How are the attachment points of the roof truss system created? Strut truss system. The main shortcomings in the installation of attachment points for the truss system

The structure of the rafters is the skeleton of the roof, which is obliged to take on and evenly distribute the weight of the roofing materials. If you correctly assemble the wooden skeleton for insulation, waterproofing film and top coat, you will be able to achieve a noticeable increase in the load capacity of the truss system.

The main elements of the truss system

The wooden frame of the roof is assembled from parts such as:

• mauerlat - a kind of base for roofing elements, attached around the entire perimeter of the building to the upper edge of the outer walls in order to disperse the pressure of the roofing pie;

  Mauerlat serves as the basis for the roof frame

• rafter legs - irreplaceable details of the wooden skeleton of the roof, which determine the angle of inclination of the slopes and the view of the upper part of the house;
• ridge run - a bar fixed in a horizontal position and, like a spine, connecting all the rafters of the roof frame in their upper part;

  The ridge run is located exactly in the middle of the building

• side run - a horizontal beam, which differs from a ridge run in that it is fixed in the middle of the rafter legs of each roof slope;
• puff - a spacer that unites two opposite rafters so that they do not move apart;

  Tightening and struts are necessary to properly distribute the load on the Mauerlat

• racks - vertical frame elements placed under the ridge and side runs to support the rafters and the ridge beam, and also, if necessary, substituted under the middle part of the rafter legs;
  

  Racks can support not only the ridge of the roof, but also the rafters

• struts - parts that rest against the bed, due to which the rafter legs become more stable;
• bed - a bar placed on the upper edge of the inner wall of the building parallel to the ridge and serving as a platform for attaching racks and struts;

  The bed is located on the inner wall parallel to the mauerlat beam

• roof ridge - the area of ​​​​combination of two slopes, along which a continuous crate is installed, necessary to strengthen the described part of the roof;

  The ridge is formed in the highest zone of the truss system

• filly - elements used in the arrangement of the overhang, when the rafter legs are not long enough;
  

  Fillies lengthen rafter legs

• roof overhang - a wooden frame area that protects the walls of the house from contact with a large amount of precipitation;

  The cornice overhang is constructed to protect the walls from rain.

• lathing - bars or boards nailed perpendicular to the rafters and serving as a platform for attaching roofing materials.

  Sheathing boards are laid out perpendicular to the rafters

Main connecting nodes

The main nodes of the truss system are:

• roof truss - connection of a rafter pair, stretch marks, as well as racks and braces;
• ridge knot - combination of two opposite rafters;
• a link from a Mauerlat and a rafter resting on it;
• a module that includes a run, a rack and a bed;
• connection of the rafters with a strut and a rack.

The most complex link of the roof frame, according to the author, is a truss truss, which is distinguished by the fact that:

The ridge knot also has several features:

Rafters and Mauerlat become a single link, which is characterized by the following:

A module from a run, a rack and a bed is formed by driving building brackets, steel dowels or linings from steel strips into their joints.

A node of a bed, a rack and a run allows you to share the load between the external and internal walls of the building

Struts, racks and rafters are assembled into a single module, creating cuttings. To ensure that their connection is not weak, construction brackets are used.

A knot of struts, racks and rafters allows you to soften the pressure on the inner wall of the house

Ways of fastening rafters

In the lower part, the rafters can be connected both to the Mauerlat and to the floor beams. Sometimes, for example, during frame construction, they are fixed directly on the wall. And in the upper part, the rafter legs are combined with the ridge. Each labeled node can be created in several ways.

Mauerlat connection

The rigid fastening of the rafters on the Mauerlat guarantees the absence of any displacement of the assembly elements. It is performed by cutting in a certain sequence:

1. To speed up work, a template is made from a piece of board or thick cardboard. A line is drawn on the workpiece, stepping back from the side edge a distance equal to 1/3 of the width of the rafter, and then mark the point of contact with the Mauerlat beam, along which a second line is drawn perpendicular to the first.

