The distance between the metal rafters of a gable roof. Distance between rafters for different types of roofs and materials

It is pointless to argue about the importance of the roof for any building. It is not for nothing that over a dozen different types of roofs have been invented in the history of mankind, from simple to quite complex in design and construction. An important element in planning the construction of a roof is the step between the rafters - strong bars that are the basis of the structure. This will be discussed in this article.

The distance between the base of the roof slopes is not a constant value and depends on the following components:

• type of roof;
• slope angle;
• the type of roofing material to be installed;
• rafter section dimensions.

Before proceeding with the process of erecting the upper structure of the house, a calculation should be performed by determining the optimal distance between the rafters.

Gable roof rafter pitch

The most widespread in our country are gable roofs. They are a structure that has two parallel planes, with an angle of inclination relative to the horizon from 20 to 50 degrees.

With an insufficient slope of the gable roof in snowy areas, there is a danger of accumulation of large snow masses, which can lead to the destruction of the structure. An increase in the slope angle in regions with a predominance of strong winds is also fraught with a high load and the risk of breaking not only the roof, but the entire structure as a whole.

Mansard roof truss system

Most private houses have an exploited under-roof space called an attic. This design is characterized by an increased height of the slope, which is caused by the need to create a living space of a comfortable height. As a rule, the slopes of the mansard roof are broken, having a varying angle of slope. For their installation, a double truss system is used.

The steepness of the lower slopes of the mansard roof significantly exceeds the slope of their upper extensions. The plane load perceived by them is not great. Thanks to this, the rafters in the lower part can be installed with a maximum pitch. The upper ridge slopes are recommended to be mounted with a reduced gap from each other.

Rafters in a shed roof

For outbuildings and some private houses, roofs with one slope are used. Due to the limited angle of inclination, high pressure is exerted on them. Experts recommend using lumber of increased cross-section for the rafters of a single-pitched roof, with the installation of a minimum step from each other.

When calculating the distances at which roof beams are installed, special attention should be paid to the amount of snow load in a particular area. With a small slope, this characteristic is of great importance. Roofing material for such roofs is best chosen with a minimum dead weight, which will reduce the bending load.

Hip roof truss system

The hip roof truss system is considered the most difficult in construction. This type is called four-pitched, since the roof is formed not only by side, but also by additional end slopes, where the installation of rafters is carried out not on the ridge, but on the corner bowstrings. This places special demands on the organization of the roof frame.

Under the hip roof, the attic is not often arranged. This is due to the small angle of inclination of the rafters and the roof as a whole. In the case of an increase in the angle of the slopes to the horizon, the distance between the rafters is increased, with a decrease, vice versa. An additional aspect of the calculation is the roofing material used.

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

In addition to variable snow and wind loads, a constant (static) one also acts on the roof, the force of which depends on the roofing material used. It is no secret that different types of roofs have their own weight, which can differ by 10 or more times.

The right choice of material affects not only the top, but also all other parts of the structure of a residential building and other buildings. Not without reason, when designing the foundation, it is necessary to decide in advance on the choice of the roof.

Roofing from profiled sheet

Currently, one of the most common roofing materials is a profiled sheet, which is produced galvanized or followed by a polymer coating. The distinguishing features of the profiled sheet include the following parameters:

1. High corrosion resistance;
2. As a result, a long (more than 15 years) service life;
3. Easy installation even without the necessary qualification;
4. Small sheet weight (weight 1 m 2 is 4-5 kg).

Since this roofing material does not exert a high load on the rafter system, the distance between the elements is chosen as much as possible for a particular angle of inclination. In addition, the profiled sheet does not require high strength characteristics from the roof lathing. All this together allows minimizing the total load on the foundation and walls.

Roofing from a metal tile

The second common type of steel roofing materials is metal tiles. This type of profiled sheet, which successfully imitates natural clay material, but with a lower mass (10 or more). A feature of the rafters under the metal tile is the smaller section size.

When choosing at what distance to install the rafters, first of all, you should be guided by the dynamic load. Like a profiled sheet, a metal tile is not demanding on the size of the rafter legs and is well mounted on a crate made of an inch coniferous board. All this makes a metal roof low-cost.

Rafter system for ondulin

In the 21st century, corrugated sheet materials were replaced by a more durable and lightweight analogue - ondulin. Among others - the most lightweight material. The weight of the sheet does not exceed 6 kg.

The small thickness of ondulin sheets at slope angles of less than 15 ° requires the construction of a continuous crate of plywood sheets, for example, which will require an appropriate rafter pitch. This should be taken into account in the calculations.

slate roof

Not so long ago, a wavy material from an asbestos-cement mixture, called slate, was widespread. High mass and fragility are the main disadvantages, however, even today he finds his fans in the construction of various outbuildings.

