Roof fasteners. Rafter system nodes - how to make a reliable roof? How to connect the elements of the roof structure

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

Requirements for the truss system

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

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

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

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

Varieties of truss systems

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

• Hanging rafters;
• Overhead rafters.

Hanging truss system

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

Attention! The role of the tightening may not necessarily be performed by a wooden beam, it can also be a ceiling made of reinforced concrete structures, 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 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.

The main attachment points of the truss structure include:

• Beam knot;
• Mauerlat knot;
• Skate knot.

beam knot

With such a node for connecting elements, an insertion of teeth into a spike is made into the rafter, and a recess corresponding to the teeth is made in the transverse section of the crossbar. Such a recess or nest should not exceed 30% of the timber thickness.

Fastening is carried out with special hardware with metal corners, or wooden beams, spikes and overlays.

Attention! If the roof is made of materials with low weight, and the slope of its slope does not exceed 35º, then the bases of the supports should be placed so that they rest against an area larger than the beam itself.

Mauerlat knot

Such fastening can be performed both by rigid technology and by sliding technology. Rigid technology involves the installation of a strong connection between the Mauerlat and the rafters, preventing the possibility of slipping, deflecting or popping out. For this, special support corners with bars are used. The resulting knot is fastened with wire using hardware. At the same time, nails should be hammered obliquely so that they enter the wood crosswise. The last nail must be driven in vertically.

In the case of a sliding fastening, alignment is performed using a special mechanism that allows you to move the rafter leg in the required direction. To do this, a tie-in is made on the supports, on which the Mauerlat is then laid. The structure is fixed, as in the previous case, with crossed nails. This method of arranging the connection nodes allows all nodes of the truss structure to move within certain limits.

Attention! Rigid fastening with inexperience of builders can lead to damage to the walls of the building.

ridge knot

In this case, the fastening can also be made in two types - butt and overlap. With a butt joint, the top of the supports is cut with a bevel, as is the angle of the roof. They rest on the same undercut opposite supports. Fastening is carried out using nails, in the amount of two pieces. They are hammered from above at a certain angle. The seams that form between the supports are connected with metal plates or plates. In the second case, fastening is carried out by overlapping, not by end parts, but by lateral sections and fixed with bolts.

Conclusion

When performing work on the installation of the roof, the arrangement of the truss system should be given careful attention, avoiding disruption of technological processes. This will provide the structure with strength, durability and reliability.

In order for the constructed building to serve for more than one year, it needs both a reliable foundation and a strong roof system that resists the vicissitudes of the weather. The roof must withstand heavy loads with dignity: heavy snowfalls, sharp gusts of wind, torrential downpours. The roof truss system is best suited for this.

Roof trusses and its types

The truss system is the basis of the roof, which focuses on the load-bearing elements of the structure and also serves as a frame for various types of roofing materials: insulation, waterproofing, various coatings.

The dimensions and design of the rafters depend on:

• purchased material;
• the size of the building;
• dimensions of the house;
• building material for rafters;
• individual preferences of the customer;
• roof loads relevant for a particular region.

The rafter system has:

• crate - bars, in a perpendicular direction, fit on the rafter legs;
• screeds that perceive tensile forces;
• wooden racks, located in a vertical position;
• mauerlat - a bar, the installation of which is carried out along the wall, the rafters focus on it;
• rafter legs are a kind of wooden beams that take on the main load of the roof.

Each of these factors is very important, because it is necessary to understand what type of truss system will be best suited for a particular situation.

When it comes to low-rise buildings, wooden structures are the most common. In many cases, three types of truss trusses are used: hanging rafters, layered rafters and a mixed rafter system.

Characteristics of hanging rafters

Hanging rafters are the most elementary type of truss systems, their characteristics:

If the roof of the house is of complex construction, the types of rafters can be alternated. For example, in the presence of supports or the middle main wall, they install layered rafters, and in the absence of such elements, hanging rafters.

Features of layered rafters

For a layered rafter system, the house must be additionally equipped with a load-bearing wall located in the middle. There are layered rafters according to the following features:

The design of the combined system is the most complex, since it includes parts of two other types of rafters - hanging and layered. It is used for mansard roofing. The walls of the rooms, which are located on the second floor, form vertical supports, these supports are also intermediate racks for truss beams.

Part of the rafters that connect one end of the uprights functions as a crossbar for the slopes located on the side, and for the upper part of the structure they are a puff.

At the same time, the horizontal bars perform the following functions: for the upper slopes - a Mauerlat, for the side ones - a ridge beam. To increase the strength of the roof, struts are mounted that connect the side slopes and vertical racks.

The combined sling system is the most complex and time-consuming to manufacture, but these shortcomings are fully compensated by an increase in the bearing qualities of the roof in the absence of extra supports, especially when there is a need to cover significant spans in the building.

You can increase the bearing qualities of the roof using a mixed truss system

Rafter trusses for various types of roofs

During the construction of a certain building, roof systems of one kind or another are necessarily used, and the type of roof will completely depend on the design of the future building.

Rafter truss for a gable roof

A gable roof is a common roof construction for residential buildings that have no more than three floors. Preference is given to just such a design because of the technical characteristics of the inclined shape of the truss system, and also due to the fact that installation work is carried out easily and simply.

The truss system of a gable roof includes two rectangular inclined planes. The upper part of the building from the front side resembles a triangle. The main components of a gable roof are the Mauerlat and rafter legs. In order to properly distribute the load along the rafters and walls, struts, crossbars and racks are mounted, thanks to which you can create a durable, rigid, elementary and easy installation scheme for a gable roof structure.

