At what distance to install rafters. Distance between rafters for different types of roofs and materials

The rafter is one of the individual elements of the supporting structure of the roof, with the help of which its slope is formed. In the design, the rafter is attached with its upper end to the ridge, and the lower end rests on the Mauerlat, with a straight slope, or on a rack (with a sloping roof). Rafters are made from edged boards with a section of 150x60 mm or a beam of 150x100 mm. The distance between the rafters at which they are located from each other after installation is called a step, which can be in the range of 600 - 1200 mm.

Rafter systems their types

Depending on the type of installation of rafter legs, systems are divided into 3 types:

What may determine the installation step of the rafters

The step of the roof rafters depends on such factors, as:

Taking into account all these indicators when calculating, you can get a solid and reliable roof structure, which for a long time will be a high-quality support for the roof.

It is the calculation, subject to the basics of regulatory loads, allows you to choose the right distance between the rafters. As a rule, the standard values ​​can be determined from the Sheaves, and the calculated ones are derived on their basis separately for each structure.

At the same time, it is customary to use rafter legs with a section of 150x50 mm with an optimal distance between the rafters within 0.8 - 1.8 m / p. but it should be remembered that when the slope of the roof slope changes, the distance between the rafters also changes.

Calculation of the truss structure

The strength and stability of the entire roof directly depends on the quality of the calculation for the selection of the section of the rafter legs and the distance between them. Regardless of which type of coating is chosen: profiled sheet, slate or metal tile, the initial calculation should remain unchanged. After all, each calculation is based on structural strength under mechanical loads, and other effects are no longer important.

When calculating the choice of the optimal distance between the rafters for the roof, are based on the following parameters:

1. Type of roofing.
2. View of the truss system and design features of the roof.
3. feasibility and economy.

For a small house, the design calculation for the roof can be done by yourself. True, the method of calculating the elements for the roof truss system is rather complicated, and it is recommended to do it with the help of programs specially created for this. Especially if you need to calculate a complex sloping roof with a large area, most likely, you will not be able to do without a specialist. At the same time, the calculation of the step of the rafters will also be based on the standards - the minimum step is 0.6 m, the maximum step is 1.2 m.

Method of calculation

Produced in this way.

- The length of the building is measured along the eaves.

- The resulting length is divided by the estimated distance between the rafters. For example, the estimated pitch of the rafters will be 0.8 m / p. (mean distance is considered to be 950 mm).

- After performing this action, one should be added to the result obtained, and the resulting amount should be rounded. Thus, the required number of rafters is obtained on one side of the slope. After that, the length of the building must be divided by the number of rafters received, and as a result, the exact axial pitch of the rafters is determined.

Example, - building length 26.5 m / p. the distance between the rafters is supposed to be 0.8 m. So:

- 26.5 m ˸ 0.8 m = 33.1 33.1+1 = 34.1. As a result, after rounding, it turns out that 34 rafters need to be installed on one slope.

26.5 m/s ˸ 34 art. = 0.77 m - this value is the distance between the rafters along their central axes.

But this is only a general calculation method, which does not take into account the peculiarity of the planned roofing. Therefore, it is recommended by experts to calculate the step between the rafters for a certain roofing material and insulation, for example, for the most popular roofing metal tile today.

Roof structure for metal roofing

metal tile visually imitates ceramic roof tiles. It is made from thin sheet steel by cold stamping. Due to the polymer coating, it has a high resistance to weathering and a rather attractive visual appearance, it is not afraid of sudden temperature changes.

The advantage of metal tiles

Often used in the construction of most mansard roofs.

The cross section of wooden rafters under a metal roof is usually standard 150-50 mm, but the distance between them can be from 600 mm, but not exceed 900 mm (depending on their angle of inclination, which can vary between 22 - 45 degrees). This limitation of the pitch of the rafters is due to the fact that the crate under the metal tile is mounted with a distance from each other within 300 mm. The standard timber, which is used for the crate, has a section of 30x50 mm or 50x50 mm. And this means that each rafter is subjected to additional load.

The stability of the roof structure against various mechanical loads depends on four factors:

An important factor in the calculation of the truss structure, is the estimated maximum load on the roof, the formation of which includes:

1. The weight of the entire truss structure.
2. The weight of the crate under the cover.
3. Weight of insulation and roofing.
4. Snow load (determined according to a special, unique for each region, reference book).
5. Wind load (also according to a special guide for the region).
6. The weight of a person with a tool (repair work, estimated weight - 175 kg / m²).

When installing the rafter system, the distance of the rafter legs should not exceed an average value of 0.9 m / p. except for certain, foreseen in advance cases.

If, when calculating the loads, any inaccuracy is made in the selection of material for the roof and the location of the rafters, it may occur its deformation and destruction of the roofing. A reliable roof structure will be guaranteed only with the correct calculation of the cross-section of the rafters and their installation step.

It should be remembered. There is no universal value for the calculation of truss structures. Each building requires an individual calculation.

Rafters for a shed roof

Shed roofs can often be found on small outbuildings. They can also be used in private residential buildings, but quite rarely. In such cases, the angle of inclination of the roof is rather small, and with this arrangement of the load-bearing beams of the floor, they are under a lot of pressure, especially in winter.

