Rafter work. How to install rafters on the roof. Design of a gable roof truss system

A gable roof or gable roof is a roof with two slopes, i.e. having 2 inclined surfaces (slopes) of a rectangular shape.

Frame gable roof by virtue of design features ideally combines simplicity of design and maintenance with reliability and durability. These and many other parameters make the construction of a gable roof practical and rational decision for private and commercial housing construction.

In this article, we will look at how to make a rafter system for a gable roof with your own hands. For effective perception of the material, it is presented in the form of step-by-step instructions from A to Z, from selection and calculations, to installation of the Mauerlat and sheathing under the roof. Each stage is accompanied by tables, diagrams, drawings, drawings and photos.

The popularity of the house roof is due to a number of advantages:

• design variability;
• simplicity in calculations;
• naturalness of water flow;
• integrity of the structure reduces the likelihood of leaks;
• efficiency;
• preservation usable area attic or the possibility of arranging an attic;
• high maintainability;
• strength and wear resistance.

Types of gable roof

The installation of a gable roof truss system depends, first of all, on its design.

There are several options for gable roofs (types, types):

The most common roof installation option due to its simplicity and reliability. Thanks to symmetry, a uniform distribution of loads on the load-bearing walls and mauerlat is achieved. The type and thickness of the insulation does not affect the choice of material.

The cross-section of the beam makes it possible to provide a reserve of bearing capacity. There is no possibility of rafters bending. Supports and struts can be placed almost anywhere.

An obvious drawback is the impossibility of arranging a full attic floor. Due to sharp corners, “dead” zones appear that are unsuitable for use.

The arrangement of one angle of more than 45° leads to a reduction in the amount of unused area. There is an opportunity to do living rooms under the roof. At the same time, the requirements for calculations increase, because the load on the walls and foundation will be distributed unevenly.

This roof design allows you to equip a full second floor under the roof.

Naturally, a simple gable rafter roof differs from a broken line, not only visually. The main difficulty lies in the complexity of the calculations.

Design of a gable roof truss system

Building a roof of any complexity with your own hands requires knowledge of the purpose of the basic structural elements.

The locations of the elements are shown in the photo.

• Mauerlat. Designed to distribute the load from the rafter system onto the load-bearing walls of the building. To arrange the Mauerlat, a timber made of durable wood is selected. Preferably larch, pine, oak. The cross-section of the timber depends on its type - solid or glued, as well as on the expected age of the structure. The most popular sizes are 100x100, 150x150 mm.

  Advice. For a metal rafter system, the Mauerlat must also be metal. For example, a channel or an I-profile.

• Rafter leg. The main element of the system. For the manufacture of rafter legs a strong beam or log is used. The legs connected at the top form a truss.

The silhouette of the roof truss defines appearance buildings. Examples of farms in the photo.

The parameters of the rafters are important. They will be discussed below.

• Puff- connects the rafter legs and gives them rigidity.

• Run:

• Ridge run, is mounted at the junction of one rafter to another. In the future, the roof ridge will be installed on it.

• Side purlins, they provide the truss with additional rigidity. Their number and size depend on the load on the system.

• Rafter stand- vertically located beam. It also takes on part of the load from the weight of the roof. In a simple gable roof it is usually located in the center. With a significant span width - in the center and on the sides. In an asymmetrical gable roof, the installation location depends on the length of the rafters. If there is a broken roof and one room is arranged in the attic, the racks are located on the sides, leaving free space for movement. If there are supposed to be two rooms, the racks are located in the center and on the sides.

The location of the rack depending on the length of the roof is shown in the figure.

• Strut. Serves as a support for the stand.

Advice. Installing the brace at an angle of 45° significantly reduces the risk of deformation from wind and snow loads.

In regions with significant wind and snow loads, not only longitudinal struts are installed (located in the same plane as the rafter pair), but also diagonal ones.

• Sill. Its purpose is to serve as a support for the rack and a place for attaching the strut.

• Lathing. Designed for movement during construction work and fixation of roofing material. Installed perpendicular to the rafter legs.

Advice. An important purpose of the sheathing is to redistribute the load from the roofing material to the rafter system.

Having a drawing and diagram indicating the location of all the listed structural elements will help in the work.

Advice. Be sure to add information about the passage of the ventilation shaft and chimney to the gable roof rafter system diagram.

The technology of their installation is determined by the type of roof.

Selection of material for rafters

When calculating the material for a gable roof, you need to choose quality wood without damage or wormholes. The presence of knots for beams, mauerlat and rafters is not allowed.

For sheathing boards, there should be a minimum of knots, and they should not fall out. The wood must be durable and treated with the necessary preparations that will increase its properties.

Advice. The length of the knot should not exceed 1/3 of the thickness of the timber.

Calculation of the rafter system of a gable roof

Calculating the material parameters is an important step, so we present the calculation algorithm step by step.

It is important to know: the entire rafter system consists of many triangles, as the most rigid element. In turn, if the stingrays have different shape, i.e. are an irregular rectangle, then you need to divide it into separate components and calculate the load and amount of materials for each. After calculations, summarize the data.

1. Calculation of the load on the rafter system

The load on the rafters can be of three types:

• Constant loads. Their action will always be felt by the rafter system. Such loads include the weight of the roof, sheathing, insulation, films, additional roofing elements, finishing materials for. The weight of the roof is the sum of the weight of all its constituent elements; such a load is easier to take into account. On average the value constant load for rafters is 40-45 kg/sq.m.

Advice. To make a safety margin for the rafter system, it is better to add 10% to the calculation.

For reference: The weight of some roofing materials per 1 sq.m. presented in the table

Advice. It is desirable that the weight of roofing material per 1 sq.m. roof area did not exceed 50 kg.

• Variable loads. They act at different times and with different strengths. Such loads include: wind load and its strength, snow load, precipitation intensity.

In essence, the roof slope is like a sail and, if you take into account the wind load, the entire roof structure can be destroyed.

The calculation is carried out according to the formula: wind load is equal to the regional indicator multiplied by the correction factor. These indicators are contained in SNiP “Loads and Impacts” and are determined not only by the region, but also by the location of the house. For example, on a private house surrounded by multi-story buildings, there is less load. Standing separately Vacation home or the cottage experiences increased wind loads.