A gable roof is considered the simplest roof system; it is used for residential buildings no more than three floors.

On top of the rafters, you can mount a sparse crate or a solid one, and then attach a bituminous coating, tiles or some other type of material to it. The rafters and sheathing itself are usually made of beams or boards, which are fastened with nails, bolts or metal fittings. Metal profiles can be used as rafters, due to which significant spans overlap. There is no need to use extra racks and struts.

The device of the truss system for a gable roof allows you to evenly distribute all the existing load along the perimeter of the building. The lower ends of the system focus on the Mauerlat. They are fixed with metal fasteners or staples. By the angle of inclination of the bars for the rafters, you can determine at what angle the roof slopes will be inclined.

The truss system for a gable roof allows you to evenly distribute the load from the roof along the perimeter of the building

Rafter system for a hip roof

When arranging a system for a hip roof, you will need to install different types of rafters:

• conjurers (shortened);
• side;
• hip main;
• sloping (diagonal elements that form a slope in the shape of a triangle).

The rafter legs located on the side are made of board, and they are mounted identically to the details of a traditional pitched roof with a layered or hanging structure. Hip main rafters are layered parts. For sprigs, boards or bars are used, which are attached not only to the Mauerlat, but also to the diagonal beams.

To install this type of construction, the angle of inclination is accurately calculated, as well as the cross section of the sloping beams. The dimensions of the parts also depend on the length of the span.

So that the hip roof does not deform from a heavy load, you should accurately calculate the angle of inclination of the diagonal beams for the rafters

Observe symmetry when installing diagonal beams for rafters, otherwise the roof is deformed from a significant load.

Rafter system for sloping roofs

A broken roof is a construction with rafters, which consist of several separate elements. Moreover, they should be located at different angles relative to the horizon. And since the lower rafter part is almost vertical, the attic of the building receives additional space, so that it can be used as a living space. The device of this type of roof is carried out during the construction of a four- or gable rafter structure.

Professionals need to calculate a four-pitched rafter system, but a gable broken roof can be made independently, since its installation is very simple. To do this, it is necessary to install a support frame, which should consist of runs, as well as racks. Horizontal parts are fixed with hanging rafters. But to the Mauerlat, the supports of the sloping roof are fixed with shortened legs of the rafters.

The assembly of rafters for a broken gable roof can also be performed by non-professionals, since the installation of such a roof is very simple.

"Cuckoo" in the roof truss

The so-called cuckoo on the roof is a small ledge that is located on the attic floor. Here is a window for better illumination of the attic room. The installation of the "cuckoo" is carried out carefully, while controlling the parameters of the entire structure: the depth of the cut, the angle of inclination and other factors. However, before that, the necessary measurements are made.

The first stage of work begins with the installation of a power plate (a beam with a section of 10x10 cm, which is needed to support the lines). The truss system acts as a skeleton for the roofing material. To stiffen the structure, spacers are used, which are mounted between the two legs of the rafters.

After the installation of the truss truss is completed, a sheathing is laid, the type of which depends on the roof covering purchased. The installation of the crate is done continuously or with a certain step. Boards, OSB and plywood sheets are usually used for it. In addition, the installation of roofing material must be identical throughout the entire roof.

The main difficulty in installing such a rafter system is the location of the internal corners. In these places, snow can accumulate, which means that the load will increase, which is why a continuous crate is made.

"Cuckoo" on the roof is called a small ledge on the attic floor, under which there is an additional window

Chalet roof truss truss

A feature of a device of this design is the removal of visors, as well as overhangs outside the house. In addition, there must be rafters and beams for the roof, which extend up to three meters on the sides of the building. Each of these elements is fixed with a bracket to the wall of the building in the lower part. Next, tie the edges of the beams. They serve as a support for covering the roof of the building.

But when creating large overhangs, it is necessary to install the reinforced belt in parallel with the installation of the Mauerlat studs. It is necessary to make anchors that help fix the consoles. In this case, the rafters will be perfectly fixed with anchors and, in addition, tie-ins.

To carry out the side cornices, a ridge beam is made, after which beams are taken out at the Mauerlat level, which must be identical to the length of the ridge. The truss is based on these structural details, and in the future - building material for the roof.

When designing a building, the angle of the roof-chalet is calculated based on the characteristics of the local climate and other factors. With a slope angle of about 45 °, the load from snow is not taken into account, since with this option it will not linger on the roof. At the same time, the sloping roof will withstand the load from the snow, but it is necessary to install a reinforced roof truss. Before installing the roof-chalet, a building project is prepared, because the originality of the roof itself, as well as long cornices and its overhangs, oblige this.

The roof in the style of a chalet is characterized by visors, taken out several meters outside the house.

Roof truss designed for soft roofing

Soft roofing is done in various ways, but there are common characteristics in the technological methods of its construction. Initially, you need to prepare. When equipping a roof for a house made of foam concrete or other material, a Mauerlat is first installed, then a cut is made under the ceiling beams in increments of up to one meter in the upper crowns of the building. The distance between the boards is calculated based on the type of rafter structure.

1. Mount individual parts of the rafter system. To completely eliminate the risk, the boards of the rafter legs on the ground are attached with screws. After creating a truss truss, it is raised to the top of the building.
2. All elements of the rafters are fixed with ceiling overlap, internal boards, jibs, and also crossbars. Further, this basis for the roof will become a single whole structure.
3. The next stage is a crate, which is installed under a soft roof with small gaps or no gaps at all. Gaps of no more than 1 cm are allowed. Quite often, leveling plywood is installed on top of the boards. Its sheets are laid according to the brickwork method. The resulting joints do not align with the gaps between the plywood and the board.

