The distance between the rafters on a shed roof. All about gable roofs: the optimal distance between the rafters

The roof frame must be reliable and durable. But without well-conducted calculations, this is difficult to achieve. In the process of carrying out the calculations, it is determined at what distance to put the rafters on the roof.

What can lead to an incorrect or inaccurate calculation of the loads that the truss structure will undergo? To the most negative consequences, ranging from deformation of the rafter legs and damage to the roof covering and ending with the collapse of the base of the roof frame. Therefore, when designing buildings, the list of mandatory calculations contains data on what should be the distance between the roof rafters. There is a certain technique that allows you to calculate this value.

Method for calculating the distance between the rafters

The distance between the rafters on the roof is called the pitch of the rafters. As a rule, the step of the rafter legs in the roof structure usually exceeds one meter, and the minimum gap varies within 60 centimeters.

The calculation of the required number of rafters for a roof of a certain length and the pitch of the rafters is carried out as follows:

Roof structure for metal roofing

During the construction of suburban private real estate, metal roofing can be found most often. This roofing material is similar to the flooring made of clay tiles, but in comparison with it has a number of advantages. Sheet metal tiles are easy to install, so you can build a roof in a shorter time, the rafter system for metal tiles is also not difficult.

Metal tiles are lighter than ceramic products, the difference in weight sometimes reaches 35 kilograms per square meter, depending on the thickness of the products (read also: ""). Due to a significant reduction in the weight of the roofing, it becomes possible to reduce the thickness of the elements of the truss structure and the cross-sectional dimensions of the lathing bars, and increase the installation step of the rafters.

Under the metal-tiled coating, the rafter legs are mounted with a distance of 600 to 950 millimeters, while the cross section of the construction material is 150 by 50 millimeters. According to experts, in this case, if a heater 150 millimeters thick is placed between the rafters, then such thermal insulation will create comfortable conditions for staying in the attic room. At the same time, for greater reliability, it is advisable to choose a 200 mm insulation.

When installing rafters, to ensure ventilation of the space that is filled with insulation, holes with a diameter of 10-12 millimeters are drilled in the rafters near the upper roof.

The technology for creating a truss system for metal tiles does not differ significantly from structures for other types of roofing materials. The only feature is that at the rafters, the upper support is mounted on the ridge run from above, and not on the side of the ridge beam. The presence of a free zone between the rafters ensures air circulation under the roofing, and this, due to the use of metal material, reduces the risk of condensation.

Shed roof truss system, main advantages and characteristics ").

The distance between the rafters of a gable roof is made taking into account the size of the heat insulator that is laid between them. An approximate step between the rafter legs is 1-1.2 meters (read: ""). Rafters regulate the size of the roof overhang.

The roof is one of the main elements of the house, so you should pay special attention to the correct calculation of the roof frame. Which will serve as a skeleton in your home. Incorrect calculation of all loads can lead to disastrous results in the form of deformation of the roof with its subsequent collapse.

Before proceeding with the installation of the roofing, it is necessary to calculate the truss system, which will depend on the material used, construction, and climatic conditions.

What you should pay attention to before making a calculation

Before starting the construction of the roof, it is necessary to choose the type of truss system. Then calculate all the loads that will fall on the roof. The main loads include the weight of the frame, roofing material, insulation, ceiling, and temporary loads are taken into account, among which are the weight of the snow cover, possible gusts of wind, the weight of a person during the installation and operation of the roof.

The distance between the rafters is calculated based on the selected type of rafters and the material with which the roof will be covered.

Types of rafters

In the construction of roofs of various designs, hanging or layered rafters are used. Sloped - used when installing one- or two-slope roofs. They have two points of support - load-bearing walls or a load-bearing wall and a ridge beam. Hanging rafters are used when it is necessary to cover large spans or create a sloping roof. In this case, the rafters rest with one end on the wall, and the other on the opposite rafter. The quality of the material from which the frame is made will directly affect the reliability of the entire roof.

Material for rafters

Currently, wood and metal are used. A wooden beam or log is used in the construction of residential buildings, garages and other buildings. Reinforced concrete or metal rafters are used in the construction of industrial facilities, shopping centers, where wide spans are needed.

