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Fastening points of the puff to the rafter leg. Roof truss system

The attachment points of the rafters must provide the necessary strength of the roof frame. It is important to choose the right technology for mounting the elements of the truss system among themselves and attaching them to the supporting contour so that the finished roof is able to withstand the design loads.

Features of roof structures

The task of layered and hanging roof truss systems is the most uniform transfer of the load of the sub-rafter structure, which, in turn, distributes the load on the load-bearing walls and the foundation of the building. The under-rafter structure is usually a mauerlat (a beam laid lengthwise on each load-bearing wall). It can also be floor supports (laid across the wall) or the upper crown of a log house made of timber or logs.

The choice of the method of attaching the rafters to the Mauerlat depends on their type. The layered design makes the Mauerlat work in shear, while the hanging trusses work in compression, the direction of which coincides with the orientation of the load-bearing walls.

Puff setting

Installation of a gable roof requires the installation of a rafter system of a layered or hanging type. In order to mount a rigid hanging truss truss that does not transfer spacer loads to the walls, it is necessary to correctly perform the fastening points of horizontal jumpers - puffs and crossbars.

Depending on which roof structure was chosen, the puff can be mounted at the base of the rafters and serve as a floor beam. The truss truss, which is attached to the Mauerlat, is equipped with a crossbar to stiffen it - a jumper located closer to the ridge. In mansard roofs, the crossbars serve as the basis for the ceiling sheathing.

The connection node when installing the puff is recommended to be performed by the method of "cutting into the rafter with a half-pan" using a fixing screw. This mounting method requires precise fitting of the elements, since with large gaps, at the interface points, the attachment point under load may collapse.

An easier way is overlap installation. In this case, the jumper is made of a board or two boards installed on both sides of the rafter leg. Nails are used as fasteners. The knot can also be a bolted connection, but this will reduce the bearing capacity of the rafters by 20%.

Another option is to install the crossbar by surprise. Installation of this type of assembly became possible after the invention of nail plates. The design is able to withstand high loads - reliability is ensured due to the tight fit of parts and strong fixation on both sides due to the large number of teeth on the plate.

The cross section of a beam or board for the manufacture of an expansion crossbar must match the cross section of the rafter.

Mauerlat: attachment points for rafter legs

The support of wooden rafters on the Mauerlat can be performed using two technologies:

rigid attachment to the Mauerlat;
sliding fastening to Mauerlat.

With rigid fastening, any kind of displacement of the rafter leg, which rests against the Mauerlat (bends, shifts, torsion), is completely excluded. To this end, when installing the roof rafter system, the installation of rafters can be carried out using a hemmed bar, which prevents the rafter leg from slipping at the point of support. Lateral shifts with this connection method are excluded due to the installation of metal corners.

In the second variant of the rigid attachment of the rafter leg to the Mauerlat, it is necessary to make a gash (saddle) at the bottom of the rafter or board. The plane of support must be horizontal; for this, the cut in the rafters is made at an angle corresponding to the slope of the slope. To fix the knot on both sides, the rafters are driven at an angle along the nail (they must be crossed inside the Mauerlat), the third nail is driven vertically through the rafter into the Mauerlat.

A sliding mount is usually used when building a truss system on a house from a bar or log. The basis for supporting the rafter legs in this case is not the Mauerlat, but the upper crown of the log house. To avoid deformation of the roof during shrinkage of the house, it is necessary to perform a node with a certain degree of freedom for the rafter leg. Often, for this purpose, a special fastener made of metal is used - a sliding support ("sled"). Its upper part is a loop, which is displaced along the guide, fixed on the rafter leg, when the log geometry changes.

Other methods of mounting the sliding knot are also used. A cut is made in the rafter leg, the beam is installed with a cut on the upper crown, after which it is fixed in one of the following ways:

by means of one vertically hammered nail;
with the help of nails hammered from both sides, crossing in the Mauerlat;
by means of a bracket;
by performing a single fixation with steel fixing plates.