If the length of the boards of the crates is not enough, then the joints of the parts must be located in different places. In this way, areas that have been weakened can be correctly distributed.

Self-manufacturing of the truss system

Before the installation of the truss system begins, the Mauerlat must be fixed to the longitudinal walls with anchors. Next, you need to decide on the desired section of the legs for the rafters, depending on the distance and their length. If there is a need to increase the length of the rafters, then connect them with various fasteners.

When using different insulation, you need to choose the ideal distance between the elements of the rafters in order to reduce the number of thermal insulation scraps.

Installation of the truss system must be carried out in the following order:

1. A template is made according to which the farm is assembled. 2 boards are taken, corresponding to the length of the rafters, and connected to each other from only one edge with a nail.

   
   A rafter template called "scissors" will help you quickly assemble the entire roof truss system

2. You get a design called "scissors". Its free edges are placed on supports at the points of contact of the rafter legs. The result should be the final angle, that is, the angle at which the roof slope will be tilted. It is fixed with several long nails and transverse boards.
3. A second template is made, thanks to which the cuts on the rafters are installed. It is made from plywood.
4. Special mounting cuts are cut out on the rafters (a prepared template is used for this purpose) and connected at an angle of inclination of the slope. You should get a triangle that rises to the roof along the stairs. Next, it must be attached to the Mauerlat.
5. Initially, two side gable rafters are mounted. Their correct installation in the vertical and horizontal plane occurs due to temporary struts attached to the rafters.

   
   For the correct installation of the entire rafter system, the first pair of rafters is installed on the roof

6. A cord is stretched between these tops of the rafters. It will indicate the future skate and the level of other rafters located in the gap.
7. Raise and mount the remaining rafters at the initially calculated distance, which should be at least 60 cm from each other.
8. If a bulky construction of rafters is provided, then it is additionally strengthened with struts, supports, and so on.

   
   The bulky construction of the rafters is additionally reinforced with struts and supports.

9. On special supports, a ridge beam is installed, to which not only short, but also diagonal and intermediate elements of the rafters are attached.

   
   Proper fastening of the ridge beam ensures the reliability of the entire rafter system

Typical nodes of a standard truss system

The structural strength of the rafters depends on the ideally selected section of the boards, as well as on the high quality of the rafter units. The connection of parts for the roof structure is done in accordance with established rules.

The main typical nodes in the truss system:

• supporting knot of rafters on the Mauerlat;
• ridge;
• a node for combining the upper puffs and the entire truss system;
• fixing the strut, rack, as well as rafters and beams.

After the design of the rafter system has been chosen, it is necessary to draw up a plan in which to select all the nodes. In each design, they are made in different ways, since it depends on different nuances: the type of roof, its size, and the angle of inclination.

A rafter from a profile pipe is a metal structure that is assembled using lattice rods. The very production of such farms is a very time-consuming process, but also more economical. Paired material is used for the manufacture of rafters, and scarves are connecting elements. The construction of rafters from profile pipes is assembled on the ground, while riveting or welding is used.

Thanks to such systems, any spans are blocked, but it is necessary to make the correct calculation. Provided that all welding work will be done with high quality, in the future it remains only to transfer the structural elements to the top of the building and assemble them. Bearing rafters from a profile pipe have many advantages, such as:

Crossbar in the truss system

Rigel is a fairly broad concept, but in the case of roofs it has a certain meaning. The crossbar is a horizontal bar that connects the rafters. Such an element does not allow the roof to "burst". It is made of wood, reinforced concrete, and also metal - it all depends on the type of structure. And the crossbar serves to distribute the load exerted by the truss system.

It can be fixed in various places between the legs of the lines. There is a direct pattern here - if the crossbar is fixed higher, then the timber for its installation must be selected with a large cross section.

There are many ways to fix the crossbar to the truss system:

• bolts;
• nuts;
• studs with washers;
• special fasteners;
• nails;
• mixed fasteners, when different types of fasteners are used in parallel.

Mounting exists with a tie-in or overhead. In general, the crossbar is a design unit, as, indeed, the entire roof sling system.

The crossbar in the truss system is designed to reinforce the roof structure

Rafter system fastening

To ensure the reliability of the rafter system, it is necessary to initially find out how they are fastened to the supporting roof and the ridge. If fastening is done to prevent deformation of the roof during shrinkage of the house, then the rafters are fixed on top with a hinged plate or a nut with a bolt, and on the bottom with a sliding support.

Hanging rafters need a tighter and more reliable fastening in the ridge, so in this case you can apply:

• overhead metal or wooden plates;
• cutting method;
• connection with long nails.

In the layered system, the rafter legs are not connected to each other, since they are attached to the ridge run.

The rafters are fastened to the Mauerlat by cutting down, which is done in the rafter leg. Thanks to this method of fastening, the support of the roof will not be weakened. Cutting is also done when installing rafters on floor beams. In this case, the cut is also made in the support beam.

Video: how to make rafters with your own hands

Thus, a perfectly matched system of rafters and their structural characteristics will help create the basis for a reliable roof for your home.

December 12, 2017
Specialization: facade finishing, interior finishing, construction of dachas, garages. The experience of an amateur gardener and horticulturist. He also has experience repairing cars and motorcycles. Hobbies: playing the guitar and much more, for which there is not enough time :)

Any roof is subjected to various loads every day, as it is affected by wind, precipitation, and it also holds the roofing. In order for the roof to cope with all these loads for many decades, it must be properly designed. Therefore, for everyone who wants to do construction on their own, I recommend to figure out what parts and nodes of the truss system exist, and what function they perform.

