Supports for the roof mounting scheme. Rafter system nodes - how to make a reliable roof? How to connect the parts of the truss system

In any building, the main elements on which the maximum load falls are the foundation, walls and roof. The quality of the installation of the roof largely depends on whether the truss system is installed correctly or not. If the attachment points of the truss system do not meet certain requirements, then such a roof will not last even a minimum operational period without repair work.

Requirements for the truss system

The truss system of any roof must meet such important requirements as:

• Maximum rigidity. Any frame node must withstand loads without being subjected to deformation or displacement. The triangle obtained during the arrangement of the truss system must ensure the rigidity of the structure and its maximum stability;
• Optimal weight. Depending on the roofing material, the material used for the rafters is selected. Usually a wooden beam is chosen, but metal can also be used for heavy roofs.

  Important! To prevent damage to the rafters, their rotting and the formation of fungus on wood, it is treated with an antiseptic, and metal structures with anti-corrosion compounds.

• The high quality of the materials used. The wood used as rafter legs should not have cracks and chips.

Varieties of truss systems

The roof can be equipped with one of the types of truss system, of which there are only two:

• Hanging rafters;
• Overhead rafters.

Hanging truss system

Such a system is optimal in the case of a gable roof, when the span between the walls is no more than 6 meters, but when installing additional elements, it is also applicable for wider openings. The Mauerlat serves as the lower basis for the support, while the upper part of the structure abuts against each other. This design also contains a puff - necessary to relieve the load from the walls, by reducing the expansion of the rafters. Beam puffs are installed below the rafter legs and can serve as floor beams.

Attention! The role of the puff may not necessarily be played by a wooden beam, it can also be reinforced concrete flooring, which in some houses is equipped with an upper floor.

If the puff is located above the bottom of the truss system, then it is called a crossbar. Important points in the arrangement of this type of truss system include:

• The roof overhang should not be allowed to rest on the lower part of the rafter legs, which extend beyond the wall. In such a situation, it is best to use a filly (the width of the overhang is set within one meter). With this arrangement, the rafter will be based on the Mauerlat. The cross section of the beam for the filly is chosen smaller than for the rafters;
• To give the roof additional rigidity, and prevent it from swaying and being destroyed by strong gusts of wind, a wind board is nailed on the slope, to the Mauerlat from the ridge;
• If the moisture content of the material used to equip the truss system is more than 18%, unsteadiness should be foreseen, which will cause gradual drying of the wood. That is why fastening should be done with bolts or screws, not nails.

Layered truss system

This arrangement is applicable for roofs with distances between walls from 10 meters (maximum 16 meters). The slope can be made at any angle, and inside the building there are load-bearing walls or supporting columns. From above, for the rafters, the ridge run serves as the main support, and from below this function is performed by the Mauerlat. The inner purlin is supported either by the inner wall or by the studs. Due to the presence of only vertical type of loads, there is no need to install the tightening.

With a 16-meter span, the replacement of the ridge run is carried out by two side structures, the support for which will be the racks.

Important! The absence of bends in the rafter legs is ensured by such nodes as struts and crossbars.

Particular attention to the arrangement of the roof using a layered truss system should be paid to such nuances:

Features of calculations of the gable roof truss system are shown in the video:

The main nodes of the truss systems

The main nodes of the roof truss system include:

• Rafter. They perform the function of a skeleton, supporting the internal and external elements of the roof, and also serve as the basis for laying communications;
• Mauerlat. This is a kind of roofing foundation, which is a beam on which the entire structure is installed. It performs an important function - uniform distribution of the load of the entire structure;
• Run. Designed for fastening rafter legs together and can be located both on top and on the side;
• Puff. Serves for fixing the rafters in the lower part of the structure;
• Struts and racks. Provide the most stable location of the rafter beams;
• Skate. The junction of the roof slopes;
• Filly. These are continuations of the rafter legs, which are sometimes equipped;
• Rigel. It is necessary for high-quality and reliable support of load-bearing elements;
• Sill. Cross bar necessary to distribute the load.

In addition to the listed elements, the design includes attachment points for the roof truss system. When performing them, it is necessary to follow certain rules.

Important! It is absolutely not worth performing a simple fastening of the base to the crossbar, as this can lead to the complete destruction of the truss system.

The following types of fasteners should be used:

• With emphasis on the end of the crossbar;
• Teeth point-blank;
• Teeth in a spike.

The number of teeth should be chosen depending on the slope of the slope, and additional structural reliability can be created using metal corners.

Description of the main fasteners for mounting the truss system

If during the construction of the house a rounded log or timber was used, then it is not necessary to create an armored belt. produced on the upper beam or on the log of the wall. For this purpose, connecting the Mauerlat with the rafters uses different methods of cutting (tie-ins).

What fasteners fasten metal rafters:

1. Plates.
2. Fasteners LK.
3. corners.
4. Brackets WW.
5. Self-tapping screws.
6. Varieties of the corner of the KR.
7. Wire ties.
8. Mounting tape perforated TM.
9. Bolts with nuts.
10. Brackets WW.

If brackets are used when connecting the rafters to the Mauerlat, then they are not cut into the rafters, which helps to strengthen the bearing capacity. Metal brackets are usually produced, and the metal is galvanized and has a thickness of 0.2 cm. The brackets are strengthened with nails, anchor bolts or screws.

You can use the LK fastener by creating attachment points not only for rafters with a Mauerlat, but also for various other elements that make up the roof structure. The LK fastener is fixed to the wood, as are the brackets, with the exception of the use of anchor types of bolts.

Mounting perforated tape allows you to strengthen the connecting nodes in the construction of roofing systems. It is used not only to create stronger nodes, but also to strengthen elements for additional use in order to give rigidity or strength to the system as a whole. They fix the perforated mounting tape with screws or nails, so it is used to strengthen the structure of the rafter system of any roof, the integrity of which will not be violated.