   If the width of the rafter is more than 200 mm, then washed down is done at a depth of 70 mm

2. At an angle of inclination of the roof slope, the template is substituted to the edge of the Mauerlat, making sure that the point marked on the piece of wood is strictly opposite the corner of the beam. Two lines are drawn from it with a pencil - vertical and horizontal, as a result of which a triangle is obtained on the workpiece, which is carefully cut out.
3. The made template is assessed for correctness by putting it on the Mauerlat in several places. If the groove made turned out to be smaller or larger than necessary, then the pattern is made anew, correcting the mistake made.
4. The template is placed on a horizontally located rafter. The triangle in the pattern is circled with a pencil. The same is done with other rafter legs. At the same time, make sure that the horizontal line of the groove in the pattern is always in the same place on the rafter. Otherwise, notches will be created at different distances from the ridge.
5. The triangles drawn on the rafters are cut out with a hand saw. The tool is operated slowly so as not to accidentally increase the depth of the groove in the rafter leg. Possessing the skills of working with an electric saw, recesses can be made with this device. True, it must be borne in mind that a tool powered by the mains is much worse at listening to the hand and is able to go to the side.

   The triangular cut allows the rafter to rest against the Mauerlat

6. The correctness of the size of the grooves made is checked with a pattern. If discrepancies are found, the notch is corrected with a hacksaw.
7. Two extreme rafter legs are placed on top of the house. They are inserted into the Mauerlat with grooves, fixed on the sides with metal corners or brackets.
8. A rope is pulled along the bottom edge between the two installed elements. Then the remaining rafter legs are attached to the Mauerlat one by one.

The technology of attaching the rafter legs to the Mauerlat with a patch of a thrust bar can be taken into account by builders without experience. With this method of creating a node, as the author of the article noted, it is possible to change the position of the rafters until it becomes completely correct.

To connect the main elements of the roof frame with the Mauerlat with a stripe of a thrust bar, do the following:

When building a roof frame for a wooden frame, which always shrinks, it is preferable to use the sliding method of attaching the rafters to the Mauerlat. Thanks to it, it is possible to avoid deformation of the truss structure and deterioration in the stability of the upper row of logs, which replaces the Mauerlat.

The choice of sliding rafters is justified only when a ridge beam is provided for the main elements of the roof frame, against which they could abut with their upper part.

When the rafters are fixed on the Mauerlat using the sliding method, certain steps are taken:

The layered method of attaching rafters to the Mauerlat is adopted when the purchased lumber turned out to be shorter than necessary. Also, this method of fixing the main elements of the rafter system is used during the repair of a roof of complex configuration.

When fixing the rafters on the Mauerlat using the layered method, only 3 tasks are performed:

Video: installing rafters

Combination with floor beams

It is possible to fasten the rafters to the floor beams only being sure that the walls of the building will withstand the pressure of the roof frame. Still, in the absence of a Mauerlat, the load on the house is not uniform, but point.

Without fear and doubt, the rafters are attached to the floor beams if they are building a light mansard roof. At the same time, boards with a section of 5x15 cm are used as ceiling beams.

The rafters are not connected to the Mauerlat, but to the beams of the attic, if they know for sure that they will withstand the pressure exerted

To firmly fix the rafter legs on the floor beams, perform the following tasks:

wall mount

If for some reason the rafters have to be fixed directly on the walls, then they will definitely need to be connected with a puff. She, as the author of the article personally made sure, who helped build the roof of the utility room, will remove part of the stress transmitted by the rafters from the house.

Rafters should never be directly connected to the outer walls of the building if they are built from foam or gas blocks. These materials freely transfer their moisture to the wood and are unable to retain fasteners.

On the wall, the rafters can be fixed using a sliding method, but this is not the most reasonable solution.

To securely fix the rafter legs on the walls, it is necessary to take certain measures:

1. At the right angle, make on the rafters washed down with one tooth.
2. Install the rafters on the walls with the butt end and drive a nail 10-12 cm long into them.
3. If necessary, attach metal corners to the sides of the rafters.