Frame elements

All details of truss systems can be conditionally divided into two types:

• Basic. These parts form the roof frame, called the truss system. Not a single roof can do without them;
• Additional. This group includes elements that may be present in some types of roofs, while others do without them. The task of additional elements is to increase the rigidity and strength of the frame.

Main knots

So, the following elements belong to the main nodes and details of the truss system:

• Mauerlat. This, one might say, is the basis of all roofing systems, since rafter legs rest on the Mauerlat. Its design is extremely simple, in fact, it is an ordinary bar (a log in log houses), laid along the perimeter of the walls. Its task is to evenly distribute the load from the roof to the walls of the building.

I must say that at a gable roof, the Mauerlat can be located not along the perimeter, but only on the side walls, since there are pediments on the end walls, which are a continuation of the wall;

• Rafter legs (hereinafter CH), or simply rafters. These parts are the supporting element that forms the slope and its angle of inclination. They take on the wind and snow load, as well as the weight of the roofing material, and transfer it to the walls through the Mauerlat and other elements.

Rafters are lateral (main), diagonal (installed at the junction of hip roof slopes) and shortened (diagonal rafters rely on Mauerlat);

• Rafter farms. They are formed by paired (reciprocal) rafter legs. It must be said that truss trusses are present on all pitched roofs except for shed roofs, since they do not have reciprocal rafters;
• Skate knot. It is the top of the roof truss, i.e. formed by the junction of two CHs. The ridge knot, like the trusses themselves, is absent only from shed roofs.

That's all the main knots of wooden roof structures that form them.

Additional

Additional details include:

• Run. This is a horizontal beam that connects all CHs within one slope;
• Skate run. It is the same horizontal beam as a regular run, but which runs in a ridge knot, i.e. connects two legs of each truss at the same time.

I must say that the ridge run can be installed in several ways - above the junction of the rafters, in the center of the junction, i.e. legs rest on the run, or under the rafters;

• Puff (bolt, fight). It is a beam that connects two reciprocal legs, preventing them from moving apart. We can say that the tightening removes the spacer load from the bearing walls;

• Supports. Can support rafters, all types of runs or puffs. Supports transfer the load to the internal walls of the building, columns or ceilings;
• Struts (rafter legs). They are inclined supports, which have the same function as the vertical racks. The only thing is that they support only the legs, i.e. are one of the elements of wooden trusses. Rafter legs transfer the load to the load-bearing elements of the building, or to the ceiling;
• Filly. These elements form the overhang of the slope in the event that the CHs do not go beyond the walls. In fact, they lengthen CH, i.e. are their continuation.

That's all the elements that make up the frames of pitched roofs.

A few words about the types of systems

So, we figured out the nodes, now let's look at the main types of truss structures. There are several of them:

• Shed. As I said, these structures do not have trusses. The angle of the slope is formed due to the different heights of the walls on which the CHs are laid, or due to the run, which is laid on racks installed on one of the walls;

• Gablesloping. Rafters are called rafters, which are supported by racks or struts that transfer the load to the internal load-bearing elements of the building. The frame of such structures is formed only by trusses, i.e. they do not have diagonal legs.

• gable hanging. Hanging rafters differ from layered rafters in that they transfer the entire load from the roof only to the outer walls;

• Hip. Unlike gables, at the ends instead of vertical gables they have inclined hips, i.e. end slopes. As I said, the hips form diagonal and short legs;

• broken lines. They are a gable structure, each CH of which is divided into two parts and is located at a different angle. Skating, i.e. the upper legs form a gentle slope, and the lower legs are steep. This design allows you to increase the attic space, as a result of which it can be used as an additional floor.

Typical broken (mansard) systems have racks on which the upper and lower CHs rest. The reciprocal racks are interconnected by puffs (attic floor beams).

There are also semi-mansard structures, which, in fact, are the usual hanging gable roof systems. The only thing is that their fastening with a Mauerlat is usually made sliding (movable), which allows you to increase the CH deflection, and thereby reduce the spacer load on the walls.

Despite the fact that the designs of all the above systems are different, they consist of the same parts that we have already familiarized ourselves with.

One last thing about fasteners

Finally, I propose to consider how the connections of the main nodes are made, such as:

• Rafter / Mauerlat;
• Skate knot.

The rest of the details do not deserve special attention, since their docking most often occurs by washing down the interface (to increase the area of ​​\u200b\u200bfitting the parts) and lining the steel plastic / corners, which are fixed with screws. Sometimes fasteners are not even used, i.e. parts are fastened to each other with screws without any overlays.

Connection of rafters and Mauerlat

The leg and Mauerlat mount can be made in several ways:

• With grooves. In this case, grooves are cut out under the Mauerlat, into which CH is inserted. Then it is additionally attached to the Mauerlat on both sides with a steel corner;

• Tooth and thorn. This method is usually used to attach the CH to the puff. Its principle is based on the fact that a spike is selected at the end of the sawed CH, and a groove is selected in the puff. In addition, the leg itself rests against the so-called tooth, i.e. protrusion in the puff, which takes on the expansion load.

It must be said that in recent times, fasteners such as a tooth with a spike are rarely used, since it is much easier to use special fasteners, the same corners and plates;

• By washing down. In this case, the CH is sawn so that a right angle is formed at the junction with the Mauerlat, as a result of which the rafter not only rests on the beam, but also rests against its side surface, thus transferring the spacer load. I must say that instead of washing down, you can fix the bar, as shown in the diagram below.

