Gable roof: truss system for corrugated board, photo, drawing. Calculation, do-it-yourself installation of a gable roof truss system

The distance between the rafters of a gable roof is one of the most important parameters in its construction. It is this distance that affects the strength of the frame and the truss system, respectively, the strength of the entire roof also depends on it. To correctly determine it, it is necessary to make quite complex calculations. In this case, it is strongly recommended to contact an architectural studio for their implementation. Incorrect calculations and, as a result, an incorrectly chosen distance between the slopes can lead to serious negative consequences, such as deformation of the supports of the truss system, deformation and violation of the integrity of the roofing, roof collapse. Therefore, in the process of designing a gable roof, it is extremely important to use the most accurate initial data, reference values ​​\u200b\u200bmust be taken strictly in accordance with the specific construction conditions, and the calculation must be made according to the method indicated below.

The distance between the rafters of a gable roof is one of the most important parameters in its construction.

Primitive calculation method

Usually builders refer to the spacing between rafters as their pitch. Almost always, the rafters are separated by a maximum of 1 m (at the base), while the minimum allowable interval between them is usually within 0.5 m. The algorithm for calculating the required number of supports for the construction of a solid roof is as follows:

1. First, the length of the slope along the eaves of the roof is measured (actually the length of the wall parallel to the slope + the expected ledges).
2. The value obtained during the measurement is divided by the selected interval between the "legs" of the truss system. Next, choose the interval for which the "legs" will be divorced. For example, 80 cm. In this case, the denominator of the fraction will be 0.8.
3. The last stage: a unit is added to the resulting quotient, if the resulting number is not an integer, then it is increased to an integer, always upwards.

Such a simple calculation will allow you to determine the number of rafters, as well as the distance between the supports. It is important to remember that the values ​​obtained will determine the number of supports for only one of the two slopes. When the count is completed, the longitudinal size of the slope is divided by the estimated number of truss supports. The result of this will be the exact distance between the supports. Consider one example: the length of the slopes of a gable roof (not total) is 20 m. Initially, a step of 0.75 m was selected. We make a preliminary calculation: 20/0.75 = 26.7. We add 1 to the obtained value, we get 27.7. Then we round up to a larger one and as a result we have 28 pieces. rafters. That is how many "legs" the rafter system of one slope will have. Next, we determine the exact distance between them: 20/28 \u003d 0.72 m. Using this simple technique, you can determine the minimum interval at which the rafters will be placed. However, it is also important to consider which roofing material is selected.

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If decking is selected

The professional flooring is though not heavy, but at the same time very flexible material. Therefore, for it, the minimum allowable step should be 0.5 m, and the maximum should not exceed 0.9 m. At the same time, the frame of the truss system must withstand not only the mass of the profiled sheet, but also the battens. For a profiled sheet, the crate is stuffed from timber or boards with a minimum size of 30x100, the average installation step of the crate should be 0.5 m (it depends only on the thickness of the sheet). The boards of the crate, which go to the eaves when stuffing the corrugated board, should be 1.5-2 cm thicker than the main crate. At the same time, it is important not to forget about the need for ventilation of the structure.

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Ceramic tiles

The main feature of this material is that ceramic tiles are very heavy. This is logical, because the raw material is ordinary clay, which has a large specific gravity. If we compare metal tiles and ceramics, then they differ in mass by more than 12 times. The weighted average pressure of such a coating is 45-70 kg per square meter of crate.

Ceramic tiles are very heavy, because the raw material is ordinary clay, which has a large specific gravity.

The frame with supports for such material should be made of perfectly dried timber, with about 15% moisture. For mounting, use bars approximately 50x150 mm (recommended 60x180 mm). The step of supports for ceramic coating will be in the range of 0.8-1.25 m. This value is greatly influenced by the angle of inclination of the slopes.

For example, if the angle is 15 °, the minimum interval is taken - 0.8 m. With a slope of about 45 ° - all 1.25 m. For this type of roofing material, specialists also calculate the length of the rafters (when calculating the interval between supports).

So, if the length is maximum for a particular roof, then the step value should be minimal. Short rafters require the largest possible interval between them. In this case, it is possible to move along the roof only if the rafter pitch is not more than 0.8-0.9 m with a slope of 45 °. One should also not forget about the need for ventilation of such a design.

For this, holes in the insulation are usually provided, the diameter of which is in the range of 9-12 mm. The process of erecting a rafter system under a metal tile is similar to the process of building rafters for other types of coating.

