Roof installation is a complex multi-stage process. In order to independently assemble and install the truss system, it is necessary to carefully study the methods of connecting the elements, calculate the length of the rafters and the slope angle, and select the appropriate materials. If not necessary experience, it is not worth taking on complex structures. The best option for a residential building small sizes- do-it-yourself gable roof.
A standard roof of this type consists of the following elements:
Mauerlat is a beam laid on top of the walls along the perimeter of the building. It is fixed with threaded steel rods immured into the wall or anchor bolts. The beam must be made from softwood and have a square section of 100x100 mm or 150x150 mm. Mauerlat takes on the load from the rafters and transfers it to the outer walls.
rafter legs- these are long boards with a section of 50x150 mm or 100x150 mm. They are attached to each other at an angle and give the roof a triangular shape. The design of their two rafter legs is called a truss. The number of farms depends on the length of the house and the type of roofing. The minimum distance between them is 60 cm, the maximum is 120 cm. When calculating the pitch of the rafter legs, one should take into account not only the weight of the coating, but also the wind load, as well as the amount of snow in the winter.
It is located at the highest point of the roof and most often represents a longitudinal beam connecting both slopes. From below, the timber is supported by vertical racks, and the ends of the rafters are attached to the sides. Sometimes the ridge consists of two boards, which are nailed to the top of the rafters on both sides and connected at a certain angle.
Racks - vertical bars with a section of 100x100 mm, located inside each farm and serving to transfer the load from the ridge run to the load-bearing walls inside the house.
The struts are made from timber scraps and set at an angle between the uprights and the rafters. The side faces of the truss are strengthened with struts, the bearing capacity of the structure is increased.
Puff - a beam connecting the lower parts of the rafters, the base of the truss triangle. Together with struts, such a beam serves to strengthen the truss, increases its resistance to loads.
Lying is a long bar with a section of 100x100 mm, laid along the central load-bearing wall, on which vertical racks rest. Lying is used when installing layered rafters, when the run between the outer walls is more than 10 m.
The crate is a board or timber stuffed on the rafters. The crate is solid and with gaps, depending on the type of roof. It is always attached perpendicular to the direction of the rafters, most often horizontally.
If there is no more than 10 m between the outer walls and there is no load-bearing wall in the middle, arrange hanging rafter system. With such a system, the upper ends of adjacent rafters are sawn at an angle and connected to each other with nails, excluding the installation of racks and ridge timber. The lower ends of the rafter legs rest on the outer walls. Due to the lack of racks, the attic space can be used to equip the attic. Very often, floor beams perform the function of puffs. To strengthen the structure, it is recommended to install the upper puff at a distance of 50 cm from the ridge.
In the presence of a central supporting wall, the arrangement is more justified layered truss system. A bed is laid on the wall, support posts are attached to it, and a ridge beam is nailed to the posts. This installation method is quite economical and easier to perform. If the ceilings in the interior are designed at different levels, the racks are replaced brick wall dividing the attic into two halves.
The installation process of the roof includes several stages: fastening the Mauerlat to the walls, assembling the truss trusses, installing the rafters on the floors, installing the ridge, fastening the batten. All wooden elements before starting the assembly, they are carefully treated with any antiseptic composition and air-dried.
For work you will need:
- timber 100x10 mm and 150x150 mm;
- boards 50x150 mm;
- boards 30 mm thick for lathing;
- ruberoid;
- metal studs;
- jigsaw and hacksaw;
- hammer;
- nails and screws;
- square and building level.
in wooden houses Mauerlat functions are performed by logs of the last row, which greatly simplifies the workflow. To install the rafters, it is enough to cut grooves of the appropriate size on the inside of the logs.
IN brick houses or buildings from blocks, the installation of the Mauerlat is as follows:
Mauerlat bars should form a regular rectangle and be in the same horizontal plane. This will facilitate further installation of the roof and provide the structure with the necessary stability. In conclusion, markings are made on the bars for the rafters and grooves are cut along the thickness of the bar.
When choosing a hanging truss system, it is necessary to assemble the trusses on the ground, and then install them above the floors. First you need to draw up a drawing and calculate the length of the rafter legs and the angle of their connection. Typically, the roof slope is 35-40 degrees, but in open, heavily ventilated areas, it is reduced to 15-20 degrees. To find out at what angle to connect the rafters, you should multiply the angle of the roof by 2.