Therefore, for a shed roof, load-bearing floor beams are installed from a beam of large section from 60x150 to 100x220 mm, depending on the width of the overlapped span. At the same time, the distance at which the rafters are laid from each other should be within 400 - 800 mm, depending on the angle of the roof.

For pitched roof no complex rafter construction required, they can simply be laid on the walls, without even using a Mauerlat. In regions where winters are quite snowy with a lot of snow, it is recommended to build a roof slope at a maximum angle of 35 ⁰ and place the roof in the “wind”. This reduces windage and leads to its self-cleaning.

Gable roof

Represents a structure assembled from rafters interconnected in the form of a triangle. The upper part, which rests on the ridge, and the lower part on the Mauerlats, located parallel to each other on opposite walls. In simple words, this is a roof consisting of two opposite slopes, connected by a ridge.

Double pitched roof structure, depending on its area, is mounted from separate rigid elements that enhance the strength of the roof. These include racks that support rafters, puffs that connect rafters to each other, jibs, girders, support beams, etc.

For a gable roof, often the rafters are mounted taking into account the insulation in increments of 0.9 - 1.2 m / p. In this case, the strength of the mounted structure will be the highest if the resulting triangle is isosceles. In regions with strong winds, it is recommended to mount the rafters with a slope of approximately 20⁰, and in snowy areas, the optimal angle should be 45⁰.

Although the gable roof is considered classic, it has several alternative "related" types.

mansard roof

For mansard roof, for the calculated parameter for determining the step between the rafters and their number, a load is taken in the range of 40-60 kg for every 1 m / p. rafters, and the maximum deflection from its length is 1/250. Usually, with a properly selected section, this distance along the centers of the rafters is, as for a gable roof, 0.6 - 1.2 m / p.

It should be noted that the average load on the attic is approximately 200 kg / m2. So, with the standard calculation of the section of the rafters, it is recommended to add a small percentage of the margin of safety.

hip roof

Among all roof structures, it is considered one of the most difficult . It's almost a hipped roof., while the rafters of the end slopes are attached with their upper ends to the corner bowstrings, and not to the ridge. Therefore, certain requirements may be imposed on this type of roof during construction. In this case, the rafters are installed similarly to a gable roof at a distance of 60 cm - 1.2 m / p.

Attic rooms under such a roof are made in rare cases, since its slopes “eat up” some area of ​​​​the attic room, especially in height.

An attic is an attic space that can be used as a living space. The mansard roof should ensure the normal functioning of such a room. In the construction of the roof, a truss structure is usually used, and the pitch between the rafters of the mansard roof is an important indicator of its reliability.

Huge loads caused by the weight of the roof, wind, climatic factors are perceived by the rafter system. The distance between the rafters of a mansard type roof determines how much of the load falls on each element. Only the right choice of distance will ensure the stability of the entire roof.

Attic: system features

Rafters are called load-bearing beams, on which protective, additional and external coverings of the mansard roof are attached.

The elements are usually made in the form of a durable wooden beam or board with a thickness of at least 50 mm. Sometimes a log can be used. For particularly durable buildings, metal and reinforced concrete beams are used.

For the roof of the attic, one of two options for truss systems (layered or hanging) is used, as well as a combination of both options in one design. The layered type is characterized by the support of each of the rafters on the wall of the structure. The hanging type implies linking the elements into a common frame, which is fixed only on the extreme supports.

According to the type of truss system used, mansard roofs are conditionally divided into the following types: single-pitched, gable, broken, hip, hipped and vaulted. In private construction, single-pitched, double-pitched or sloping roofs are most widely used. In a shed roof, the rafters rest on walls of different heights, which ensures that the roof slopes (slope) in one direction. The gable roof has two inclined planes, with each of the rafters resting at one end on the wall, and at the other end connected to another beam. This design forms a triangle, and the angle between the elements determines the slope of the slope. The sloping roof also has two slopes, but each of them has a break line in which the laying angle changes.

Mounting Features

When installing the attic roof truss system, fastening and installation of rafters in the form of simple geometric shapes are used. The greatest rigidity (strength) has a linkage into a triangle, which is used in the construction of a mansard roof. So, the most common gable roof includes a series of triangles of rafters, connected by longitudinal lags (girders). The linkage of the rafters into a triangle is provided by the lower transverse beam (Mauerlat). To facilitate the fastening of the outer roof covering and the redistribution of its weight on the rafters, a lattice is made in the form of transverse bars or boards.

A sloping roof combines two types of rafter connections. The lower rafters with the help of a Mauerlat and a rack are connected into right-angled triangles, which, in turn, are fastened with a longitudinal run between themselves at the top. At the bottom, the attic rafters rest on the wall of the house. The upper ones are connected into a triangle by analogy with a gable design.

Figure 1. Table for selecting the section of a beam for rafters.

The lower end of the rafter is fixed on the transverse log, and the upper ends are connected together through the longitudinal upper run. The lower corners of the bonded triangle are interconnected using a longitudinal lower run. The system formed is fixed on the lower truss system. To strengthen the upper triangles, additional vertical racks are used. Thus, the mansard roof is a surface with a break on each side. From the wall, a slope with greater steepness begins, and then it takes on a more gentle appearance.