With the use of KR corners and their various modifications, the attachment points are reinforced so that they can effectively participate in the connection of the Mauerlat and rafters. Ensuring appropriate strength to the roof units is permissible when using corners, which improves the load-bearing characteristics of the roof structure.

The use of connecting elements made of metal is not associated with inserting corners into the roof system. This will not cause a decrease in the bearing capacity of the roofing system. You can use corners for connection using screws or nails, the protrusions of which resemble a ruff.

How are the knots connected in the ridge part?

There are three main types of fastening in the ridge parts of the roofing system:

1. Butt connection.
2. Mounting on the basis of a ridge run.
3. Ridge joint overlap.

For the purpose of fastening, in the first way, the ridge part is cut off from the upper edge at an angle that is the same as the angle of the roof slope. Then it rests on the necessary rafter, which should also be cut at an angle, but on the opposite side of the roof. A special template is sometimes used to trim corners.

Nails for connecting the rafters under the ridge should be 150 mm or more in size, two of them will be needed. Each nail is driven into the rafters at the top of the rafters at the appropriate angle. The sharp end of the nail usually enters the cut of the rafter from opposite sides. Strengthening the ridge joint can be achieved by applying a metal plate to it on the side or a wooden lining so that it is enough to pull it with bolts or nails.

The connection in the second way, that is, through the ridge run, is associated with the strengthening of the rafters on the ridge beam. The run is one of the additional support beams or beams, which is a support for the rafters. It is located parallel to the ridge or Mauerlat. The method differs from the previous one in that a ridge beam is laid between the rafters, which are sawn at an angle, which is a laborious process, so this method is used less frequently.

A more common method is similar to the first, but it differs in that the fastening is overlapped, and the joint method is not used. The rafters should be in contact with the ends, and not the side surfaces. The rafters should be pulled together with a bolt or hairpin, nails. This connection is used by many masters in practice.

In general, it is possible to install rafters on a Mauerlat by creating structures for roof truss systems that are expansion or non-expansion. This determines the choice of the appropriate method of connecting the power plate and rafters, which can be similarly strengthened to the ridge.

The main shortcomings in the installation of attachment points for the truss system

The problem of choosing the method of attaching the truss system to the structure of the building is very important when creating attachment points. Often, when creating nodes, the Mauerlat serves as a support for the rafters. The fastening of the Mauerlat beam is carried out “tightly” with the help of anchor bolts to the reinforced stiffening belt.

A possible drawback is an unanchored stiffening belt, which can lead to the overturning of the Mauerlat beam and the stability of the roof truss system. There is a loosening of the roof, and the roof is sliding down. Due to erroneous placement of anchor bolts or incorrectly made holes, the fastening is no longer effective.

If the nuts are screwed onto the bolts with an overtightening, then the fastening assembly becomes fragile and is subject to rapid destruction. In this case, wire twisting is sometimes used to create an attachment point.

During the construction of the truss system, the safety of the joints should be observed.

For example, if the truss structure is combined with the floor without taking into account the bearing capacity of the attic floor, then this is the most dangerous moment that can lead to the destruction of the building.

If the tightening is changed to a precast concrete floor beam intended for bending, then the use of precast concrete beams should be effective due to their rigid fixation in the reinforced floor stiffener, which is arranged using a reinforcing cage. Its axis must go in the same direction as the acting forces.

At the same time, the presence of shortcomings in the process of creating a truss system, which is a load-bearing wooden floor structure, often arises due to a misunderstanding of the functions performed by the puff and crossbar in the entire roofing system. The puff differs from the crossbar in that it is a longitudinal, and the crossbar is a transverse beam.

The construction of the truss system is associated with the creation of a spacer system that works on the principle of divergence at the bottom of the planes, which occurs under the influence of not only their own weight, but also the load that falls on the line of intersection of the planes, which should be prevented by the transverse beam, that is, tightening.

Getting to the roof device, you should find out all the points associated with the assumption of certain errors that occur when performing work on the installation of the truss system. The device of the roof of the house is associated with possible difficulties and shortcomings that do not allow achieving the goal.

Mauerlat is one of the main elements of the roof structure. Rafters are attached to it. The operational period of the entire roof depends on the quality creation of the truss structure.

The main ways of supporting rafters

There are several technologies for supporting rafters on the Mauerlat. It is possible to carry out a rigid fixation of the structure. It does not allow any displacement of the rafter leg. To do this, use a hemmed beam, which prevents the rafters from slipping at the point of support, and metal corners that eliminate any lateral shift of the structure.

The sliding connection of the rafter leg is used in wooden houses. Moreover, the main element for its emphasis is the upper crown, and not the Mauerlat. To prevent damage to the roof, the rafter support assembly is made as free as possible. To do this, use a sliding support, which, when the frame shrinks, is displaced along the guide fixed on the leg.

The sliding support unit can also be made using a different technology. A notch is made in the rafters, which should adjoin the upper crown of the log house. To fix the beams, it is permissible to use any fasteners: staples, nails or steel plates.

Fasteners for installation work

To qualitatively connect the nodes of the rafters with the Mauerlat, you will need materials and tools such as:

• dry timber;
• boards;
• axe;
• hacksaw;
• a hammer;
• roulette;
• plumb;
• level;
• screwdriver;
• drill;
• Bulgarian.

Particular attention should be paid to the presence of all fasteners. Beam consoles are fixed using galvanized steel beam brackets, which do not reduce the bearing capacity of the structure. Brackets do not need to be cut into the beams.

You also need to buy perforated mounting tape, which will strengthen the Mauerlat nodes. With its help, a strong connection of all structural elements is made. The tape also does not crash into the beams. For its reliable fixation, nails and self-tapping screws are used.