Knowing the length of the run between outer walls and the angle of connection of the rafters, you can calculate the length of the rafter legs. Most often, it is 4-6 m, taking into account the cornice overhang 50-60 cm wide.
The upper ends of the rafters can be fastened in several ways: overlap, butt and "in the paw", that is, with cut grooves. For fixing use metal pads or bolts. Next, the lower and upper puffs are mounted, and then the finished trusses are lifted up and installed above the ceilings.
The extreme trusses are attached first: with the help of a plumb line, the rafters are set vertically, the length of the overhang is adjusted and attached to the Mauerlat with bolts or steel plates. So that during the installation process the farm does not move, it is strengthened with temporary jibs from a bar. After installing the extreme rafters, the rest are exposed, keeping the same distance between them. When all the trusses are fixed, they take a board with a section of 50x150 mm, the length of which is 20-30 cm longer than the length of the eaves, and nail it along the upper edge of the slope. Do the same on the other side of the roof.
The first option: on the rafter leg, at the place of contact with the Mauerlat, a rectangular groove is cut out 1/3 of the beam width. Stepping back from the top of the box 15 cm, a steel crutch is driven into the wall. The rafter is leveled, the grooves are aligned, then a wire clamp is thrown on top and the beam is pulled close to the wall. The ends of the wire are securely fixed on the crutch. The lower edges of the rafters are carefully cut off circular saw leaving an overhang of 50 cm.
The second option: the upper rows of walls are laid out with a stepped brick cornice, and the mauerlat is placed flush with the inner surface of the wall and a groove is cut in it for the rafter. The edge of the rafter leg is cut at the level of the upper corner of the eaves. This method is simpler than the others, but the overhang is too narrow.
Third option: ceiling beams are released over the edge outer wall by 40-50 cm, and truss trusses are installed on beams. The ends of the rafter legs are cut at an angle and rest against the beams, fixing with metal plates and bolts. This method allows you to slightly increase the width of the attic.
The device of layered rafters
1 shows the cutting of the struts of the rafters into a bed laid on intermediate supports, and in Fig. 2 - supporting the rafter leg on the Mauerlat
The procedure for installing a layered truss system:
When the main elements are fixed, the surface of the rafters is treated with flame retardants. Now you can start making the crate.
A beam of 50x50 mm is suitable for the crate, as well as boards with a thickness of 3-4 cm and a width of 12 cm or more. Waterproofing material is usually laid under the crate to protect the truss system from getting wet. The waterproofing film is laid in horizontal stripes from the eaves to the roof ridge. The material spreads with an overlap of 10-15 cm, after which the joints are fastened with adhesive tape. The bottom edges of the film must completely cover the ends of the rafters.
Between the boards and the film, it is necessary to leave a ventilation gap, so first they fill the film wooden slats 3-4 cm thick, placing them along the rafters.
The next stage is the sheathing of the truss system with boards; they are stuffed perpendicular to the rails, starting from the roof eaves. The step of the lathing is affected not only by the type of roofing, but also by the angle of inclination of the slopes: the larger the angle, the greater the distance between the boards.
After the installation of the battens is completed, they begin to sheath the gables and overhangs. You can close the gables with boards, plastic panels, clapboard, waterproof plywood or corrugated board - it all depends on financial capabilities and personal preferences. Sheathing is attached to the side of the rafters, nails or self-tapping screws are used as fasteners. Overhangs are also hemmed various materials from wood to siding.
Video - Do-it-yourself gable roof
Properly designed and assembled according to technology, the roof serves as a barrier that prevents cold air and moisture from entering the house. Outside, with the naked eye, we see only a small part of the structure - the roofing. But the roof frame, which is the most important component, performs the main supporting functions and absorbs the effects of wind and snow loads.
So that it does not deform as a result of operation, it is necessary to correctly calculate the cross-sectional value of its elements and determine the distance between them, taking into account the weight of the roofing material, slope and climatic conditions. In this article we will tell you what the truss system is pitched roof at home, what it consists of, how it is designed and assembled with your own hands.
truss system for gable roof houses - a system of interconnected supporting elements, which together form the frame of the structure.
It is made of wood or metal in accordance with the calculation of the loads that will affect them during operation. The roof truss frame performs the following functions:
- Gives roof slopes the necessary slope. The traditional shape in the form of an equilateral rectangle of a gable roof is given precisely by the truss frame, which forms a slope between the base of the roof and its ridge. The angled surface allows snow and water to slide freely off the slope.