A high mass, comparable to the weight of a clay tile, will not allow the use of the same truss system as under a metal tile. Building codes define a minimum angle of slope for a slate roof of 22 degrees or more. Otherwise, the load from the material itself and the truss system with the crate exceeds the permissible parameters. The step of the inclined bars, as well as their cross section, are selected individually in each case.

Polycarbonate roof

In recent years, more and more often on the roofs of verandas and gazebos, an artificial polymer material, polycarbonate, has been used. Produced in two versions - monolithic and honeycomb. The first in its properties is similar to ordinary quartz glass, but significantly exceeds it in strength. The second one has less mechanical properties, but high thermal insulation and light transmission.

Cellular polycarbonate is standardly much lighter than a monolithic counterpart. It is used as a roof without the use of lathing, provided that the step does not exceed ½ of the width of the sheet of material. The high strength of the monolithic analogue also makes it possible to avoid elements transverse to the rafters. Sufficient flexibility allows you to cover semi-circular roofs on a metal frame, the pitch of which does not exceed 0.9 meters.

Thematic material:

Rafters under a soft roof

The original pattern can be obtained through the use of soft roofing materials, which are spread with an adhesive layer. They are installed on a continuous crate made of plywood or OSB. The step of the rafters should allow you to fix the sheets, so it is chosen as a multiple of ½ of the width. Given the standard dimensions of plywood 1520x1520 mm, the center distance between the rafters will be: 1520: 3 = 506 mm.

Rafter step for insulation

The installation of residential under-roof spaces is often combined with the laying of insulation sheets in the rafter gap. The most common plates with dimensions of 600x1000mm. These parameters are used as starting points.

Rafter pitch calculation scheme

According to building codes, the pitch of the roof rafters is in the range of 0.6 - 1 meter. Its final calculation is performed according to a simple formula, depending on the total length of the roof. For the calculation, you must perform the following list of actions:

1. determine how much distance should be between the rafters for your specific building conditions. According to the reference book, the magnitude of wind and snow loads in the area is determined.
2. the length of the roof is divided by the desired distance by adding one. The result will be equal to the number of rafter legs that are installed on one roof slope. If the value is not an integer, it is rounded off.
3. the length of the roof is divided by the number of rafters calculated above, we get the final step in meters.

For example, with a slope of 30 degrees, the maximum distance between the rafters of a gable roof under a metal tile is 0.6 measure. The length is assumed to be 16 meters. Hence:

1. 16:0,6+1=27,66;
2. rounding the result, we get 28 rafters per slope;
3. 16:28 \u003d 0.57 meters - the center gap of the rafter legs for these specific conditions.

As you can see, the calculation technology is not complicated, but this is just an approximate scheme. Taking into account many other parameters mentioned above can make certain adjustments.

One of the important stages of any construction is the construction of the roof of the building, the basis of which is the installation of a truss system. The uniform distribution of the weight of the roof on the frame, the reliability of the roof and the duration of its operation as a whole will completely depend on how correctly the pitch of the rafters is chosen, that is, the distance between them. With any slight calculation error, damage and collapse of the entire roof can occur.

Collection of the required calculated values ​​\u200b\u200bto establish the pitch of the rafters

The rafter system includes the following components:

• farms;
• ridge and side runs;
• Mauerlat;
• diagonal elements.

Farms consist of a crossbar, base, rafter legs, binding and fastening elements. The rafter legs are beams located along the slopes, the lower ends of which are connected to the Mauerlat, and the upper ends to the girders.

Rafter pitch is the exact distance between two rafter legs.

To get the exact indicated value, you must first find out the values ​​​​of some quantities important for this.

All calculations for the roof covering system should be correctly made at the design stage of the house. Such a responsible business can be carried out by yourself or entrusted to its specialists. The more accurate the calculations are, the stronger the base for the roof will be.

In order to correctly make all the required calculations, including the rafter pitch, you need to know:

• permanent and temporary loads;
• their size;
• slope angle;
• type of roofing;
• material for the manufacture of rafters;
• roof type.

One of the indicators that must be taken into account when calculating the pitch of the rafters are permanent and temporary loads. These include:

• the weight of the roofing and truss structure;
• weight of the interior roof finish;
• snow cover weight;
• the weight of the person carrying out the maintenance of the roof.

It should be noted that these data are taken in special tables developed by scientists, depending on climatic zones, for various territorial regions.