Since the roof ridge is under serious pressure from the entire truss system, roofers with extensive experience create a ridge knot in five ways: butt, on a beam, overlap, in a groove, in half a tree.

To create a ridge knot by connecting opposite rafters end-to-end, do the following:

When attaching rafters to a beam, or rather, to a special ridge run, they act in a special way:

When the rafters are connected to the beam, the ridge is not pointed, but flat.

If the ridge knot is made by fastening the rafters with an overlap, then you will need to perform a few simple tasks:

To connect the rafter legs into a ridge knot using a groove, several skillful carpentry actions are performed:

Having chosen the method of connecting the rafters to half a tree, do the following:

Video: building a roof frame with connecting rafters with a ridge run

The construction of the rafter system should not be started until it is possible to understand the features of fastening the rafters to other elements of the roof supporting structure. By the way, among the various ways of fixing the rafter legs, there are options not only for experienced builders.

The rafter system is the frame of the roof of the house, which bears and evenly distributes the weight of the roofing pie, sometimes reaching up to 500 kg / m2. The reliability of this kind of skeleton depends on three factors: the accuracy of the calculation, on the basis of which the number and cross section of the supporting elements are selected, the material from which it is made, and also on the correct fastening technology. Knowing how to properly fix the rafters, you can significantly increase the bearing capacity of the frame, making it more durable and reliable. Installation errors, on the contrary, lead to noticeable strength losses and roof deformations. In this article we will talk about the main types and methods of fastening, with which you can install the rafters with your own hands.

The truss frame of the roof of the house is a system of interconnected supporting elements made of wood or metal, which give the structure a shape, slope, and also evenly distribute its weight between the bearing walls. Its main component is the rafter legs, which are angled beams that are connected in pairs along the slope, forming a ridge at the top of their connection. There are two main types of rafters:

• Layered. Rafters are called supporting elements, which in the roof structure have two points of support - on the ridge run and the Mauerlat. This type of rafter system is used in structures that have one or more load-bearing walls inside, on which the rafters can be “leaned”. This fastening of the rafters allows you to unload them through the use of additional vertical supports.
• Hanging. Hanging elements are called elements that have only one point of support, located where the rafters are attached to the wall or Mauerlat. The hanging type truss system experiences a load not only in bending, but also in bursting, therefore it is reinforced by horizontal compensating elements (crossbars, puffs, contractions).

Note! In most of the most popular truss systems, the rafters are attached to the Mauerlat. Mauerlat is a massive bar or beam with a section of 150x150 mm or 200x200 mm, laid along the load-bearing walls of the structure, on which the rafter legs will subsequently rest. It softens the pressure on the walls of the house, and also evenly distributes the weight of the roofing cake. You can attach the Mauerlat to the upper belt of the walls using anchor bolts or embedded metal studs.

Main connecting nodes

The rafter frame is called a system because all its elements are closely interconnected and fixed, as a result of which the roof structure acquires a stable shape, rigidity and high bearing capacity. Each connecting node between its parts is a weak spot that can easily be deformed under load, so all fastenings must be carried out strictly according to the technology. Experienced craftsmen distinguish types of connections in the roof structure:

1. Fastening rafters to the ridge beam. This connecting node is typical only for layered truss systems, in which the upper part of the rafter leg rests on a ridge run, mounted on vertical posts. The rafters can be fastened to it with the help of metal plates, nails or sliding sliders.
2. Fastening rafters to the Mauerlat. The most important fastening unit of the rafter frame is the junction of the Mauerlat beam with the rafter legs. You can fix the rafters on it with nails, metal corners or wooden bars.
3. The connection of the rafters to each other. To lengthen the rafter legs, if the length of the slope exceeds the standard length of lumber, they are assembled from several elements interconnected with nails, glue or metal linings.
4. Connection of rafter legs with auxiliary supporting elements. In the design of the truss frame, the rafters can be connected to a puff, crossbar or struts to increase rigidity, strength and bearing capacity.

Please note that any cuts made to attach the rafters to beams, mauerlat or other structural elements of the frame lead to a decrease in their strength, so experienced craftsmen recommend connecting them together using corners and overlays.