Mansards with longitudinal bars (including floor beams) are made by cutting rafters into a bar by a third of its height. Fastening to the cross beams is advisable to produce a screw connection. With such fastenings, the functions of two different truss systems are separated, and they are calculated as separate systems.

Parameters taken into account when choosing rafters

When choosing the design of the rafter system, the size of the beam and the number of elements, it is important to take into account all the loads acting on the rafters. These loads can be divided into permanent and temporary, periodic or short-term nature. Under a permanent load, the weight of all elements of the attic roof should be taken: the truss structure itself with a grate, external roofing, additional protective and insulating layers, elements of the attic interior. The weight of the external roof can vary greatly depending on the type and material of the coating.

Natural factors should be taken into account as temporary or periodic loads. This is, first of all, the weight of snow in winter. The wind has a significant impact, and the direction of such a load can be different. For some areas, this factor may be decisive. The possibility of storm water flows cannot be ignored either. In addition, it is necessary to take into account the weight of people and materials when carrying out repairs on the roof.

The geometry of the roof and rafter system has a significant impact on the distribution of loads. The main parameters include the length and width of the roof, as well as the steepness of the slope. The length of the roof greatly affects the distribution of the load, so for long lengths it is necessary to use reinforcing vertical posts. An increase in the width of the roof leads to an increase in the load on all attic rafters, as their length and the total weight of all elements increase. For wide roofs, a broken type is more suitable due to the presence of intermediate vertical racks in them and the redistribution of loads between different truss systems.

Changing the slope slope affects the parameters ambiguously. An increase in steepness, on the one hand, reduces the accumulation of snow cover and redistributes the load on the load-bearing walls of the house, on the other hand, the length of the rafters and the windage of the roof increase, which is dangerous in windy areas. The concentration of loads on the walls can also adversely affect the reliability of the house, because with a decrease in loads on the rafters, constant loads on the masonry walls increase.

Requirements for the material of the truss system

The calculation of the number of rafters and installation parameters is based on the fact that high-quality material was used during construction. In this regard, the material for the truss system should be selected based on the following conditions.

Only high-quality timber with a section of at least 50x100 mm should be used as the main rafters.

All wooden elements during installation must be well dried (permissible moisture content - no more than 15%). The number of even small defects on the beam cannot exceed 3 pieces per 1 m. The tree is treated with an antiseptic before installation. Coniferous wood performed the best. Vertical racks are made of a bar with a size of at least 100x100 mm with a check of their vertical location using a plumb line.

Features of the calculation of rafters

After choosing the design of the mansard roof (based on the recommendations of experts and in accordance with the reference data), the main design parameters are the distance between the rafters () and their number. Usually the distance between the rafters is from 0.6 to 1.5 m. The calculations are based on the fact that the optimal load should be 40-60 kg per 1 m of the rafter length, and the maximum allowable beam deflection is 1/250 of its length.

The number of rafters per slope is calculated after measuring the length of the slope and selecting. The length of the slope is divided by the step value, 1 (one) is added to the result. The result is rounded up to the nearest whole number.

A specialist can calculate the distance between the rafters, taking into account all factors, but in practice they use reference recommendations. So, for example, for rafters from a board measuring 50x180 mm and a slope length of 3 m, the average step is 1.5 m; with a length of 3.5 m - 1.2 m; and with a length of 4 m - 0.9 m.

Distance between rafters for different roofs

The distance between the rafters varies significantly for roofs with different coatings. Ceramic tiles are one of the heaviest roofing materials. For rafters from a bar measuring 50x150-60x180 mm, the recommended distance between them is 80-130 mm (depending) on ​​the steepness of the slope. With a slope of 15 °, the pitch is chosen to be 80 cm. With an increase in the length of the rafter, the pitch is increased within the recommended range.

The distance between the rafters for roofs with metal roofing is set smaller than for natural tiles. The optimal step is 60-95 cm for a bar measuring 50x150 mm. When using a corrugated board coating, the step is in the range of 60-90 cm with a sufficient beam cross section from 50x100 mm to 50x150 mm.

The lightest coating is obtained when using ondulin. The optimal distance between rafters measuring 50x50 mm is 60-80 cm and decreases when a larger beam is installed. When covering the roof of the attic with slate, a beam measuring from 50x100 mm to 50x150 mm is used. The step is set in the range of 60-80 cm.

Required Tools

When installing rafters on a mansard roof, the following tools are used:

• Bulgarian;
• drill;
• hacksaw;
• saw;
• axe;
• chisel;
• a hammer;
• plane.

When installing a truss system on a mansard roof, it is important to determine the optimal distance between the rafters. The correct choice of this parameter will allow you to calculate the optimal amount of material and ensure the reliability of the entire roof.

The roof structure is one of the main enclosing elements of the building, the quality characteristics of which are subject to rather stringent requirements.

One of the most common roof sheathing materials is metal shingles, which are made from thin sheets of steel, aluminum, or copper.

From above, the elements are equipped with a polymer coating, which protects metal from aggressive external influences.

Externally, the metal tile is similar to ceramic, but it is more durable. This material is used to cover pitched roofs, the slope of which must be at least 14 degrees.