2. Calculation of snow load on the roof

The roof calculation for snow load is carried out according to the formula:

The total snow load is equal to the weight of the snow multiplied by the correction factor. The coefficient takes into account wind pressure and aerodynamic influence.

The weight of snow that falls on 1 square meter. roof area (according to SNiP 2.01.07-85) is in the range of 80-320 kg/sq.m.

Coefficients showing the dependence on the slope angle are shown in the photo.

Nuance. When the slope angle is over 60 ° the snow load does not affect the calculation. Because the snow will quickly slide down and will not affect the strength of the beam.

• Special loads. Accounting for such loads is carried out in places with high seismic activity, tornadoes, and storm winds. For our latitudes, it is enough to make a safety margin.

Nuance. The simultaneous action of many factors causes a synergy effect. This is worth considering (see photo).

Assessment of the condition and load-bearing capacity of walls and foundations

It should be borne in mind that the roof has significant weight, which can cause damage to the rest of the building.

Determining the roof configuration:

• simple symmetrical;
• simple asymmetrical;
• broken line

How more complex form roof, the greater the number of trusses and sub-rafter elements needed to create the necessary safety margin.

The angle of inclination of a gable roof is determined primarily by the roofing material. After all, each of them puts forward their own demands.

• soft roof - 5-20°;
• metal tiles, slate, corrugated sheets, ondulin - 20-45°.

It should be noted that increasing the angle increases the area of ​​space under the roof, but also the amount of material. What affects total cost works

Nuance. Minimum angle The slope of the gable roof should be at least 5°.

5. Calculation of rafter pitch

The pitch of the gable roof rafters for residential buildings can be from 60 to 100 cm. The choice depends on the roofing material and the weight of the roof structure. Then the number of rafter legs is calculated by dividing the length of the slope by the distance between the rafter pairs plus 1. The resulting number determines the number of legs per slope. For the second, the number must be multiplied by 2.

Rafter length for attic roof calculated using the Pythagorean theorem.

Parameter "a"(roof height) is set independently. Its value determines the possibility of arranging a living space under the roof, the convenience of being in the attic, and the consumption of material for the construction of the roof.

Parameter "b" equal to half the width of the building.

Parameter "c" represents the hypotenuse of the triangle.

Advice. To the obtained value you need to add 60-70 cm for cutting and moving the rafter leg beyond the wall.

It is worth noting that maximum length timber - 6 m.p. Therefore, if necessary, the timber for the rafters can be spliced ​​(extension, joining, joining).

The method of splicing rafters along the length is shown in the photo.

The width of the roof rafters depends on the distance between opposite load-bearing walls.

7. Calculation of the rafter cross-section

The cross-section of the rafters of a gable roof depends on several factors:

• loads, we have already written about it;

• type of material used. For example, a log can withstand one load, timber - another, laminated timber - a third;

• rafter leg lengths;

• the type of wood used in construction;

• distances between rafters (rafter pitch).

You can determine the cross-section of the beam for the rafters, knowing the distance between the rafters and the length of the rafters using the data below.

Rafter cross-section - table

Advice. The larger the rafter installation step, the greater the load on one rafter pair. This means that the cross-section of the rafters needs to be increased.

Dimensions of lumber (timbers and boards) for a gable rafter system:

• thickness (section) of the Mauerlat - 10x10 or 15x15 cm;

• the thickness of the rafter leg and tie is 10x15 or 10x20 cm. Sometimes a beam of 5x15 or 5x20 cm is used;

• run and strut - 5x15 or 5x20. Depending on the width of the foot;

• stand - 10x10 or 10x15;

• bench - 5x10 or 5x15 (depending on the width of the rack);

• thickness (section) of the roof sheathing - 2x10, 2.5x15 (depending on the roofing material).

Types of gable roof rafter system

For the roof structure under consideration, there are 2 options: layered and hanging rafters.

Let's consider each type in detail in order to make an informed choice.

Hanging rafters

They are used for roof widths of no more than 6 lm. Installation hanging rafters is performed by attaching the leg to the load-bearing wall and the ridge girder. The design of hanging rafters is special in that the rafter legs are under the influence of a bursting force. Hanging rafters with a tie installed between the legs reduce its impact. The tie in the rafter system can be wooden or metal. Often the ties are placed at the bottom, then they play the role of load-bearing beams. It is important to ensure that the tie is securely attached to the rafter leg. Because a bursting force is also transmitted to it.

Advice.
The higher the tightening is located, the greater strength it should have.
If the tightening is not installed, the load-bearing walls may simply “move apart” from the pressure created by the rafter system.

Layered rafters

They are used for arranging roofs of any size. The design of layered rafters provides for the presence of a beam and a stand. The bench lying parallel to the Mauerlat takes on part of the load. Thus, the rafter legs are, as it were, inclined towards each other and supported by a stand. The rafter legs of the layered system work only in bending. And the ease of installation also tips the scales in their favor. The only drawback is the presence of a stand.

Combined

Due to the fact that modern roofs They are distinguished by a wide variety of shapes and complexity of configurations; a combined type of rafter system is used.

After choosing the type of rafter system, you can accurately calculate the amount of materials. Write down the calculation results. At the same time, professionals recommend drawing up drawings for each roof element.

Installation of a gable roof rafter system

After the gable roof rafters have been calculated, installation can begin. We will divide the process into stages and give a description of each of them. It will turn out to be unique step-by-step instruction, containing additional information for each stage.

1. Attaching the Mauerlat to the wall

The beam is installed along the length of the wall on which the rafters will rest.

In log houses, the role of the mauerlat is played by the upper crown. In buildings built from porous material (aerated concrete, foam concrete) or brick, the Mauerlat is installed along the entire length of the load-bearing wall. In other cases, it can be installed between the rafter legs.

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Since the length of the Mauerlat exceeds standard sizes lumber, it has to be spliced.

The connection of the Mauerlat to each other is done as shown in the figure.

How to connect the Mauerlat?

The beams are cut only at an angle of 90°. Connections are made using bolts. Nails, wire, wooden dowels are not used.

How to attach the Mauerlat?

The Mauerlat is installed at the top of the wall. The installation technology provides several ways to attach the Mauerlat:

• strictly in the center of the load-bearing wall;
• with a shift to one side.

Advice.
The Mauerlat cannot be placed closer than 5 cm to the outer edge of the wall.

To protect the timber for the Mauerlat from damage, it is laid on a layer of waterproofing material, which most often is ordinary roofing felt.