In addition to brackets and perforated tape, in order to securely support the rafters to the Mauerlat, you should purchase:

• universal bar connectors;
• fasteners for rafters;
• mortgage supports;
• wire rod;
• steel corners;
• rack mount;
• self-tapping screws;
• nails;
• staples;
• plates;
• galvanized nails;
• studs with washers and nuts;
• anchor bolts.

Creating a ridge and installing the bottom of the rafters

Installation work begins with the ridge part of the roof structure. You can install the rafters in one of three ways:

• butt;
• for the run;
• overlap.

Butt-joining the structure involves cutting the upper part of the rafter leg. This is done at an angle that is equal to the slope of the roof slope. On the skate, a pair of legs joins. To obtain the same support node for the Mauerlat elements, you should use a ready-made template.

A feature of fixing the rafters on the run is the presence of a ridge beam. This option for arranging the Mauerlat is characterized by increased reliability. But often such a rafter support system provides for the installation of additional supporting structures, which will lead to a decrease in the functionality of the attic. Naturally, this method is not suitable for small roofs.

The technology for installing overlapping rafters is in many ways similar to installing them on a ridge run. The main difference is that the connection of the upper part of the legs overlaps. This leads to a strong connection of the structure, since the studs hold two elements at once.

The connection of the lower ends of the rafters is carried out depending on the material of the walls. In the presence of wooden housing construction, the upper wall trim can act as a supporting element. If foam blocks (or aerated concrete) were used during the construction of the house, then the rafters are supported on the Mauerlat.

The device of a reinforced concrete belt is the optimal solution in the case of the use of masonry building materials. This technology does not provide for the creation of any methods of fixing the truss system. Vertically located anchor bolts act as fasteners for the timber. The main thing is that when pouring the concrete solution, the studs are located in a strictly vertical position.

Connection of rafters with beams and Mauerlat

After fixing the upper and lower parts of the rafters, they should be fixed to the beams. It is clear that you can connect the rafters to the beam with just nails. But this is not the best solution. Such a mount will not be as reliable as possible. To prevent slipping of all elements, the truss structure is fixed to the beams by using “thorn” and “tooth” connections.

In the presence of a steep roof slope (more than 35º), cutting technology is used with a single tooth. A tooth with a spike is made at the bottom of the rafter. Nests created in the beam should be at least 30% of the beam thickness deep. The device of rafter connections is carried out at a distance of 0.3-0.4 m from the extreme part of the beam. This prevents the splitting of the beams resulting from the high load from the pressure of the legs.

When arranging a roof with a slope of up to 35º, the installation of rafters is carried out by expanding the mating area of ​​\u200b\u200bthe main structural elements. Usually the rafter leg is covered with a beam. For this purpose, holes are cut in the rafter leg for two teeth:

• spike with emphasis;
• one more emphasis.

The depth of the cut when fixing the rafters to the beam is within 30% of the thickness of the beam.

Better connections can be obtained by using bolts or clamps. This technology involves the use of wire loops, with the help of which the assembly is fixed to the anchor bolts located in the wall of the building.

Relying on the Mauerlat is the most common option for fixing the lower part of the rafters. A cutout of such a size is made in the rafter leg so that it can be put on the Mauerlat without any problems. Otherwise, during the operation of the roof, a displacement of the bar may occur.

In some cases, the Mauerlat must be “equipped” with a reverse notch. It depends on the type of wood from which the beam is made. If hardwood was used for its production, then a slot is made, which, in combination with the recess of the rafters, will create a lock element. When making a beam from coniferous wood, a cutout is not required, as it will lead to a weakening of the structure.

The most acceptable option for the Mauerlat is the rigid connection of the truss system.

This technology can be done in one of two ways:

• with the help of hemmed bars and corners made of metal;
• by arranging saddles on rafters.

The first option is that a support beam is used to place the rafters on the Mauerlat. Rigid support of the rafter leg is made. Reliable fixation of the structure is carried out by metal corners. This prevents lateral movement of the structure.

The second option is more popular. For fasteners, nails are used that are directed towards each other and hammered at an angle. Two hammered nails cross. Then another nail is driven in. The third nail should be in a vertical position. The fastening point made will be characterized by maximum rigidity if additional fastening is carried out using wire rod.

At the beginning of the attic roof layout, a rafter system is selected that acts as a supporting structure. The required type of truss system is determined based on the type of roof.

Depending on the system chosen, these can be wooden beams, used as a roof frame, holding back the composite building materials of the entire structure, or specific elements that create supports called rafters. Before starting work, the wooden components are impregnated with special compounds that protect the roof from fire and decay. The durability of the roof directly depends on the quality of this procedure.

Varieties of truss systems and the arrangement of their nodes

The truss system is divided into two main types: layered and. Since the joints in each system have different characteristics, the specific type of rafter is selected based on the properties of the preferred roof, including its architectural features.

The main factors in choosing the right type of system:

• overall functionality of the roof;
• pressure force of roofing building materials on the structure;
• the prevalence and frequency of precipitation in the area where the house is located.

The hanging type of rafters does not have supports located in the gaps. For this reason, an increased thrust occurs, which is transmitted horizontally to the walls of the building. To reduce this figure, a protracted element made of wood or metal is introduced into the support assembly, designed to combine the rafter legs. Thus, the nodes of the hanging rafters take the form of a triangle. The tightening element is located at the base of the legs, it performs the function of a crossbar (most often used in gable roof structures) and works on bending and compression. The strength of the connection with the base of the supports depends on the height of the tightening element.

The layered type of rafters is often equipped in buildings where there is a central supporting column or load-bearing wall. The rafters rest with their limbs on the sides of the building, and the central part rests on a column or other support inside the house. Such a structural assembly is designed for flexural functioning. Layered supports create less load on the component parts of the building, so their installation is not as laborious as in the case of hanging rafters. In addition, it does not require large material costs.

There are also options for arranging the roof, combining both types of rafters. In this case, each type alternates, that is, zones without load-bearing walls are equipped with hanging rafters, and areas with the necessary supports are layered.