- Distributes the load from the weight of the roofing cake. The weight of the roofing cake, taking into account the snow load, can reach up to 500 kg / m2, so the gable roof is subjected to intense load, especially in winter. The rafters of a gable roof evenly distribute the weight that falls on them, and then transfer the load to the load-bearing walls and foundation of the house.
- Serves as a basis for fixing thermal insulation and roofing material. The rafter frame of the roof serves as a kind of skeleton of the structure around which its “body” is built. Thermal insulation should be installed between the rafter legs, and a roofing covering is fixed on the crate, which protects against moisture penetration.
Please note that the design of the gable roof truss system is quite complicated to design and assemble, especially if the master does not have enough experience. Indeed, in order for it to be able to withstand heavy loads, it is necessary to correctly calculate the cross-section of the rafters and the pitch of the rafters, taking into account the slope and length of the slopes, the roofing material used, and also draw up a drawing according to which the assembly will be performed.
Types of truss systems
Rafter systems differ in many factors, their composition depends on the layout of the wooden or brick house, the total weight of the roofing cake, the material from which the frame is made, as well as the type of roofing.
An important characteristic of the design is their bearing capacity, which determines how much weight they can withstand without deformation. By characteristic features There are the following types of truss systems:
Layered
A rafter frame of a layered type is a frame whose rafters have 2 points of support. The upper end of the leg rests on a ridge run, mounted on vertical posts fixed to the inner wall. And with the lower end it is installed on the Mauerlat.
The assembly of a rafter system of a layered type on a gable roof is possible only if there is at least 1 load-bearing partition or capital column inside the house. Such a construction is often called non-thrust, because the second fulcrum of the rafters compensates for the bursting load on the walls of the house, which is assumed by the hanging frame installation scheme.
Rafter legs of a layered type experience only a bending load, which can be eliminated by various struts. The layered truss system allows you to cover houses up to 14 meters wide.
hanging
The hanging truss system is distinguished by the fact that its rafters rest only with their lower end on a Mauerlat beam mounted on external load-bearing walls. The upper end of the rafter legs of this design does not rest on anything, but, as it were, hangs in the air, which causes 2 types of load: bending and bursting.
The bursting load of such an arrangement of elements on the outer walls is so great that it has to be compensated with the help of numerous crossbars and ties, due to which the rafter pairs are tied together.
The device of a gable roof with hanging rafters consists of triangular trusses, the rigid form of which is not subjected to loads. It is believed that the complexity of the hanging circuit is much higher.
Do-it-yourself do-it-yourself rafter system of a gable roof is mounted without difficulty, if you correctly calculate the pitch of the rafters, that is, the distance between the rafters and the size of their cross section.
Combined
Combining the best of both systems, it is recognized as the most reliable. It is used in cases where, indoors, not walls, but columns are used as a support inside the house. Then the hanging and layered rafters can be alternated to strengthen the structure with additional elements, without increasing the consumption of building materials.
Important! sliding rafter roof- another type of frame, which differs in that the rafter legs are installed on the Mauerlat not with the help of a rigid mount, but using a movable support. The sliding mount allows the roof to change dimensions within the power reserve during the shrinkage of a wooden house.
Design
The device of the truss system of a gable roof of any of the listed types is a combination of auxiliary and supporting elements. They evenly distribute the weight of the roofing cake, and also compensate for the bursting and bending loads that occur between them.
The cross section, length and pitch of the rafters are determined using an engineering calculation that takes into account the weight of the roofing pie, the climatic conditions in the construction region, and the slope of the structure. The composition of the truss frame of a gable roof usually includes the following elements:
- Mauerlat. Mount the Mauerlat beam on the outer walls of the house, on which the roof slopes rest. It serves to soften the pressure on the supports and evenly distribute the load from the weight of the roofing cake. It is made of a durable beam with a section of 150x150 mm or 200x200 mm and is attached to the upper belt of the walls using anchor bolts or long metal studs.
- Sill. This is an analogue of the Mauerlat, only it is installed on internal load-bearing walls, and vertical stands must be placed on it for mounting a ridge run.
- rafter legs. This term refers to the elements of the frame, which are made of boards with a cross section of 150-40 mm and are installed at an angle to the base of the roof, forming the angle of inclination of the slope. What to do the distance between the rafters, their length and thickness is determined by calculation, taking into account the total load to which they are subjected during operation.