Method of calculation

The distance between the rafter legs is called the pitch of the rafters. It should not exceed one meter, and the minimum value - 60 cm. Before making a calculation, it is necessary to measure the size of the roof slope. Then we divide the obtained value by the approximate value of the step between the rafters. One is added to the result and rounded up to the next whole number. So we find out the number of rafters that we need. In order to find out the exact distance between the rafters, for this we need to divide the length of the roof bevel by the number of rafter legs.

For greater clarity, consider an example calculation:

roof bevel length - 28.5 m

the step between the rafters is chosen equal to 80 cm

add one to the resulting number: 35.625 + 1 \u003d 36.625

as a result, we get that we need 37 rafter legs

the exact step of the rafters will be: 28.5 / 37 = 0.77 m

This is a general calculation method that requires adjustment depending on the roofing material.

The dependence of the pitch of the rafters on the material of the roof

The most common roofing materials are slate, metal tiles, corrugated board, ondulin, soft roofing.

Roof truss structure for slate roofs

Slate is widely used as a roofing material, due to its low cost, resistance to temperature extremes. Due to the severity of the material, it is necessary to install a powerful truss system. The distance between the rafters in this case will depend on the cross section of the timber. The optimal value is a distance of 80 cm, which will allow not only to withstand increased weight, but also significant snow and wind loads. In this case, the crate is made with a board at least 3 cm wide. Depending on the type of slate, the crate is made continuous for smooth sheets or sparse for wave ones.

Important: the slate must have at least three support points along the edges and in the center.

Step between rafters for metal tiles

Metal tiles are becoming more and more common among roofing materials. Which is characterized by a simple installation process, and will also help to create your own unique look for your home. Sheets of metal tiles are lightweight, which allow you to increase the distance between the rafters from 600 to 950 mm, with a beam section of 150x50 mm. The crate in this case will depend on the pitch of the sheet wave. So for a wave of 350 mm, a distance between the boards of 30-40 cm is possible.

Important: on the overhangs of the cornices, the edges of the bevels, the step of the lathing is made minimal for greater reliability of the roof.

Rafter pitch under corrugated board

Decking is a galvanized steel sheet coated with a special coating that protects it from the harmful effects of the environment. A large selection of colors and corrugation widths will allow you to create a reliable and aesthetically attractive roof. The step of the rafters under the corrugated board will directly depend on the characteristics of the type of profile used, the angle of the roof, its configuration. You should also take into account the fact that the crate under the profiled sheet is attached perpendicularly. The rafter system is made of beams with a section of 50-75 mm or from a board 20-50 mm thick and no more than 15 cm wide. sparse - the distance between the boards is 50-75 cm. The step of the rafters under the corrugated board is calculated according to the general scheme and is 60-90 cm.

Step of roof rafters from ondulin

Ondulin is a wavy sheet that has high strength and durability. With such a roof, the truss system is made of pine boards with a section of 50x200 mm, in increments of 60-90 cm. A sparse crate of 40x50 cm is made from above.

Important: if the roof has an angle of inclination greater than 50 degrees, then the crate must be solid.

Determining the pitch of the rafters for a shed roof

A shed roof is simple and does not require any special installation skills from you. Most often it is installed on garages, baths, extensions. The roof frame consists of beams that rest on the walls of the building. The distance between the rafters of a shed roof will depend on the length of the rafters. Here you should correctly approach the choice of the section of the beam, since the greater the distance, the greater the load on the rafters. For the correct selection of the pitch of a shed roof, use the data from the table:

The distance between the rafters for a gable roof

The gable roof is the most common, not only because of the simplicity of the device, but also because of its high reliability. The pitch of the rafters of a gable roof is calculated according to the general scheme. If the bevels are the same on both sides, then one part can be calculated. To do this, we determine the angle of inclination of the bevel, here you should take into account the material with which you will cover the roof. So at an angle of 45 degrees or more, you can use all types of coatings. For slate, tiles, the minimum angle of inclination is 22 degrees, for corrugated board and soft tiles - 12 degrees, for metal tiles - 14 degrees, for ondulin - 6 degrees. The length of the rafters for a gable roof is calculated using the Pythagorean theorem, in which the length is the hypotenuse, and the height of the roof and half of its width are the legs. If the spans are more than 6 meters, then the rafter system is additionally reinforced with struts and headstocks, which will not allow the rafter legs to deform under the weight of the roofing material.