Competent arrangement of the truss system

The main factor in the high strength of the roof in the future construction is the competent arrangement of all nodes and reference points.

In the case of rafters for a mansard roof, at least 3 strong points are assumed. This value may change if the span exceeds standard limits. For example, if the span is not more than 10 m, only one additional support will be required.

The hanger assembly is assembled based on span dimensions. On small spans, the protracted element is most often replaced by a crossbar. With large spans, the lingering elements sag, and the supports bend.

Thus, dangling nodes can have the following differences regarding the span size:

Figure 1. Diagram of the Mauerat device.

1. 9 m. Supports must be restrained with a wooden block, which is installed perpendicular to the attic floor. In the base area, it is reinforced with staples, and the protracted elements are fastened with special clamps.
2. 13 m. Fastening is carried out with the help of struts, which abut against the base with the top, and with the lower part against the perpendicular beam. The interval between the supports should not be more than 5.5 m.
3. 17 m. The base must be strengthened with special devices. A trussed structure is used for the top: the protracted elements are attached to two wooden bars, and a crossbar is mounted between them.

Knot attachment methods

Regardless of whether it is required to replace the existing rafter system or build it from scratch, it is necessary to follow a certain set of rules when attaching its nodes.

First of all, the simplest fastening of the crossbeam and the base of the support should be avoided, as this can have a devastating effect on the entire roofing system.

Figure 2. Fastening the rafter leg to the Mauerlat.

In other words, from the load created by building materials or precipitation, the ends of the supports slide off, and the rafter system is damaged. This leads to its complete collapse. To prevent this outcome, it is necessary to increase the reliability of these nodes. This is achieved using the following types of fastening:

• teeth into a tenon;
• point-blank teeth;
• emphasis on the end of the crossbar.

One or two teeth can be used depending on the slope. To increase the reliability of the connection, you can create additional fasteners using metal corners.

Roof framing attachment points

The main attachment points of the truss system are:

• beam;
• Mauerlat;
• ridge.

Beam mount

Figure 3. Scheme of the ridge connection of the truss system.

In the rafter leg, teeth are created into a spike, and a nest is cut out in the crossbar, which corresponds to the cut teeth. In this case, the nest should occupy no more than 30% of the entire thickness of the crossbar.

If lightweight materials were used in the construction of the roof, and its slope is less than 35 °, the bases of the supports are placed so that their area of ​​support is much larger than the beam. This can be achieved by using a mortise with two teeth in 2 studs, a stop (with or without a stud), and two studs in the lock.

The nodes of the system are fastened either with hardware with metal corners, or with wooden bars, overlays and spikes.

Mauerlat mount

There are 2 technologies for Mauerlat fastening of supports: rigid and sliding (Fig. 1).

In the first case, a strong connection is established between the rafter and the Mauerlat without the possibility of slipping, deflecting and popping out. This is achieved by placing special corners with a support bar. The formed knot must be fastened with a reliable wire using hardware. Nails are hammered under a certain slope from the side so that they are in the Mauerlat in a crossed state. The last nail is nailed vertically. This method is the most popular.

In the second case, fastening is carried out using a special mechanism that allows a certain element (in this case, the rafter) to move in the right direction (Fig. 2).

To create such a connection, you will need to make a tie-in on the supports, and then lay them on the Mauerlat. As in the previous case, both parts of the knot are fixed with two crossed nails and one vertical one on top. The boards are fixed to the Mauerlat with metal brackets. After that, the support base is extended beyond the wall and fastened with plates and sleds. Thus, the emphasis is on the Mauerlat, but all components of the truss system can move within acceptable limits.

This method is most often used in the construction of the roofing system of wooden buildings (logs, log cabins), which are prone to subsidence. It is worth remembering that with rigid fastening there is a possibility of damage to the walls of the building.

Ridge mount

Such a knot can be created in two ways: butt and overlap (Fig. 3).

The first method involves cutting the top of the supports at the same slope as the corner of the roof. They rest against opposite supports, which also need to be cut. The fastening is created using two nails (150 mm) hammered from above at a certain angle so that they are proportionately located inside each rafter. To increase reliability, the seams between the supports are fastened with wooden plates or metal plates.

The second method is the most popular. It is distinguished from the first method by the overlapping method. In this case, the supports are connected not by the ends, but by the side parts, after which they are fixed to the bolts.

At the stage of building a house, special attention should be paid to the roof. The reliability of the entire structure will largely depend on how reliably, correctly and efficiently it will be done. One of the important parts of the roof is the truss system, which holds the finishing material, insulation, waterproofing and other elements. For gable roofs of houses, hanging rafters are often used, the design and components of which, as well as installation, are described in this material.

Rafters are the main load-bearing element of a pitched roof, which takes on the main load experienced by this structure. The rafter system is of two types - hanging or layered. You have to choose between them, based on whether there are internal walls in the structure under construction, which can serve as a support for parts of the roof. The hanging rafter system is used if there are no such walls, and here only the outer walls of the building will serve as a support. That is, these rafters do not have a central support as such and rest on the wall on one side, and on the opposite rafter on the other. The fastening of individual elements is carried out using slotted spikes, nails, anchors or metal plates.

Hanging rafters are usually used to cover spans with a width of 7-10 m. The scope of application may be different - such a system is used for the construction of roofs in warehouses, industrial buildings, residential buildings.

On a note! The maximum distance between the walls, which allows the use of a hanging rafter system, is 14 m.

Despite the fact that such rafters are installed at a slope, they do not act on the walls like spacers - they transfer only vertical loads. This can be achieved through the use of stretch marks made of timber, located at the base of the roof.

On a note! The tightening between the legs of the rafters is located the higher, the greater the load it experiences.