This method of fastening leaves the possibility for the elements of the system to move relative to each other when the geometry of building structures changes.

Ridge connections

The device of the roof truss system with two slopes implies the presence of a horizontal rib in the upper part of the roof, formed as a result of the junction of the slopes - the ridge. The ridge knot can be performed in several ways, the choice depends on the type of truss system and the features of the building itself.

The layered design involves attaching the rafter legs to the ridge run - a horizontal beam located on racks parallel to the long walls of the house. The upper ends of the rafter legs should be cut at an angle corresponding to the angle of inclination of the slopes. The junction of the cut ends of the rafters to the ridge should be as tight as possible. Nails are used as fasteners. Slanted rafters are used if it is possible to install racks on the inner wall or columnar supports for attaching a ridge run. In addition, the walls must be equipped with a power plate to support the rafters.

Assembling a hanging type truss requires joining the upper ends of a pair of rafter legs. To do this, the end of each of the rafters is cut at an angle equal to the angle of the roof, the beams are connected by cut planes - it is required to ensure their tightness. They are fixed with two nails hammered at an angle into the upper planes of the rafters. Then, on each side, a wooden overlay or metal plate is nailed, which close the junction.

To provide the ridge with the necessary strength, cutting into half a tree can be performed: in this case, instead of the mating plane of the butt joint, the rafters are connected by a ledge. Next, a through hole is drilled for a stud or bolt with a diameter of 12 or 14 mm, nuts with wide washers are used for fastening.

If you have to install sliding supports on the wall of the log house or create adjunctions (rafter junctions with the Mauerlat) with a certain degree of freedom, special attention should be paid to the ridge. It is recommended to make a movable connection unit so that the roof does not deform during uneven shrinkage of the structure. To this end, the ends of the rafters are connected by a metal plate hinge.

The nodes of the hip roof truss system

A feature of the hip roof is the shape of its slopes: long slopes are trapezoidal, end slopes (hips) are triangular. The installation of such a rafter system requires the installation of diagonal (sloping) rafter legs, which form triangular slopes. The principle of fastening the diagonal rafters in the upper part depends on the design features of the main part of the roof. It can be formed from hanging trusses, or it can be a frame with a ridge run and layered rafters attached to the Mauerlat.

If the layered rafter legs of the trapezoidal slopes rest on the ridge beam (run), then the rafters must be supported on the console of the ridge run. Console outlets for the sub-rafter frame should be 100-150 mm. The lower part of the diagonal rafter legs are attached to the Mauerlat or a beam mounted on the wall.

If the rafters need to be supported on the extreme hanging truss, then the principle of creating the attachment point depends on the section of the side rafter legs. Sprengel with a stand is mounted if the rafter legs are made of a board. Diagonal rafters rest on the sprengel. In a situation where a beam was used to make the rafter legs, the rafters can be attached to the surf - a board with a thickness of 5 mm or more, fixed to the truss truss.

On the sloping rafters, washed down at an angle corresponding to the angle of inclination of the hip slope to ensure a tight connection with the truss or surf. For the strength of the nail connection, clamps and wire twists can be additionally used.

The shortened rafter legs (spreaders) are supported by the upper part on the rafter, the lower part is attached to the Mauerlat on the wall. The attachment point to the diagonal beam can be performed:

washed down with a nail fastening method;
via socket connection;
by fastening bars with a section of 50x50 mm on both sides and along the entire length of the diagonal rafters and splints.

Auxiliary elements

To enhance the rigidity and reliability of roof structures, it is often necessary to install a strut, an additional run or support posts. Rafter purlins provide the rafter leg with an additional point of support. The run is a horizontal beam, fixed on vertical posts, parallel to the ridge. The attachment point is made using metal corner plates or an internal metal rod and an external straight bracket.

