thing is when a certain region is often subject to the arrival of cyclones and the strong winds they bring. Here the slope should already be made smaller, then the situation with the disruption of individual structural elements will be practically excluded.

Mistakes can be avoided if you look at houses already built nearby and operated for a long time. By accurately reproducing their roof structure and the rafter system interconnected with it, one can best take into account local specifics. But not everyone follows this path, sometimes the task is to develop an exclusively original project. Then you will have to carefully collect the initial data, carry out scrupulous calculations. In the absence of special knowledge, it is better to attract qualified performers to help.

After analyzing the total load created by wind and snow, it can sometimes be found that certain parts of the truss complex need selective reinforcement. When assessing the required angle of inclination of the roof, attention is also paid to the type of coating used. A heavy metal tile or corrugated board with a very large slope can spontaneously slide down, you have to additionally fix them, complicating your work and increasing the cost of installation. In addition, certain materials have a tendency to retain water or become soaked with it, which can only be combated by making the slope steeper. Creating a good roof and truss system that meets such conflicting requirements is not always accessible to non-specialists.

What does it consist of?

The structure of the truss system, as you can see, is quite complex and even contradictory. Each part of this design has a strictly defined role. So, Mauerlat is a long bars of coniferous wood, and strictly resinous wood is used for work. Such elements are laid out along the external load-bearing walls, attached to the base with anchors or rods of a special design (threaded). This part transfers the load from the roof to the wall.

Next comes such a device as a rafter leg. Under this name appears a wooden beam used to build the contour of the slopes. The shape of the structure is always triangular, because it is the best way to help the roof withstand the destructive effects of winds, snow and other atmospheric processes. Rafter legs are placed at uniform distances along the entire roof, the step cannot exceed 120 cm.

The bed is also of some importance for supporting the roof - this is a wooden block that replaces the Mauerlat in some cases. Beds are placed on the internal supporting walls. They turn into the basis of the roofing triangle. Thanks to them, the slopes do not crawl under their own weight. And it is also worth mentioning about the racks - these are bars with a square section placed vertically. They perceive the pressure exerted downward by the ridge assembly and transmit it mechanically to the inner bearing plane. Sometimes the racks are under the rafters.

Struts are designed to strengthen the entire structure of the roof, they connect the legs and beds into one whole. This detail is shaped like a rhombus. The community formed by the puff and struts is called the farm. In addition to them, you also need a crate, which is thin boards stuffed at right angles to the legs of the rafters. It helps to keep the rafter legs as a single system. Absolutely any roof covering is attached to the crate.

Under soft materials, the crate should be made inseparable, and plywood is considered the best tool. At the very top is a ridge, which logically and physically completes the roofing triangle. The connection of a pair of opposing legs of the rafters is provided by a square piece of wood which prevents the entire roof from collapsing. And at the very bottom of the pitched roof there is an overhang, which extends approximately 0.5 m from the perimeter. Thanks to him, the streams of rain leaving the roof do not flood the outer bearing planes and do not harm them.

Fillies are used only in the situation when the rafter legs cannot be made along the length that would allow organizing the overhang. Connecting with boards of reduced section effectively solves this problem. For fastening the wooden elements of the rafters, it is most often recommended to use clamps, staples. It is undesirable to use nails, because the tree pierced by them becomes weak and fragile after a few years. Therefore, if professionals use connections made directly on the construction site, they use bolts.

But even a bolted connection weakens building structures, albeit relatively slightly. The strongest are the connections with the help of clamps or staples made of metal. Only their industrial production can maximize the quality of products, since deviations from the norms and deterioration in quality are excluded only under strictly standardized and fully controlled conditions. You can assemble a truss structure from completely finished trusses very quickly, there is no risk in using it. Another thing is that it is required to collect information about the necessary characteristics as accurately as possible and transfer it to the manufacturer without distortion.

In addition to these elements, the truss system borders on the valley. This is the name given to a special connection of a geometrically complex roof at points where its trajectory changes. The difference from the ridge is that in such places the roofing parts form a negative angle. The technical essence of the product lies in the fact that the gutter helps to divert liquid to the side. The more complex the configuration, the greater the number of such gutters should be.

The cornice beam serves to abut a strut against it, the other end of which rests against the frontal board, while the dropper is not deformed and its configuration is not distorted. Wind connections are those elements of the truss system that transfer the load created by the wind from the roof to the foundation. They not only increase the overall stability of the structure, but also help to avoid tipping over in case of instability of individual parts. The roof will retain spatial rigidity even with very strong winds.

Horizontal wind connections are such elements as:

• braces;
• parabolic puffs;
• complexes of conventional puffs;
• trusses, complemented by a cross-shaped lattice.