Before the construction of the truss system and the organization of the roof, a number of simple measures must be carried out, which will be the key to the integrity of the structure. This includes choosing the type of roof.

It can be hanging or layered, or maybe a combined version. This is when two types are combined in one building.

Live loads are snow cover on the roof in winter, water flows from rain in summer, wind, the load that a person exerts while carrying out maintenance work during the operation of the roof, etc.

Permanent loads include the weight of the rafter system itself, the weight of the roofing material and the roofing pie, the mass of interior decoration, if it is planned to organize an attic in the attic of the building.

When creating a project for a single-pitched or dual-pitched roof, first of all, they choose the type of truss structure, the angle of inclination of the roof slopes, as well as materials for the construction of the structure. When calculating the distance between the rafters, one should take into account the loads that will affect the roof of the building during operation.

• The weight of the roofing material;

• The weight of the building materials from which the roof truss frame is built;

• Weight of insulation, vapor barrier, waterproofing;

• The weight of the finishing material of the attic or residential attic space.

The following temporary loads also affect the roof of the structure:

• Snow weight;

• The weight of a worker performing maintenance and repair of the roof.

For the correct calculation of the pitch of the rafters, it is necessary to take into account the cross section of the elements of the structure under construction, the presence of thermal insulation of the roof, the type of lathing and roofing. Calculations should be performed on the basis of SNiP 2.01.85 "Loads and impacts".

Video on how to calculate the truss system:

Scheme for calculating the distance between the rafters

All calculations are carried out at the design stage of the building. They are carried out by design engineers of the organization where the house project was ordered.

If the project has not been drawn up and the person relies only on the experience of the masters who are entrusted with the construction of the roof, then in this case you need to familiarize yourself with the relevant documentation. These are SNiP 2.01.85 "Loads and Impacts" and "Changes from SNiP 2.01.85".

There is a detailed calculation scheme and a map of the country's climatic zones.

Further, they are determined with the type of roofing system and the purpose of the attic space. Indeed, depending on whether it is an unheated attic or a living room, the loads on the rafters will be different, and, consequently, the course of calculations also changes.

The calculations must necessarily take into account the climatic zone where the work is carried out, the structural material of the rafters and its cross section.

So, the pitch of the rafters is the distance between the rafter legs. It can vary within 0.6 m - 1.0 m.

Calculation progress:

1. First, the length of the roof slope is measured. Further, this value is divided by the step length of the rafters of the selected material. This indicator is taken from the SNIP and is unique for each building material and also depends on the beam section used;
2. one is added to the result of previous calculations and rounded up. Thus, an integer value is obtained and it indicates the required number of beams;
3. the length of the roof slope is divided by the resulting integer. The result will show how many beams are needed to build a high-quality and durable roof.

Experts point to the following feature of roofs with a steep slope. When erecting them, you can reduce the distance between the rafters. This is due to the transfer of the load from the beams to the wall of the house.

The distance between the rafters for different types of roofs

However, the calculation of the distance between the rafters cannot be carried out so unambiguously. After all, this indicator also depends on the type of structural material used for the roof.

The distance between the beams for a roof made of metal

The average weight exerted on the roof is 35 kg/m². To withstand it, the roof must have a step of 0.6-0.9 m. In this case, a beam with a section of 50x150mm is used.

However, metal tiles are often used in the construction of country houses and cottages. And in such structures, the attic space is often equipped as a living room.

This leads to the installation of a roofing pie and all kinds of heaters, which, in turn, put an additional load on the rafters. Therefore, it is recommended to increase the cross section of the beam for beams. This is especially true for regions with low air temperatures in winter. The recommended dimensions of the rafters are 50x200mm.

In addition, the distance between the rafters can be adjusted to the width of the insulation. This will not only increase the bearing capacity of the roof, but also simplify the arrangement of the heat-insulating layer, and reduce the consumption of insulation.

The distance between the beams for the roof of corrugated board

The recommended rafter pitch for a roof is 0.6 m - 0.9 m. However, here it is necessary to take into account the operational characteristics of the corrugated board itself. If the step is large, then the corrugated board will “sag” under its own weight, thereby changing the geometry of the roof and its technical characteristics.

To prevent this, you need to mount additional boards with a large section as a crate. They will act in some way as rafters.