- puff. A puff is called beams that are placed horizontally and connect the legs of one rafter pair to each other in order to reduce the bursting load on the outer walls of the structure. A crossbar is a puff installed under the very ridge of the structure.
- Racks. Rack is called vertical bar, put on the bed to support the ridge run. It is easy to determine what distance should be between the racks, because it repeats the step of the rafters.
- Struts. Diagonally located supports that support the rafter legs in the middle or at the bottom, preventing their deflection, are called struts.
Please note that only the calculation of temporary and permanent loads to which they will be subjected during operation can determine how to properly position the elements of the truss system. Calculating the total weight of the roofing cake helps determine the correct distance between the rafters, calculate their length and the required thickness.
The calculation of the gable roof truss system is based on the fact that in the frontal dimension it has the shape of an equilateral triangle, the sides of which can be easily calculated using simple trigonometric formulas.
These simple calculations help determine the optimal distance between the rafters, their thickness and length. The design calculation is performed in the following sequence:
- Determine the design and slope of the roof. There are various ways to choose the type and slope of the roof structure. This parameter depends on the climatic conditions and performance characteristics of the selected roofing material.
- Determine the total load on the structure. To do this, they sum up the constant loads (the weight of the roofing, their weight of the frame, thermal insulation and ceilings) with the temporary loads (snow load, wind load), multiply by a correction factor that takes into account the slope of the slopes, and then add 10-15% to this figure to the frame had some margin of safety.
- Calculate the length of the rafter legs. To do this, use the Pythagorean theorem, because the truss truss is an equilateral triangle. It turns out that the square of the length of the rafter leg is equal to the sum of the squares of the height of the blood and half the length of the laying. Knowing how to calculate the length of the rafters, you can calculate the height of the ridge.
- Determine the section of the elements. The optimal section of the elements is selected according to the tables in accordance with the length of the rafter legs and the distance between them. The higher these indicators, the thicker the rafter should be.
Remember that before you calculate the rafters on the roof, you need to decide on the basic design parameters. In particular, it is necessary to know exactly the height of the ridge and the slope of the roof, as well as the dimensions of the room to be covered. The result of the calculation of the elements of the roof should be detailed diagram truss system, reflecting their dimensions and the angles between them.
We calculate the angle of inclination
The angle of inclination of the slopes is selected not depending on aesthetic preferences, but based on weather conditions, taking into account the roofing material. Steeper slopes of 40-45 degrees are built in areas with a large amount of snow cover, and more gentle slopes of 10-20 degrees in places with strong gusty winds.
Keep in mind that the steeper the slope, the higher the consumption of materials, the greater the total cost of the roof. Be sure to take into account the requirements of the material:
- Tiles, slate require a slope of at least 22 degrees, otherwise, precipitation seeps through the joints between the elements.
- The metal tile is laid at an angle of at least 14 degrees, as it suffers greatly from gusts of wind, it can deform or even fly off.
- Soft roofing allows a slope angle of up to 5-10 degrees, making it possible to cover slopes of any geometry with it.
- Ondulin is considered one of the most reliable materials and can even be used for roofs with a slope of less than 6 degrees.
- Profiled sheets cannot be laid at an angle of less than 15 degrees, however, even slopes with an acceptable slope should be treated with a sealant for better waterproofing.
Assembly technology
Before mounting the roof frame, it is necessary to calculate the parameters of its elements, based on the calculation of the total load on the structure, and also create a detailed drawing reflecting its results.
Having a frame diagram in front of you, it is much easier to qualitatively install the gable roof truss system. The assembly technology of the structure implies the following sequence:
- First, a Mauerlat is laid on the upper belt of the outer walls, on which the slopes will rest, and on internal partitions if the system is layered, mount the bed. These elements must be firmly fixed with anchor bolts or studs.
- Then the rafters are fastened. They are fixed with nails to the Mauerlat, and are also interconnected using a metal lining. It is worth recalling that in the rafters they make a drink under the Mauerlat beam, and not vice versa. First, the installation of rafters located on the edge is carried out in order to set the level along which the rest of the pairs will be aligned.
- After installing the rafters, auxiliary supporting elements should be installed that will support them - struts, puffs, contractions. To more securely fix the crossbar, its end is made with a protrusion half the thickness of the beam and it is hemmed to the rafters, fixing it with nails in several places.
