Roof truss attachment points. Mounting points for the roof truss system

When designing any residential building, architects pay special attention to the roof, as it performs not one, but several functions at once, depending on its design features. It must be said that not all future homeowners are satisfied with the usual gable roof, although it can be called the most reliable, since it has only two pitched planes and one joint between them. Many are attracted to more complex designs that add a special appeal and originality to the structure. Other, more practical homeowners prefer attic structures that can simultaneously serve as a roof and a second floor.

The basis of any roof is an individual truss system, which has its own design features. Making the choice of the desired roof frame will be much easier if you figure out in advance which ones types and schemes of truss systems used in building practice. After receiving such information, it will become more clear how complex such structures are in installation. This is especially important to know if the roof frame is supposed to be built independently.

The main functional tasks of truss systems

When arranging pitched roof structures, the truss system is a frame for covering and for holding materials of the "roofing pie". With proper installation of the frame structure, the necessary conditions will be created for the correct and non-insulated types of roofs that protect the walls and the interior of the house from various atmospheric influences.

The roof structure is also always the final architectural element of the exterior design of the building, supporting its stylistic direction with its appearance. Nevertheless, the design features of the truss systems must first of all meet the requirements of strength and reliability that the roof must meet, and only then - aesthetic criteria.

The frame of the truss system forms the configuration and angle of inclination of the roof. These parameters largely depend on the natural factors characteristic of a particular region, as well as on the desire and capabilities of the homeowner:

• The amount of precipitation in different periods of the year.
• Direction and average wind speed in the area where the building will be erected.
• Plans for the use of the space under the roof - arranging residential or non-residential premises in it, or using it only as an air gap for thermal insulation of the premises below.
• Variety of planned roofing material.
• Financial capacity of the homeowner.

Atmospheric precipitation and the strength of wind currents give a very sensitive load on the structure of the roof. For example, in regions with heavy snowfalls, you should not choose a truss system with a small angle of inclination of the slopes, as snow masses will linger on their surface, which can lead to deformation of the frame or roofing or leaks.

If the area where the construction will be carried out is famous for its winds, then it is better to choose a structure with a slight slope of the slope so that the sharp gusts that occur do not rip off individual elements of the roof and roof.

The main elements of the roof structure

Details and nodes of truss systems

Depending on the chosen type of truss system, the structural elements used can vary significantly, however, there are details that are present in both simple and complex roof systems.

The main elements of the pitched roof truss system include:

• Rafter legs forming roof slopes.
• - a wooden bar fixed on the walls of the house and serving to fix the lower part of the rafter legs on it.

• The ridge is the junction of the frames of two slopes. It is usually the highest horizontal roof line and serves as a support on which the rafters are fixed. The ridge can be formed by rafters fastened together at a certain angle or fixed on a ridge board (run).
• Lathing - these are slats or beams mounted on rafters with a certain pitch and serving as the basis for the flooring of the selected roofing material.
• Retaining elements, where you can take beds, girders, racks, struts, ties and other parts, serve to increase the rigidity of the rafter legs, support the ridge, link individual parts into a common structure.

In addition to the structural details mentioned above, other elements can be included in it, the functions of which are aimed at strengthening the system and optimal distribution of roof loads on the walls of the building.

The truss system is divided into several categories depending on the different features of its design.

attic space

Before proceeding to the consideration of different types of roofs, it is worthwhile to figure out what an attic space can be, since many owners successfully use it as utility and full-fledged living quarters.

The design of pitched roofs can be divided into non-attic and attic. The first option is called just that because the space under the roof has a small height and is used only as an air layer that insulates the building from above. Such systems usually include or have several slopes, but located at a very slight angle.

The attic structure, which has a sufficiently large ridge height, can be used in different ways, be insulated and not insulated. These options include attic or gable option. If a roof with a high ridge is chosen, then it is imperative to take into account wind loads in the region where the house is built.

Slope slope

To determine the optimal slope of the roof slopes of the future residential building, first of all, you need to look at the already built low-rise neighboring houses. If they have been standing for more than one year and steadfastly withstand wind loads, then their design can be safely taken as a basis. In the same case, when the owners set the goal of creating an exclusive original project, unlike the buildings standing nearby, it is necessary to familiarize yourself with the design and operational features of various truss systems and make appropriate calculations.