Wooden rafter braces allow to reduce the span of rafter legs (including rafters). The angle of inclination of the brace to the horizontal plane must be at least 45°. If the rafter is made of a log or timber, the strut is cut with the installation of a steel dowel at an angle of 90 ° to the junction, or the joint is closed from the outside with a plate.

If it is necessary to strengthen the roof frame, it is necessary to install a strut under each rack on which the layered rafter rests. In this case, all the struts of one slope rest against a common bed. Staples are used for fastening.

The struts of the extreme spans, which are subject to the maximum snow and wind load, require special attention. Attachment points when mounting the strut to the rack or run are made using pads and bolts.

In any building, the main elements on which the maximum load falls are the foundation, walls and roof. The quality of the roof installation 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 staggering 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:

Plates.
Fasteners LK.
corners.
Brackets WW.
Self-tapping screws.
Varieties of the corner of the KR.
Wire ties.
Mounting tape perforated TM.
Bolts with nuts.
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:

Butt connection.
Mounting on the basis of a ridge run.
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.

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 unit 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 against 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.

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.
13 m. Fastening is carried out with the help of struts, which abut against the base with the top, and the perpendicular beam with the bottom. The interval between the supports should not be more than 5.5 m.
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 crossbar 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 truss 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.

The main obstacle for novice developers, even if we are talking about a simple roof, may be a lack of knowledge about what the nodes of the truss system are. How to fulfill them in order to get a strong, reliable and stable roof?

The beginning of the design of a pitched roof is the choice of a truss system, which should perform the functions of a supporting structure. The type of structures is determined based on the type of roof.

In one case, rafters are beams or boards that act as the "skeleton" of the roof, which holds the weight of the insulation and roofing material. In another, they can be composite, and are assembled from separate elements, known as rafter legs.

The board and bars must undergo a special impregnation - fire-fighting and antiseptic. The better it is done, the longer it will last..

Composite frames are divided into two types: layered and hanging. The choice of a particular system, in addition to the architectural preferences of the owners, depends on some parameters of the roof:
- its functionality
- the number of loads tested, including those related to the climatic features of the region.
Hanging rafters do not have intermediate supports, therefore they create a significant bursting force, which is transmitted to the walls in the horizontal plane. To reduce it, a puff (wooden or metal) is used, which, connecting the legs, completes the triangular structure. The legs in it work on bending and compression. The puff can be located at the base, and in this case serves as a floor beam (this option is more common when installing attics), or higher.

The higher the location of the puff, the more powerful it is, on the one hand, and more securely connected to the rafters, on the other.

Layered views are arranged in houses with an average load-bearing wall or columnar intermediate supports. They rest with their ends on the outer walls, the middle part - on the supports or the inner wall. As a result, the elements work on the principle of beams - only for bending. The weight of the truss system in the case of layered ones with the same width of the house is less: it requires less lumber, and therefore, cash costs.

If a single roof structure is installed over several spans, hanging and layered trusses can alternate: for sections without intermediate supports - hanging ones are installed, where there are - layered ones.

How to properly install the truss system

One of the conditions for the reliability of the future structure is the correct arrangement of the attachment points of the truss system.

Pitched roof rafters usually have at least three points of support. Their number may vary depending on the size of the span. With a span width of up to 10 m, one additional support is required; for large values, their number increases.
The design of the hanging also depends on the width of the span. If it is small, the puff is usually replaced with a crossbar. With an increase in span, the puff begins to sag, and the legs begin to sag.

With a span
up to 9 m, hanging rafters are supported by a headstock - a special vertical bar. The ends of the legs are attached to its upper end with the help of staples or clamps, the headstock with a puff - with a clamp.
up to 13 m - strengthening is carried out with the help of struts. With their upper ends they rest on the leg, and its length between the supports should not be more than 5.5 m, and on the lower ends - in the headstock.
up to 17 m, the legs in the lower part are reinforced with help, for the upper part they use a trussed system: the puff is attached to two grandmothers and a crossbar is installed between them.