It is important to remember that in addition to carefully calculating the required number of rafters, the step for the crate should also be calculated.

It differs depending on the type of ceramic tiles. For example, the length of a ceramic tile tile is 0.4 m, while the joint overlaps 0.5-0.9 m. In this case, the sheathing step will be 0.31-0.35 m. It is important to remember that for each slope it is necessary make a separate calculation, since it is impossible to build an absolutely identical truss structure (even if it is the same according to the project): errors and inaccuracies in the assembly can give an error of 0.2 m.

The gable roof is the most popular design in private housing construction. The truss system of a gable roof should provide a support platform for mounting the roof. Properly calculated pitch of the rafters of a gable roof allows you to ensure the strength and stability of the structure to all external loads, create a durable and reliable roofing. This article discusses the design features of the truss system, the calculation and installation procedure. This information will allow you to correctly understand the methodology for creating a gable roof so that you do not ask unnecessary questions to workers during construction.

The distance between the rafters for a gable roof

Among the people involved in the construction of a private or country house, there are constant discussions about the most successful roof design and the number of supporting elements. In order to understand these opinions and take one side or another, it is necessary to consider the general structure of the roof.

There are two types of rafter construction:

hanging.

Layered.

They are used on relatively small houses with a length of supporting elements of not more than 6 m. The structure consists of a number of truss trusses having the shape of an isosceles triangle. The trusses are installed on a strapping made of timber (Mauerlat), interconnected by batten strips. The bearing capacity of hanging rafters is relatively small, but the simplicity of design, economy and high speed of installation are their advantages. There are quite a few options for implementing hanging rafters, which is explained by the prevalence of small buildings that do not need a complex and massive roof structure.

Design layered truss system somewhat more difficult. Along the perimeter of the ceiling of the upper floor, a strong timber is laid - Mauerlat. Two (or more) vertical racks are installed along the longitudinal central axis, the height of which determines the angle of inclination of the slopes. A ridge run is installed between the posts, which runs along the entire length of the roof and serves as a reference line for the rafter legs. Each of them has two points of support - at the bottom it is a Mauerlat, and at the top - a ridge run.

For the formation of additional support, which excludes sagging of the supports, struts are used - inclined strips attached to the rafter legs at an angle close to a straight line and abutting in the lower part against the central lower bar - lying.

The step lag for the roof is the distance between two adjacent rafters. It is determined by the number of lags evenly distributed along the length of the longitudinal axis of the roof. The main supporting structures for the roof are rafters and lathing, forming inclined surfaces with a given geometry and area. The angle of inclination determines the wind and snow loads, and, with an increase in the angle, the wind load increases, and with a decrease, the snow load on the roof.

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What determines the pitch of the rafters

Consider the factors that determine the step between the rafters of a gable roof, in more detail. It must be immediately taken into account that the number of rafters determines the bearing capacity. Reducing their number complicates the installation of insulation, contributes to the sagging of the laths of the crate and the roof installed on them.

At the same time, too frequent placement of rafters also creates difficulties in the installation of insulation. It has to be adjusted in width, which creates waste, i.e. waste of material. Therefore, the size of the heat insulator is often used as a criterion for determining the pitch of the rafters. For example, many types of mineral wool are 60 cm wide, which is quite suitable for most gable roof designs.

In addition, the pitch of the rafters directly depends on their number. This is a calculated value, which is determined based on the bearing capacity of the supporting elements. The loads acting on the roofing, as well as the weight of the roofing itself, are quite large, so a stable and durable structure is needed to accept them. It should be borne in mind that the type of rafter system also matters, since layered rafters are much heavier than hanging rafters, they form a noticeable load on the walls and foundation of the house.

Wind and snow loads are external factors that affect the roof structure. The weight of snow in winter can crush or even break a roof if its design is not properly designed. The SNiP applications contain special data on the average annual amount of snow in different regions. Some of them have up to half a ton of snow per square meter.

In addition to snow, wind creates serious loads. At the same time, if the snow load is static, then the wind effects are sudden and uneven. The wind can rise at any time of the year, both in winter and in summer, which makes us take it seriously. When choosing the angle of inclination, you should find out the strength and direction of the prevailing winds in the region, find out about the possibility of hurricane gusts. Available in SNiP applications.

All these factors determine the parameters of the truss system and the distance between the individual supports.

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

There are many types of roofing. Most of them are noticeably outdated and are little used in modern construction. The most popular today are:

profiled sheet.

metal tile.