Fixation methods

When deciding how to attach the rafters to the Mauerlat or ridge run, it is necessary to choose the right mounting hardware. The modern construction market has a huge assortment of fasteners of various designs and sizes. The main criteria for choosing fasteners are the material used to make the rafters, their cross section, as well as the type of load to which they are subjected. There are the following ways of fastening rafters:

Experienced craftsmen believe that the most reliable way to fix the rafters is to use metal corners that firmly connect the wooden elements to each other, rigidly fixing the angle between them. The corner that overlaps the joint between the rafter leg and the ridge beam or Mauerlat serves as a kind of spacer between them.

Varieties of fasteners

Wood is a natural material that, in the process of leveling moisture and drying, shrinks significantly, due to which the linear dimensions of the structure change. That is why experienced craftsmen recommend building a roof for timber and log houses, a year after construction, when the shrinkage process passes from an active to a passive phase. If you fix the wooden elements of the frame rigidly, then after drying the roof of the house may be deformed. Therefore, the following types of fasteners are used to connect the rafters:

Interestingly, there are several options for combinations of movable and fixed connecting nodes. The most common are truss systems with one rigid and two sliding fasteners, which provide sufficient mobility with high strength and rigidity of the structure.

Types of fasteners

Among experienced roofers, disputes do not subside, the more efficient it is to fasten rafters to floor beams and Mauerlat. However, in most cases, the catch is that in these conditions it is more practical to use nails or self-tapping screws. Both of these fasteners have their own advantages and disadvantages:

• Nails are good because only a hammer is needed to drive them, which is in every household. However, some masters complain that it takes too long to hammer them manually. It is worth recalling that special jagged nails are used to fix the rafters, which securely adhere to the wood.
• To assemble the rafter frame, galvanized self-tapping screws are used, which are not afraid of corrosion. Due to the thread, they are firmly screwed into the thickness of the wood, securely fixing the elements together. Screw them quickly and conveniently with a portable screwdriver. The disadvantage of this type of fastener is that during dismantling, removing self-tapping screws from wood is long and dreary.

Most experienced roofers agree that it is better to use galvanized ruff nails to fix the rafter legs, the length of which is 5-3 mm longer than the thickness of the lumber. Properly selected fasteners are the key to high-quality and long-term fixation of the roof frame, which will not be afraid of either mechanical stress or wind load.

Video instruction

At the heart of each roof is a large number of beams, rafters, racks and runs, 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.

The truss system is the skeleton of the roof. It is she who is responsible for the strength of the roof, its reliability and resistance to stress. When building a house on your own, you need to know how to properly make the attachment points of the truss system so that the roof is reliable and safe.

The device of the truss system

The truss system consists of many elements, each of which performs its task.

• Mauerlats are responsible for distributing loads on the walls. These beams take on the weight of the entire roof and lie on the walls.
• rafter legs- these are inclined beams, which create the necessary angle of inclination of the roof.
• Runs are horizontal beams that hold the legs together. There is a ridge run, located at the top, and side ones, located with slopes.
• The puffs are located horizontally and do not allow the rafter legs to part, forming rigid triangles with them.
• Racks and struts(rafter legs) - additional elements on which the rafter legs rest. They rest on the beds.
• Lying - a horizontal beam located under the ridge; racks and struts rest on it. The task of the bed is to redistribute the point load from the racks.
• The ridge is the junction of the roof slopes.
• Sheathing - bars or boards that are stuffed perpendicular to the rafters. Roofing material is laid on it. The task of the crate is to distribute its weight.
• Overhang - an elongated edge of the slope that protects the walls from precipitation. If the length of the rafter legs is not enough to create an overhang, additional elements are used - filly.

The device of the truss system is shown in the figure.