It should be borne in mind that the change in the tangent and normal values ​​​​of the wind force depends on how large the slope of the roof slopes is - the steeper the angle of inclination, the greater the importance of the normal forces and the smaller the tangents. If the roof is sloping, then the structure is more affected by the tangential wind load, since the lifting force increases on the leeward side and decreases on the windward side.

Winter snow load should also be taken into account when designing the roof. Usually this factor is considered in combination with the wind load, since the snow load on the windward side will be much lower than on the leeward slope. In addition, there are places on the slopes where snow will definitely collect, giving a big load on this area, so it should be strengthened with additional rafters.

Roof slopes can vary from 10 to 60 degrees and must be selected not only with regard to the consolidated external load, but also depending on the roofing that is planned to be used. This factor is taken into account because roofing materials differ in their mass, their fixing requires a different number of elements of the truss system, which means that the load on the walls of the house will also vary, and how large it will be, also depends on the angle of the roof slope. Equally important are the features of each coating in terms of resistance to moisture penetration - in any case, many roofing materials need one or another slope to ensure the free flow of storm water or melting snow. In addition, when choosing a roof slope, you need to think in advance how the process of cleaning and repair work on the roof will be carried out.

When planning a particular angle of the roof slopes, you need to know that the fewer joints between the sheets of the coating, and the tighter they are, the less you can make the slope of the slope, of course, if it is not supposed to arrange a residential or utility room in the attic space.

If a material consisting of small elements, for example, ceramic tiles, is used to cover the roof, then the slope of the slopes must be made steep enough so that water never lingers on the surface.

Given the weight of the roofing material, you need to know - the heavier the coating, the greater the angle of the slopes should be, since in this case the load will be correctly distributed to the rafter system and load-bearing walls.

The following materials can be used to cover the roof: either a profile sheet, galvanized steel, corrugated asbestos-concrete and bitumen-fiber sheets, cement and ceramic tiles, roofing felt, soft roofing and other roofing materials. The illustration below shows the allowable slope angles for various types of roofing.

Basic structures of truss systems

First of all, it is worth considering the basic types of truss systems regarding the location of the walls of the house, which are used in all roof structures. The basic options are divided into layered, hanging, and also combined, that is, including elements of both the first and second types of systems in their design.

fasteners for rafters

Layered system

In buildings where internal load-bearing walls are provided, a layered truss system is often installed. It is much easier to install than a hanging one, since the internal load-bearing walls provide reliable support for its elements, and in addition, fewer materials will be required for this design.

For rafters in this system, the defining reference point is the ridge board, on which they are fixed. The non-thrust type of the layered system can be equipped in three versions:

• In the first version, the upper side of the rafters is fixed on a ridge support, called a sliding one, and their lower side is fixed by cutting to the Mauerlat. Additionally, the rafters in the lower part are fixed to the wall with wire or staples.

• In the second case, the rafters in the upper part are cut at a certain angle and interconnected using special metal plates.

The lower edge of the rafter legs is attached to the Mauerlat with movable fasteners.

• In the third version, the rafters are rigidly fastened in the upper part with bars or processed boards located horizontally, parallel to each other on both sides of the rafters connected at an angle, and a ridge run is pinched between them.

In the lower part, sliding fasteners are used to fix the rafters, just as in the previous case.

It is necessary to explain why sliding fasteners are often used to fix the rafters on the Mauerlat. The fact is that they are able to save the load-bearing walls from excessive stress, since the rafters are not rigidly fixed, and when the structure shrinks, they have the ability to move without deforming the overall structure of the roofing system.

This type of fastening is used only in layered systems, which also distinguishes them from the hanging version.

However, in some cases, a spacer system is used for layered rafters, in which the lower end of the rafters is rigidly fixed to the Mauerlat, and in order to remove the load from the walls, puffs and struts are built into the structure. This option is called complex, as it includes elements of a layered and hanging system.

Enter the requested values ​​and click the "Calculate rafter length" button

Excess value Lbc (meters)

The length of the horizontal projection of the rafter Lsd (meters)

Calculation conditions:

Required eaves width (meters)

Number of overhangs:

Gable truss system

Gable truss systems are the most popular for one-story private houses. They look neat, fit well into any style of construction, are reliable and can be used, depending on the angle of their slope, to equip the attic for living rooms, utility rooms, or simply to create an air gap that retains heat in the building.

wood screws

Rafters and lathing - the roof frame, which bears the brunt of the roofing cake, thermal insulation, snow load, so they must have a high bearing capacity, strength. The idea of ​​using metal rafters to make the roof structure more rigid is not new, but in the past it was mainly used to cover industrial or utility structures. Now the rafter frame and the metal profile crate are considered a real alternative to wooden roof elements if the slope length exceeds 10 meters.