It should be noted that profiled sheet and corrugated board are one group of profiled coating. Some sources consider them to be different names for the same material, others separate them by wave height. The profiled sheet has a higher wave height, and the corrugated board is somewhat flatter. The first type can be used not only as a roof covering, but also as a material for the construction of fences, fences, metal garages, etc.

The corrugated board has a smaller wave and is intended for laying as a roof. Both materials have a common specific feature - profiling is performed only in the longitudinal direction, which expands their capabilities and allows you to make roofs for round roofs and canopies.

The step of the rafters of the gable roof under the corrugated board is selected taking into account this feature of the material. If the value is too high, it will be possible for the roof to sag between the rafters. In addition, there will be an excessive load on the battens, which may not be ready for it. An important parameter also becomes the area of ​​​​the slope. The pitch of the rafters of a shed roof under corrugated board is much less than that of a gable roof, since the length of the supporting elements and the magnitude of the load in it increase significantly and require an increased number of supports.

The metal tile looks like a canvas made of natural ceramic tiles. In all its operational qualities, it is very similar to corrugated board or profiled sheet, but physically it has an important feature - the presence of not only longitudinal, but also transverse waves. This allows you to slightly increase the step between the rafters of a gable roof under a metal tile, or be guided when choosing the size of a heat insulator.

When using slate or ondulin, the pitch of the rafters is taken according to the degree of rigidity of these materials. Alternatively, increase the density of the lathing, or install a solid version of thick plywood.

Method for calculating the distance between the rafters

There are two calculation options:

Engineering calculation using appropriate formulas and techniques.

Using online calculators, giving an answer after entering their own initial data.

The first method is only suitable for a professional roof system designer. For an unprepared person, it is extremely difficult to perform such calculations, since various specific data, coefficients, tabular values ​​are needed, which are difficult to find and must be used correctly. Calculations obtained using online calculators are also not recommended for use in real construction, but as an option to refine or verify the results of calculations performed by specialized organizations.

Video description

In the video you can see what the step of the rafters should be:

Conclusion

In conclusion, it should be recalled that all design and calculation activities must be carried out by trained and specially trained specialists. The pitch of the rafters is an important and crucial value that determines the bearing capacity of the roof. The damage caused by the inability to take on existing loads is quite serious and can call into question the possibility of living in a house, so it is necessary to take this issue as seriously as possible.

The distance between the rafters under the metal tile without fail takes into account the efforts made up of the wind, snow load, own weight of structures, roofing. In addition, the following factors affect the pitch of the rafters under the metal tile:

• the location of the pipes - the wooden elements of the roof should be 25-35 cm from the chimney, should not interfere with the direct paths of the ventilation ducts, fan pipes;
• roof configuration - it is necessary to have a rafter leg at the junction of the ridge of a gable, hipped roof.

All wooden elements of the truss system are made from coniferous trees, the humidity of which does not exceed 20%.

The step of the rafter legs is calculated at the design stage for budgeting. This will significantly reduce the amount of waste, cuttings of sawn timber.

What you need to know when choosing the optimal distance between the rafters?

The scheme of the roof with hanging rafters.

Having collected the loads present during the strength calculation, the designer evenly distributes them on the load-bearing walls. The principle of calculation is the same for layered, hanging rafters, only the schemes for fastening the elements in the ridge, on the Mauerlat, differ.

The minimum, maximum step of wooden rafters under the metal tile is regulated by 0.7 m, 1.2 m, respectively.

When choosing a step of 60 - 100 cm, the length of the rafters cannot exceed 6 m, with its decrease, a run-up of up to 1.2 m is allowed. If you put your feet more often than 60 cm, this will unnecessarily make the roof heavier and increase the construction budget. If you increase the step more than 1.2 m, the bearing capacity and the resource of the structure will sharply decrease.

A solid crate of wood-containing boards adds strength and rigidity to the truss system. In this case, it is allowed to increase the step by 0.3 - 0.2 m compared to a periodic crate made of a bar or edged board. However, to save the construction budget, a continuous crate for metal tiles is used extremely rarely. The material has sufficient strength and rigidity due to additional transverse profile ribs.

A step of more than 1.2 m is not used even when using rolled metal rafters, despite a sufficient margin of safety of the material. This is due to the possible deflection of the roof sheets during heavy snowfalls, hurricane winds.