The angle of the slope can be determined by knowing the length of the wall of the house and the height of the roof. The steeper the roof, the more installed, since the load on such roofs will be transferred mainly to the load-bearing walls. After making further calculations, the length of the rafters is easily calculated. Most often they have standard sizes: 4 and 6 m.

Coniferous wood is well suited for the manufacture of a roofing system. Lumber must be of high quality, without knots, rot. Before work, all wooden elements must be treated with antiseptic special compounds.

The step of the rafters will also depend on the type of roof, that is, on the functional features and its shape. The size of a simple and complex roof will be different.

How the type of roofing will affect the pitch of the rafters should be considered in more detail.

General technology for calculating the distance between the rafters

Having made all the necessary measurements, it is possible to make a constructive calculation of the pitch of the rafters. Based on practice, this indicator is in the range from 0.6 to 1.0 m.

In order to correctly perform this calculation on your own, you must adhere to the following technology:

1. The total length of the roof slope is taken.
2. The optimal step of the truss truss is selected.
3. The length of the slope must be divided by the pitch of the rafters.
4. One is added to the resulting value.
5. To get a whole number, the result is rounded up.
6. This calculation is the number of trusses (rafter legs) located on one roof slope.
7. Now the entire length of the roof slope is divided by the resulting value, showing the number of trusses. This determines the pitch of the rafters.

It should be noted that this calculation is made in the center of future rafters. However, the calculations cannot be considered accurate and constant. In each case of the construction of the roof of a house, the angle of the roof slope, the features of the selected roofing material, and other indicators are taken into account. In this regard, it is necessary to consider the features of choosing a rafter pitch for the most common roofing materials: metal and ceramic tiles, corrugated board, slate and ondulin.

Features when choosing the distance between the rafters for metal and ceramic tiles

Metal tiles as roofing are extremely common in both urban and suburban construction. The very design of the roof truss system when using metal tiles will differ little from the general scheme. However, due to the fact that this building material is light in weight, rafters and other elements of the system can be taken with a smaller section, i.e. with a smaller margin of safety. The distance between the rafters when using metal tiles is 60-95 cm. All work on the installation of roofing from metal tiles is much easier than from other roofing materials. A feature of the lathing device of this material is that the board near the cornice should be about 1.5 cm thicker than the others. Usually, the cross section of metal rafters is 50x150 mm.

Ceramic tile is a roofing material that has a significant weight, which is 10 times the weight of a metal tile. In this regard, it is necessary to more thoroughly approach the calculation of the roof truss system. should be slightly increased - up to 60x180 mm. The average distance between the rafters for covering ceramic tiles is set in the range of 0.8-1.3 m. The angle of the slopes of the slopes is necessarily taken into account: the distance between the rafters is made larger, the higher the roof.

The length of the rafter legs in this case will have a strong influence on the result. The distance between the rafters decreases with increasing their length.. With their long length, increased deflection loads may occur, which can be significantly reduced if an additional system of struts, supporting racks and other elements is installed.

Features when choosing a rafter pitch for slate, corrugated board and ondulin

The most common roofing material is slate. This is due to its low cost, ease of installation, and the possibility of replacement if individual elements of the roof are damaged.

The features of the crate for slate is its thinned type, consisting of any type of board or timber, but with a mandatory cross section of at least 30 mm. This is necessary for the correct and high-quality distribution of the weight of the slate on the crate.

The optimal distance between the rafters, when combined with the load from the weight of the slate sheets, should be 80 cm. It is worth constantly taking care of the margin of safety of the truss system, which may be due to various unforeseen circumstances. Otherwise, its installation under a slate roof does not differ from other options.

Now you should pay attention to some features when installing a truss system for roofing materials such as corrugated board and ondulin.

The weight of corrugated board and ondulin is much lighter than that of ceramic tiles or slate, so the technology for installing rafters for these materials is practically no different from installing metal tiles. The distance between the rafters for a corrugated roof is 60-90 cm, and from ondulin - 60-100 cm.

If it is necessary to increase the distance between the rafter legs, it is necessary to strengthen the structure of the system with transverse elements of the crate.

The sheathing device for corrugated board is very similar to the sheathing device made of metal tiles. It is important to remember that in this case, the last board should also be slightly thicker than all the others.

A feature of the installation of the crate for ondulin should be considered the need for its continuous type for high-quality resistance to various loads. In some cases, a thinned type crate can also be used, but then the step between the rafters should be no more than 30 cm.

Thus, being able to make all the necessary measurements, knowing the basics of installing a truss system for basic roofing materials (tiles, corrugated board, slate and ondulin), you can correctly calculate the distance between the rafters.