Connection of rafters and ridge run

The connection of CH and run can be done as follows:

• With a groove. In CH, two reciprocal cuts are made, as a result of which, after the junction of the rafters, a groove is formed for the ridge run;
• Hard pinching. The principle is based on the fact that puffs are installed under the run and above it;

• Got drunk on the way. This is the simplest and most common method, the principle of which is based on sawing CH for maximum fit to the beam. In this case, fixation is carried out with a steel corner.

Here, perhaps, are all the main nuances of assembling truss systems.

Conclusion

We have found out what parts the truss systems consist of, what types they are and how their main elements are connected. If I missed some points or something is not clear to you - write comments, and I will be happy to answer your questions.

December 12, 2017

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In order for the roof to have high strength and reliability, special attention will be required to be paid to the truss system. In addition to correctly made calculations and drawings, fasteners for rafters and all its elements are of no small importance in the stability of the structure.

Construction of the truss system.

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

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

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

The main nodes of the connection of the truss system

The scheme of fastening the Mauerlat to the wall.

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

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

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

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

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

The main nodes of roof trusses.

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

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

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

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

Sliding connection example..

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

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

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

Nodal ridge connection

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

Scheme of the ridge connection of the truss system.

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

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

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

Types and features of metal fasteners for rafters

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

Types of fasteners for rafters.

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

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

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

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

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

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

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

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

Fasteners for rafters: the strength and reliability of the roof

In order for the roof to have high strength, fasteners for rafters require special attention. The type of connection will depend on the shape of the roof and the type of rafter system.

Fastening rafters to the Mauerlat: connection methods

Rafters are the main load-bearing structural elements of the roof. Proper and reliable fastening of the rafters to the Mauerlat eliminates the risk of deformation and collapse of the roof under its own weight and external loads.

Basic fasteners

To install the rafter legs on the Mauerlat and firmly fix them, various types of cuts (inserts) and metal truss fasteners are used:

• wire ties;
• corners;
• plates;
• brackets WB;
• corner KR;
• fasteners LK;
• self-tapping screws;
• nails;
• perforated mounting summer TM;
• bolts, studs complete with nuts and washers.

The connection of rafters and mauerlat can be done using brackets. In this case, no tie-in is made in the rafter, so this key structural element is not weakened. Brackets for mounting are made of 0.2 mm thick steel with anti-corrosion zinc coating. The brackets are attached to the wooden beam and rafters with self-tapping screws, nails or anchor bolts.

Fasteners LK allow you to attach the rafter to the Mauerlat, as well as connect other elements of the system. When installing this fastener, anchor bolts are not used.

The use of perforated mounting tape allows you to strengthen the connection node. The perforated tape makes the connection of the rafters with the Mauerlat more durable, does not weaken the supporting structures, as it does not violate their integrity. For its installation, screws or nails are required.

The KR corner and its modifications are a widely demanded fastener of the truss system. It is used if necessary to securely install the rafter legs on the Mauerlat. The corner adds strength to the connection nodes, increases the bearing characteristics of the structure, eliminates the displacement of the rafters under high operational loads. The corner does not need to be cut into the wooden elements of the truss system, it is mounted with self-tapping screws or sharp nails (equipped with special protrusions).

Metal fasteners for the truss system must be made of high-quality material with reliable anti-corrosion protection - this guarantees its strength and durability.

In what cases is a Mauerlat required?

Mauerlat is often called the foundation of the roof. This design, made of logs or timber, allows not only to securely fasten the rafters, but also to ensure uniform load transfer to the walls and foundation of the structure.

During the construction of houses from timber or logs, the role of support for the rafters is performed by the upper wall trim, installation of additional structures is not required.

For structures whose walls are made of piece materials (brick, foam concrete or aerated concrete blocks, etc.), the installation of a Mauerlat is necessary. This is due to the fact that walls of this type do not cope well with point, undistributed loads. In addition, foam blocks are not strong enough to securely fix the truss system - fasteners under load can be torn out of the block. Thus, the installation of a Mauerlat is required.

In order for a wooden beam laid on the longitudinal walls of the building or along the entire perimeter (depending on the type of roof) to be firmly attached to the base, it is recommended to first create a reinforced concrete belt in the upper part of the walls. In a monolithic beam with a height of 200 mm and a width coinciding with the width of the wall, fasteners for the support beam are embedded. These are anchor bolts or studs with a diameter of 14 mm or more, located strictly vertically. To eliminate the possibility of tearing them out of concrete under high load, the lower ends of the studs or bolts should be bent. Mortgage fasteners are located in increments of no more than 1.5 m.

The use of studs with a diameter of less than 14 mm can lead to deformation of the fastener under loads.

In the beam from which the Mauerlat is mounted, holes should be made corresponding to the location of the studs. The beam is put on the studs, washers are put on the free threaded end of the fasteners and nuts are screwed on. This technology allows you to securely fix the roof base on the wall.

Before installing the timber, it is required to lay a waterproofing layer to prevent damage to the wood under the influence of moisture.

Principles of attaching rafters to Mauerlat

Installation of rafters on a support beam may be required when creating expansion and non-expansion truss structures. The installation of layered or hanging rafters on the Mauerlat is carried out using a rigid or sliding connection. Depending on the design features, the methods of attaching the rafters to the Mauerlat are selected.