Reliability of Mauerlat fastening important aspect construction. This is due to the fact that the roof slope is like a sail. That is, it experiences strong wind load. Therefore, the Mauerlat must be firmly fixed to the wall.

Methods for attaching the Mauerlat to the wall and rafters

Anchor bolts. Ideal for monolithic structures.

Wooden dowels. Used for log houses and beams. But, they are always used with additional fasteners.

Staples.

Stud or fittings. It is used if the cottage is built from porous materials (aerated concrete, foam concrete).

Sliding mount (hinge). Tying in this way allows for the displacement of the rafter legs when the house shrinks.

Annealed wire (knitting, steel). Used as an additional mount in most cases.

2. Manufacturing of trusses or pairs

Installation is carried out in two ways:

• installation of beams directly on the roof. It is not used often, since it is problematic to carry out all the work, measurements, and trimming at height. But it allows you to completely do the installation yourself;

• assembly on the ground. Those., individual elements(triangles or pairs) for the rafter system can be assembled at the bottom and then raised to the roof. The advantage of such a system is more fast execution high-altitude works. The disadvantage is that the weight assembled structure roof truss can be significant. To lift it you will need special equipment.

Advice. Before assembling the rafter legs, you need to apply markings. It is very convenient to use templates for these purposes. The rafter pairs assembled according to the template will be absolutely identical. To make a template, you need to take two boards, the length of each of which is equal to the length of one rafter, and connect them together.

3. Installation of rafter legs

The assembled pairs rise to the top and are installed on the Mauerlat. To do this, you need to make a gash at the bottom of the rafter legs.

Advice. Since the slots on the Mauerlat will weaken it, you can only make cuts on the rafter leg. To ensure that the cut is uniform and fits tightly to the base, you need to use a template. It is cut out of plywood.

Methods of fastening the rafter leg are shown in the figure.

You need to start installing rafter pairs from opposite ends of the roof.

Advice. To correctly install the rafter legs, it is better to use temporary struts and spacers.

A string is stretched between the fixed pairs. It will simplify the installation of subsequent rafter pairs. It will also indicate the level of the ridge.

If the rafter system is mounted directly on the roof of the house, then after installing the two outer rafter legs, the ridge support is installed. Next, the halves of the rafter pair are attached to it.

It is worth noting that the opinions of professionals differ on this issue. Some advise using a staggered fastening pattern, which will allow the increasing load to be distributed more evenly on the walls and foundation. This order involves installing one rafter in a checkerboard pattern. After part of the rafter legs is installed, the missing parts of the pair are mounted. Others insist that it is necessary to mount each pair in a sequential manner. Depending on the size of the structure and the configuration of the truss, the rafter legs are reinforced with supports and racks.

Nuance. Connect additional elements structures using cutting. It is preferable to fix them with construction staples.

If necessary, you can lengthen the rafter leg.

Methods for splicing rafter legs are shown in the photo.

Advice. The method by which the mauerlat is lengthened (cut at 90°) cannot be used in this case. This will weaken the rafter.

4. Installing the ridge of a gable roof

The roof ridge unit is made by connecting the rafter legs at the top.

Roof ridge structure:

• Method without using a support beam (see figure).

• Method using rafter beams. The beam is needed for large roofs. In the future, it can become a support for the rack.

• Method of laying on timber.

• More modern variety The method shown in the photo can be considered for making a ridge assembly.

• Cutting method.

After the rafter system is installed, we perform major fastening of all structural elements.

5. Installation of roof sheathing

The sheathing is installed in any case, and is designed for more convenient movement along the roof during work, as well as for fastening roofing material.

The sheathing pitch depends on the type of roofing material, for example:

• for metal tiles - 350 mm (the distance between the two lower boards of the sheathing should be 300 mm).
• for corrugated sheets and slate - 440 mm.
• We lay a continuous sheathing under the soft roof.

Rafter system of a gable roof with an attic - video:

Conclusion

As you can see, despite its apparent simplicity, the installation of a gable roof rafter system contains many pitfalls. But, based on the recommendations given, you can build without any problems reliable design with your own hands.

The rafter system is the basis of the roof; the reliability and strength of the roof, its ability to withstand precipitation and wind depend on it. The design of the rafter system is determined by the shape of the roof and the layout of the house, as well as the materials used. A do-it-yourself rafter system is usually made of wood, but other materials can also be used, for example, a metal profile.

Types of rafters and their application

Choosing a rafter system is a crucial step that requires knowledge of the design of each type of roof. Rafters can be:

1. Layered rafters supported by a ridge girder and a mauerlat. They are used in the construction of a single-pitch roof, a simple gable roof, and also as one of the elements of a hip and sloping roof. mansard roof.
2. Sliding rafters are a type of layered rafters used for wooden buildings, giving greater shrinkage. Their difference is the sliding fastening of the rafters to the Mauerlat, which makes it possible to compensate for the shrinkage of the walls without deforming the roof.
3. Hanging rafters - a system of rafters tied together with crossbars or tie rods, usually used in the construction of a simple gable roof, as well as as the top rafters of an attic roof. In a hanging rafter system, there is no ridge purlin, and in the upper part the symmetrical rafter legs rest directly on each other.
4. Sloping rafters, otherwise called corner or diagonal. They are used to make three-pitched or hipped roofs, as well as for roofs with complex geometry.

Elements of the rafter system

Any rafters are designed to distribute and transfer the roof load to the walls of the house. The main elements on which the rafters rest are:

• Mauerlat is a beam fixed to the upper plane of the walls along the perimeter of the entire house;
• Bedding - support beams laid on internal load-bearing partitions or columns;
• Floor beams of the upper floor;
• Racks and supports;
• Purlins are horizontal supporting elements laid along the axis of the roof on racks.

The roof truss consists of the following elements:

• Rafter legs - boards or timber that form the contour of the roof and are laid at a certain pitch;
• Tightenings or crossbars – horizontal elements, pulling paired rafter legs together;
• Struts - supports placed at an angle and supporting the rafter legs;
• Fillers are boards attached to the lower end of the rafters and forming roof overhangs;

Rafts are short rafters resting on diagonal rafters in a hip roof.

All these elements in private construction are usually made of wood - timber or boards coniferous species, dried naturally. The wood is impregnated with an antiseptic, which extends its service life. The thickness and cross-section of the elements is determined by calculation.