A shed type of roof is rarely seen in private housing construction. Although, according to some, this is in vain, because the installation of a shed roof is much easier than the installation of a gable roof. On the other hand, such a roof design will not be able to keep the heat in the room so well. That is why shed roofing is most often used to build a garage, country house or barn.

True, if the work on thermal insulation is correctly performed, then the structure may well be warm. In this case, a living room is made under a pitched roof. Let's look at the advantages of a shed roof, what types of truss systems exist, how the design is calculated. In addition, we will consider how to install this type of roof.

Pros and cons of a shed roof for a house

Beginners in the construction business will be delighted that such a shed construction is quite simple and can be done by hand. True, it is impossible to call the work the easiest, but with detailed instructions, a shed roof will be created. But before considering the design features of the roof, you need to find out its features and advantages. They characterize this type of roof.

Advantages of a pitched roof:

1. Profitability. For the device of the roof, a lot of building materials are not needed, on which the bulk of the funds are spent.
2. The simplicity of the truss system and the shed structure as a whole. The best thing for beginners. Installation will be easier than with a gable roof.
3. The building will have a small weight. This means that there is less load on the walls and foundation.
4. Thanks to this shape, a shed roof perfectly resists wind loads, as well as the weight of snow that accumulates on the surface.
5. The angle of inclination is very different, depending on the needs. It varies from 5° to 45°.
6. If you make the angle of a shed roof small, then it can be used for various purposes. For example, if this is a barn, then install a tank for heating the liquid. If this is a living space, then on a shed roof you can equip a great place to relax. Alternatively, install solar panels as an alternative power source.
7. The versatility of a one-slope building. It is covered with almost any material available on the market. It all depends on the operating conditions and the chosen angle of inclination.

Despite all its advantages, a shed roof has its drawbacks. This is not surprising, since nothing is perfect, but it is better to know about the cons and use them profitably.

Cons of a shed roof:

• The first concerns insulation. There is no more space with an air gap under the structure, so the issue of insulation should be taken more seriously. If you do not make thermal insulation of the structure, then in summer the attic will be too hot, and in winter, on the contrary, it will be supercooled. In either case, the temperature (high or low) will be transmitted to the house. Correct calculations and high-quality insulation will help eliminate this;
• when creating a ceiling immediately under the roof, made at a slight angle, the house will not have an upper air gap and an attic. And in this case, living space cannot be organized;
• due to a slight slope, which reaches from 5 to 10 °, snow and moisture will accumulate on a shed surface.

Despite all the obvious disadvantages, a shed roof is an ideal option for creating a garage and other buildings on the site.

Calculation of the construction of a single-pitched roof

This is the first stage before the installation of the truss system. It is recommended to draw up a detailed plan or drawing, which will be guided by when working. To create this schema, you need to highlight the following data:

• the total width of the roof construction, as well as the length of the spans that is formed between the bearing walls;
• slope angle, desired or obtained;
• the length of the single-pitched roof;
• selected roofing material;
• what is the height and width of the load-bearing walls.

Note! When a shed roof is created for a barn, garage or country house, you can simply raise the front wall of the structure above the back.

As a result, the angle of the slope will depend on the height of the rise. The second option involves the creation of supports, on which the run will fit. The second way allows you to save building materials.

For drawings, you need to know the following nuances:

The drawing of the future shed roof should have all the necessary information about the elements. The dimensions, distances between them, fastening features, etc. are indicated. Below is an example of such a drawing of a pitched roof.

Choosing the corner of a pitched roof

The angle of the slope is chosen taking into account the fact that the resulting roof forms a triangle, one corner of which will always be right. The legs are the floor beams and the gable part of the building, and the rafters serve as the hypotenuse. This is clearly seen in this diagram.

The designations are as follows:

• Lc - the length of the rafter used;
• Lbc - our leg, indicating the height of the pediment from the floor beam to the roof plane;
• Lsd - the width of the building;
• A - the selected or desired angle of a pitched roof.

Given the basic values, it is possible to calculate all the parameters of a single-slope structure. There is a formula for this. The first is used when the width of the building and the planned height of the pediment are taken as the basis. In this case, the formula is:

When you have decided on the angle of the shed roof, then you need to calculate the future height of the gable. For this, the formula is:

In this case, the length of the roof rafter legs is calculated as follows:

Note! This length of the rafters does not take into account the canopy from the rear or the facade of the room.