A rigid connection implies the complete exclusion of the displacement of elements relative to each other, the absence of such influences as shear, torsion, bending. The necessary rigidity of the connection is ensured if the rafters are attached to the Mauerlat with corners with a support bar, or a special “saddle” cutout is made in the rafter leg. The place of the cutout in the rafter is additionally fixed with self-tapping screws, nails, staples, bolts. In addition, it is necessary to perform a wire twist, which connects the rafter attachment to the Mauerlat and the anchor mounted in the wall.

During the construction of the roofs of wooden houses, a special fastener (“sled”) is used, which allows you to make a sliding connection. The attachment point of the rafters to the Mauerlat with a certain degree of freedom of the rafters makes it possible to avoid deformation of the roof during shrinkage of a house made of timber or logs.

Installation of rafters using a corner

When choosing how to attach the rafters to the Mauerlat, it is necessary to proceed from the design features of the roof. If we are not talking about wooden buildings, then the articulation should be rigid.

If the installation of the rafters is carried out with a “saddle” cut, then the technology of work is as follows:

• a cut is made in the rafter leg so that the horizontal part of the rafter can be installed on a wooden beam, while the angle of inclination of the rafter leg must correspond to the angle of inclination of the slope;
• the rafter is fixed with three nails, two of which are driven in on both sides of the rafter leg at an angle (crossing must occur inside the Mauerlat), and the third nail is driven in vertically from above;
• additionally, the attachment point is fixed with brackets, wire rod.

Such fastening of the rafters to the Mauerlat provides the necessary rigidity and strength of the assembly.

A fairly common technology is the installation of rafters using a metal corner and a hemmed beam. The rafters are attached as follows:

• the rafter leg is cut at the required angle to ensure the slope of the roof slope specified by the project;
• along the edge of the mauerlat, a hemmed beam is mounted, the length of which is about 1 meter, the rafter firmly rests against it along the pressure line - this design eliminates the shift of the rafter leg under thrust loads;
• on the sides, the rafter should be attached to the Mauerlat using metal corners - fastening the rafters to the Mauerlat with these elements makes it possible to avoid transverse displacement of the rafter leg;
• the finished attachment point is additionally reinforced with wire rod.

The fastening of the rafters to the Mauerlat should be carried out following the instructions, the details of the work technology can be found in the video.

The rafters are attached to the wooden support beam using special corners. The subspecies of the corner of the KR include:

• models KR11 and 21 (improved KR1 and KR2) are equipped with oval holes for anchoring, which can significantly reduce the risk of breaking the fastener when the building settles or the structure is loaded;
• model KP5 allows you to fasten structural elements with a high load-bearing capacity;
• model KR 6 (reinforced angle) is made of 3 mm steel, has an oval hole for anchoring, and is used for mounting heavy structures.

The load-bearing and auxiliary elements of the wooden truss structure are also fastened using a KM mounting bracket made of perforated steel. Its advantages include the possibility of fastening with self-tapping screws and screws, the absence of the need to use special equipment for installation.

The KMRP reinforced elbow is used for 90° connections. Its use allows you to securely install wooden rafters on the support beam. The angle can be adjusted.

Proper fixation of the rafter legs on the Mauerlat is a guarantee of durability and reliability of the roof structure. The scheme for attaching rafters to the Mauerlat may be different, but there are general installation rules:

• it is important to ensure a snug fit of the planes of the wooden elements, which requires accurate and accurate cuts and cuts;
• using bolted connections, it is necessary to install washers or metal plates in order to avoid sinking the nut into the wood - this can lead to the destruction of the fastener.

It is forbidden to use linings, as they deform over time, which leads to an incorrect distribution of loads on the roof and entails deterioration in performance, destruction.

Fastening rafters to the Mauerlat: how to fasten, attachment point, methods

Learn how to attach rafters to the Mauerlat. Types and methods of connecting rafters, a diagram of Mauerlat fasteners and rafters along with a video.

How to choose the right fasteners for mounting the truss system

The frame of the truss system and the foundation of any roof is the Mauerlat. In wooden houses, its functions can be performed by the upper crown of the log house, and a powerful base made of timber is mounted on brick and concrete walls.

Mauerlat mount

1. In houses made of glued laminated timber or logs, Mauerlat is not required. If the height of the bearing walls is not enough, an additional mauerlat crown is laid. For its fastening, forged brackets and steel pins (thorns) are used.

2. Mounting the Mauerlat on brick walls is possible in several ways:

- in the process of laying load-bearing walls to a depth of 3 or more upper rows of bricks, studs with a diameter of at least 14 mm are immured. The lower end of the stud should be bent at a right angle in the shape of the letter "L". The length of the free part of the hairpin should be 3-4 cm more than the thickness of the Mauerlat;

- at the final stage of laying the bearing walls, a reinforced belt is poured. “L”-shaped studs or anchor bolts with a diameter of at least 14 mm are embedded in it. The length of the open part of the fasteners should be 3-4 cm greater than the thickness of the Mauerlat.

The distance between the studs (anchor bolts) is selected as a multiple of the pitch of the rafters and is equal to 1.0. 1.5 m

Before installing the Mauerlat, a layer of waterproofing material must be laid on the stone walls.

Rafter fastening

1. Houses made of logs or timber shrink during operation, and their geometric parameters change. In such conditions, the roof must have some independence. With a rigid fastening of the rafter system, the roof of a wooden house warps, and the roofing materials are destroyed. In the worst case, this can lead to the destruction of the frame of the house, so the joints of the rafters are made movable.

The rafters in the ridge can be attached in two ways:

– movable connection with M16 bolt;

- connection with a lamellar hinge. In this case, on each rafter with 4 M10 bolts. M12 are attached by two steel plates. The role of the hinge is performed by the M16 bolt.