The design of the roof truss frame consists of many interconnected elements that form trusses. The step, the size of the section between the rafters and other supports determines the calculation of the loads to which they are subjected during operation. The roof frame performs the following functions:

1. Load distribution. Interconnected nodes, reinforced with corners, evenly distribute the weight of the roof, which can reach up to 500-600 kg, taking into account the snow load. The larger the cross section of the rafters and the smaller the pitch between them, the greater the bearing capacity of the structure.
2. Giving slope and shape. The rafters, located at an angle to the base of the roof, form an inclined plane of slopes, so that snow and water do not accumulate on the roof surface.
3. Formation of the base for fixing the roofing material. The top coat of the roofing pie is fastened to the roof frame. The crate acts as a basis for fixing the coating, distributing its weight evenly over the rafters.

Note! What should be all the nodes, rafters and lathing of the roof structure determines the engineering calculation. To determine the required bearing capacity of the frame, it is necessary to calculate the total load to which it will be subjected. To do this, add up the weight of the roofing material, insulation, waterproofing, the maximum snow load with the weight of the truss system.

Types of truss systems

The most common material from which the crate and rafters of the roof frame are made is wood. However, if the weight of the roofing material is large enough, and the length of the slope is more than 6 meters, then the structure is too massive. Builders have to reduce the step between the rafter legs, increase their cross section, which is why the roof units acquire a lot of weight, increasing the load on the foundation. You can unload the load-bearing walls and the base of the building using stronger, but lighter metal rafters. According to the type of material used, the following types of truss systems are distinguished:

• Wooden. Rafters and lathing made of wood are used for the construction of roofs, the slope length of which does not exceed 7-10 meters. The fastening of the frame elements to each other occurs with the help of self-tapping screws, nails or movable metal elements. The step between the legs is usually in the range of 50-80 cm.
• Metal. Metal roof frames are made of zinc-coated steel profile, which is not afraid of moisture. The rafters and the crate made of this material are light, durable, so the step between them can be increased to 1.5-2 meters. The fastening of the metal profile is carried out by welding or fasteners. Metal roof units are used with a slope length of 10 meters or more.
• Combined. The truss frame, combining metal and wooden knots, is called combined. The combination of wooden and galvanized steel support elements allows for a cheaper structure with a high load-bearing capacity by increasing the spacing between the rafters.

Please note that metal and wooden frame elements cannot be connected to each other without a gasket made of waterproofing material or treated with an antiseptic preparation. Since the metal has a high thermal conductivity, its proximity to the tree leads to the formation of condensation and rotting of the rafters.

Fastening methods

Metal rafters are assembled into triangular, trapezoidal or arched trusses. Internal stiffeners are attached to the frame beams, which form corners that significantly increase the load-bearing capacity of the frame. Such a system allows you to take a step between the rafters more, taking into account the support capabilities of each truss. The fastening of the metal elements of the roof frame is carried out by one of the following methods:

1. Fastening by welding. If you weld the details of the truss system using a welding machine, you can get a rigid structure with high strength and bearing capacity. If you correctly calculate the roof, you can lighten the frame and reduce the load on the foundation of the structure. The disadvantage of this method is that only a professional with the help of special equipment can perform welding.
2. Fastening with bolts. Fixing the rafters with fasteners allows for less rigid fastening. This method of assembling a truss frame based on a metal profile is used in private housing construction, where the length of the slopes does not exceed 10 meters. Rejection of welding allows you to speed up the installation of the roof.

Experienced craftsmen rely on the fact that the rafters can withstand more weight than wooden ones, so you can increase the step between them and reduce the thickness of the section of the elements. Moreover, ready-made roof trusses are sold in hardware stores, the fastening of which was carried out by welding, suitable for overlapping buildings of standard width.