Rafter elements are made of timber, boards or logs, metal. Without fail, before starting installation work, the material must be treated with special protective compounds that will provide the tree with a long service life. They will protect it from fungus, mold. If the material is treated with fire-fighting compounds, then the house will gain additional protection against fires.

What does the hanging rafter system consist of?

A system of this type has several components. And it is necessary to get acquainted with them in order to understand the purpose of each of them and not to get confused in concepts.

Table. The constituent elements of the system.

Bar prices

Types of structures

There are five main types of roof structures of this type that can be used in construction, which can be obtained on the basis of hanging rafters. They differ in the presence of some structural elements, configuration, etc.

The simplest option is triangular articulated arch. Its shape is triangular, the puff here is under tensile load, and the rafters are under bending. Such a scheme is used only if the height of the ridge is at least 1/6 of the entire span between the walls, otherwise it will not function correctly. Quite often used in the construction of attics. In this case, two rafters are joined and connected to each other in the ridge part. At the bottom, the triangle can be connected with a long puff. The system can only be used if the span between the walls is no more than 6 m.

Slightly different from the above system - articulated arch with headstock. In this case, the design has a support in the form of a headstock installed under the ridge. Due to the tightening, it works in tension. The headstock can be made of either metal or wood. The system is used if the spans between the walls are 6 meters or more. The headstock will not allow the puff to sag - it acts as a kind of suspension and allows you to adjust the degree of deflection of the horizontal part.

Articulated arch with puff that is raised, is usually used when planning the construction of attics and spacious attic spaces - that is, where the ceiling height is important. In this case, puffs will be installed at the top of the rafters. And the higher the puff is located, the greater the tensile force it perceives.

If the support is a fixed hinge element, then the structure will be called arch with crossbar. Here the roof is attached to the Mauerlat by forming a tooth on the rafters. The bolt itself resembles a small puff, but in this case it works not in tension, but in compression. Rafter legs are fixed quite rigidly.

Arch with struts and headstock resembles an arch system with a suspension. Here, during the installation of the rafters, struts are used, which ensure that the structure is relieved of excess stress. The option is suitable for closing spans with a width of 9-14 m.

On a note! Any scheme for the design of hanging rafters involves accurate calculations that will clarify all external and internal loads.

The rafter system is quite difficult to install, sometimes its parts are assembled directly on the ground, and then rise to the roof. But also rafters can be mounted right on the spot. In general, a roof with hanging rafters is the simplest option, therefore it is often made by novice builders or on their own.

Perforated plates used for attaching rafters

Prices for various types of fasteners for rafters

Fasteners for rafters

Ways of fastening rafters

These structural details can be fixed in two ways.

1. Bolt and clamp, where in this case the end part of the rafter is cut off, and she herself is placed on the beam in the place where the notch is made. The fastening of individual elements is carried out with the help of bolts. They are connected so that the attachment point is perpendicular to the upper part of the rafter. Sometimes clamp systems are used for connection.
2. double tooth. The method is applicable if the slope of the roof slope relative to the horizontal is less than or equal to 35 degrees. In this case, two stops are made on the beam, a special hole is made in the rafter leg, and a spike is cut out at the place of the extreme stop on the beam. In size, these elements must correspond to each other.

System design

To correctly create a system layout, it is important to consider:

• rafter installation step;
• load on the structure and structure;
• section of rafters;
• material that will be used to create the roof;
• construction type;
• roof pitch angles
• the dimensions of the building as a whole;
• climatic conditions of the region.

The more accurately the calculation is made and the more correctly the rafter system is designed, the stronger and more reliable the whole structure will turn out. For convenience, you can use the existing online calculators, which is important for those who are not friends with the exact sciences, or for beginners.

Video - Roof truss system, what you need to know for proper design

Installation rules

Installation of hanging rafters must be carried out in compliance with certain rules. Only in this case it will be possible to make a correct and stable design. The work rules are as follows:

Installation of hanging rafters

For the construction of the truss system, certain tools and materials may be required. The list below is quite approximate, but can be used as a basis during preparation for the start of work.

Tools for creating a rafter system:

• a hammer;
• axe;
• jigsaw or hacksaw;
• building level, twine, tape measure;
• thread with a load (plumb line);
• pencil, ruler.

Prices for popular models of jigsaws

As necessary materials, you can directly list the beams and boards for rafters, self-tapping screws and nails, anchor bolts, waterproofing material, antiseptic compounds for wood processing.

Sigma-Extra - outdoor work, antiseptic for wood

Consider the installation process of the truss system step by step.

Step 1. All wood material is treated with antiseptic agents that prevent the development of decay processes, the occurrence of fungus and mold. Prior to installation, the material is well dried.

Step 2 Building material is delivered to the top of the building.

Step 3 A mauerlat is nailed along the perimeter of the load-bearing wall, consisting of two boards of such a width that they can cover the entire upper part of the wall with themselves. Between the Mauerlat and the wall, it is recommended to lay a layer of waterproofing material (for example, roofing material). This will seal the joint, protect the material from moisture and reduce drafts in the future.

Step 4 Next, beams are created from the timber, which will be attached to each pair of rafters in the lower part. They are attached to the Mauerlat and connect two load-bearing walls together. You can temporarily move along them during the work, and boards that are used to create rafters are also folded on them.

Step 5 To form the top of the roof, a ridge beam is cut out. It should have a length from one part of the future roof to another and be parallel to the long load-bearing walls.

Step 6 The required roof height is determined - the level at which the ridge beam will be attached. The angle of inclination of the slope is recommended to be done within 25-45 degrees. You can find out the angle of the roof and the length of the rafters using the Pythagorean theorem. To do this, you need to measure the distance from the ridge, the height of the roof and the distance to the outer wall.

Step 7 The ridge board is installed at the place of the future docking of two rafter legs.

Step 8 From the prepared lumber, future rafters of the desired length are measured and cut. They will be attached with the selected pitch to the ridge board and Mauerlat.