Many criteria influence the choice of slope angle. The main one is the choice of roofing material. Each of them is recommended to buy for a particular angle of inclination. Here are recommendations for popular roofing materials:

1. For the installation of corrugated board, the slope must be at least 8 °.
2. When using metal tiles, you will need to make a roof with an angle of inclination of 30 °.
3. For a slate device, indicators from 20 ° to 30 ° are needed.
4. As for rolled roofing materials (roofing material, shingles and soft roofing), the angle of inclination should be 5-7 °, no less.

Advice! A roof without a heating system in an area where there is a lot of snow in winter, a shed type roof with a slope of 40° is ideal, regardless of the roofing material. So all precipitation will quickly descend from it.

Varieties of the truss system of a shed roof

There are three options for creating a truss system. The choice of design depends on the size of the room and its type.

Now that we have dealt with the design of the truss system and learned its types, we can consider the process of creating a shed roof.

Installation work on the creation of a pitched roof

Having on hand the drawings and the selected type of system, you can get to work. You will also need the appropriate tools and lumber. The installation of the truss system is performed as follows:

1. For safety, the building should be covered with beams. They are placed on the wall. To extend their service life, roofing material is glued to the wall. It will protect the beams from moisture and decay. You need to position the floor sticks in the same way as the rafters. Fastening pitch -500-800 mm.
   
   
2. Mauerlat is laid on top of the beams. This is a massive beam that will serve as a support. It fits on the back bottom wall of the building.
3. To safely move around the roof, flooring from wooden boards is laid on the floor beams. He is temporary.
   
   
4. Now you need to build a gable wall. It is made from the same material as the building itself. You can use lighter material. For example, if the walls are brick, then the pediment rises by means of bars or boards.
5. Floor beams must be covered with waterproofing and walled into the wall. The pediment rises to the chosen height, according to the drawings.
6. On the finished pediment, you can fix the Mauerlat. It turns out that two Mauerlat are parallel to each other.
7. Markings are applied to the lower wall for attaching the rafter legs. The fastening elements themselves are fixed.
8. To firmly fix the rafter, based on the drawings, grooves are cut on it. This is a good mounting option. The grooves are in two places, top and bottom, to enter the Mauerlat. There are other methods of fixing the rafter leg, as shown in this photo.
   
   
9. After that, the legs are fixed with special corners and fasteners. From above, at the pediment, the legs are screwed rigidly. But the lower part is made depending on the chosen truss system of a pitched roof. It can be rigidly fixed or made sliding.
   
   
10. There is a certain sequence of inserting rafter legs. First, the extreme elements of the truss system are mounted. A cord is stretched between them, serving as a guide and level for subsequent rafters. Do not forget that the step of the rafters corresponds to the step of the floor beams.
11. The rafters that are already installed are connected to the floor beams through racks, struts and other elements to give them stability. We talked about them above. Fixation is carried out with metal corners and staples.

    Tip! If you want to lengthen the rafters and bring them out of the wall, then “fillies” are attached to the bars. So you can protect the adjacent part of the structure from precipitation.

    

12. When the construction of a shed roof is ready, you can begin to insulate and create a roofing pie.

The photo shows what layers the correct insulated shed roof should consist of.

Insulating material is laid between the rafters. He has to hold on tight there. After that, a counter-lattice for ventilation is made on top. A waterproofing film is laid on the counter-lattice. It protects the insulation from moisture, which can ruin it.

As for the crate for laying roofing material, it is selected depending on what kind of roofing material it will be. For example, a solid crate of boards or plywood is needed when installing soft tiles and other rolled materials. If metal tiles, corrugated board, slate, ondulin and other types of hard roofing are used, then the crate is done in a row. The step depends on the roofing material.

And in order to protect the insulation from the inside of a shed roof, you need to sheathe it with a vapor barrier film. Now we can say that the shed roof is completely ready.

Note! If a shed roof is made for a barn or other non-residential structure, then it is not necessary to insulate it. It is better to spend them for another purpose.

Conclusion

Creating a roof, whether it is a gable or single-pitched, is a dangerous, time-consuming and responsible process. That is why caution is required and strict adherence to the instructions for creating a structure. Only then can the best result be achieved.

The service life and the final reliability of the roof lie in the correct preparatory work, which includes the correctly chosen distance between the rafters. It is from this element of the supporting frame that the distribution of the load on the supporting frame directly depends, an error in the calculations of which can lead to deformation and collapse of the entire roof. So, the calculation of the total distance between the truss elements is one of the most important tasks in planning and calculating the load-bearing house.