Advantages

The metal truss frame is used for the construction of roofs of any shape, any slope with a slope of 1-2 degrees. As the material from which the rafters and lathing are made, steel corners, pipes of round and rectangular cross-section, and tauri are used. In order to correctly select the thickness of the frame elements and choose the step between them, the calculation of the roof structure is performed, taking into account the permanent and temporary loads that are transferred to the rafter beams during operation. The advantages of a truss system made of this material are:

• Fire safety. Unlike wooden beams, metal frame beams are not flammable, which increases the fire safety of the building.
• Ease of maintenance. Zinc galvanized coating, which covers the steel corners, protects the roof frame from corrosion during the entire service life. They, unlike wooden ones, do not require annual antiseptic treatment.
• Zero waste. Although metal structures are quite expensive, it is considered cost-effective, since the fastening is carried out by welding, and there is practically no waste left.
• Long service life. If you correctly calculate the loads, then the metal roof frame will last more than 100 years, which exceeds the life of even the most stable roofing.

Professional roofers believe that it is advisable to use welded metal structures for the manufacture of a roof truss frame with a slope length of 10-12 meters. In this case, the main task is to correctly calculate the loads, and then determine the step between the legs in accordance with the climatic characteristics and properties of the roofing material.

disadvantages

Despite the obvious advantages, metal truss systems are not the most popular design solution in private housing construction. Even a large step between the rafters and a sparse crate at a high cost of metal cannot make the structure cheaper than wood. The disadvantages of metal rafters are:

1. High thermal conductivity. The metal has a high coefficient of thermal conductivity, so the rafters and form bridges are cold. From the point of view of energy efficiency, a metal profile frame is not the best solution.
2. Difficulty in transportation and installation. When choosing a metal rafter system, take into account that transporting, lifting and securing long and heavy elements is more difficult than standard length lumber rafters.
3. Difficulty of installation. To rise to a height and fix the trusses, special equipment is used, the rental or purchase of which is expensive.
4. Deformation under high temperature. Although metal is considered a non-combustible material, during a fire it is highly deformed, which usually leads to the collapse of the roof.

To determine whether it makes sense to use more expensive metal profile truss elements, you need to calculate the roof frame. If the slope length exceeds 10 meters, and the load is more than 450-600 kg, then the installation of a metal frame is economically feasible.

Video instruction

The roof system is the outside part of the roof structure that is supported by the load-bearing structure. It includes a crate and a truss system. The triangle underlying this system should be a rigid and most economical structural element that contains the attachment points for the roof rafters.

The main characteristics of the nodes of the truss system

The main attachment points of the roof truss system are shown in fig. 1. They imply the presence of a rafter leg (Mauerlat - 1), a rafter leg (ridge run - 2), a rack (puffs - 3). The design of the truss system is the main load-bearing element of the roof.

All roof fasteners must be of sufficient strength to eliminate a significant degree of risk associated with roof collapse. The consequences of a mistake made when connecting elements can be the most unpredictable.

Figure 1. The main attachment points of the roof truss system: 1 - mauerlat, 2 - ridge run, 3 - puffs.

First, the rafters are installed on the Mauerlat if the building has brick walls. Similar nodes are provided for concrete blocks, then it is necessary to create a reinforced concrete stiffening belt, and it is necessary to insert studs into its design. Their location should be at a distance of 1 to 1.5 m from each other, and their diameter should be more than 14 mm. The top of the studs must be equipped with a special thread.

Mauerlat is drilled, making holes that are necessary for attaching elements to it. Each of the holes should be the same size as the diameter of the stud, and its pitch should correspond to the distance between the studs. A nut is put on each protruding end of the stud and tightened, which ensures the strength of the connection between the Mauerlat and the wall. The rafters should be connected to the Mauerlat in such a way that their bearing capacity is not weakened.

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 supporting 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.

Rafters are the most essential part of the roofing skeleton. The legs of the rafters transmit thrust to the Mauerlat and the load-bearing walls of the house. What determines the quality of the entire rafter system and the roof as a whole? Experts remind that the reliability of any roof structure will depend, first of all, on the quality of fastening the rafters to the Mauerlat. What principles and features of this process every novice builder should know and how to fix the rafters to the Mauerlat with your own hands, you will learn right now.

Fastening rafters to the Mauerlat: a little "materiel"

To begin with, we propose to consider an illustration that shows two types of truss systems:

The place of attachment of the rafter leg with the base is called the support node. There are many such nodes in the system, but we will touch in detail on the lower fasteners of the frame with rafters. Mauerlat and rafter legs are almost always made of wood, less often of metal. It is more profitable and convenient to use wood, as this material is light in weight, easy to install and durable with proper installation and operation.