This is the national team roof frame structure, consisting of many wooden or metal parts. She is rests on load-bearing walls, which are a reliable basis for all overlying elements. The rafter system serves as a kind of skeleton, on the basis of which it is made, - and the roof, as well as laying the roofing finish roofing layer.

truss system

The constituent elements of the truss roof, and their main characteristics:

• Mauerlat. A softwood beam, which is a connecting element between the rafters and the underlying structures. It has a square cross section with a side of 100 or 150 mm. Mauerlat is laid along the load-bearing wall along its entire length. With the help of the Mauerlat, the loads from the roof are evenly distributed throughout the building.
• Sill. A beam having a square section similar to a Mauerlat. It is laid transversely to the bearing walls, as it serves to redistribute the load from the roof racks.
• Rafter leg. From these elements, the main triangular roof structure is created, which experiences the full burden of external atmospheric influences (rain, wind, snow, hail, etc.).
• Rack. Vertical connecting elements that distribute compressive loads from the ridge assembly over the entire area of ​​​​bearing walls. They are made of square bars, the length of the edge of which is determined by calculation.
• Puff. It is the final horizontal element of the triangle of rafter legs, which does not allow them to crawl under the pressure of external loads and the own weight of the roof. It is used in systems with hanging rafters.
• Struts. Perceive and redistribute bending loads from the ridge assembly.
• Crate. It consists of boards, bars or plywood sheets (in the case of subsequent laying of bituminous tiles), which are located at a right angle relative to the rafter legs, while being an additional rigid element.
• . The junction of two roof slopes.
• Overhang. A roofing element protruding from the load-bearing wall structures at a distance of about 0.4 m. Its purpose is to limit the penetration of moisture to the walls.
• Filly. These elements are attached to the ends of the rafters if they are not long enough to organize an overhang.

Varieties of pitched roofs

Depending on the number of inclined planes, roof structures can be divided into:

In private housing construction, the most commonly used option gable roof, since he has a number of advantages. These include:

1. Practicality. The gable roof has a significant angle of inclination, thanks to which rainwater does not accumulate on its surface, and snow and wind loads are distributed in the most optimal way.
2. Ease of device and operation. The assembly and joining of two pitched elements is much easier than with complex roof structures. In addition, the repair of such a roof will also be simple.
3. Aesthetics. A roof with a gable structure is organically written into the surrounding infrastructure.
4. Reliability(if done correctly).
5. Democratic price constituent materials.

Types of pitched roofs

Gable roof - truss system for metal tiles

Frame from rafters under a gable roof from a metal tile has no significant differences from structures with other covering roofing materials.

But, in view of the fact that metal thin sheets have a low specific gravity, the rafters will experience less constant load.

This allows you to reduce the value of their cross section, due to which can save a lot on the purchase of wood materials.

Ideal for metal roofing the angle of inclination must be at least 14 degrees.

For a roof with two pitched elements, the following apply: frame options:

Laminated rafters under a metal tile.

In this case, 2 load-bearing rafter legs are fastened together using lying down(horizontally) and racks(vertically). The bed is laid parallel to the Mauerlat element, while taking on some of the force effects. The rafter system under the metal tile is taken over only bending loads, which significantly affects the selection of the calculated cross section. Such a system can be used for buildings with large and small spans.

Types of rafters

Hanging rafters.

Unlike layered systems, in this embodiment, two rafter legs fastened together only in the ridge knot. In this case, significant bursting forces arise on the bearing elements, which limits the use of hanging rafters only for buildings with a span of no more than 6 m.

They can be made of wood or metal, as well as installed at the bottom (acting as a supporting beam) or at the top of a triangular structure. It is worth considering that the higher the puff is located, the greater the effort it will take.

NOTE!

To ensure the quality of the tightening, care must be taken on the reliability of fastening with load-bearing rafter legs.

Combined variant

Used to create an original roof structure. Includes elements of both hanging and layered systems.

How to calculate the angle of inclination of the rafters?

To implement a gable roof, you need to know a few geometric values ​​of the building, namely:

• Half span - L;
• The distance from the load-bearing wall to the roof ridge (or the height of the support post) - H.

Standard formula: α = arctg(L/H)

Where α is the desired angle of inclination of the roof.

Knowing this value, you can calculate the length of the supporting rafter leg:

l = H/sinα.

Where l is the length of the truss element.

Rafter Angle

How to calculate the load?

To carry out the correct selection of parts of the roof frame, it is necessary calculate live and permanent load values acting on its structural elements.

The constant load includes the weight of all elements, as well as the mass of the load-bearing elements themselves and the crate.

The composition of temporary loading options includes force effects from wind, snow cover, rain masses, as well as the weight of a person (to take into account options for subsequent repairs).

Dead Load Calculation

Roofing cake weight.

It is determined by adding the masses of all its elements, namely steam, hydro and thermal insulation, as well as roofing from metal tiles. In this case, the weight of one running meter (can be found in the regulatory documentation) is multiplied by the value of its length.

The weight of the truss system.

It is determined by adding the weight values ​​​​of the crate, rough flooring, as well as the supporting frame. The mass of each element is calculated by the formula:

M=V*p,

Where V is the volume of the element, calculated depending on the geometric characteristics of the cross section and the length of the element;

P - The density of the wood used (depending on the species).

Total permanent load \u003d weight of the rafter system + weight of the roofing pie.

Calculation of live loading

Conducted in accordance with regulatory documents ( SNiP 2.01.07-85 "Loads and impacts" or Eurocode "Actions on structures" part 1-4).