The fastening of the rafters to the Mauerlat is carried out using the so-called “sled”. The bracket and bracket are fastened with nails, while the rafter has the ability to move slightly relative to the Mauerlat along its longitudinal axis.

2. If the house is made of brick or cinder block, rigid fastening of the rafters is used. In this case, the ridge connection is performed in the following ways:

- fixed butt joint. In this case, the rafters are fastened with nails, and the entire assembly is reinforced with an additional steel or wooden lining - a crossbar. The crossbar is attached to the rafters with M10 bolts. M12 or nails, respectively;

- a fixed connection with a half-tree tie-in. In this case, the rafters are connected with an M16 bolt, and the knot is reinforced with a crossbar.

The rafters are fastened to the Mauerlat using reinforced steel corners. M10 bolts are used to fasten the corners. M12 and nails.

Clamps, wire ties and mounting perforated tape are used as additional fasteners for fixed assemblies.

All threaded connections are made using metal washers or plates.

When fastening construction details with nails, the following rule must be followed: the length of the nail should be 2-3 times the thickness of the element being punched.

How to choose the right fasteners for mounting the truss system

For novice craftsmen building a house with their own hands, the truss system is perhaps the most complex structure. The greatest number of questions are caused by the methods of fastening individual elements and the fasteners used. The stability and durability of the roof largely depends on these nodes, so we will talk about them in more detail.

Fastening rafters to Mauerlat

The reliability of the roof structure directly depends on how correctly its entire supporting system will be mounted. And its main elements are rafters. The whole system consists of rafter legs that support and expand additional elements, such as struts, puffs, crossbars, side runs, support posts and extensions. The rafter legs are connected on the ridge beam from above, and their lower edges very often rest on the Mauerlat, fixed on the side load-bearing walls of the building.

Fastening rafters to Mauerlat

Since the biggest load falls on the Mauerlat, it is made from a powerful beam. Its cross section is determined by the massiveness of the entire truss system, but basically the size is from 150 × 150 to 200 × 200 mm. This load-bearing element is designed to evenly distribute the load from the entire structure of the roof and roof onto the load-bearing walls of the building. The fastening of the rafters to the Mauerlat is carried out in various ways. They are selected locally depending on the type of truss system (which can be layered or hanging), its complexity and massiveness, on the magnitude of the total loads to which the entire roof structure will be subjected.

Varieties of connecting nodes "rafters - Mauerlat"

First of all, there are sliding and rigid fastenings of rafters to the Mauerlat.

1. Sliding mounts consist of two separate elements, one of which has the ability to move relative to the other.

These mounts can be of different designs - closed and removable.

Closed sliding mount

• The closed mount consists of a corner, which is attached on one side to the Mauerlat, and on the other side has a special slotted eye. A metal loop with holes for fastening to the rafters is installed in it. Thanks to the free, not fixed vertical side of the corner, the fastening allows the rafter to move slightly if necessary, without causing a deforming effect on the walls of the building.

Movable sliding fastening of open type

• The open mount is arranged according to the same principle, and differs only in that the metal loop is not inserted into the eye, but simply the upper part of the vertical shelf of the corner is bent down after installation, thereby fixing the connection.

Video: an example of installing a movable mount on a rafter leg and Mauerlat

2. There are many more types of rigid fasteners. They are selected depending on the massiveness of the wooden structural elements and the method of installing the rafters on the Mauerlat.

Various hard mounts

These include metal corners of various sizes, LK fasteners, which will securely fix the rafters installed with a gash without damaging it with fixing screws or nails.

• LK fasteners are produced in several sizes, so they can be matched to any bar or board thickness. The thickness of the metal from which these fasteners are made is 2 mm, no matter what size they are. Depending on the size, fasteners have a different designation.

It should be noted that these fasteners are suitable not only for connecting rafters on the Mauerlat - they are also used to fix the nodes of the "floor beam - Mauerlat".

LC mounts in action

The main advantage of this fastener is the maximum rigidity and reliability of the connection of wooden elements.

• The fastening of the rafters with a gash on the Mauerlat with the help of corners is carried out on both sides, which provides the required rigidity.

Corner with reinforced rib at the bend

There are corners designed for attaching rafters without cuts. They have higher shelves and are screwed with a large number of self-tapping screws. They are made from metal with a thickness of 2; 2.5 or 3 mm.

Fastening rafters to the Mauerlat with corners

KP 11 and KP21 are improved corners, often marked as K P1 and KP2. These elements have an oval-shaped anchor hole, which reduces the risk of bolt breakage in the event of structure shrinkage.

KR series corners

КР5 and КР6 are corners used for fastening elements on which a large bearing load falls. The corner to K P6 is also equipped with an oval hole, and it is recommended to use it when creating a truss system on a new house, which will still shrink. These models are in demand for the installation of structures that have a lot of weight.

Corner to K M is made of perforated steel and is used for fastening rafters with a large section. It is especially well suited for wooden buildings. This corner fixes the structural elements very reliably, and when using it, it is not necessary to cut the rafters into the Mauerlat - it is enough to cut the correct angle at the first.

Reinforced corner KMRP series

The KMRP corner is used to fasten parts of the truss system at right angles, including rafters with Mauerlat. It also differs from conventional angles in that it has an elongated hole, which allows displacement during shrinkage without damaging the fixing bolt. It can be used in a design where it is impossible to cut one element to another.

KMRP corners are produced from 2 mm thick steel. Three varieties are produced:

• Another option for fixing the rafters on the Mauerlat is to install them between two boards, sawn at a certain angle, and additionally fixed at the bottom with metal corners or LK mounts.