How to properly fix the rafters

Whether the truss system is being replaced or it is being installed in a new house, certain rules should be followed.

A simple fastening of the leg and the beam can even be destructive - when pressure is applied to the rafter, its end begins to slide along the beam, which leads to the destruction of the roof .

To avoid slipping and ensure reliability, the following types of connections are used:
- spiked tooth,
- pointed tooth,
- stop at the end of the beam.
It is possible to use two teeth - it depends on the angle of inclination. For fastening, in addition to this connection, metal corners are also used.

The main nodes of the roof frame

Attachment to the beam
- A tooth with a spike is made in the heel of the rafter, and an emphasis is cut out in the beam with a corresponding socket for the spike.
- The nest depth is about 25–30% of the beam thickness.
- The cut is performed at a distance of 0.25–0.4 m, starting from the edge of the beam, which hangs down.
- A single tooth is performed, as a rule, together with a spike, which does not allow shifting to the side. Therefore, such a connection is called a "tooth with a spike and an emphasis."
In the case of a hollow roof, the angle of inclination of which is less than 35 °, the rafter legs are installed so that the bearing area per beam increases. To do this, use a cut with two teeth:
- in two spikes;
- emphasis with and without a spike;
- two spikes to the castle.
All connections in the structure are made using fasteners:
- metal - screws, nails, bolts with washers, various corners;
- wooden - bars, triangular overlays (kerchiefs), spikes.
To Mauerlat:

There are two technologies according to which .

Rigid - in this option between these structural elements, the possibility of any influences (shifts, turns, bends, torsion) is completely excluded. To achieve a similar result:
- when fastening, corners with a hemmed support bar are used;
- a saddle (washed down) on the leg is performed, the resulting connection is additionally fixed with wire, nails and staples. The nails are nailed from the sides, towards each other at an angle (they cross inside the Mauerlat), then the third nail is hammered in a vertical position. This is the more common mounting method.
Sliding (articulated)- such a pairing, which has two levels of freedom, is achieved through the use of special fasteners, which allows one of the mating elements to move freely (within specified limits).

The following options for sliding fastening of rafters and Mauerlat can be distinguished:
- washed down, after which the rafters are washed down on the Mauerlat:
- the elements are connected obliquely with two nails towards each other;
- they are connected with one nail, which is nailed vertically from top to bottom into the body of the base beam through the leg;
- an alternative to nails can be steel plates with holes for nails;
- fasten the boards to the Mauerlat with a bracket;
- release the rafter leg behind the wall and perform a single fixation with fixing plates;
- use special steel fasteners - "sleds".
In all these cases, the foot rests on the Mauerlat, but when moving, the elements of the system have the ability to move relative to each other.

Such a pairing is especially important for wooden houses erected from timber or logs, which shrink over time. Using a hard mate can cause damage to the integrity of the walls.

The truss system can be "floating" or rigidly fixed. The floating one is mounted on special brackets that allow the wooden frame to “sit down” simultaneously with the shrinkage of the gables and prevent them from hanging over the ridge log.

Ridge knot

There are three ways to connect in the ridge part.

butt
The upper edge of the rafters is cut at the same angle as the angle of the roof, rest against the desired rafter located on the opposite side, it should be cut in the same way. Corner trimming is usually done according to a template. For fixing under the ridge, two nails (150″) or more are used. One nail at an angle is hammered into the upper plane of the first and second rafters, while they must enter the cut of the opposite. The ridge joint is additionally strengthened by placing a wooden lining or a metal plate on the side of it, which is attracted with bolts or nails.

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 that holds 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 rafter 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.

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.

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

Figure 1. Diagram of the Mauerat device.

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.
13 m. Fastening is carried out with the help of struts, which abut against the base with the top, and the perpendicular beam with the bottom. The interval between the supports should not be more than 5.5 m.
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 crossbar 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.

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.