The cross section of the rafters for roofing from corrugated board is 50x100 mm or 50x150 mm. The crate is made of a board with a section of 30x100 mm.

The distance between the beams for a roof made of ceramic tiles

Ceramic tiles are a heavy material for roofing. It exerts a load on the rafters in the range of 40-60 kg per m². That is why the distance between the rafters in this case will be minimal - 80-130 cm. The greater the weight, the smaller the distance. However, the latter indicator may decrease, depending on the angle of the roof. The larger it is, the less often you can mount beams.

Installation of the structure for ondulin

The step of the rafter legs under the ondulin should be 60-100 centimeters. For the manufacture of rafters, lumber with a section of 200 × 50 mm is used. This is enough to create the most durable and reliable truss frame.

It should be noted that under this roofing material it is necessary to make a continuous crate. Due to this, the material will better resist snow loads and solar exposure.

Sometimes a thinned type of crate is used. For its manufacture, a wooden beam is used. The distance between adjacent elements should be less than 30 centimeters. This option, as a rule, is more expensive compared to a continuous crate.

Rafter system under slate

Slate roofing is considered the most common in Russia. The main reason is the low cost of this roofing material, the ease and speed of installation work. Also an important advantage is the possibility of replacing individual damaged slate sheets with new ones.

The distance between the rafter legs for a slate roof should be 80 centimeters. This distance is considered the most optimal.

The crate under the slate should be thinned out. For its manufacture, a board or timber with a cross section of at least 30 millimeters is used. It is this thickness of the timber or board that is required for the qualitative distribution of the weight of the roofing and winter precipitation.

When erecting a rafter system, one should remember about a constant margin of safety. It may be needed in case of bad weather and under mechanical stress.

Rafter frame for a soft roof

Soft roofing includes soft tiles, bitumen-polymer and bituminous roll materials, as well as roofing membranes. The main advantages of this type of roof include low weight, as well as the absence of the need to build a massive rafter system.

The minimum pitch of the rafters is 60 centimeters, and the maximum is 150 centimeters. When erecting a rafter frame under a soft roof, the angle of inclination of the slopes should be taken into account. In other words, the smaller the slope of the roof slopes, the less you need to make the distance between the rafter legs for a continuous crate.

The distance between the rafters also depends on the material from which the crate will be made. The greater the thickness of the plywood or OSB sheet, the greater the pitch of the rafters can be.

Roof made of sandwich panels

Roofing of this type, as a rule, is erected on hangar-type buildings or houses made of sip panels. Sandwich panels have bending rigidity, so their installation does not require the installation of traditional rafter legs.

If the spans from the top of the wall to the ridge of the gable roof are small, then the sandwich panels are mounted without additional supports.

With a span length of more than 400 centimeters, it is necessary to install additional runs. When building a roof from sandwich panels on a residential building, a traditional truss frame is often erected. However, in this case, the distance between the rafter legs can be made large, since they serve as a support for the runs.

Choose the distance between the rafters based on the length of the bearing walls and the length of the material for the runs. Roofing made of sandwich panels is able to withstand high operational loads.

Construction of a truss frame for polycarbonate

Recently, polycarbonate is often used in the construction of roofing. It is used in the construction of sheds, winter gardens and arbors. The rafter frame and crate are made of metal or wood.

Polycarbonate differ in weight, which depends on the thickness of the sheet. The step of the crate for polycarbonate should be from 60 to 80 cm. The crate made of metal or wood is attached to the rafters (straight or arched).

The distance between the rafter legs for polycarbonate, as a rule, is 150-230 cm. To correctly calculate the distance between the rafters, it is necessary to take into account the glazing area, the thickness and dimensions of the sheets. It should also be remembered that polycarbonate sheets are mounted with small gaps.

The distance between the rafters is one of the key parameters that affect the strength of the structure. Competent calculation of the installation step of the rafters allows you to build a roof that is resistant to high operational loads.

Roof loads and rafter system calculation

The development of a single-pitched or dual-pitched roof project begins with the choice of the type of truss system, the angle of inclination of the slopes (roof height) and materials for the construction of the structure. The calculation of the distance between the rafter legs is carried out taking into account the loads that the roof will experience during operation. Permanent loads include:

• the weight of the materials from which the truss system is made;
• roofing weight;
• weight of roofing cake materials (waterproofing, vapor barrier, insulation);
• the weight of the finishing elements of a residential attic or attic.