- A crate is nailed over the rafter legs, on which the roofing material is fixed. The material and pitch of the lathing is selected in accordance with the characteristics of the roofing material and the slope of the roof.
Remember that a well-designed and high-quality assembled truss system is a guarantee of strength, reliability and durability of a gable roof. Therefore, do not neglect the help of professional roofers and designers when creating a roofing design for your home.
Video instruction
The truss system is the roof frame, which is the basis for the flooring. roofing.
The rafter system is designed to withstand the load of the roof, taking into account natural loads: winds, snow, rain.
The roof option is approved at the design stage.
The purpose of the roof includes several functions: warmth in the house, protection of the premises from natural phenomena, therefore truss system must be given Special attention.
You can read how to calculate the truss system.
It is customary to classify truss systems so that the task of choosing a variant of the future roof is easier to solve:
- Shed. The most simple. More suitable for utility rooms, baths, small private houses, arbors. Provides for the inclined position of the structure at a slight angle (no more than 25°);
- gable. Used for small houses and suburban buildings. They look like a triangle, in which the rafters are connected by a beam and are at a certain angle;
- Gable broken lines. They have two slopes with a fracture, thanks to which it is possible to increase the area of the attic;
- Tri-slope (semi-hip). They have two trapezoidal slopes, which are connected by one end triangular slope (hip);
- Four-slope (hip). Used for residential buildings require a significant amount of labor. They have two end triangular slopes and two trapezoidal;
- Tent. Used for square buildings. They consist of four triangular slopes, the upper corner of which is connected in the center of the roof;
- Multi-forceps. Consist of trapezoidal or other slopes of various shapes, interconnected.
The most suitable designs for - and broken gable. There are others, but they are less common and not as practical as those listed above.
Rafter structures are also classified into:
- Hanging. With this type of roof frame, due to the lack bearing walls in room;
- Layered. Option truss installation, supporting on a carrier inner wall or support in the building.
The calculation of the material for the roof frame when designing a building is based on the intended configuration and load. Do-it-yourself rafters are not difficult to do, it is important to approach the matter wisely.
Rafter systems of layered and hanging type
Calculation of the load on the rafters
For correct calculation loads on the rafters, it is necessary to take into account many factors that can affect the severity of the structure.
Important metrics to consider:
- Constant load: includes a mass of roofing cake, covering material;
- Temporary load: constant and maximum amount of snow, rain, intensity of wind gusts, and in areas with high seismic activity - the action of storm winds, tornadoes, hurricanes.
In addition, you should keep in mind the mass and strength of the rafter legs, as well as pay attention to the fastening of the gable roof rafters and the installation option.
Scheme of truss systems
The distance between the rafters of a gable roof and the thickness of the rafters
The rafter pitch of a gable roof is the empty space between the rafters. The functionality of the roof depends on the correct calculation of the pitch. As a rule, the step is about a meter.
For a more accurate calculation of the distance between the rafters, there is a certain calculation scheme:
- Determine the length of the slope.
- The length of the slope is divided by the distance between the rafters.
- To determine the number of rafter boards, one is added to the resulting value and rounded up. This determines how many boards are needed per slope.
- The length of the slope is divided by the number of boards, get the distance between the rafters.
This calculation is not always final.
Additionally, you should take into account the load of the roofing (its mass), the thickness of the rafters, as well as the dimensions of the rafters for a gable roof.
The thickness of the rafter board largely depends on the covering material:
- . Boards are used with a section of 5x20 cm at a step of 60 to 90 cm with a decking of a batten with a section of 4x5 cm;
- . Rafter boards - 5x15 cm, step - from 60 cm to 95 cm;
- . The cross section of the board is 6x18 cm or 5x15 cm, the distance between the bars is from 80 cm to 130 cm;
- . The cross section of the rafter is 5x15 cm, 5x10 cm with a step of 60 cm to 90 cm;
- . The cross section of the beam is the same as on the corrugated board with a step of 60-80 cm.
All indicators should be taken into account and the thickness of the rafter should be accurately calculated so that there is no excessive load on the foundation.
Incorrect calculation of the length of the gable roof rafters, as well as incorrect calculation of the pitch indicators, can lead to sagging of the roof.
Do-it-yourself installation of gable roof rafters requires taking into account the weight of the rafter board and all additional structural fasteners.