Types of support nodes according to the level of rigidity

Support nodes - places where the rafters are attached to the roof elements:

In the case of iron joints, the nodes are fixed, rigid (welds or bolts). Wood is a softer and more dynamic material that can swell, dry out and deform. In this regard, experts recommend performing support nodes, adjusted for possible changes in the shape of the wood. Such nodes can have different degrees of mobility:

• Zero Mobility Node- rigid fastening with corners on both sides, in which the fastening of the rafters to the Mauerlat remains motionless.
• Connection of the first degree of mobility- the beam can rotate in a circle.
• Connection of the second degree of mobility- circular rotation with offset, the installation of special sliders or sleds is provided.
• Movable connection of the third degree– the possibility of horizontal, vertical and circular movement.

For any node, whether it is movable or not, at least two types of fixation should be used. For example, notched planks are additionally fixed from the inside with a support beam, while dynamic connections are strengthened with bolts and special steel angles.

About the types of fasteners for rafters to the base

Let's talk about modern fasteners. For the strength and durability of the support units, a variety of metal fasteners are used: beam holders, equilateral, fastening, anchor, reinforced corners, plates, supports, profiles, connectors, anchors, etc. All these spare parts are made of high-quality metal. For dynamic nodes (types 1, 2 and 3), sliders, corners and perforated plates are used. For rigid fastening, stationary connectors, anchors and corners are used.

Such fasteners for the truss system are most often used:

For self-assembly, more than others, perforated mounts are suitable, as they have many holes for self-tapping screws and bolts.

Rigid or movable connections: what to choose

So, we noted that the support nodes connecting the Mauerlat with the boards can be of varying degrees of mobility: from "0" to "3". Zero degree - these are rigid fasteners that exclude any changes in the position of the beams.

Rigid connections: when you need them

Mauerlat is installed when it is necessary to transfer the spacer load from the rafters to the load-bearing walls. This is done mainly in houses made of bricks, panels and blocks. In this case, they try to exclude deformation and shrinkage of the roof in order to prevent changes in the load on the supporting walls. This is where the need for a fixed connection of the truss system with the Mauerlat appears.

Fixed knots fixed with gash

Many experts recommend making appropriate cuts at the point where the rafters are attached to the floor beams for greater strength and immobility of the connecting nodes. These cuts should fit snugly with the Mauerlat. Additionally, such nodes are strengthened with bolts, anchors and metal plates:

Or long screws:

And one more important point: the size of the washed down bar should not exceed 1/3 of its section. Otherwise, the rafter system may lose its bearing capacity:

Rigid knots without notching rafters

The fastening method using a hemmed bar is used in layered truss systems. The rafter is cut according to the template and beveled (to give the roof the desired slope) at the point of contact with the Mauerlat. From the inside, such rafters are reinforced with supporting bars and reinforced with corners on both sides to the base frame:

Another option for a non-butt joint is a rigid fastening of the rafters, reinforced with overlay bars on both sides. Two boards at least a meter long border each rafter leg. One end of such supports is cut at an angle that corresponds to the slope of the roof slope (including rafters). The boards are fastened with a cut to the Mauerlat using long bolts and reinforced steel corners. The bars are attached to pre-marked places, first one at a time. Then, close to the overlays on one side, the rafters themselves are mounted, which are immediately reinforced with the same overlay on the other side. There is an option to install two overlay bars at once, and after that, rafters, but this method is used less often, since it requires more accurate calculations.

When do you need to make mobile connections?

So we come to dynamic reference nodes - connections that can change their position. What is it for? We recall the physical properties of materials - many of them shrink or swell. First of all, this applies to buildings made of pure wood - timber, log house, etc. Natural wood necessarily shrinks, due to which your roof can not only be deformed, but also completely destroyed. To avoid such fatal consequences, the masters recommend performing sliding fastenings of the rafter legs with a Mauerlat (or the upper crown of the log house).

A prerequisite for the installation of sliding nodes is the support of the truss frame on a strong ridge beam. Since the supporting lower nodes are dynamic, the maximum rigidity must be achieved at the roof ridge. The upper edges of the rafters are sawn for a tight connection between themselves and the ridge beam, connected and reinforced with crossbars, metal tapes, plates and corners. It is better to connect a truss element already fixed in the ridge with the crown of the log house.

What is a sliding mount?