In addition to permanent loads, the roof also experiences temporary ones, which include:

A step is the distance between the rafters of one slope. When calculating a shed, gable or complex roof, the following scheme is usually followed:

• the length of the future roof slope is measured;
• the resulting value is divided by the optimal numerical value of the pitch of the rafters;
• one is added to the obtained value, the result is rounded off;
• the length of the roof slope is divided by the rounded result.

The final result will determine how far the rafter legs should be placed. The determination of the step cannot be extremely accurate, since it is necessary to take into account a number of additional factors, including the width of the insulation, the particular installation of the crate for various types of roofing material. If a roof with a chimney is being designed, the pitch can be adjusted according to its location so that it is not necessary to remove part of the rafter in the future and install a supporting structure, such as a special rafter system.

The distance between the rafters under the slate

Slate is a traditional roofing material. Its advantages include such characteristics as resistance to external influences (excluding mechanical ones) and low cost. Slate allows you to create a roofing, the repair of which can be reduced to the replacement of individual elements. Slate is heavy and requires the installation of a sufficiently powerful truss system. The calculation of the distance at which it is necessary to put the rafters under the slate is carried out taking into account the cross section of the beam for the manufacture of rafter legs.

The optimal solution is to install the system under the slate, in which the gap between the rafters must be at least 800 mm. In order for the slate structure to withstand not only the weight of the material, but also increased external loads, the crate is made of timber or boards with a cross section of at least 30 mm. When calculating the truss system for slate, it should be read that this material has rather large restrictions on the choice of the angle of inclination of the slopes.

Rafters for metal roofing

Metal tiles are actively used as a practical and aesthetic roofing material when arranging a shed, gable, hip or complex roof. The frame for the metal tile is built according to standard principles. To calculate at what distance it is better to place the rafters, it is necessary to take into account the loads and the angle of the roof. The metal tile is characterized by a relatively small weight, so it can serve as a replacement for the old roofing of slate or ceramic tiles. In this case, the rafters do not need to be strengthened or the pitch of their installation changed.

The standard pitch of rafters for metal tiles is 600-900 mm. The cross section of the elements can be 50-150 mm - this is enough to create a reliable frame for a metal tile. But if it is planned to use insulation, the layer of which in areas with low winter temperatures should be 200 mm, it is recommended to use a 200x50 beam for rafters under metal tiles so as not to mount an additional system that holds the insulation. The gap between the rafters under the metal tile is best adjusted to the width of the sheet or roll heat insulator.

Decking: rafters and crate

The professional flooring belongs to easy and convenient roofing materials in application. Galvanized or coated with a decorative and protective layer, corrugated board can be used both for mounting a shed roof of a utility room or garage, and for a gable roof of a residential building. How to calculate the distance required to install the rafters under the corrugated board?

To ensure the necessary rigidity of the structure, it is enough to install the rafters under the corrugated board in increments of 600-900 mm. In this case, it is necessary to pay attention to the angle of inclination of the roof. The calculation shows that with high external loads, it is better to lay the corrugated board on the system with a minimum step. But if the distance between the rafters under the corrugated board is close to the maximum, and the angle of the roof slope is small, then the structure is strengthened by using a more frequent crate. In this case, the step of the crate under the corrugated board should be about 50 mm, the width of the elements should be at least 100 mm.

Rafter system for soft roofing

Soft roofing includes bituminous and bitumen-polymer roll materials, roofing membranes, as well as soft tiles. A soft roof is characterized by a relatively low weight and no need to install a massive truss structure.

The minimum distance between the rafters is 600 mm, the maximum is 1500 mm. When installing a support under a soft roof, it is important to take into account the angle of inclination of the slopes: the smaller the angle, the smaller the distance between the supports for a continuous crate should be. The choice of step is also influenced by the thickness of the material for the crate - the thicker the sheet of plywood or OSB, the greater the installation step of the rafter legs can be.

Ondulin: calculation of rafters

Ondulin (bituminous slate) is laid on a flat, continuous crate made of sheet material. This allows the roofing to successfully resist wind and snow loads. The crate under the ondulin rests on the rafters, which should be located in increments of 600 - 1000 mm, depending on the angle of inclination of the gable or shed roof.