To determine the value of the wind effect, the roof structure is conventionally divided by height into several parts. For each of them, the value of the wind load is calculated. To obtain the total wind pressure, they must be summed.

Formula for calculation:

Wm=Wo×k×c,

Where Wm is the value of the wind load;

Wo is the normative value of wind pressure determined from zoning maps;

k - wind pressure coefficient (determined depending on the height according to the regulatory documentation);

c - aerodynamic coefficient (for a gable roof - 0.8).

Determined by the formula:

S = µ×So;

Where So is the normative value of the snow load, determined from the zoning map.

µ is a coefficient that is determined depending on the angle of the roof:

• For α≤30 deg. — µ=1
• For α≥60deg. -µ=0
• For 30≤α≤60 deg. – µ=0.033×(60-α)

Snow load areas

How to choose a beam and calculate the pitch of the rafters under the metal tile?

Determining the value of the cross section of the beam of the truss element is carried out in several stages.

Calculation of the load distributed on each linear meter of the structure:

Qр = L×Q;

L - Step of the rafters.

The L value is calculated as follows:

The length of the roof slope is divided by the estimated step of the structures (for convenience, it is most often taken equal to 1). Then 1 is added to the resulting value. The resulting value reflects the number of rafters that need to be installed on one pitched roof surface. At the last stage, the value of the axial distance between the rafter elements is determined by dividing the length of the roof slope by the number of rafters.

The distance between the rafters under the metal tile - the standard step is 0.6-0.95 m.

Rafter step

Then we determine the maximum working area of ​​\u200b\u200bthe rafter leg (Lmax). We proceed to the calculation of the cross section. To do this, we find its height using the formula:

H ≥ 8.6*lmax * sqrt(Qp/(b*r)), with roof slope α<30 град;

H ≥ 9.5*lmax * sqrt(Qp/(b*r)), with a roof slope α≥30 degrees;

Where b is the width of the cross section,

r - the value of the normative resistance of wood to bending loads (determined according to regulatory documentation, depending on the type of wood).

To simplify the calculations, you need to use the standardization table for truss elements (GOST 24454-80 “Softwood lumber. dimensions").

If the inequality is not observed, it is necessary to increase the value of the geometric characteristics of the section and repeat the calculation.

What is the difference between the truss system for cold and warm roofs?

The main difference between these two roofs is the support system of the truss elements. In the case of a warm attic, the main supporting element is the Mauerlat, as well as the supporting beam system. In a cold roof, rafters are installed directly on load-bearing walls.

Installation of rafters under the metal tile

All installation work on the installation of the roof is carried out at a sufficiently high height. To minimize the risk of falls, as well as greatly simplify work at height, you can assemble the frame of the supporting truss system on the ground.

To do this, you need to create a template from the boards, according to which further assembly will be carried out.

It is made in several stages:

• The boards are raised above the walls of the building, leveled, and then fasten together with the help of a nail.
• Align the angle of the boards in accordance with the project, by lowering and raising them. The elements are fixed.
• The result should be a structure that resembles in shape the future truss system, made in accordance with the estimated geometric dimensions of the roof.
• The template is lowered to the ground, in accordance with it, the finishing elements are fixed to each other. More details in the video below.

Then you should take care of installing the support element - Mauerlat. As mentioned earlier, it is laid on load-bearing walls in the longitudinal direction. Fastening is carried out using studs (on an armored belt or masonry) or using a wire rod (for buildings with a small roof height).

CAREFULLY!

When using a hairpin connection, connecting elements do not need to be tightly sealed into the wall. They should protrude from the wall by 30-40 mm, as the nut will be screwed onto the studs.

The next step is to create ridge run, serving as a supporting part for the entire structure of a gable roof. It is made from timber or hewn logs. If the span of the building is not more than 6 m, it can be supported without additional supporting elements. Otherwise, construction trusses must be used for installation.

Mounting. Part 1

After installing these elements, it is possible to carry out the lifting and installation of the main truss element, assembled according to the template. Fastening with a Mauerlat can be carried out in 2 ways:

Rigid connection. It is carried out with the help of corners and beams. Less often, fastening is used by means of washing down on rafter legs, followed by fixation with nails or staples.

Features: in addition to the main connection, it is necessary to tie the rafters to the wall using anchors or a wire structure.

Sliding. It is based on the creation of a swivel joint. It is made by joining elements using cuts. The elements are connected with a metal embedded part with holes for bolts, or with 2 nails that need to be hammered in at an angle.

It is necessary to carry out the installation of wooden trusses in a certain sequence. First, extreme trusses are installed, located at the ends of the building. Then a cord or rope is pulled between them, with the help of which the verticality of their installation is checked. Further, under the cord, further installation of truss structures is carried out in accordance with the specified design step.

Mounting. Part 2

Creating a roof from a metal tile is a rather laborious process that requires certain skills and a full hand. Therefore, for proper installation, you must at least work under the supervision of a competent specialist.

Useful video

Video instruction for self-installation of rafter legs:

A shed type of roof is rarely seen in private housing construction. Although, according to some, this is in vain, because the installation of a shed roof is much easier than the installation of a gable roof. On the other hand, such a roof design will not be able to keep the heat in the room so well. That is why shed roofing is most often used to build a garage, country house or barn.