Basic calculation technology

Rafter pitch is the exact distance between two legs of one truss truss. Most often, in private construction, the distance between the legs is about one meter, but the exact figures should come from a detailed calculation of the bearing capacity of the selected type of roofing system. In order to independently perform such a calculation, you must adhere to the following scheme of actions:

1. Having measured the eaves of the roof structure, it is necessary to determine the total length of the roof slope.
2. The resulting value must be divided by the selected and most optimal step of the rafters. In other words, if exactly one m is chosen in the rafters, then the length of the slope must be divided by this unit of measurement.
3. One is added to the result, after which you can round the finished value. It is this method that allows you to determine the number of roof trusses on one roof slope.
4. Now it’s worth dividing the length of the roof slope by the resulting number of trusses, which will allow you to determine the pitch of the rafters.

It is worth recalling that this method of calculating such a building element as the pitch of the rafters cannot be considered extremely accurate, because in such calculations it is necessary to take into account the features of the selected roofing material, which can be a problem in the absence of proper experience in this matter. It is for this reason that methods will be described below that will allow you to choose the right rafter pitch for popular roofing materials.

Ceramic tiles and rafter installation

The main feature of the manufacture and installation of a truss bearing system for ceramic tiles is the extremely large weight of the roofing material, which in its totality is ten times greater than the weight of any roofing material.

As a rule, this type and size of roofing material provides for up to 60 kg per square m of the truss bearing system. All this becomes the reason for the use of only dry lumber on the roof, which eliminates the possibility of further deformation during drying and pressure.

When using a wooden beam on the roof, the cross section of which is 150x50 mm, the step between can vary from 70 to 120 cm.

In addition, the distance between the rafters may depend on the overall slope of the roof.

Do not forget about the length of the rafter-type legs themselves. The longer this length is, the smaller the distance should be between the legs of the rafters, otherwise the supporting frame of the roof will be deprived of maximum strength and stability.

Experts recommend using no more than 80 centimeters of pitch between trusses if the roof slope is up to 45 degrees. Special attention should be paid to the lathing system when using ceramic roofing material on the roof.

To determine such a step, it is necessary to take into account the characteristics of each individual element of the roofing material, namely each tile. In order to perform the correct calculation of the crate step for such material, it is necessary to subtract the length of the lowest row and the distance between the last bar and the row of the crate from the pitched length.

As a rule, all varieties of such roofing material have a length of no more than 40 cm. When laying tiles, they are overlapped, which takes up to 9 cm from the bottom row. In other words, the correct step in this calculation is from 31 to 35 cm.

Metal tiles and laying methods

As a rule, the use of metal tiles in private construction is considered the most common, for which there are a number of reasons and positive characteristics of this roofing material on the roof.

If we compare such a roofing type material with the one described above, then several striking differences can be noted, each of which can be safely considered a positive feature of the material. First, it is worth recalling the simplicity and speed of installation of such material, which is made in a sheet type, allowing you to cover a significant area of ​​\u200b\u200bthe roof at a time.

The second feature of metal roof tiles can be considered the extremely low weight of the material, which has a positive effect on installation, work on the roof and the load on the supporting frame of the roofing system.

This feature can be considered the most important, because it is responsible for the lower costs of labor and time in organizing the truss carrier system. When using this roofing material, the pitch of the rafter bearing legs is from 60 to 95 cm, because the reduced weight and size of the roof does not require high load resistance parameters.

With such indicators, it is worth using a heat-insulating material, the thickness of which is at least 15 cm, which is placed between the rafters. When organizing, the thickness of the insulating material should or may be greater, because this is necessary for arranging a residential floor in the attic. This also affects such an element as the thickness of the material that is used to make the rafter load-bearing legs.

All this indicates the absence of significant differences in the truss system for metal roof tiles. This roofing material provides standard knowledge about the construction of truss and roofing systems, which is simply necessary to install. The main difference of such a system may be the fastening of the upper type support to the ridge run, and not through the ridge type beam itself.

The free space at the top of the system, obtained through the installation of rafter legs, is ideal for ventilation of the entire under-roof space, which is often covered with condensate in metal roofing material.

In the event that changes are made to the roof of an old wooden house, it is necessary to completely remove the mauerlat, replacing it with a common top-type crown. In such a crown, it is necessary to put marks and make selections with the desired step, into which the elements of the rafter bearing legs will be installed. This allows you to more accurately calculate the pitch of the rafter bearing legs and install them.

Decking and determining the distance between the racks

When using such a roofing material as corrugated board, the calculation of the correct pitch of the rafter bearing legs is 60-90 cm, which practically coincides with all the types of structures and roofing materials described.

If necessary, put more distance between the elements of the rafter legs, it is necessary to insure the transverse elements of the crate with a greater thickness and cross section. This will strengthen the entire supporting structure, which will extend the life of the entire roof. The step between is about 50 centimeters, when using a board that is at least 10 centimeters in size.