What is the truss system
truss structure - a complex system and installing a gable roof truss system is not an easy task. truss system consists not only of rafter boards, but also of other additional elements:
- Mauerlat. An element that distributes the entire load evenly on the supports;
- Run. Boards fastening the legs of the rafter: at the top - a ridge, on the side - a side run;
- Puffs. Connecting beam, which prevents the divergence of the rafter legs;
- Struts, racks. Bars that fix the stability of the rafters, resting on the bed;
- . Lattice of bars, which is superimposed perpendicular to the rafters. Transfers the load of the covering material to the truss frame;
- . Connecting beam, which serves as a union of roof slopes;
- Filly. If the length of the rafter legs is insufficient, they are mounted to form an overhang;
- Roof overhang. Goes beyond the bottom line of the slope to prevent precipitation from falling on the walls.
The rafter system implies rafters, stretch marks, braces and racks located in the same plane. They are located in such a way that the main load of the roof structure falls vertically on the external load-bearing walls. Therefore, the manufacture of gable roof rafters is a very important process.
What is the gable roof truss system
Installation of a rafter system with layered rafters
A layered rafter system is used when the span does not exceed 6.5 meters.
In the presence of load-bearing structures inside the building, it is possible to install additional racks.
The main support of the rafter legs is the Mauerlat.
Mauerlat installation
Before mounting the Mauerlat, it is necessary to install an armored belt. It consists of a formwork in which reinforcement is laid and poured with concrete. At the base, with concrete that has not yet hardened, studs are installed, to which the Mauerlat is then attached.
Mauerlat - a beam that is laid on a support (bearing wall) and is the base of the truss frame. Pre-laid layer waterproofing material. If the length of the beam is not enough for the length of the wall, then it is increased.
- Check if the diagonals are equal. A discrepancy of a few centimeters can lead to a frame conversion;
- Fix the corners of the Mauerlat;
- Attach the Mauerlat with studs or wire. The studs are tightened in two stages, having previously drilled holes for them.
The stability of the roof structure depends on how firmly the Mauerlat is installed.
Therefore, it is necessary to take seriously the fastening of the Mauerlat to the bearing support.
Mauerlat installation
Sill
After the Mauerlat has dried (after 5 days), the installation of the bed is marked on the Mauerlat beam: its axis should be with the same indentation on each side of the Mauerlat beam. The bed is attached to a two-layer waterproofing layer with anchor bolts. To the wall with inside the bed should be fixed with twists of wire or staples. Next, markup is made for installing the rafters.
Installation of a gable roof truss system
The anchor points of the layered rafters are the walls and racks inside the frame. The rafters are mounted with hinged attachment points. When using sliders for fastening, a slight lowering of the roof frame is ensured in the first years of the roof's service life.
This installation method is necessary to prevent distortion, as in the early years the building settles a little.
Rafter beams should be fixed either by installing them in prepared grooves and strengthened with fasteners, or by attaching plank linings.
Installation of rafters
ridge knot
The rafters are joined end-to-end, cutting off the edge of the bar so that the angle when connecting opposite beams corresponds to the angle of the slope. Hammer the rafters under the ridge with nails. A variant is possible in which the beams are connected by bolts, a nail or a hairpin, that is, they overlap.
If necessary (if provided by the project), a cut is made in the rafter beams for attaching the ridge beam (purlin).
ridge knot
Racks
Racks are attached with a short span - in the center, on the sides and center - with a wider roof base. Fastening is carried out vertically from the ridge to the inner wall.
Run
Run - a connecting beam for fixing rafter legs. Fastens with bolts or brackets to the rack.
Filly installation
The final step in the installation of the layered system is the installation of filly with a short length of rafter legs for overhang. To install the visor, it is necessary to install additional small rafter boards.
Installation of a rafter system with layered rafters
Do-it-yourself gable roof truss system: installation with hanging rafters
truss system, equipped with hanging rafters, is a triangular structure, where the sides are rafters, and the base is a puff connected to the lower heels of the rafters.
Installation of a hanging-type truss frame can do without installing a Mauerlat: a board that is fixed on a two-layer waterproofing can replace it.
If the structure has a large span, then struts, headstocks, crossbars are attached to it.
Racks in the hanging system are not provided.