Technology for making layered rafters

1. Before construction begins, it is necessary to sketch the roof and calculate its dimensions. The cross-section and pitch of the rafters, as well as the need to install additional supports and struts, are also determined by calculation.
2. Supporting elements are laid and positioned: mauerlat, floor beams and beams, racks, ridge and intermediate purlins. These operations are described in detail in articles dedicated to various types roofs:
3. Make a rafter template. To do this, take a board with a width corresponding to the estimated length of the rafters, with the same width, but with less thickness - it is lighter and easier to precisely adjust to the location. The board is applied to the installation site of the outer rafter with one end to the ridge girder and the other to the mauerlat.
4. At the top of the template, mark the top notch. The shape of the cut should be such that the board rests on the ridge girder and at the same time fits tightly to the opposite rafter. The depth of the cut should be no more than 1/3 of the width of the board.
5. After cutting out the top cut, the template is once again applied in place and the bottom cut is marked - it should rest on the Mauerlat without leaving large gaps. The end of the template is filed at an angle so that the cut is in a vertical plane.

   

6. The resulting template is applied to the installation site of all rafter legs, checking whether adjustment will be necessary in place. If the template fits perfectly (which rarely happens), you can immediately make required amount rafter legs. If adjustments to the bottom cut are needed, then only the upper part of each rafter is cut out using templates, and the bottom cut is made in place each time.
7. The rafters are placed with established calculation step. Typically it ranges from 50 to 120 cm and depends on the type of roofing, namely its weight, and the expected snow load. The heaviest coverings are slate and ceramic tiles, but they are currently rarely used. More often, the choice is made in favor of more modern, lightweight and reliable materials: metal tiles, ondulin, soft roof. For them, the rafter pitch can be chosen to be about 100 cm without performing complex calculations.
8. First, install the rafters on the gable side. The rafter leg is supported on the ridge purlin and the Mauerlat and secured to two nails 100-150 mm in each fastening point. Having installed the rafter pair, they additionally fasten it: in the upper part with the help of metal plates and screws on one side and corners with a stiffener on the other, in the lower part with staples or also with corners.

   

9. After installing the rafters from both gables of the roof, string is pulled between them and the remaining rafters are aligned along it. The rafters are fastened in the same way.

   

10. Install struts if the calculation results require it. The struts are made of the same material as the rafters. Apply a board of suitable length at the desired angle to the rafters and mark the bottom cut. It is important to consider what the strut will rest on: the floor beam or the beam; the shape of the bottom cut depends on this. After completing the bottom cut, the strut is placed in place and the cutting line along the rafters is marked. The prepared strut is placed between the beams and rafters and secured with metal plates or corners.

Installation of roof struts

Technology for making hip diagonal rafters

1. Since the rafters for a hip roof are installed diagonally, usual ways their fastenings are not suitable. In addition, the load on diagonal rafters is much higher than on layered or hanging ones, so the material for their implementation must have a larger cross-section. You can use timber with a thickness of 100 mm or more, but practice shows that it is more convenient to make these rafters from two folded and fastened boards of standard thickness.
2. The upper end of the diagonal rafters rests on the racks, and the lower end on the mauerlat bars converging at right angles. They are marked in place, and their main feature is that the cuts are made not perpendicular to the plane of the board, but at an angle of 45 degrees. When making rafters from spliced ​​boards, first one side is made with oblique cuts, then the second, in a mirror image.
3. The boards are pulled together using screws, nails or studs. The hip rafters are secured using overlays and self-tapping screws.

The video will help you better understand the basic techniques for constructing a rafter system with your own hands.

When making any rafter system with your own hands, it is important to carefully secure all components and connections and remember that the roof is the main protection of your home from bad weather. Therefore, it is important not only to make a high-quality frame, but also to choose a suitable one, for example, corrugated board, and lay it correctly.

21.02.2017 1 Comment

The rafter system of a gable roof is a simple design that can be installed with your own hands even by a novice developer. You just need to make preliminary calculations, familiarize yourself with the details and stages of roof construction, and calculate the materials needed for installation. When making calculations, it should be taken into account that the load-bearing capacity of a gable roof depends on the influence of loads from wind, snow, and the weight of materials on it.

To make the process of building a gable roof rafter system as easy as possible for you, below is detailed step-by-step instructions for installing a rafter system with your own hands.

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Requirements for building materials

For the installation of a rafter system the best option There will be the use of lumber from coniferous wood - pine, spruce or larch, grades I - III.

The material for the rafters is taken at least grade II, the mauerlat is made from boards or timber of grade II, material of grade II is taken for racks and purlins, the sheathing is made from lumber of grades II-III, it depends on the roof. Crossbars and tie-downs are made of Grade I material. Grade III material can be used on linings and linings.

Note! The lumber must be dry with a moisture content of no more than 20%. Before installation, it should be treated with fire retardants and antiseptics against fungal diseases.

Lumber should be stored under a canopy, providing protection from the sun and moisture. Level the storage area and cover the lumber with pads for ventilation.

For installation you will need fastening elements: ties, plates, studs, bolts with washers and nuts, self-tapping screws with EPDM gaskets, 2.8 mm thick, mounting tape, galvanized brackets.

Brackets are used when attaching the Mauerlat; they are secured with nails or self-tapping screws.

KR corners serve to attach the rafters to the mauerlat and prevent the rafters from moving.

All fastening material must be made of high quality material and have corrosion protection.

Tools for constructing a rafter system

To install a gable roof rafter system, you will need the following set of tools:

• tape measures of different lengths 5, 10, 20 meters;
• markers, pencils;
• cord for tensioning;
• hammers, for various purposes, nail puller;
• scissors, for cutting;
• roofing knife;
• putty knife;
• scotch;
• hacksaws, electric saw, electric drill with various drills and attachments;
• screwdriver with attachments;
• markings, horizontal and vertical levels;
• slats, rulers;
• polyurethane foam;
• safety belt and rope - for safe work.

Keep all tools on the roof in a tool bag for safety reasons.

Types of rafter systems for a gable roof

Sent rafters

They rest on the mauerlat and racks installed on the internal wall, with a pitch equal to the rafters. To provide rigidity for spans of 6 m, additional struts are installed.