Step 9 To make it possible to attach the rafters to other elements, special triangular cutouts are made. To do this, the board is installed so that one side lies on the ridge board, and the other on the Mauerlat. The cut mark is applied. Next, the marked sections are cut.

Step 10 The second rafter is prepared in the same way. Now they should be docked with each other. To do this, the boards are moved as close as possible to each other, markings are applied indicating the place of the cut. The cut is made and the boards can be joined.

Step 11 The rafters are attached to the Mauerlat using metal corners and self-tapping screws. With the help of them, the boards are also fixed on the roof ridge.

Step 12 Two rafters are interconnected using metal plates and self-tapping screws. Thus, the first two structures are installed, which will be located at the edges of the roof.

Step 13 In order to make it easier to evenly install other rafters, a rope is stretched strictly horizontally between the extreme structures.

The process of installing rafters

Step 15 If necessary, the rafters can be reinforced with puffs that are attached to two joining rafters.

Video - Installation of the truss system

Video - Installation of rafters

Video - Using a crossbar (screed) for rafters as an interior element

Hanging rafters are considered a fairly simple design compared to other types of truss systems. But there should be no rush during their installation. It is important to remember that at the slightest skew, all work will go down the drain, so you need to work carefully and carefully.

In addition to correctly made calculations and drawings, fasteners for rafters and all its elements are of no small importance in the stability of the structure.

In addition to the load of atmospheric precipitation, the rafters must withstand the weight of the crate and the total weight of the roofing pie, which must be taken into account when choosing a fastener.

The truss system is a spatial structure consisting of the following elements:

• Mauerlat;
• rafter legs;
• valleys;
• ridge beams;
• runs;
• crate.

In order to understand how all parts of the truss system are attached to each other, you need to figure out what nodes it consists of, what fasteners are used in each case and what they are. When assembling the supporting structure of the roof, fasteners, both steel and wooden, are used.

The main nodes of the connection of the truss system

Before connecting the Mauerlat and the rafter leg to each other, the first one will need to be firmly connected to the wall. Mauerlat is a thick beam (15x15), laid along the axis of the wall and parallel to the ridge of the beam, on which the rafter legs rest. The functions assigned to this element of the supporting structure are to distribute the load from the rafters, the weight of the roofing pie and atmospheric precipitation throughout the wall, including internal supports. In other words, the Mauerlat is the foundation for the entire roof. It is laid on the axis of the wall and fixed to it. In this case, there are several connection methods.

Method one. When constructing a roof of a large area along the entire length of the wall, an armored belt is poured, where metal pins are immediately embedded under the M12 thread every 2 m. In this method, there will be studs that pass through the beam through the wall and are attracted to the wall with a nut and pucks. With a small area of ​​\u200b\u200bthe roof, where there is no large load on the wall, they do without a Mauerlat and the rafters are attached directly to the studs embedded in the masonry process.

Method two. Another quite affordable way to make the truss system stable is to attach the Mauerlat to the wall with a wire. To do this, you need to lay the middle of the wire between the rows of bricks 3 rows before the end of the masonry. Its length should be sufficient to tie and pull the Mauerlat to the wall. You can also do without the Mauerlat and fix the rafter with wire directly to the wall. But such a connection will give a point load on the wall, which may affect its integrity.

The scheme for attaching the rafter leg to the Mauerlat can be rigid and sliding. The type of connection depends on the shape of the roof and the type of rafters, which can be hanging or layered.

Rigid and sliding connection of the lower part of the rafters with Mauerlat

Connection nodes in this case will be made of wood and can have several types:

1. A tooth that has only an emphasis.
2. A tooth with a spike and an emphasis.
3. Emphasis directly on the beam.

A single tooth notch is used for a roof with a large angle of inclination, where the angle between the mauerlat and the rafter leg is more than 35º. To do this, you will need to cut a tooth with a spike in the rafter leg, and create a nest under it in the Mauerlat. The use of a spike avoids lateral displacement of the rafters. The double tooth notch is used when installing more gently sloping roofs. The latter method is used extremely rarely.

Recently, more and more often, a wooden mount for rafters has been replaced by a metal one, since it allows not only to get a more reliable one, but also to significantly reduce the installation work. Therefore, metal rafter bolts, brackets, plates, clamps, hinges and various corners are used as additional fasteners.

The most used method of rigid connection is driving nails from the sides at an angle into the mauerlat. Thus, internal crossing takes place within it. Further, for the final fixation of the connection, the third nail is driven vertically. Another way to prevent transverse displacement of the rafter leg is to fix it on the sides with metal corners.

The scheme for movable fastening of rafters in the lower part is used for houses built from logs or timber. Since during operation the truss system is in motion due to a change in its physical properties, i.e., the building shrinks.

The rigid fastening scheme in this case is unacceptable, since such movements can lead to the destruction of the wall. This means that the attachment points need to provide mobility. In such cases, special swivel joints are used, which are called skids or corners with an oblong hole for fasteners. The sliding interface in this fastener achieves two levels of freedom by free movement of one of the fastener elements.

Nodal ridge connection

The ridge connection of the truss system can be obtained in three ways: butt, overlap and on the ridge beam.

Butt. The upper part of the rafter leg must be cut at an angle equal to the slope of the roof. The opposite leg is also adjusted to the appropriate angle, but with an inclination to the other side. Further, they are interconnected at the top point with the help of a nail, which must be driven into the end of the rafters with the capture of the opposite end. In addition to nails, special plates are used for a more durable connection of joints. Both a 30 mm wooden board and a double-sided metal fixing plate can act as such fasteners. For its installation, bolts or nails are used.

The next two methods will be similar to the first, but have a slight difference. When fastening with an overlap, the upper parts of the rafter leg will be interconnected by their sides. The latter option is carried out by connecting each rafter directly to the ridge beam. In this case, threaded studs with washers and bolts are used as fasteners.