Puffs
The puff is the longest beam of the roof frame. To prevent it from sagging, it is necessary to fasten headstock - boards that are attached to the top of the structure on one side, and to the puff - on the other. Fasten with bolts or overlays made of wood. The slack can be adjusted using the threaded collars.
The device of the truss system
Installation of strut beams
The headstock can be supplemented with strut beams, forming a rhombus, where two struts are the lower sides, and the rafters are the upper ones, the upper corner is the ridge. Thus, the struts rest against the headstock, distributing the load.
Strut beams
rafters
Rafters of a hanging structure are mounted like a layered one. When installing attics, the puff is installed closer to the ridge, providing more space under the ceiling. The tightening in this case is fastened by cutting with bolts.
ATTENTION!
When installing a hanging system, a prerequisite for installation is the accuracy of calculations and the strength of the rafters and puffs.
The presence of errors leads to the displacement of the axes of the elements of the system, which provides a distortion of the structure.
How to install rafters for a gable roof will tell you this photo:
Rafter installation
hanging rafters
How to strengthen the rafters of a gable roof
It is necessary to reinforce the rafters of a gable roof when the load calculation is incorrect or frame defects are found.
Strengthening can be done with:
- Balok, which are installed in order to transfer the load to them;
- Strut mounting with an inclined mount with an emphasis on lying down;
- Overlays of double-sided rails;
- Increase in the section of the rafter beam in the place of supports on the strut by applying planking from boards with nails or bolts;
- board wall, which are attached to the rafters in places where snow is expected to accumulate to increase the bearing capacity of the rafters.
You can resort to strengthening the Mauerlat beam and the base of the rafter beam. Due high humidity and reduced ventilation, these parts of the frame are more prone to decay, therefore, when arranging the roof special attention needs to be paid
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The calculation of the truss system should be done not after the construction of the box of the house, but even at the stage of manufacturing the building project. It must be remembered that for very responsible and prestigious buildings, it is recommended to order such work from professional architects, only they will be able to perform correct calculations and guarantee the duration and safety of the operation of the facility.
Although this is one of the simplest types of systems for residential buildings, there are several types of construction. Diversity allows you to increase the options for using roofs in the construction of houses according to standard or individual exclusive projects.
| Type of gable roof truss system | Architectural features and brief description |
|---|---|
| The most commonly used option has two completely identical rectangular slopes. The loads between the individual elements are distributed evenly, regardless of their location. The number of additional stops is not limited, specific solution taken depending on the plans for the use of attic space. Calculations can be done using free programs posted on construction sites. |
| The skate is shifted to one of the sides of the house or slopes with different angles of inclination. The roof truss system is more complex for calculations. If in a simplified version one slope can be calculated and the data obtained automatically applied to the second, then this option cannot be used for an asymmetric truss system. Advantages - original appearance. Disadvantages - the complexity of calculations and installation and a decrease in the used attic space. |
| Most often used during the construction of attic spaces, it allows you to significantly increase the volume of attic spaces. Calculations on complexity belong to the middle category. Rafter system with an external break. Rarely there are systems with an internal break, except for the original appearance, they have no advantages. |
Structural elements of the truss system
We will give a list of all the elements that need to be calculated for each specific case.
The simplest element of the truss system can be made from timber 150 × 150 mm, 200 × 200 mm or boards 50 × 150 mm and 50 × 200 mm. On small houses, it is allowed to use paired boards with a thickness of 25 mm or more. Mauerlat is considered an irresponsible element, its task is only to evenly distribute point forces from the rafter legs along the perimeter of the facade walls of the building. It is fixed to the wall on a reinforcing belt using anchors or large dowels. Some truss systems have large bursting forces, in these cases the element is calculated for stability. Accordingly, the optimal methods for fixing the Mauerlat to the walls are selected, taking into account the material of their masonry.
Bar prices
They form the silhouette of the truss system and perceive everything acting loads: from wind and snow, dynamic and static, permanent and temporary.
They are made from boards 50x100mm or 50x150mm, they can be solid or extended.
The boards are calculated according to the resistance to bending, taking into account the data obtained, the species and types of wood, the distance between the legs, and additional elements to increase stability are selected. Two connected legs are called a truss, in the upper part they may have puffs.
Puffs are calculated for stretching.
Runs
One of the most important elements of the gable roof truss system. They are calculated for maximum bending forces, they are made of boards or timber of the section corresponding to the loads. A ridge run is installed at the highest point, side rails can be mounted on the sides. Run calculations are quite complex and must take into account a large number of factors.