The cross section of the beam from which the rafter legs are made also affects the pitch of the rafters, since the area of ​​\u200b\u200bsupport of the crate and the weight of the roof change. The best option is considered to be a beam of 150 x 50 mm with a discharged crate in increments of 4 - 7 cm, depending on the pitch of the transverse wave.

Calculation example for a gable roof

During the implementation of the project, specialists at the initial stage know the roofing material. In order to find out the recommended pitch of the rafters, you can use the SNiP tables, and then adjust the value in accordance with the operating conditions. An example table is shown below:

The table values ​​correspond to the rafters of simple single-gable roofs. First, the section of the leg, the length of the element, the distance between the centers of the log, the beam is obtained automatically. At the next stage, the length of the slope in the ridge is divided by the pitch of the rafters with the addition of one. Thus, the number of legs is counted, rounding the number up. Then it remains to adjust the distance between the wooden rafters in fact. For example, with a ridge length of 7.5 m, a rafter leg with a section of 16 x 2 cm (board) 4 m long, you get:

7.5 / 0.7 \u003d 10.7 + 1 \u003d 11.7 pcs. round up to 12 rafters.

The specification of the size allows you to calculate the center-to-center distance for mounting after installing the outer legs:

7.5/12 = 62.5 cm.

Dormer windows are located between adjacent rafters, in the places where pipes and chimneys pass, the legs are displaced by the distance specified in SNiP. All other elements of the system remain in place, the area of ​​​​adjacency to the pipes, if necessary, is enhanced:

• a bed is cut into two adjacent legs;
• a short rafter cuts into it at one end, the second adjoins the element of the opposite slope in the ridge;
• the offset legs in the upper part rest on a ridge run attached to at least two roof trusses.

Thus, the system receives the necessary rigidity without loss of bearing capacity, the fire safety requirements of wooden roof parts are met.

Rafter leg material

The material of the rafters is often a beam of 25 x 10 cm - 15 x 4 cm, which allows to reduce the construction budget.

When choosing lumber of natural moisture, the developer is guaranteed to shrink the structure in the first year and a half by 5-7 cm in height. By increasing the cost estimate for the arrangement of the truss system by 70%, you can purchase glued laminated timber, significantly reducing structural loads, and doubling the roof resource.

The distance between the rafters will remain unchanged, however, instead of a planed beam of 17.5 x 5 cm, recommended by building codes for five-meter legs spaced every 0.6 m, you can get by with a glued beam of a smaller section of 15 x 4 cm. Transportation costs will decrease, work at height will be facilitated , cut material.

Prefabricated rafters from boards are used with the same scheme for attaching hip roof trusses. The upper slopes are made of single boards, the lower ones are made of three boards sewn with self-tapping screws with an offset in the rows.

The choice of metal rafters is justified with a complex configuration of the roof, an abundance of ventilation pipes, chimneys, which cannot be bypassed in compliance with the requirements of SNiP, fire safety. In this case, the step between the rafters is maximized, since rolled metal is much stronger than lumber.

If the rafters are attached at the bottom to the Mauerlat, the step of the legs is not critical, the elements can, if necessary, move to the desired distance in any direction. If the scheme of support on puffs, which are floor beams, is used, it is much more difficult to displace individual elements. In this case, the amount of cutting waste increases when sheathing the draft ceiling, the floor of the attic or attic space.

The rafter is one of the individual elements of the supporting structure of the roof, with the help of which its slope is formed. In the design, the rafter is attached with its upper end to the ridge, and the lower end rests on the Mauerlat, with a straight slope, or on a rack (with a sloping roof). Rafters are made from edged boards with a section of 150x60 mm or a beam of 150x100 mm. The distance between the rafters at which they are located from each other after installation is called a step, which can be in the range of 600 - 1200 mm.

Rafter systems their types

Depending on the type of installation of rafter legs, systems are divided into 3 types:

What may determine the installation step of the rafters

The step of the roof rafters depends on such factors, how:

Taking into account all these indicators when calculating, you can get a solid and reliable truss structure, which for a long time will be a high-quality support for the roof.

It is the calculation, subject to the basics of regulatory loads, allows you to choose the right distance between the rafters. As a rule, the normative values ​​can be determined by Sheaves, and the calculated ones are derived on their basis separately for each structure.

At the same time, it is accepted as a template value to use rafter legs with a section of 150x50 mm with an optimal distance between the rafters within 0.8 - 1.8 m / p. but it should be remembered that when the slope of the roof slope changes, the distance between the rafters also changes.