When it comes to such a moment as calculating the crate on the truss system, then do not forget that the last board should be 1.5 centimeters thicker than all the other elements of the system. Before installing the elements of the crate, it is worth remembering the presence of a chimney and a special system that should be on each roof. This will save time on the calculation and alteration of the truss system, and the crate as a whole.

Ondulin and construction installation methods

As in the cases described above, ondulin provides for the calculation of the pitch of the rafter bearing legs from 60 to 100 cm, which makes such sizes standard when using the most popular roofing materials.

The truss trusses themselves are made of lumber with a section of 200x50 millimeters, which is quite enough to ensure that the strength and reliability of the truss system are at the maximum level, and it is easy to install them. It is immediately worth noting the fact that the described roofing material needs a continuous lathing system, which will allow the material to qualitatively resist the loads from snow thicknesses, as well as solar exposure.

In some cases, a thinned type of crate can also be used, the calculation of which is quite simple if a wooden beam is used for this, the step between the elements of which is no more than 30 cm. As a rule, this option is more expensive than necessary for a continuous crate. In other words, it is irrelevant to use the thinned type of system in this case.

Slate and truss structure under it

As a rule, slate coating is considered the most common in our country. The reason for this indicator can be considered the extremely low cost of the material, the simplicity and speed of installation, as well as the possibility of replacing individual sheets in case of damage to individual sections of the roof.

The distance between the rafters for this type of roof should be 80 cm. It is this distance that is considered the most optimal solution when combining the load from the weight of slate sheets.

The crate in such a system needs a thinned type using a board or timber of any type, but of a certain section, which should not be less than 30 mm. Such a thickness of a board or timber is needed for high-quality and correct distribution of weight from the roofing material itself, as well as from winter precipitation.

Do not forget about the constant margin of safety when organizing the truss system, which may be required in case of unforeseen circumstances associated with mechanical loads and bad weather. All other features of the truss and crate system do not have any special differences from the options listed above. In other words, for all other types of coatings, we determine the distance in the same way as for the above roof.

The distance between the rafters is a fundamental parameter on which the strength and reliability of the roof structure, its service life, and the possibility of using certain roofing materials depend.

The strength and service life of the roof depend on many factors: the quality of building materials, climatic conditions, the reliability of the crate.

But the supporting structure of the roof is the foundation on which the entire structure rests.

The rafter system must be accurately calculated, correctly mounted and reliably protected from destructive external influences.

General scheme for calculating the rafter pitch

The truss system is the supporting structure of the entire roof. It consists of rafter legs, vertical struts and inclined struts.

Each rafter is located at a certain distance from the next - this distance is called the "rafter step".

The strength of the roof structure, the maximum allowable load per square meter and the materials that can be used for roofing depend on it.

According to GOSTs, the minimum allowable value of the rafter pitch is 60 cm, the average is more than 1 m.

To determine the approximate pitch, you can use the following formula: D / (D / m + 1), where D is the length of the roof from ridge to ridge, m is the approximate rafter pitch.

All results must be rounded up to the nearest higher integer. It is obvious that such a formula serves only for approximate calculations.

To determine the exact step size, the following factors must be taken into account:

• own weight of the truss system, i.e. the materials from which it is made;
• the weight of the material with which you plan to cover the roof;
• weight of additional heaters, seals, hydro and vapor barrier systems;
• crate weight;
• weight of attic finishing materials;
• climatic loads (wind, snow accumulation).

In addition to the loads listed above, the roof must be capable of supporting the weight of at least one adult person, so that in the event of a repair or installation of an antenna, the installer can safely climb onto the roof.

If you plan to install a chimney, then its location must be included in the calculations initially so that in the future it will not be necessary to remove part of the roof and install additional support points.

Shed and gable roof: the difference in truss systems

For a shed roof, building a truss system is quite simple. Most often, the rafters are laid directly on the crown, without the use of additional supports and supporting structures.

That is why the maximum angle of inclination of a shed roof is limited to 30 degrees: the absence of additional load-bearing structures and supporting beams means that the entire load falls on the walls of the building and the foundation.

The optimal angle of inclination is 15 - 25 degrees. The maximum allowable span of rafters does not reach 6 m.

When building a shed roof, be sure to take into account the direction of the wind and the possible additional load from the weight of snow accumulated on the roof.

For houses located in regions with strong winds and low rainfall, you can guess a slope angle at which the roof is cleared of snow due to gusts of wind.

A gable roof is a system of two inclined slopes connected by a ridge. One of the main advantages of this design is the ability to more evenly distribute the load between the truss system and the load-bearing walls of the building.