They can be vertical and inclined. Inclined work in compression, attached at right angles to the rafters. The lower part rests against floor beams or concrete slabs, options for resting on horizontal beds are acceptable. Due to the stops, it is possible to use thinner lumber for the manufacture of rafter legs. Vertical stops work in compression, horizontal stops in bending.
lying down
They are laid along the attic, rest against several load-bearing walls or interior partitions. Purpose - simplification of the manufacture of a complex truss system, the creation of new points of transfer of loads from various types stops. For beds, beams or thick boards can be used, the calculation is made according to the maximum bending moment between the support points.
crate
The type of crate is selected taking into account technical parameters roofing and does not affect the performance of the truss system.
What crate is needed for corrugated board? When to mount wooden, and when metal? How to choose the right step of the crate and what factors should be taken into account?
Prices for building boards
Building boards
Stages of calculating a gable roof
All works consist of several stages, each of which has a great influence on the stability and durability of the structure.
Calculation of the parameters of the rafter legs
Based on the data obtained, the linear parameters of lumber and the truss pitch are determined. If the loads on the rafters are very large, then vertical or angular stops are installed to evenly distribute them, the calculations are repeated taking into account new data. The direction of the impact of forces, the magnitude of torque and bending moments change. During the calculations, three types of loads should be taken into account.
- Permanent. These loads include the weight of roofing materials, lathing, insulation layers. If the attic is operated, then the mass of all finishing materials should be taken into account internal surfaces walls. Data on roofing materials are taken from their technical characteristics. The lightest of all metal roofs, the heaviest of all are natural slate materials, ceramic or cement-sand piece tiles.
- Variable loads. The most difficult to calculate efforts, especially at the present time, when the climate is changing dramatically. For calculations, data are still taken from reference books of SNiP of an outdated model. For his tables, information was used fifty years ago, since then the height of the snow cover, the strength and the prevailing direction of the wind have changed significantly. Snow loads can be several times higher than those in the tables, which has a significant impact on the reliability of calculations.
Moreover, the height of the snow varies not only taking into account the climatic zone, but also depending on the location of the house on the cardinal points, the terrain, the specific location of the building, etc. Data on the strength and direction of the wind are just as unreliable. Architects found a way out of this difficult situation: data is taken from outdated tables, but a safety factor is used in each formula to ensure reliability and stability. For critical roof systems on residential buildings, the standard is 1.4. This means that all linear parameters of the system elements increase by 1.4 times, and this increases the reliability and safety of the structure operation.
The actual wind load is equal to the figure in the region where the building is located, multiplied by the correction factor. The correction factor characterizes the features of the location of the building. The same formula is used to determine the maximum snow load.
- individual loads. This category includes specific efforts that affect the gable roof truss system during an earthquake, tornado and other natural disasters.
The final values are determined taking into account the probability of the simultaneous action of all the above loads. The dimensions of each element of the truss system are calculated using a safety factor. According to the same algorithm, not only rafter legs are designed, but also lintels, stops, stretch marks, girders and other roof elements.
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 load-bearing elements buildings 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 applied for mansard roof. 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 block 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 structure.
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 carried out easily and simply.
As part of the truss system 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 on 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, installation will be required different types 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.
count four-slope system rafters are needed by professionals, 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 attic floor. Here is the window for better lighting 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 installation is complete roof truss lay the crate, the type of which depends on the roof covering purchased. The installation of the crate is done continuously or with a certain step. For it, boards, OSB and plywood sheets. 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. At a slope angle of about 45 °, the snow load is not taken into account, since at this option he won't stay 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 roof is being done different ways, however, 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.
- 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.
- Fix all elements of the rafters with ceiling overlap, internal boards, jibs, as well as crossbars. Further, this basis for the roof will become a single whole structure.
- 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:
- 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 - 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.
- A second template is made, thanks to which the cuts on the rafters are installed. It is made from plywood.
- 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.
- 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 - 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.
- Raise and mount the remaining rafters at the initially calculated distance, which should be at least 60 cm from each other.
- 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. - 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 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 according to 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 differently, as it depends on different nuances: type of roof, its size, angle of inclination.
Rafter from profile pipe- this 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. For the manufacture of rafters used paired material, and gussets 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
Crossbar is a fairly broad concept, however, in the case of roofs, it has certain value. 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 from below - 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.