True, if the work on thermal insulation is correctly performed, then the structure may well be warm. In this case, a living room is made under a pitched roof. Let's look at the advantages of a shed roof, what types of truss systems exist, how the design is calculated. In addition, we will consider how to install this type of roof.

Pros and cons of a shed roof for a house

Beginners in the construction business will be delighted that such a shed construction is quite simple and can be done by hand. True, it is impossible to call the work the easiest, but with detailed instructions, a shed roof will be created. But before considering the design features of the roof, you need to find out its features and advantages. They characterize this type of roof.

Advantages of a pitched roof:

1. Profitability. For the device of the roof, a lot of building materials are not needed, on which the bulk of the funds are spent.
2. The simplicity of the truss system and the shed structure as a whole. The best thing for beginners. Installation will be easier than with a gable roof.
3. The building will have a small weight. This means that there is less load on the walls and foundation.
4. Thanks to this shape, a shed roof perfectly resists wind loads, as well as the weight of snow that accumulates on the surface.
5. The angle of inclination is very different, depending on the needs. It varies from 5° to 45°.
6. If you make the angle of a shed roof small, then it can be used for various purposes. For example, if this is a barn, then install a tank for heating the liquid. If this is a living space, then on a shed roof you can equip a great place to relax. Alternatively, install solar panels as an alternative power source.
7. The versatility of a one-slope building. It is covered with almost any material available on the market. It all depends on the operating conditions and the chosen angle of inclination.

Despite all its advantages, a shed roof has its drawbacks. This is not surprising, since nothing is perfect, but it is better to know about the cons and use them profitably.

Cons of a shed roof:

• The first concerns insulation. There is no more space with an air gap under the structure, so the issue of insulation should be taken more seriously. If you do not make thermal insulation of the structure, then in summer the attic will be too hot, and in winter, on the contrary, it will be supercooled. In either case, the temperature (high or low) will be transmitted to the house. Correct calculations and high-quality insulation will help eliminate this;
• when creating a ceiling immediately under the roof, made at a slight angle, the house will not have an upper air gap and an attic. And in this case, living space cannot be organized;
• due to a slight slope, which reaches from 5 to 10 °, snow and moisture will accumulate on a shed surface.

Despite all the obvious disadvantages, a shed roof is an ideal option for creating a garage and other buildings on the site.

Calculation of the construction of a single-pitched roof

This is the first stage before the installation of the truss system. It is recommended to draw up a detailed plan or drawing, which will be guided by when working. To create this schema, you need to highlight the following data:

• the total width of the roof construction, as well as the length of the spans that is formed between the bearing walls;
• slope angle, desired or obtained;
• the length of the single-pitched roof;
• selected roofing material;
• what is the height and width of the load-bearing walls.

Note! When a shed roof is created for a barn, garage or country house, you can simply raise the front wall of the structure above the back.

As a result, the angle of the slope will depend on the height of the rise. The second option involves the creation of supports, on which the run will fit. The second way allows you to save building materials.

For drawings, you need to know the following nuances:

The drawing of the future shed roof should have all the necessary information about the elements. The dimensions, distances between them, fastening features, etc. are indicated. Below is an example of such a drawing of a pitched roof.

Choosing the corner of a pitched roof

The angle of the slope is chosen taking into account the fact that the resulting roof forms a triangle, one corner of which will always be right. The legs are the floor beams and the gable part of the building, and the rafters serve as the hypotenuse. This is clearly seen in this diagram.

The designations are as follows:

• Lc - the length of the rafter used;
• Lbc - our leg, indicating the height of the pediment from the floor beam to the roof plane;
• Lsd - the width of the building;
• A - the selected or desired angle of a pitched roof.

Given the basic values, it is possible to calculate all the parameters of a single-slope structure. There is a formula for this. The first is used when the width of the building and the planned height of the pediment are taken as the basis. In this case, the formula is:

When you have decided on the angle of the shed roof, then you need to calculate the future height of the gable. For this, the formula is:

In this case, the length of the roof rafter legs is calculated as follows:

Note! This length of the rafters does not take into account the canopy from the rear or the facade of the room.

Many criteria influence the choice of slope angle. The main one is the choice of roofing material. Each of them is recommended to buy for a particular angle of inclination. Here are recommendations for popular roofing materials:

1. For the installation of corrugated board, the slope must be at least 8 °.
2. When using metal tiles, you will need to make a roof with an angle of inclination of 30 °.
3. For a slate device, indicators from 20 ° to 30 ° are needed.
4. As for rolled roofing materials (roofing material, shingles and soft roofing), the angle of inclination should be 5-7 °, no less.

Advice! A roof without a heating system in an area where there is a lot of snow in winter, a shed type roof with a slope of 40° is ideal, regardless of the roofing material. So all precipitation will quickly descend from it.

Varieties of the truss system of a shed roof

There are three options for creating a truss system. The choice of design depends on the size of the room and its type.

Now that we have dealt with the design of the truss system and learned its types, we can consider the process of creating a shed roof.