Vertically, the preservation of characteristics under strong air pressure is ensured by wind supports and beams. Sometimes a monolithic reinforcing core is used. Engineers have come up with many other options for designing a wind connection. It is provided with frames and semi-frames, pinched props. In small buildings, rigid (resisting compression) or stretched diagonals are used, some covering two spans at once. The location of each of the elements is accurately reflected in the project documentation.

It is not so difficult to understand the qualitative characteristics of truss systems and their composition, if you show care and diligence. But it is equally important to calculate the quantitative parameters of these systems. If you do not do this or make the calculations incorrectly, you can either spend too much money, or encounter leaks, even with the destruction of individual elements.

• roof bends;
• average annual snow mass;
• unevenness in its distribution along the slopes, depending on the steepness of the slope and the wind rose;
• wind transfer of already fallen snow;

• descent of snow and ice masses, runoff of liquid water down;
• aerodynamic characteristics and windage of the structure;
• differences in the strength of the impact on individual points.

It is not so easy to calculate everything necessary, moreover, by simulating realistic situations and including a reasonable margin of safety in the project. Moreover, it is necessary to pay attention to the addition of various loads, to their cumulative effect. But still, any customer is quite capable of evaluating the quality of the work of designers. The loads applied to the truss systems are divided into three key groups: main, additional and extreme.

The main category includes:

• stable factors - the severity of the roof and roof structures, additional elements installed on top of them;
• long-term effects - snow, temperature;
• periodically changing factors - full calculations of snow and temperature effects, taking into account all the subtleties.

An additional group is the pressure exerted by the wind, builders and repairmen, ice and rain. The extreme category includes all natural and man-made emergencies that may occur in a particular place. Their level is predicted with a margin to ensure the exclusion of unpleasant consequences. When calculating the frame roof and the structures under it, the ultimate load is taken into account, if applied, the entire structure crumbles. Additionally, an indicator or a group of indicators is given, upon reaching which various deformations inevitably appear.

The snow drift coefficient reflects how much more snow will be deposited on the lee side and in front of objects (parts) that block the air flow. In problem areas, you will have to bring the rafters as close as possible and thoroughly calculate the required thickness of the front material. The most accurate assessment of all parameters can be given only by multiplying any received figures by the reliability factors. As for the wind, the force developed by it is aimed at dropping steep roofs and lifting from the leeward section of a flat roof. We must not forget that the air flow acts simultaneously on the facades and roof slopes.

When hitting the facade, the air breaks up into two waves: one goes down and is no longer of interest, and the other tangentially presses the roof overhang, trying to raise it. The action on the slope occurs at a right angle, this area is pressed inward. At the same time, a vortex is formed, which tangentially affects the windward sector of the ramp. This vortex bypasses the ridge and begins to create lift already applied to the leeward segment. For your information: when calculating the mass of the roof, you need to take into account the severity of the rafters, insulation, waterproofing and vapor barrier.

The standard load per 1 square meter of the roof is up to 50 kg, regardless of its size and other significant circumstances. By changing the distance from one rafter leg to another, you can set the actual distribution of loads on them. According to most experts, indicators from 60 to 120 cm will be acceptable values. But on an insulated roof, it is worth choosing such distances that are equal to one sheet or roll of insulation materials. At the same time, it should be borne in mind that among several suitable options for arranging rafters, the one that gives the best effect with the minimum consumption of materials used is preferable.

When calculating the loads carried by the rafters, they always look at the fact that they do not exceed the ultimate endurance of the roofing material. After all, there is no point in such an excess. If, under the planned impact, the roof will still begin to sag, it is impossible to talk about a solid result. In calculations, the payload from structures connected to truss trusses is calculated according to the contact area that is plotted on the drawing. Such structures include ventilation chambers, attic and ground floor ceilings, and water tanks placed on the roofs. In addition to the amount of pressure on the rafter system, the sharpness of the roof slope is also calculated.

Tilt angle: value

On forums with consultations of specialists and in professional literature, one can find references to three units of measurement of inclination at once. In addition to the usual and expected degrees, there will be percentages and ratios between the parties. Often they get along together even within the same publication or instruction from the manufacturer of roofing materials. But in fact, there is nothing mysterious in this, any consumer can understand the essence. Under the angle of inclination of the roof, experts understand the angle that occurs at the intersection of the horizontal with the roof slope.

In this case, there can be no obtuse angles in principle. Moreover, you can meet a slope steeper than 50 degrees only in decorative elements, all kinds of turrets. The only exceptions to the general rule are the slopes on the lower rows of the rafters of the attic roof. In all other cases, the angles range from 0 to 45 degrees. The relative proportions of the sides are calculated as the ratio between the height of the slope and its projection on the horizontal. This indicator is equal to half the span for a uniformly constructed roof with a pair of slopes.