Scheme of layered rafters of a gable roof

Hanging rafters

If the building is small in width, you can arrange a rafter system where the rafters rest on the mauerlat or walls, without intermediate supports. The maximum span is 9 meters. Such roofs can sometimes be installed without a Mauerlat. The rafters are installed on the wall using spacers; in this embodiment, a bending moment acts on the rafters.

To unload, wooden or metal plates are installed. They securely strengthen the corner. For hanging rafters of a larger span, a headstock and struts are installed. For hanging systems, the rafters are made with a larger cross-section, and lumber is chosen at least grade I II.

Scheme of hanging rafters of a gable roof

Calculation of the rafter system

You can determine the cross-section of a gable roof beam required in a rafter system by collecting all the loads acting on it: the weight of the covering, sheathing, snow, wind pressure, precipitation.

Constant loads can be determined by the weight of 1 m 2 of roofing and sheathing. It is important that the weight per 1 m 2 of roofing be in the range of 40-45 kg.

Variable loads from snow and wind are calculated using tabular values ​​of SNiP normative documents, depending on the height of the building and temperature zone. The load from snow is equal to its weight multiplied by a coefficient depending on the slope of the slope. All these calculations are performed during the project.

What if there is no project and the roof is being erected on a small building? You need to look at the construction of a house in the neighborhood, which is being carried out according to a design whose roof area is the same as your building. The gable roof rafter system will serve as a model.

Dimensions of timber for rafters

At the top point a ridge is laid that connects the rafters. The height of the ridge depends on the slope of the roof. The slope is affected by the choice of coating material. Minimum dimensions are:

• for tiled roofs, slate 22 gr.;
• for metal tiles - 14 g;
• ondulin - 6 g;
• corrugated sheeting - 12 gr.

The optimal angle is 35-45 degrees. tilt, ensures rapid discharge of water and snow. In regions with strong winds, the roofs are made flat and then the angle of inclination is within 20-45 degrees.

The height can be determined using the formula: H=1/2Lpr*tgA. Where A is the angle of inclination, L is the width of the building.

The task is simplified when using a ready-made table. The coefficient depends on the width of the building and the angle of inclination. Multiply the coefficient by 1⁄2 the width of the building.

The rafters are made from pine or spruce bars, with a section of 50x100 mm, 50x150 mm.

The size of the rafters depends on the pitch. The pitch of the rafters is smaller, a larger number is installed, and the cross-section will decrease. The distance between the rafters on a gable roof ranges from 600 mm to 1800 mm, it all depends on the design of the roof and the materials used for its construction.

Table of rafter sizes, depending on the step of their installation

Length rafters, mm	Distance between rafters, mm	Rafter beam cross-section size, mm
up to 3000	1200	80×100
up to 3000	1800	90×100
up to 4000	1000	80×160
up to 4000	1400	80×180
up to 4000	1800	90×180
up to 6000	1000	80×200
up to 6000	1400	100×200

The roof does not end at the level of the walls; it is extended outward by 500 mm. The rafter leg can protrude, or a board or block can be built up. In this case, moisture does not get on the wall and the foundation is not poured.

Step-by-step installation of a gable roof truss system

The rafter system of a gable roof consists of the following elements:

1. Mauerlat.
2. Lay down.
3. Racks.
4. Rafters.
5. Struts.
6. Puffs.
7. Lathing.

Mauerlat installation

Fastening the Mauerlat to a monolithic reinforced concrete belt

Mauerlat evenly distributes the load on the walls of the building; its installation can be done in several ways:

• attached to the wall through a reinforced concrete belt with studs;
• studs are inserted into the masonry;
• simple and common way to simple roofs, fastening with wire rod.

For it, take timber with a cross section of 100×100 mm, 150×150 mm or 200×200 mm. Which section to choose depends on the size of the roof and its covering. The Mauerlat is joined along its length; to do this, make 100 mm cuts, 500 mm long, fold the bars and fasten them with pins.

In the corners, the mauerlat is tied with notches into the floor of the timber, fastened with staples or bolts. U wooden buildings, Mauerlat is the last crown. On brick walls, make a monolithic reinforced concrete belt with a cross-section of 400×300 mm. Along the belt, place threaded pins 12 mm in diameter, every 120 mm, for fastening.

Drill holes with a diameter of 12 mm in the Mauerlat, lay them so that the pins go into the holes. Tighten the top with nuts. First, we lay two layers of roofing felt or roofing felt under the block. WITH outside brick the walls and mauerlat. Lay the Mauerlat on a horizontally and vertically level base. You need to check with a level that the surface is horizontal. Check diagonals. If necessary, level with pads.

Installation instructions for beds, racks, rafters, struts and tie rods

The installation of a gable roof rafter system with your own hands is carried out in the following order:

1. Install the beam with the rafters in place.
2. Mark the installation step of the rafter legs.
3. Prepare according to the size of the rack.
4. Install them if there is a need to secure them with spacers.
5. Lay the purlin. Check geometry. Install fasteners.
6. Try on the first rafter leg and mark the cutting areas.
7. Mark the points and install the rafters at the beginning and end of the roof, stretch the cord between them in order to align the remaining elements along it.
8. Having installed the rafter leg, we first attach it to the mauerlat, then to the ridge purlin, to each other.
9. Screw each second leg to the mauerlat with wire.

The rafters are fastened to the mauerlat using notches, stop corners and a hemmed support bar. Secure with nails or staples.

Methods for attaching rafters to the Mauerlat

Install the support posts on the beds or pads and overlays. A log is a beam 50×100 mm or 50×150 mm, laid on the middle wall along a layer of roofing felt. Place brick pillars under the linings, 2 bricks high.

The rafter legs are connected to each other at the ridge. Let's consider the common connection nodes of the rafter system:

1. They make cuts at one leg and cut down at the other. Insert one leg into the cut of the other and fasten with a bolt.
2. Install overlays, wooden or metal.
3. Using notches in the purlin, they are secured with nails or bolts.

Methods for connecting rafters on a ridge

To ensure the roof's resistance to wind loads, tie-rods, struts and purlins are installed. The tightening is a 100×150 mm block, purlins and struts are made from a 50×150 mm or 100×150 mm block.

With the installation of contractions, the reliability of the rafter structure increases. The sections of the timber are the same as the rafters. They are attached to the legs with bolts or nails. The device of struts adds rigidity to the structure. They are installed tightly to the surface of the rafters

The lumber has a standard length of 6 m. The rafters can be longer. Then you need to dock them. There are several connection methods:

1. Fasten by placing bars on both sides at the junction, connecting them with nails in a checkerboard pattern.
2. Connect with an overlap, one part of the rafters to another, at a distance of 1 meter, fasten with nails in an alternating order.
3. Make a cut obliquely, cut out part of the rafter legs, connect them, strengthening them with bolts.