Installation work on the creation of a pitched roof

Having on hand the drawings and the selected type of system, you can get to work. You will also need the appropriate tools and lumber. The installation of the truss system is performed as follows:

1. For safety, the building should be covered with beams. They are placed on the wall. To extend their service life, roofing material is glued to the wall. It will protect the beams from moisture and decay. You need to position the floor sticks in the same way as the rafters. Fastening pitch -500-800 mm.
   
   
2. Mauerlat is laid on top of the beams. This is a massive beam that will serve as a support. It fits on the back bottom wall of the building.
3. To safely move around the roof, flooring from wooden boards is laid on the floor beams. He is temporary.
   
   
4. Now you need to build a gable wall. It is made from the same material as the building itself. You can use lighter material. For example, if the walls are brick, then the pediment rises by means of bars or boards.
5. Floor beams must be covered with waterproofing and walled into the wall. The pediment rises to the chosen height, according to the drawings.
6. On the finished pediment, you can fix the Mauerlat. It turns out that two Mauerlat are parallel to each other.
7. Markings are applied to the lower wall for attaching the rafter legs. The fastening elements themselves are fixed.
8. To firmly fix the rafter, based on the drawings, grooves are cut on it. This is a good mounting option. The grooves are in two places, top and bottom, to enter the Mauerlat. There are other methods of fixing the rafter leg, as shown in this photo.
   
   
9. After that, the legs are fixed with special corners and fasteners. From above, at the pediment, the legs are screwed rigidly. But the lower part is made depending on the chosen truss system of a pitched roof. It can be rigidly fixed or made sliding.
   
   
10. There is a certain sequence of inserting rafter legs. First, the extreme elements of the truss system are mounted. A cord is stretched between them, serving as a guide and level for subsequent rafters. Do not forget that the step of the rafters corresponds to the step of the floor beams.
11. The rafters that are already installed are connected to the floor beams through racks, struts and other elements to give them stability. We talked about them above. Fixation is carried out with metal corners and staples.

    Tip! If you want to lengthen the rafters and bring them out of the wall, then “fillies” are attached to the bars. So you can protect the adjacent part of the structure from precipitation.

    

12. When the construction of a shed roof is ready, you can begin to insulate and create a roofing pie.

The photo shows what layers the correct insulated shed roof should consist of.

Insulating material is laid between the rafters. He has to hold on tight there. After that, a counter-lattice for ventilation is made on top. A waterproofing film is laid on the counter-lattice. It protects the insulation from moisture, which can ruin it.

As for the crate for laying roofing material, it is selected depending on what kind of roofing material it will be. For example, a solid crate of boards or plywood is needed when installing soft tiles and other rolled materials. If metal tiles, corrugated board, slate, ondulin and other types of hard roofing are used, then the crate is done in a row. The step depends on the roofing material.

And in order to protect the insulation from the inside of a shed roof, you need to sheathe it with a vapor barrier film. Now we can say that the shed roof is completely ready.

Note! If a shed roof is made for a barn or other non-residential structure, then it is not necessary to insulate it. It is better to spend them for another purpose.

Conclusion

Creating a roof, whether it is a gable or single-pitched, is a dangerous, time-consuming and responsible process. That is why caution is required and strict adherence to the instructions for creating a structure. Only then can the best result be achieved.

It is pointless to argue about the importance of the roof for any building. It is not for nothing that over a dozen different types of roofs have been invented in the history of mankind, from simple to quite complex in design and construction. An important element in planning the construction of a roof is the step between the rafters - strong bars that are the basis of the structure. This will be discussed in this article.

The distance between the base of the roof slopes is not a constant value and depends on the following components:

• type of roof;
• slope angle;
• the type of roofing material to be installed;
• rafter section dimensions.

Before proceeding with the process of erecting the upper structure of the house, a calculation should be performed by determining the optimal distance between the rafters.

Gable roof rafter pitch

The most widespread in our country are gable roofs. They are a structure that has two parallel planes, with an angle of inclination relative to the horizon from 20 to 50 degrees.

With an insufficient slope of the gable roof in snowy areas, there is a danger of accumulation of large snow masses, which can lead to the destruction of the structure. An increase in the slope angle in regions with a predominance of strong winds is also fraught with a high load and the risk of breaking not only the roof, but the entire structure as a whole.

Mansard roof truss system

Most private houses have an exploited under-roof space called an attic. This design is characterized by an increased height of the slope, which is caused by the need to create a living space of a comfortable height. As a rule, the slopes of the mansard roof are broken, having a varying angle of slope. For their installation, a double truss system is used.

The steepness of the lower slopes of the mansard roof significantly exceeds the slope of their upper extensions. The plane load perceived by them is not great. Thanks to this, the rafters in the lower part can be installed with a maximum pitch. The upper ridge slopes are recommended to be mounted with a reduced gap from each other.

Rafters in a shed roof

For outbuildings and some private houses, roofs with one slope are used. Due to the limited angle of inclination, high pressure is exerted on them. Experts recommend using lumber of increased cross-section for the rafters of a single-pitched roof, with the installation of a minimum step from each other.

When calculating the distances at which roof beams are installed, special attention should be paid to the amount of snow load in a particular area. With a small slope, this characteristic is of great importance. Roofing material for such roofs is best chosen with a minimum dead weight, which will reduce the bending load.

Hip roof truss system

The hip roof truss system is considered the most difficult in construction. This type is called four-pitched, since the roof is formed not only by side, but also by additional end slopes, where the installation of rafters is carried out not on the ridge, but on the corner bowstrings. This places special demands on the organization of the roof frame.