Rafters for ondulin are made of timber with a section of 200 × 50 mm. When choosing at what distance to put the rafter legs for the structure under the ondulin, it is recommended to take into account the width of the insulation material in order to simplify its installation. This calculation allows you to reduce the financial costs of arranging the roof.

Sandwich panel roof

Sandwich roofing is most often erected on sip-panel houses or hangar-type buildings. A feature of the sandwich is its bending rigidity, which makes it possible to dispense with the installation of traditional rafters. Small spans from the ridge of a gable roof to the upper part of the wall (or the distance between the supporting structures of a shed roof) allow the installation of a sandwich without additional supports.

If the span exceeds 4 meters, additional girders must be installed. To install a sandwich roof on a residential building, a traditional truss system is often installed, but in this case the rafters can be positioned with a large step - they serve as a support for the girders. The distance between the rafter legs is selected based on the length of the available material for the runs and the length of the load-bearing walls. The technical parameters of the sandwich allow the roof to withstand high operating loads.

Polycarbonate: erection of a supporting structure

Polycarbonate has recently been actively used as a roofing material. First of all, polycarbonate is in demand in the construction of gazebos, sheds, winter gardens. The crate and truss system for polycarbonate can be made of wood or metal.

In building a house, it is important that the roof frame and its rafter structure are reliable. To do this, you need to know the optimal size of the gap between the rafters. How to correctly carry out calculations for the gable roof truss system, taking into account various roofing materials, our experts will tell in this article.

How to correctly calculate the distance between the rafters (for a gable roof)

Distance for various roofing materials

Experts advise: when determining the step between the rafter supports, consider the roofing material from which the roof of the gable roof will be created. Consider the most common roofing options suitable for private residential buildings.

1. Decking - for this roofing material, the distance we need for a digital indicator is from 60 to 90 centimeters (if you increase the step to at least one meter, you will have to install additional transverse boards with a large section - 5 × 10 cm). At the same time, under the corrugated board, it will be necessary to install the crate, which will provide the possibility of attaching the mandatory vertical components - the chimney, the ventilation system.
2. Ceramic tiles - a roof made of such material has a rather heavy weight, therefore, the load on the truss system will be higher than when the roof is covered with corrugated board. Accordingly, the distance that we calculate will be different: from 80 centimeters to 1 meter 30 centimeters. But in this option, the steepness of the roof slope is also taken into account (if the angle of inclination is 15 degrees, then the gap will be minimal - 80 cm, at 75 degrees - 130 cm).
3. Metal tile - this roofing material is lighter than the previous one and is sold immediately in sheet form, therefore the thickness of the components of the truss system is reduced, and, consequently, the distance between the elements in it is also reduced. For roofing material with a cross section of 15 × 5 centimeters, the gap should be selected from 60 centimeters to 95 centimeters. Such a distance will make it possible to qualitatively insulate the attic space (for this, it is necessary to place the insulation material directly between the rafters). The peculiarity of the installation of the truss structure under the metal tile is that the supports are installed on top of the ridge run (usually they are mounted on the side of the ridge beam). But in this case, do not forget about the ventilation holes near the upper roof.
4. Ondulin - this material is called "Euroslate", and it is perfect for the roof of private residential buildings. For the truss structure under the ondulin, rafters from boards of 5 × 20 centimeters are used, which provides a certain margin of safety (this also takes into account the rafter runs). The distance between such rafter boards is standard - from 60 to 90 centimeters, and the wooden beam for the crate should be 4 × 5 cm in section, with an interaxal step of 60 cm.
5. Slate is one of the most common roofing materials in our country; under it, rafters should be selected with a section of 5 × 10 / 5 × 150 centimeters. The distance between them will be in a slightly smaller range - 60-80 cm. The crate of a wooden beam has its own gap between the elements, which directly depends on the angle of the slope of the roof slope: with a small slope - from 45 cm, with a larger one - from 60 cm.

Thus, the general digital indicators for determining the distance between the rafters (depending on the roofing material) will fluctuate within the following limits: the minimum is 60 cm, and the maximum is 130 cm. If you yourself cannot decide on the choice of such a digital indicator, then you should contact to qualified professionals for help.