On a shed roof, the proportion is equal to one, but in more complex configurations, you still have to carry out all the calculations and estimates yourself, without starting from ready-made values. The slope angle is usually expressed as a fraction, with the numerator and denominator separated by a colon. But when the resulting numbers cannot be rounded to whole numbers, it is recommended to use percentages: they simply divide one by the other and increase it a hundred times. Flat roofs are those that have a slope of no more than 5 degrees; a slope of 6–30 degrees is recognized as small, and all other roofs are considered to be steep. The flat design drastically increases the usable area and is quite wind resistant, but it will need to be manually cleared of snow and strengthen the waterproofing to the limit. The slope is necessarily consistent with the specific material, and the required values ​​\u200b\u200bcan be found in the instructions from the manufacturer. In order to calculate even the most complex and bizarre roof configurations, they are mentally divided into triangles and the angle is calculated separately in each.

Step, length and section of rafters

When it became clear how long the slopes are, what angles formed by these slopes with a horizontal plane, it was time to do the actual calculation of the rafters. If the roof frame is made of a 5x15 cm timber under a metal tile, the mounting pitch sways from 0.6 to 0.8 m. As the slope grows, the gap also increases. If the roof slopes at 45 degrees, you need to put rafters every 800 mm, and for slopes of 75 degrees, you can add another 200 mm.

The next important parameter is the length of the rafters. It is closely related to the step: if the blocks are made long, they are brought together as much as possible, and when a single part is shortened, they are moved apart. When calculating the step of the crate, they proceed from the type of tiles laid on top and from the fact that an integer number of rows should be laid out on each slope. If you get a fraction, it is better to round, reduce or increase the indicator a little. The rafter legs under the metal tile, the cross section of which is 15x5 cm, range from 65 to 95 cm. You cannot increase the step when the cross section of the crate is 3x5 cm.

In order for the insulation to be better ventilated, rows of holes with a diameter of 1–1.2 cm are prepared in the region of the upper edge of the rafters. Ordinary rafters under the corrugated board go every 0.6–0.9 m. with significant cross section. The crate under the corrugated board is assembled from boards with dimensions of 3x10 cm, which are placed at intervals of 0.5 m. The interval must be calculated according to the height and thickness of the materials.

With all the revealed shortcomings of slate, it remains widely in demand. Under the slate roof, rafters with a section of 5x10–15 cm are mounted, 60–80 cm apart from each other. Most often, an average distance of 0.7 m is recommended. Pauses between parts of the crate are calculated according to the steepness of the material. On relatively flat areas, the support of 4 pieces of wood justifies itself. If the roof is made steeper, put 3 bars, separated by 63–65 cm.

We must not forget that due to the responsibility of the truss system, it is better to leave a margin of safety than to make an unreasonably weak type of rafters. For their manufacture, timber is used, dried to a maximum of 15%. A non-edged board of the same dryness can serve as a replacement for a beam. Under the ceramic tiles, a 5x5 cm timber crate is used. In the places marked according to the calculated distance, slate nails or simple self-tapping screws are used.

Installation: technology

The construction of the roof involves the use of a standard range of carpentry tools and an electric drill. If metal structures are used, a grinder will be required for precise cutting. Remember that it is impossible to process metal tiles or corrugated board with it, this can damage the material. A hipped roof without racks is made using puffs that reinforce the structure.

In the hip version, it is necessary to strengthen the runs running diagonally. Paired boards and a particularly strong timber are assigned to them. Connection points always have a support (stand), and the main support is placed about a quarter of the length separating the large rafters from the ridge. Under the gables on a gable roof, rafters of a shorter length are always made. But under the main part of the four-slope structure, extremely long parts can be placed, even more than 7 m. To keep them securely, either a rack is used that transfers stress to the ceiling or a sprengel.

The first step in creating rafters under a broken roof is the formation of a support complex in the form of the letter P. It rests on the floor beams and is held by rafter legs. Next, they put three or more runs, two of them are brought to the corners of the frame, and the rest are placed in the middle of the overlap. The final step in raftering is fixing the legs. It is desirable to make truss systems according to a pattern - to connect two boards that are the same length as the rafters, and pin them to each other with a nail. The template is placed with its edges at the points of attachment of the rafter legs and fixed with a cross member.

An additional template (this time plywood) will help to make a mounting saw. Farms are attached to the Mauerlat, starting from the extreme ones. In order not to confuse with the attachment point of the ridge, the tops of these trusses are tied with a straight rope. The massiveness of the puffs increases as you approach the ridge. If the truss elements are bolted, washers or plates should be used. This will keep the nuts from digging into the wood.

How to install the rafters with your own hands, see the video below.