Also, truss trusses are distinguished in the roof device. This is a solid knot consisting of rafter legs, stretch marks, racks and struts (braces, braces). The farm can be not only triangular, but also trapezoidal, segmental or polygonal. Which type of farm to choose depends on the size of the house. If the distance between the walls is 9-18 m, then a triangular truss will do. For houses with a width of 12 to 24 m, trapezoidal or segmental trusses are used. If the width of the building is greater (up to 36 m), then polygonal trusses are used.

The main attachment points for the roof truss system are beam, ridge and Mauerlat.

Types of truss systems

Rafters can be hanging and layered.

Hanging lean on the walls and create a spacer. To reduce it, puffs are made at the base of the rafters, which connect the rafters and form triangles with them. Hanging systems of various types are used for houses with a width of no more than 17 m. Depending on the width of the building, they arrange them differently.

If the width of the house is not more than 9 m, then the rafters are supported by a vertical bar - the so-called headstock. She is under the skate.

If the width of the house is from 9 to 13 m, struts are additionally installed, which at one end rest against the rafter legs, and at the other end against the headstock.

With a house width of 13-17 m, two vertical posts are used, connected at the top with a crossbar (fitted), as in the figure.

Sloped rafters rest on a load-bearing wall or columns inside a building. With this method, the rafter has three or more support points. The layered type of truss system creates less load on the walls of the building and is more durable; it is used for buildings of greater width. Such roofs can be arranged in different ways, depending on the location of the internal walls, they can be symmetrical or asymmetrical.

How to connect the parts of the truss system

To connect wooden elements to each other, nails, bolts, studs, as well as metal plates and corners are used to strengthen the knots. Additionally, wooden bars or plates are used.

Mounting Methods:

• teeth into a thorn
• point-blank teeth
• stop at the end of the crossbar.

The use of metal fasteners does not reduce the bearing capacity, since they do not need to be tapped, in contrast to fastening, for example, by the method of teeth into a tenon.

Rafters can be not only wooden, but also metal. For fixing metal rafters, various corners, brackets, mounting perforated tape, plates, bolts with nuts or self-tapping screws are used.

Mauerlat mount

If the wall is concrete, then a reinforced stiffening belt is made in its upper part, in which studs are provided. Mauerlat will be attached to them.

Rafters to the Mauerlat can be attached in two ways: rigid and sliding.

The first way is more popular. For fastening, special corners with a support bar are used. There are several ways to attach the rafter to the Mauerlat.

• Each rafter is nailed with three nails: two of them must be crossed, and the third is located vertically.
• Fastening with a bracket: one end of it is hammered approximately into the middle of the support beam, and the other is turned 90 degrees and hammered into the rafter.
• Fastening with wire rod: a clamp is made from a wire folded in 4 rows, with which the rafter is screwed to the timber. Instead of wire, a special perforated tape is also used. Sometimes this method is used in addition to other fastening methods.
• With the help of corners: the corner is screwed with screws to the Mauerlat and the rafter leg. It is better to use corners with two rows of holes and a stiffener.

The disadvantage of the hard method is that when the building settles, damage to the walls is possible. Therefore, rigid fastening is used in brick buildings.

The sliding method implies that the rafters are connected to the Mauerlat with such fasteners that do not prevent their movement within certain limits. This method is used in wooden buildings that can settle. With the help of special fastening methods, it is possible to achieve that the rafter will have one, two or three degrees of freedom. In the latter case, a special hinge is used.

One degree of freedom means that the rafter can turn in a circle. In this case, they are fastened with one nail or screw. The two degrees of freedom are circular rotation and horizontal displacement. For this, the rafters are attached to the Mauerlat with metal brackets. Special corner-sleds are also used.

With a sliding connection in small buildings with a not very heavy roof, the fastening is done without cuts. If the building is large, it is recommended to do this knot with a gash on the rafter leg.

Important! Washed down is cut out on the rafters, and not on the Mauerlat, so as not to damage or weaken the beam.

In this case, the fixation can be either rigid (with emphasis on the beam) or movable (with a tooth on the outside). Sometimes, instead of sawing out a tooth, an additional bar is used.

Ridge connection

After the rafter leg is fixed on the Mauerlat, they move on to the ridge attachment point. This connection can be made in three ways: butt, to the ridge run and overlap.