If trusses are used to stiffen the rafter system, then to ensure good resistance to wind loads, it will be necessary to install the required number of diagonal ligaments. The presence of a brace and a brace (rafter leg) in the supporting structure helps the gables of the house to be more stable. The brace is installed by resting the upper part in, and with the lower part it rests against the main floor beam. The strut helps to reduce the load on the rafters in the center. Its installation is carried out at an angle of 45º. Diagonal connections are fixed using clamps, corners, plates.

Types and features of metal fasteners for rafters

If earlier craftsmen used wooden elements as such fasteners (bars, slips, dowels, metal staples, wooden pins, wedges), now such methods are inferior to more modern types. The construction market has a large range of metal fasteners, which are now much stronger and make the process much easier. The manufacturing technology of these elements uses metal, the thickness of which varies from 1.5 ... 3.0 mm, which allows the product to be more resistant to loads compared to any other material. In addition, rafter fasteners are available in any size and allow you to carry out the technological process with great accuracy.

The metal fasteners of the rafters, which can be perforated and nailed, include:

• perforated mounting tape;
• corners;
• plates;
• beam support;
• beam support;
• wire tie;
• self-tapping screws;
• bolts with nuts;
• corners of the KR;
• brackets WB;
• fasteners LK.

The use of perforated products allows strong enough with all parts of the system and provide good rigidity and strength at any angle. They are characterized by the presence of many holes for bolts, screws and self-tapping screws, with the help of which the attachment to the tree is carried out. The size of the product is adjusted by trimming to the desired length and width.

Also fasteners can be nailed. However, the use of this type is possible only in the factory by cutting, which bends the cone-shaped part. This operation is carried out by special machines under pressure.

KR corners have a large number of modified types, which reduce the risk of bolted joint breakage during natural settlement of the structure. Fastening is carried out without the use of special equipment using screws and nails.

Brackets WB are used for fastening the console of the supporting beam when installing wooden floors in houses made of logs or timber. At the same time, the tie-in on the rafter leg is not made, which does not weaken its bearing capacity. The connection is carried out using anchor bolts, nails or screws.

LK rafter fasteners are applicable where it is required to connect rafters and beams. It has the same advantages as WB fasteners, but the process is carried out only with screws or nails. Used in the construction of wooden houses.

Fasteners in the rafter system play a huge role. It depends on him the strength and duration of operation of the entire roofing pie. Therefore, the choice of type and method of attachment should be treated with great attention.

At the heart of each roof is a large number of beams, rafters, racks and girders, which are collectively called the truss system. Over the centuries-old history of types and methods of its organization, a lot has accumulated, and each has its own characteristics in the construction of knots and cuts. We will talk in more detail about what the gable roof truss system can be and how the rafters and other elements of the system should be attached in more detail.

The design of the gable roof truss system

In the context of a gable roof is a triangle. It consists of two rectangular inclined planes. These two planes are connected at the highest point into a single system with a ridge beam (run).

Now about the components of the system and their purpose:

• Mauerlat - a beam that connects the roof and walls of the building, serves as a support for the rafter legs and other elements of the system.
• Rafter legs - they form the inclined planes of the roof and are the support for the crate under the roofing material.
• Ridge run (bead or ridge) - combines two roof planes.
• A puff is a transverse part that connects opposite rafter legs. Serves to increase the rigidity of the structure and compensate for bursting loads.
• Beds - bars located along the Mauerlat. Redistribute the load from the roof.
• Side runs - support the rafter legs.
• Racks - transfer the load from the runs to the beds.

Filly may still be present in the system. These are boards that extend the rafter legs to form an overhang. The fact is that in order to protect the walls and foundation of the house from precipitation, it is desirable that the roof ends as far as possible from the walls. To do this, you can take long rafter legs. But the standard lumber length of 6 meters is often not enough for this. Ordering non-standard is very expensive. Therefore, the rafters are simply grown, and the boards with which this is done are called “fillies”.

There are quite a few designs of truss systems. First of all, they are divided into two groups - with layered and hanging rafters.

With hanging rafters

These are systems in which the rafter legs rest only on the outer walls without intermediate supports (bearing walls). For gable roofs, the maximum span is 9 meters. When installing a vertical support and a strut system, it can be increased up to 14 meters.

The hanging type of gable roof rafter system is good because in most cases there is no need to install a Mauerlat, and this makes the installation of rafter legs easier: no need to make cuts, just mow the boards. To connect the walls and rafters, a lining is used - a wide board, which is attached to studs, nails, bolts, crossbars. With such a structure, most of the bursting loads are compensated, the impact on the walls is directed vertically downwards.

Types of truss systems with hanging rafters for different spans between load-bearing walls

Gable roof truss system for small houses

There is a cheap version of the truss system when it is a triangle (photo below). Such a structure is possible if the distance between the outer walls is not more than 6 meters. For such a rafter system, it is possible not to calculate the angle of inclination: the ridge must be raised above the puff to a height of at least 1/6 of the span length.

But with this construction, the rafters experience significant bending loads. To compensate for them, they either take rafters of a larger section or cut the ridge part in such a way as to partially neutralize them. To give greater rigidity in the upper part, wooden or metal plates are nailed on both sides, which securely fasten the top of the triangle (also see not the picture).

The photo also shows how to grow rafter legs to create a roof overhang. A notch is made, which should go beyond the line drawn from the inner wall upwards. This is necessary to move the incision site and reduce the likelihood of a rafter breaking.

Ridge knot and fastening of rafter legs to the backing board with a simple version of the system

For mansard roofs

Option with the installation of a crossbar - used when. In this case, it is the basis for filing the ceiling of the room below. For reliable operation of this type of system, the crossbar notch must be hingeless (rigid). The best option is semi-pan (see the picture below). Otherwise, the roof will become unstable to loads.