Sheathing device

Lathing is installed along the roof rafters. It serves to distribute the load from roofing material and snow onto the rafters. Acting air gap between the roof and the rafter system.

The design of the sheathing depends on the roofing material used:

• under soft tiles make the sheathing continuous, lay an anti-condensation film on the rafters, press it on top with a counter batten, nail the sheathing onto it, then OSB boards and underlayment carpet, lay tiles on top.
• Under the roof made of corrugated sheets, the sheathing should be sparse. The pitch of the sheathing depends on the brand of corrugated sheeting, its thickness and the angle of inclination of the roof.
• The lathing for standard slate should be made in increments of 500 mm from a bar of 75×75 mm or 50×50, as well as boards from 30×100 mm. It is necessary to take into account the design features of the roof, when final choice suitable option.

The lumber from which the sheathing is made is first or second grade pine. It is advisable to take the width no more than 14 cm. With a wider width, the boards may warp and damage roofing decking. The length of the nails should be three times the thickness of the sheathing. Lay the boards along the ridge. Install the first board of greater thickness to the height of the roofing.

Install continuous sheathing along the roof slope.

The first layer is to place a board along the ridge from it at a distance of 500-1000 mm to the next one and so on. Lay the second layer of sheathing along the rafters. Place the joint between the boards only on the rafters at intervals. Sink the nail, head and all, into the flesh of the wood.

Cornice overhangs

They are installed to protect against precipitation and play an aesthetic role. Eaves overhangs are arranged tightly without gaps. The final stage on roofing.

Diagram of the eaves overhang of a gable roof

Gable

The gable roof has two gables. They have the shape of a triangle, with the apex at the ridge and the sides coincide with the slopes of the roof. The gables support the rafters and enclose the attic space. They protect from wind and precipitation and provide stability to the roof.

IN wooden buildings the pediment is made frame. IN brick buildings, frame or brick. Gables made of brick or gas block are erected before the roofing is installed. They require very precise execution.

Frame pediments fit into the finished opening when the rafter system is already assembled.

The frame is made of bars or boards. The frame elements are connected on tenons or in the wood floor, all fastened with nails. They are sheathed by nailing boards, lining or siding, maintaining the color scheme in the decoration of the building facade. To construct a window opening, an additional frame is made under it according to the size of the window. If the attic is insulated, then the gable also needs to be insulated. The insulation is placed in the middle of the frame. Mineral wool insulation with reduced flammability is used. On the outside, the frame is covered with a hydro-windproof film or windproof membrane, with inside under finishing material nail a vapor-proof film or vapor-proof membrane.

In contact with

The roof is a complex and important architectural element of any building. Its construction should be treated with special attention; it must be remembered that the installation of a rafter system requires considerable experience in performing such work and special tool. Those who are holding carpentry and measuring tool– the results of activities can be very negative.

There are two types of roofs depending on the number and placement of rafter support points, but each developer can, at his own discretion, slightly change the specific design of the rafter system. This takes into account the operating conditions of the building, the purpose of the attic space, the climatic zone of the location, and the technical parameters of lumber and roofing coverings. Of course, the type of rafter system is influenced personal experience and preferences of developers.

Before you start making rafters, you should decide on their type, method of fastening and linear dimensions. Only in this case can you be sure of the strength and safety of the structure.

How do various factors influence the parameters of rafters?

Physical factor	Brief description of the effect on rafter parameters
	The rafters must withstand snow and wind loads. During calculations you need to take from the tables building codes and the rules are the actual maximum values ​​of snow cover, take into account the strength and wind rose. The data allows you to find out the total load on the roof slope depending on its area and angle of inclination. Next, you can determine the size of the rafters, their number and pitch. In this case, a safety factor must be included. The fact is that lumber does not have stable and uniform strength values; too many unforeseen factors influence these indicators. For most cases, 50×150 mm or 50×200 mm boards are used to make rafter legs.
	Gable roofs can be layered or hanging. For hanging roofs you need to make rafters from stronger boards. In this case, the method of fixing the elements to the Mauerlat is taken into account. If a notch is made, then the width of the boards should increase by the amount of the notch. The fact is that the cut in this place automatically reduces the width of the material that takes the load. If you make a cross cut 60 mm long on a 200 mm thick board, then only the remaining width of 140 mm is taken into account. Accordingly, if, when calculating the loads, rafters from 200 mm boards are selected, but during fastening unintended cuts of 60 mm are made, then the width of the blanks for the rafters increases to 260 mm. This remark is made for those who like to abuse various notches and cuts for the persistent areas of the ends of the rafters. Currently there are many special devices, allowing you to firmly fix the rafter in the desired position without filing.
	For residential buildings, rafters must have a safety margin of at least 1.4 of the design values. For non-residential buildings the coefficient is reduced to 1.2. Conclusion - the size of the rafter boards on houses is larger than on garages and other extensions.
	Residential attic spaces (attics) must have an insulated roof. The width of the rafters must correspond to the thickness of the insulating layer. At the same time, you need to adjust the pitch between the rafter legs depending on the standard width of the insulation. If in this climatic zone optimal thickness roof insulation is 200mm, then it is recommended to choose the same width for the rafters. Various extensions of narrow rafter legs during roof insulation are not considered the right solution.

This knowledge will help you accept right decisions both during the manufacture of the rafters and during their fixation directly in place. Mistakes in the construction of a rafter system are too expensive; you should not be overly self-confident.

What influences the choicesizes andwaysfasteningsrafters

Very important point. The task of any fixation is to ensure the stability of the connection node, while it can be stationary or have one or more degrees of freedom. This cannot be achieved without knowledge of the loads affecting the rafter legs. Loads can be permanent and temporary, dynamic and static, unidirectional and multidirectional.