Attaching a rafter between two boards

This fastening of the rafters gives good rigidity and reliability. This method is well suited in cases where the rafter needs to be fixed at the right angle, lifting it above the horizontal plane of the Mauerlat, but fixing it to the vertical outer side.

• A method of attaching rafters to a Mauerlat made from a beam of not too large a section. It is carried out by reinforcing the bar with wooden linings having the required thickness.

Fastening with reinforcing lining

Pieces of boards are attached to the Mauerlat with nails or self-tapping screws, in those places where the rafter legs will be installed.

In this case, cutouts of the desired configuration and depth are made in the rafters. The rafter legs are securely fixed to the wall with the help of steel wire, which is fixed to a driven steel crutch.

Fixation with wire twist

• In addition to the above methods of fastening, the rafters are nailed to the Mauerlat using brackets. It should be noted that this method is quite common and has been used for a very long time. With proper fixing of these elements, the truss system will last for many years.

Fastening "the old fashioned way" - staples

Staples can have different sizes, driven in at different junction points.

• Another fastener that is used as an auxiliary is the TM perforated tape. It is used to strengthen the fastening unit if necessary, its additional fixation.

Often metal perforated tape comes to the rescue

In some cases, this element can be indispensable, so it also cannot be excluded when installing rafter legs on the Mauerlat.

Features of truss systems

The rafter system is selected depending on the location of the load-bearing walls of the building. Each of the systems has its own additional retaining or tightening elements.

Varieties of truss systems

Rafters

The system with layered rafters is characterized in that it has one or more reference points, in addition to the load-bearing walls. In this regard, a significant part of the load is removed from the side walls.

Laminated rafters supported by a capital partition

In the form of additional retaining elements, side racks and "grandheads" are used that support the ridge and are fixed to the floor beams. And the beams themselves, in turn, simultaneously serve as puffs for the structure, and also lighten the load from the truss system on the load-bearing walls.

Rafters with sliding fasteners

Laminated rafters are most often attached to the Mauerlat with sliding joints that can move when the walls shrink or deform, leaving the roof structure intact. This is especially important to take into account in new buildings, since any newly built building necessarily shrinks under the influence of temperature fluctuations and ground movements.

hanging rafters

Hanging rafters are called due to the fact that they do not have other supports, in addition to the two side load-bearing walls. It turns out that they seem to hang over the internal space of the building. In this case, the entire load from the roof frame structure falls on the Mauerlat.

Rafters in a hanging type system

For fastening hanging rafters to the Mauerlat, rigid fasteners are used with no degree of freedom of movement, since the frame structure has only two points of support.

To remove part of the load from the walls of the building, additional elements such as struts, “headstocks” and puffs-crossbars are used, which pull the system to the ridge bar and evenly distribute the load on all walls. Crossbars are installed parallel to the floor beams and pull the rafters together. Without these additional details, the design can become unreliable.

Calculation of the installation of rafters

In order for the rafter system to be reliable and durable, in addition to the optimal connection method, you need to choose the correct step for the location of the rafter legs. This parameter is selected depending on the size of the rafters (their cross section and length between the support points), as well as on the roof structure.

In this table, you can get information about the necessary parameters for the installation of a reliable truss system.

A few rules for attaching rafters to the Mauerlat

In order for the fasteners to be reliable, it is necessary to follow a number of rules that are provided for this process:

• If metal connecting parts are used for fastening, then they must be fixed to wooden connecting elements with the utmost care - high-quality self-tapping screws of the required length.
• If the rafters will fit into the cuts in the Mauerlat, then the dimensions must be precisely verified. This will ensure a tight, reliable installation of the rafters in the prepared gash, which should have a depth of ⅓ Mauerlat. However, it should be remembered that such a rule will be valid only if the Mauerlat is made of a powerful bar with a cross-sectional size of at least 150 × 150 mm.

Washed down on the Mauerlat

• In order not to weaken the Mauerlat, most often the cuts are made in the rafter leg itself at the desired angle, and in addition the knot is then fixed with corners. Washed down should not in this case exceed ¼ of the thickness of the rafters. This mount is rigid and can be used in a hanging rafter system.

In this embodiment, washed down is done on the rafter leg

• When using bolts to fasten rafters with slopes, puffs and other wooden elements, it is imperative to install a washer or a metal plate on the bolt in order to avoid flooding the nut into the wood and, accordingly, weakening the structure.
• Fastening rafters to the Mauerlat only with nails or self-tapping screws is considered unreliable, so it is imperative to use corners or other metal fasteners of various configurations.

Wide range of metal fasteners

• When installing rafters on wooden walls, whether it is a hanging or layered system, it is recommended to attach them to the Mauerlat with a sliding fastener, especially if the roofing material is heavy enough.

Fastening rafters to the Mauerlat - how to do it right?

One of the most important connecting nodes in the roof structure is the fastening of the rafters to the Mauerlat. There are several approaches to solving this problem.

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).
• Sheathing is slats or beams mounted on rafters with a certain pitch and serving as the basis for laying 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 above structural details, 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 version. 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 conjunction 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 this or that 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.

Specify the requested values ​​and click the button "Calculate the excess Lbc"

Base length (horizontal projection of the slope)

Planned roof slope angle α (degrees)

Rafter Length Calculator

The calculation is based on the values ​​of the horizontal projection (Lsd) and the height of the rafter triangle, previously determined (Lbc).

If desired, you can include in the calculation the width of the cornice overhang, if it is created by protruding rafters.

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.

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