In addition, the gable frame allows you to lean the rafters on each other, which gives it additional strength.

The overall strength of the roof structure increases as the slope angle approaches 45 degrees. It is this slope that is considered optimal for regions with heavy rainfall.

With an increase in the angle of inclination, on the one hand, stability increases significantly, so you can take a larger rafter step.

On the other hand, the windage of the roof increases, so for windy regions the optimal angle of inclination does not exceed 20 degrees.

Rafter system under slate

Despite the emergence of a large selection of modern roofing materials, the classic version - slate - is still very popular, mainly because of the cheapness and ease of installation.

The distance between the roof rafters under the slate is calculated taking into account the characteristics of the material: the slate is quite fragile, but at the same time it is able to withstand heavy weight loads.

The permissible range of the rafter step for slate is from 80 cm to 1.5 m. The average step length, 120 cm, is most often used.

Since the slate itself weighs quite a lot, the material for the supporting structure must be chosen durable, for example, bars with a cross section of at least 75 mm by 150 mm.

The length of the rafter pitch and the thickness of the crate are interrelated: the more durable the crate you plan to install, the smaller the pitch, and vice versa.

The slate sheet has a standard length of 175 mm, the lathing pitch is selected so that each slate sheet has at least three support points (one in the center of the sheet and two closer to the edges).

The step of the lathing depends on the degree of the slope of the roof: 63 - 67 cm is enough for a flat one- or two-slope roof. The minimum gap for a steep roof is 45 cm.

You can set the exact length of the rafter pitch for slate only by making accurate measurements and calculating the total weight of all roofing materials.

Do not forget to take into account the weather conditions (possibility of snow accumulation, strong wind gusts) and the load of additional equipment (antenna or chimney). If an attic is equipped in the attic, then consider the weight of the heaters.

The nuances of the system for metal tiles

Metal roofing is one of the most popular roofing materials on the market. It is unpretentious in handling, durable, looks beautiful.

In addition, metal tile is one of the lightest roofing materials (only 35 kg per square meter), it can be laid on a fairly light support, thereby reducing the load on the walls of the building and the foundation.

The average distance between the rafters under the metal tile is 60 - 95 cm for a gable roof with a slope of 20 - 45 degrees.

The size of the bars is chosen taking into account insulating and waterproofing materials. For a simple roof made of metal, a section of 50 - 150 mm is sufficient.

But in most cases, to create a mansard roof, it will be necessary to lay a heater with a thickness of 150 - 200 mm under the metal tile.

Taking into account the weight of the insulation, the truss system should be more durable, the recommended size of the bars increases to 200 mm by 50 mm.

When calculating the distance between the rafters, consider not only the length of the metal sheets, but also the insulation.

With the correct location of the rafters, you can significantly save on timber.

Do not forget about the peculiarities of mounting a roof made of metal: this material does not pass air well, as a result of which condensation often accumulates under the roof.

Fasten the top support of the truss system to the ridge run instead of the side part. This will create a small air gap, increase ventilation and help protect the roof from destructive moisture.

Rafter system for corrugated board and ondulin

A distinctive feature of corrugated board is lightness and rigidity, therefore, as in the case of metal tiles, the requirements for the rafter system are not so high.

The distance between the rafters under the corrugated board should be in the range from 60 cm to 120 cm. The optimal section of the rafter leg depends on the span between the supports.

So, for a span of 3 m, a beam with a size of 40 mm by 150 mm is chosen, for a span of 5 m - a size of 50 mm by 180 mm.

What distance is permissible between the rafter legs depends directly on the cross-section of the bars: the larger the rafter step, the more durable the material must be used for the rafters. When choosing a step of more than 80 cm, increase the thickness of the bars by 20 - 25%.

Do not forget to take into account the weight of the crate under the corrugated board. The distance between the rafters of a pitched roof of 60 cm will require a crate with a minimum section of beams of 25 mm by 100 mm.

With a rafter pitch of 80 cm, it is 30 mm by 100 mm, etc. The angle of inclination of the roof also plays an important role: with a slope of less than 15 degrees, it is recommended to lay a continuous crate under the corrugated board, which is much heavier than a sparse one.

Because both are relatively light weight, the supporting structure can be light enough to reduce stress on the load-bearing walls and foundation of the building.

The higher the degree of inclination, the greater the distance between the rafters is allowed.

On a gable roof with a slope of less than 10 degrees, it is recommended to install a continuous crate, which increases the load on the roof structure.

In this case, it is better to use a thicker beam measuring 40 mm by 50 mm, and minimize the rafter step (60 cm).