1. Constant vertical forces. Occur due to exposure to roofing and insulation materials roofs. Due to the fact that the rafter legs are located at an angle to the vertical force, they are subject to bending and expansion loads. The magnitude of the forces is determined after constructing the diagram; based on the specific bending and expansion forces, the thickness and width of the boards for the rafters is selected. The fastenings must prevent the rafter system from spreading.
2. Variable vertical forces. Appear in winter, the magnitude depends on the depth of the snow cover.
3. Lifting wind forces. As a result of gusts of wind, lifting forces are applied to the roof. The dimensions of the rafter legs are not affected; the forces are taken into account only when choosing the type of fixation; it must provide for and support such loads.
4. Lateral forces. The value depends on the windage of the roof. As a result of gusts of wind, lateral forces act on the rafter system. They increase bending and tearing loads. This feature also needs to be taken into account during the manufacture and installation of rafter legs.

There are options for rigid fastenings of roof trusses; for this, metal plates, corners, screws and nails are used.

Sometimes it is necessary to use floating rafter connections to compensate for changes in size wooden houses. For floating connections, special fasteners and bolts are used. The second allows the rafter legs at the top to rotate slightly.

Another example of a loose rafter connection is a sliding one. It is used on wooden log houses and makes it possible to compensate for the natural shrinkage of the house.

What elements are used to increase the stability and load-bearing capacity of rafters

As a result the right choice rafter system and methods of fixing its elements, the structure must be stable, compensate for natural fluctuations in linear parameters and withstand various loads that arise during operation. To fulfill the conditions during fixation of rafters, additional fixation elements can be used.

Runs

Most often they are mounted in the ridge part of the system; the upper ends of the rafter legs rest on them. To increase stability, cuts may be provided. The top connection is rigid or floating with bolts. On large roofs, purlins can be installed in the middle of the rafters or in other places with critical loads.

VertikAlinen racks

They are installed to strengthen rafters; through the use of racks, elements can be made from thinner lumber. Vertical racks the upper end rests against the rafters, and the lower end against the bench or ceiling beams ceilings

CornerOpores

Resists bending and expansion forces, universal use. Corner stops can be placed in any place on the rafter leg, raising concerns in terms of strength. Due to such stops, the resistance of rafters to bending and tearing forces significantly increases.

Puffs(crossbars)

The purpose is to keep the rafter legs from spreading; they are used on hanging rafter systems. Most often they are placed in the upper part of the truss; for manufacturing, you can use boards approximately 20–25 mm thick. The fact is that they work in tension, lumber holds such forces well. The boards do not work well under compression, quickly sag and lose their original strength.

Knucklehellish

They are used in the upper ridge part of the rafters; due to the use of puffs, the strength of the joint connection is increased. Pulls can be made of wood, plywood, OSB or metal.

Lugs(stops)

They have many specific names. They are ordinary pieces of boards 30–40 cm long and 40–50 mm thick, fixed at the bottom of the rafters. They rest against the mauerlat and prevent the structure from slipping. The use of bosses allows for a rigid connection of elements without sawing down the rafters. We talked about the problems that arise in connection with sawing in this article above.

Prices for various types of timber

Options for connecting the ridge assembly of rafter legs

The ridge is one of the main and most loaded elements of the rafter system. The unit has several connection options; you should choose a specific one depending on the general parameters of the roof.

If the slopes are long, it is better not to use a ridge beam, but instead install two parallel purlins and tie-down crossbars. This design is easier to make, more stable and safe.

For a suspended roof, you should choose the most reliable methods of connecting rafter legs; these systems have a minimum number of additional stops.

Prices for various types of fasteners for rafters

Rafter fasteners

Step by stepWithThand of mouthAnew rafters

For the rafter legs, 50×200 mm coniferous boards and first-grade lumber are used. The boards cannot have traces of rot or fungus, significant defects or deep cracks. The use of low-quality lumber for the manufacture of rafter systems is strictly prohibited.

To increase the protection of roof elements from rotting, it is recommended to use fire protection.

Rafter blanks should be impregnated at least twice, and the material should be dry and clean. Processing is done on a level area in dry and clear weather.

You can impregnate with a roller, brush or pneumatic remote control. It is not recommended to use household hand sprayers - they are too time-consuming and difficult. The boards can be raised to the top after the impregnation has completely dried.

Our gable roof has a ridge girder, the vertical supports rest against a beam located on the load-bearing wall in the middle of the building.

Practical advice. If the house is quite tall and the boards are heavy, then it is recommended to make a simple device to protect the window openings from damage. To do this, two boards are knocked together in the form of a square; the length and width are selected taking into account the parameters of the opening. The device is installed on the window sill, and the rafter boards do not damage the foam blocks during lifting.

Prices for fire-bioprotective impregnations

Preparatory operations

The production of rafters begins with preparatory operations.

Step 1. Raise rafter boards into the attic. For convenience, place them evenly along the length of the building, place one end on the mauerlat, and the other on the girder. First you need to install the outer rafters on both sides of the roof of the house, stretch a thread between them and install and align all the remaining ones along it.

Step 2. Check the position of the ridge run again. It should be located exactly in the middle of the roof. Its displacement by 1–2 centimeters will not affect the strength of the roof as a whole, but will somewhat complicate the manufacture of rafters and the laying of roofing materials. Besides, experienced builder may notice a discrepancy in the sizes of the slopes and, accordingly, the asymmetry of the roof. It is recommended to ensure that the ridge run is located along the line of symmetry, unless this is associated with great difficulties. The final decision is made by the foreman on site and depends on the magnitude of the displacement and the amount of work to correct the error.

How to align a run?

1. Attach a sheathing board to the mauerlat; it is lighter and easier to lift and fix. The second end should lie on the purlin. The board is nailed to the mauerlat with an ordinary smooth nail or screwed with a self-tapping screw.
2. Climb to the top of the purlin and use a tape measure to check the distance from the edge of the purlin to the mauerlats installed on opposite walls. Work very carefully, it is advisable to use insurance. Unfortunately, in practice, few people follow safety rules, but in vain. Falls from height can cause very serious injuries.
3. Center the purlin and secure the board. To increase rigidity, fix the same board on the other side of the purlin.

Now everything is ready, you can begin to manufacture and install the rafters.

Installationrafter legs

If you work alone, then you need to screw a piece of lath to the purlin at the place where the first rafter is fixed. The rafter board will be temporarily fixed to it to prevent it from sliding down.

And at this time, you can carry out work on the manufacture and preparation for connecting the upper part of the rafters.

Step 1. Lift and place the rafter board in place, using a clamp, clamp it to the previously attached batten.