For butt fastening, the rafters are sawn in the upper part at an angle equal to the slope of the roof, and connected with nails (150 mm), driving them into the upper planes of the rafters, so that the nails enter the end of the opposite rafter. For strength, a metal plate or wooden plate is attached, which is also nailed or attached with bolts.

When attaching to a ridge run, a ridge beam (run) is additionally laid between the rafters, this method is more laborious.

When fastening with an overlap, the rafters located on opposite sides overlap each other and touch the side surfaces. They are connected with bolts, nails or studs.

beam knot

The rafters are attached to the beams as follows. The main task of fastening is to prevent the rafters from sliding along the beam, so various techniques are used.

1. In the heel of the rafter, it is necessary to cut a tooth and a spike, and an emphasis of the appropriate size is cut out in the beam.
2. From the hanging edge of the beam, the attachment point should be 25-40 cm away.
3. The mounting socket should be 1/4 - 1/3 of the beam thickness deep.
4. Together with the tooth, a spike is cut out, which prevents the rafter from moving sideways. Such a connection is called a "tooth with a spike and an emphasis."

If the roof is flatter (its angle of inclination is less than 35 degrees), then the rafters are fixed in such a way that the area of ​​​​their contact with the beam increases. Then use the following methods:

When creating a truss system for a roof, it is important to remember the following.

• All wooden elements are treated with an antiseptic and a refractory compound before installation.
• The thickness of any wooden part should not be less than 5 cm.
• Rafters without racks and struts are not made longer than 4.5 m.
• Mauerlat should be located strictly horizontally.
• Racks and struts are recommended to be done as symmetrically as possible.
• You can not add elements to the calculated truss system - this can lead to the appearance of loads where they are not needed.
• At the junction of wood with stone (brick) masonry, waterproofing is needed.

Properly made truss system is the key to the reliability of the roof. It is the rafters that take on the entire weight of the roofing materials and resist wind loads. Therefore, it is very important to build a truss system in compliance with the technology.

Is it possible to single out some main detail in the roof? It is unlikely that this will work, since here each element performs its function. For example, a rafter is a part of a roof that has slopes, which can be called a frame. It is on them that the roofing material will be laid, other elements will be attached. It is on how the truss system is assembled and installed that the final shape of the roof will also depend. But if the work on creating the roof is done independently, then how to fix the rafters? In fact, this is a rather complicated stage of work, on which strength, reliability, and even the geometric correctness of the roof will depend.

The rafter system is a roof frame with slopes, assembled from the rafter legs themselves, as well as a Mauerlat and a ridge beam. Mauerlat is a support beam, which is located along the perimeter of the upper part of the walls of the house, and the ridge beam is installed directly in the upper part of the roof at the place where two opposite rafter legs are connected at an angle.

Designing a truss system is an important task, during which you have to correctly calculate the wind and snow loads that will fall on the roof, as well as take into account other parameters. The first indicators will depend on the climatic region in which the facility under construction will be located. Further, based on the data obtained, the thickness of the walls of the house (bearing) is directly calculated, and the quality and type of material for the roof itself is selected, the angle of inclination of its slopes and other points are calculated.

Attention! Shortcomings and errors made during the design can adversely affect the quality of the roof. In some cases, they can lead to rapid collapse or destruction of the roof.

The design of the rafter system may include the rafters themselves, the ties that will be located between them, runs, additional supports - the so-called rafter legs - and other elements. The assembled truss system usually relies on the same Mauerlat or on floor beams. Mauerlat helps to evenly distribute the load around the entire perimeter of the walls. This is the main difference between this method of attachment. If you fasten the truss system to the floor beams, that is, without installing a Mauerlat, then the main load will fall on the attachment points, and not be distributed evenly over all walls.

On a note! The latter case is not an option if the walls are made of brick, which will begin to collapse over time in places experiencing maximum load. But for a wooden frame, this method is quite suitable.

Table. The dependence of the cross section of the rafter legs on their length and pitch.