Please note that in this scheme there is a Mauerlat, and the rafter legs should extend beyond the walls to increase the stability of the structure. To secure them and dock with the Mauerlat, a cut is made in the form of a triangle. In this case, with an uneven load on the slopes, the roof will be more stable.

With such a scheme, almost the entire load falls on the rafters, therefore they must be taken with a larger section. Sometimes the raised puff is reinforced with a suspension. This is necessary to prevent it from sagging if it serves as a support for ceiling sheathing materials. If the puff is short, it can be secured in the center on both sides with boards nailed to the nails. With a significant load and length, there may be several such insurances. In this case, boards and nails are also enough.

For big houses

With a significant distance between the two outer walls, a headstock and struts are installed. This design has high rigidity, since the loads are compensated.

With such a long span (up to 14 meters), it is difficult and expensive to make a one-piece puff, because it is made from two beams. It is connected by a straight or oblique cut (picture below).

For reliable docking, the junction is reinforced with a steel plate mounted on bolts. Its dimensions should be larger than the dimensions of the cut - the extreme bolts are screwed into solid wood at a distance of at least 5 cm from the edge of the cut.

In order for the circuit to work properly, it is necessary to correctly make the struts. They transmit and distribute part of the load from the rafter legs to the puff and provide structural rigidity. Metal strips are used to reinforce the connections.

When assembling a gable roof with hanging rafters, the cross-section of lumber is always larger than in systems with layered rafters: there are fewer load transfer points, therefore, each element has a greater load.

With rafters

In gable roofs with layered rafters, their ends rest on the walls, and the middle part rests on load-bearing walls or columns. Some schemes burst walls, some do not. In any case, the presence of a Mauerlat is mandatory.

Bezporny schemes and knots of cuts

Houses made of logs or timber do not respond well to spacer loads. For them, they are critical: the wall can fall apart. For wooden houses, the gable roof truss system must be non-expansion. Let's talk about the types of such systems in more detail.

The simplest non-spacer scheme of the truss system is shown in the photo below. In it, the rafter leg rests on the Mauerlat. In this embodiment, it works on a bend, without bursting the wall.

Pay attention to the options for attaching the rafter legs to the Mauerlat. In the first, the support platform is usually beveled, while its length is no more than the cross section of the beam. The depth of the cut is no more than 0.25 of its height.

The top of the rafter legs is laid on the ridge beam without fastening it to the opposite rafter. Two shed roofs are obtained according to the structure, which adjoin (but do not connect) one with the other in the upper part.

It is much easier to assemble the option with rafter legs fastened in the ridge part. They almost never give a thrust on the walls.

For this scheme to work, the rafter legs below are attached using a movable joint. To fix the rafter leg to the Mauerlat, one nail is hammered from above or a flexible steel plate is placed from below. See the photo for options for attaching rafter legs to a ridge run.

If the roofing material is planned to be heavy, it is necessary to increase the bearing capacity. This is achieved by increasing the cross section of the elements of the truss system and strengthening the ridge assembly. It is shown in the photo below.

Strengthening the ridge assembly for heavy roofing material or with significant snow loads

All of the above gable roof schemes are stable in the presence of uniform loads. But in practice, this almost never happens. There are two ways to prevent the roof from sliding in the direction of greater load: by installing a brace at a height of about 2 meters or by struts.

Options for truss systems with contractions

The installation of contractions increases the reliability of the structure. In order for it to work normally, at the places where it intersects with drains, you need to attach nails to them. The cross section of the beam for the scrum is used the same as for the rafters.

They are attached to the rafter legs with bots or nails. Can be installed on one or both sides. The knot for attaching the bout to the rafters and the ridge run, see the figure below.

In order for the system to be rigid and not “crawl” even under emergency loads, it is enough in this embodiment to provide a rigid fastening of the ridge beam. In the absence of the possibility of its displacement in the horizontal, the roof will withstand even significant loads.

Rafter systems with braces

In these options, rafter legs, which are also called struts, are added for greater rigidity. They are installed at an angle of 45° with respect to the horizon. Their installation allows you to increase the span length (up to 14 meters) or reduce the cross section of beams (rafters).

The strut is simply substituted at the required angle to the beams and nailed from the sides and bottom. An important requirement: the brace must be cut accurately and fit snugly against the uprights and the rafter leg, excluding the possibility of its deflection.

Systems with rafter legs. Above is a spacer system, below is a non-spacer system. The nodes of the correct felling for each are located nearby. Below - possible schemes for attaching the strut

But not in all houses, the average load-bearing wall is located in the middle. In this case, it is possible to install struts with an angle of inclination relative to the horizon of 45-53 °.

Bracing systems are necessary if significant uneven shrinkage of the foundation or walls is possible. Walls can sit differently on wooden houses, and foundations on layered or heaving soils. In all these cases, consider the installation of truss systems of this type.

System for houses with two internal load-bearing walls

If the house has two load-bearing walls, two rafters are installed, which are located above each of the walls. Beds are laid on the intermediate load-bearing walls, the load from the rafter beams is transferred to the beds through the racks.

In these systems, a ridge run is not installed: it gives expansion forces. The rafters in the upper part are connected to one another (cut and joined without gaps), the joints are reinforced with steel or wooden plates, which are nailed.

In the upper non-expansion system, the expanding force is neutralized by tightening. Please note that the puff is placed under the run. Then it works efficiently (the top diagram in the figure). Stability can be provided by racks, or jointing - beams installed obliquely. In the spacer system (in the picture it is below), the cross member is a crossbar. It is installed above the run.

There is a variant of the system with racks, but without rafters. Then a rack is nailed to each rafter leg, which rests on the intermediate load-bearing wall with the second end.

Fastening the rack and tightening in the rafter system without a rafter run

To fasten the racks, nails for 150 mm and bolts 12 mm are used. Dimensions and distances in the figure are in millimeters.