Step 2. Draw lines to cut out the stop pad. This is done in two stages. First, draw a horizontal line. To do this, press the rail, square or other flat object tightly against the horizontal surface of the purlin.

Second, draw a vertical line. Now the ruler or square should be pressed against the side surface of the purlin.

Important. The width of the ruler should be no more than 2–3 cm, there is no need to make deep cuts and significantly reduce the width of the rafter leg, it loses its maximum design strength.

Make the same markings at the bottom of the rafters. Only now the ruler needs to be pressed against the surfaces of the Mauerlat.

Step 3. Remove the board and carefully cut out the seats. You can work with a hacksaw or an electric circular hand saw.

Practical advice. If the cuts are made with an electric circular saw, then it is better to cut in two steps. First cut to the mark, then turn the board over and cut again to the mark. Use a hammer to knock out the cut piece, and remove the remaining protrusion with a chisel or chisel. There is no need to go beyond the line with the saw and try to cut off the lip in one go. This method increases the cut by 3–5 cm, depending on the diameter of the disk, which significantly reduces the load-bearing performance of the rafters.

Step 4. Place the prepared rafter in place and check that it is made correctly. Perform the same operations with the second leg of the truss.

Step 5. Place the rafters with emphasis on the mauerlat and purlin, tighten them with a clamp at the top. Find the middle of the run and transfer the line to the rafters, use a level or construction square(only in the case when the plane of the run is strictly horizontal).

Step 6. Saw two rafters along a vertical line at the same time. The boards must be tightly clamped with a clamp. Pay maximum attention to ensure that the saw blade is perpendicular to the plane of the rafters. If you saw it obliquely, the ridge joint will not fit tightly, and this reduces the stability of the rafter system and is considered an obvious construction defect.

If there is a shortage practical experience When performing such work, the first leg may have a gap in the ridge part; if it is within 1–2 mm, then there is nothing to worry about. If it is more than 4 millimeters, then the element needs to be corrected. Look at which planes of the thrust pads do not allow the top cut to fit tightly. Approximately indicate the size of the additional cut. Remove the rafters and remove any interfering protrusions. Check the connection again, if gaps remain, repeat the operation. As practice shows, experience appears on the second or third rafter and no further corrections need to be made.

Step 8 Securely fasten the rafter legs in the correct places. To do this, it is recommended to use metal plates and corners; working with them is simple and easy; their strength fully meets the requirements for the rafter system.

For each pair of rafters you will need one large reshaped plate to connect the ridge assembly, two 50x50mm corners for fixing to the purlin and two 60x80mm corners for screwing to the Mauerlat. The thickness of the metal is at least two millimeters.

In the same way, install the outer rafters on the other side of the house, stretch the threads between them. One at the top and bottom and one in the middle. To prevent them from interfering during the manufacture of rafters, make a gap of about one centimeter between the thread and the plane.

Real professionals never make one rafter in the attic of a house. This algorithm of work significantly increases construction time, complicates the process itself and makes it unsafe. Working with electric tools on unsuitable sites is very dangerous; injuries from them are severe and often cause disability.

If the house is built with high quality and strictly adheres to the dimensions and rules, then the rafter legs are made according to one template on the ground. The finished elements are assembled on the roof. This technology increases labor productivity by 3–5 times, while at the same time improving the quality of the rafter system, it is more reliable and durable. Of course, the salaries of builders also increase proportionally. They work from the mine and receive money not for the time spent in the attic, but for the assembled roof.

Prices for popular models of screwdrivers

Screwdrivers

Video - Manufacturing and installation of rafters on a gable roof

Rafter system - any “skeleton” roofing structure. The reliability, quality and durability of the roof directly depends on the correctness of its manufacture and installation. If desired, you can handle the arrangement of the rafter system yourself. Want to know how? Check out the following guide!

There are layered and hanging rafter systems. According to statistics, layered structures are most often used. When arranging such a system, they run into the Mauerlat. The function of the central part is performed by a simple ridge run. To increase the strength of the system, supporting beams are installed.

In the case of hanging rafters, the system design is equipped with additional racks that promote optimal load distribution over the entire area of ​​the roof structure.

We take an extra pair of nails and fix the angle set between the boards. The template is ready. Additionally, secure it with a crossbar. To ensure that the set slope angle of the roof slope does not change under the influence of loads, fasten the crossbar with self-tapping screws.

Be extremely careful when creating the template. Even the slightest deviations can cause the entire structure to deteriorate.

Next, we make a new template for preparing mounting cuts on the system elements. Use plywood 0.5 cm thick. For reinforcement, use a 2.5 cm board. Select the dimensions of the cuts taking into account the cross-section of the rafters used.

By using ready-made templates we make cuts and begin to assemble the truss.

Video - Gable roof rafter system

Farm assembly procedure

The structure includes supporting legs and connecting components. The farm resembles a triangle. Perform the work in the specified sequence, and the finished structure will be able to adequately withstand all incoming

The farm can be made on the ground with further rise to the top, or directly on the roof. The first option is simpler and easier to implement.

We assemble the truss in the following order. First, we cut the prepared material to the right size, we join the bars with their upper edges and fasten them with screws. To prevent cracks from appearing at the fastening points, we pre-drill holes in the bars with a diameter of slightly smaller size fasteners.

We also use a crossbar to connect the rafter legs. We fix it half a meter below the top point of fastening the elements. Crossbars will help increase the rigidity of the structure and eliminate the risk of deflection. We fasten the crossbars in recesses previously prepared in the rafters by cutting down.

If necessary, the rafters are cut at an angle if this is required by the features of the roofing structure being installed.

Installation of a roof truss

The installation of roof trusses is carried out in the following sequence:

• we install end trusses;
• we fix the central trusses.

When installing edge trusses, we adhere to the following important rules:

After completing the installation of the outer trusses, we proceed to fixing the central and subsequent structures, if their placement is provided for by the project. The optimal installation step for trusses is 100 cm.

To secure the central rafter triangle, we use temporary jibs. After the visor is installed, the jibs can be removed. Recommendations for fastening the central and other trusses are the same as in the case of the outer structures.

After installing all structural elements, we begin attaching the sheathing and further arrangement roofing system: moisture, heat and vapor barrier, as well as installation of the selected finishing coating.

Good luck!

Prices for various types of fasteners for rafters

Rafter fasteners

Video - DIY rafters. Shed roof

Video - Hip roof. Rafter system