The movable connection is carried out by establishing sliding fasteners, called "sleds" or "sliders". Such a node provides for a certain freedom of the rafter legs, which helps prevent the deformation of the roofing system after the natural shrinkage of wooden structures:

Here are the types of sliding supports:

Do I wash down on the rafters if the house is made of timber: an alternative expert opinion

I propose to still file down, but not the rafters, but the upper crown. Firstly, in this case, the risk of curvature of the rafters is reduced, secondly, the “cold bridge” decreases, thirdly, the tangential pressure on the Mauerlat (the upper beam of the log house) decreases, and fourthly, roof insulation is simplified in the future. The disadvantage of this method is that when the upper crown of the beam is cut down, the height of the ridge decreases, therefore, if in the future it is planned to raise the height of the ceiling, one more crown should be provided. But! Such schemes are only suitable for wooden houses, since in brick and concrete buildings the mauerlat must be intact in order to maintain load-bearing qualities.

How to fix the rafters to the beams?

In simple houses, mostly frame houses, the Mauerlat can be abolished. In this case, the rafters are attached to the floor beams. The most reliable option for assembling such a system is the preparation of roof trusses. Each truss consists of two rafter legs, a connecting crossbar and a lower puff. For strength, the trusses are reinforced with central beams and struts:

Floor beams are laid in such a direction that the roof trusses cross them perpendicularly in different planes. The puff performs the main load-bearing functions, is attached to the floor beams with anchors, through bolts, studs and is reinforced with plates and metal corners.

It is possible to attach the rafter legs directly to the beam, which will additionally perform the functions of tightening. To create high-quality support nodes in such a system, two methods of fastening are recommended:

1. The connection of the rafters with the beam with a double tooth - the cuts are made on the beam and the bevel of the rafter leg (two butt notches on each).
2. Bolt and clamp fastening. Through fastening may be provided, but if the boards have a large cross section, cuts are made and the parts are connected with long bolts.

Fastening the rafter to the Mauerlat: a step-by-step description

For example, we will describe the process of rigidly attaching rafter joints to the Mauerlat on a simple gable roof.

I. Preparation of the Mauerlat and rafters for work

At this stage, it is necessary to cut out the rafter legs of a given length and mark their step on the basis. The optimal step length of the rafter legs is 60-200 cm. You should also accurately determine the angle of inclination of the rafters.

Mauerlat installation master class:

II. Creating a gash

We carry out washed down on each rafter leg for a tight connection with the base. To enhance strength, you can provide an additional notch on the frame or rafter and install a thrust beam under each rafter leg.

III. Installation of rafters on the Mauerlat

It is necessary to impose rafters carefully so as not to damage other elements of the building (windows, walls, etc.). We start the boards with a cut on the beams and rest them on the ridge beam. First, we install the extreme rafter legs, between which you need to stretch the thread to align all the other rafters.

IV. Fastening each rafter to the Mauerlat

Now that all the trusses are in place, you need to firmly fix the support nodes. We use several of the mounts proposed above for this:

• Nails+ steel corners on the left and right side of the joints between the board and the base.
• Through bolts or studs+ support bar for cutting the rafters.
• Anchors or bolts+ corners or steel plates, etc.

Two overhead boards on both sides of the rafter leg, installed on pre-marked places of the Mauerlat, will help to strengthen the fastening. You can also use wire fastening as a reinforcement of the strength of the connections. To do this, you need to prepare a steel wire twist of 2-3 wires. Its length should be enough to wrap around the rafter leg at the junction with the Mauerlat and fix the ends of the twist on a metal crutch. As a crutch, you can take a long steel bolt, which is mounted into the wall 30-40 cm below the Mauerlat, strictly under the support node.

We will also consider one of the old-fashioned ways - fastening with brackets:

And finally, we invite you to watch the video:

What is the secret of the quality of the truss system: the three main rules of the master

• High-quality lumber is half the battle on the way to successful construction. Mauerlat and rafters should not have cracks, wormholes and knots.
• The accuracy of measurements, cuts and the uniformity of the position of the fasteners is no less important. If all rafter legs are of the same length and section, then it is better to prepare a template for making cuts and notches.
• Washed down on the Mauerlat - loss of the supporting functions of the base by 50% or more. The percentage of strength reduction depends on the depth of the notches.

When the rafter system is ready, it is the turn of the installation of the crate, insulation and flooring of the roofing material. But this is another interesting topic, which we will definitely cover in the next article. In the meantime, we wish you good materials, easy work and good helpers!