Under the hip roof, the attic is not often arranged. This is due to the small angle of inclination of the rafters and the roof as a whole. In the case of an increase in the angle of the slopes to the horizon, the distance between the rafters is increased, with a decrease, vice versa. An additional aspect of the calculation is the roofing material used.

The dependence of the pitch of the rafters on the roofing material

In addition to variable snow and wind loads, a constant (static) one also acts on the roof, the force of which depends on the roofing material used. It is no secret that different types of roofs have their own weight, which can differ by 10 or more times.

The right choice of material affects not only the top, but also all other parts of the structure of a residential building and other buildings. Not without reason, when designing the foundation, it is necessary to decide in advance on the choice of the roof.

Roofing from profiled sheet

Currently, one of the most common roofing materials is a profiled sheet, which is produced galvanized or followed by a polymer coating. The distinguishing features of the profiled sheet include the following parameters:

1. High corrosion resistance;
2. As a result, a long (more than 15 years) service life;
3. Easy installation even without the necessary qualification;
4. Small sheet weight (weight 1 m 2 is 4-5 kg).

Since this roofing material does not exert a high load on the rafter system, the distance between the elements is chosen as much as possible for a particular angle of inclination. In addition, the profiled sheet does not require high strength characteristics from the roof lathing. All this together allows minimizing the total load on the foundation and walls.

Roofing from a metal tile

The second common type of steel roofing materials is metal tiles. This type of profiled sheet, which successfully imitates natural clay material, but with a lower mass (10 or more). A feature of the rafters under the metal tile is the smaller section size.

When choosing at what distance to install the rafters, first of all, you should be guided by the dynamic load. Like a profiled sheet, a metal tile is not demanding on the size of the rafter legs and is well mounted on a crate made of an inch coniferous board. All this makes a metal roof low-cost.

Rafter system for ondulin

In the 21st century, corrugated sheet materials were replaced by a more durable and lightweight analogue - ondulin. Among others - the most lightweight material. The weight of the sheet does not exceed 6 kg.

The small thickness of ondulin sheets at slope angles of less than 15 ° requires the construction of a continuous crate of plywood sheets, for example, which will require an appropriate rafter pitch. This should be taken into account in the calculations.

slate roof

Not so long ago, a wavy material from an asbestos-cement mixture, called slate, was widespread. High mass and fragility are the main disadvantages, however, even today he finds his fans in the construction of various outbuildings.

A high mass, comparable to the weight of a clay tile, will not allow the use of the same truss system as under a metal tile. Building codes define a minimum angle of slope for a slate roof of 22 degrees or more. Otherwise, the load from the material itself and the truss system with the crate exceeds the permissible parameters. The step of the inclined bars, as well as their cross section, are selected individually in each case.

Polycarbonate roof

In recent years, more and more often on the roofs of verandas and gazebos, an artificial polymer material, polycarbonate, has been used. Produced in two versions - monolithic and honeycomb. The first in its properties is similar to ordinary quartz glass, but significantly exceeds it in strength. The second one has less mechanical properties, but high thermal insulation and light transmission.

Cellular polycarbonate is standardly much lighter than a monolithic counterpart. It is used as a roof without the use of lathing, provided that the step does not exceed ½ of the width of the sheet of material. The high strength of the monolithic analogue also makes it possible to avoid elements transverse to the rafters. Sufficient flexibility allows you to cover semi-circular roofs on a metal frame, the pitch of which does not exceed 0.9 meters.

Thematic material:

Rafters under a soft roof

The original pattern can be obtained through the use of soft roofing materials, which are spread with an adhesive layer. They are installed on a continuous crate made of plywood or OSB. The step of the rafters should allow you to fix the sheets, so it is chosen as a multiple of ½ of the width. Given the standard dimensions of plywood 1520x1520 mm, the center distance between the rafters will be: 1520: 3 = 506 mm.

Rafter step for insulation

The installation of residential under-roof spaces is often combined with the laying of insulation sheets in the rafter gap. The most common plates with dimensions of 600x1000mm. These parameters are used as starting points.

Rafter pitch calculation scheme

According to building codes, the pitch of the roof rafters is in the range of 0.6 - 1 meter. Its final calculation is performed according to a simple formula, depending on the total length of the roof. For the calculation, you must perform the following list of actions:

1. determine how much distance should be between the rafters for your specific building conditions. According to the reference book, the magnitude of wind and snow loads in the area is determined.
2. the length of the roof is divided by the desired distance by adding one. The result will be equal to the number of rafter legs that are installed on one roof slope. If the value is not an integer, it is rounded off.
3. the length of the roof is divided by the number of rafters calculated above, we get the final step in meters.

For example, with a slope of 30 degrees, the maximum distance between the rafters of a gable roof under a metal tile is 0.6 measure. The length is assumed to be 16 meters. Hence:

1. 16:0,6+1=27,66;
2. rounding the result, we get 28 rafters per slope;
3. 16:28 \u003d 0.57 meters - the center gap of the rafter legs for these specific conditions.

As you can see, the calculation technology is not complicated, but this is just an approximate scheme. Taking into account many other parameters mentioned above can make certain adjustments.