Calculation of the truss structure

The strength and stability of the entire roof directly depends on the quality of the calculation for the selection of the section of the rafter legs and the distance between them. Regardless of which type of coating is chosen: profiled sheet, slate or metal tile, the initial calculation should remain unchanged. After all, each calculation is based on structural strength under mechanical loads, and other effects are no longer important.

When calculating the choice of the optimal distance between the rafters for the roof, are based on the following parameters:

1. Type of roofing.
2. View of the truss system and design features of the roof.
3. feasibility and economy.

For a small house, the design calculation for the roof can be done by yourself. True, the method of calculating the elements for the roof truss system is rather complicated, and it is recommended to do it using programs specially created for this. Especially if you need to calculate a complex sloping roof with a large area, most likely, you will not be able to do without a specialist. At the same time, the calculation of the step of the rafters will also be based on the standards - the minimum step is 0.6 m, the maximum step is 1.2 m.

Method of calculation

Produced in this way.

- The length of the building is measured along the eaves.

- The resulting length is divided by the estimated distance between the rafters. For example, the estimated pitch of the rafters will be 0.8 m / p. (mean distance is considered to be 950 mm).

- After performing this action, one should be added to the result obtained, and the resulting amount should be rounded. Thus, the required number of rafters is obtained on one side of the slope. After that, the length of the building must be divided by the number of rafters received, and as a result, the exact axial pitch of the rafters is determined.

Example, - building length 26.5 m / p. the distance between the rafters is supposed to be 0.8 m. So:

- 26.5 m ˸ 0.8 m = 33.1 33.1+1 = 34.1. As a result, after rounding, it turns out that 34 rafters need to be installed on one slope.

26.5 m/s ˸ 34 art. = 0.77 m - this value is the distance between the rafters along their central axes.

But this is only a general calculation method, which does not take into account the peculiarity of the planned roofing. Therefore, it is recommended by experts to calculate the step between the rafters for a certain roofing material and insulation, for example, for the most popular roofing metal tile today.

Roof structure for metal roofing

metal tile visually imitates ceramic roof tiles. It is made from thin sheet steel by cold stamping. Due to the polymer coating, it has a high resistance to weathering and a rather attractive visual appearance, it is not afraid of sudden temperature changes.

The advantage of metal tiles

Often used in the construction of most mansard roofs.

The cross section of wooden rafters under a metal roof is usually standard 150-50 mm, but the distance between them can be from 600 mm, but not exceed 900 mm (depending on their angle of inclination, which can vary between 22 - 45 degrees). This limitation of the pitch of the rafters is due to the fact that the crate under the metal tile is mounted with a distance from each other within 300 mm. The standard timber, which is used for the crate, has a section of 30x50 mm or 50x50 mm. And this means that each rafter is subjected to additional load.

The stability of the roof structure against various mechanical loads depends on four factors:

An important factor in the calculation of the truss structure, is the estimated maximum load on the roof, the formation of which includes:

1. The weight of the entire truss structure.
2. The weight of the crate under the cover.
3. Weight of insulation and roofing.
4. Snow load (determined according to a special, unique for each region, reference book).
5. Wind load (also according to a special guide for the region).
6. The weight of a person with a tool (repair work, estimated weight - 175 kg / m²).

When installing the rafter system, the distance of the rafter legs should not exceed an average value of 0.9 m / p. except for certain, foreseen in advance cases.

If, when calculating the loads, any inaccuracy is made in the selection of material for the roof and the location of the rafters, it may occur its deformation and destruction of the roofing. A reliable roof structure will be guaranteed only with the correct calculation of the cross-section of the rafters and their installation step.

It should be remembered. There is no universal value for the calculation of truss structures. Each building requires an individual calculation.

Rafters for a shed roof

Shed roofs can often be found on small outbuildings. They can also be used in private residential buildings, but quite rarely. In such cases, the angle of inclination of the roof is rather small, and with such an arrangement of the load-bearing floor beams, they are under a lot of pressure, especially in winter.

Therefore, for a shed roof, load-bearing floor beams are installed from a beam of large section from 60x150 to 100x220 mm, depending on the width of the overlapped span. At the same time, the distance at which the rafters are laid from each other should be within 400 - 800 mm, depending on the angle of the roof.

For pitched roof no complex rafter construction required, they can simply be laid on the walls, without even using a Mauerlat. In regions where winters are quite snowy with a lot of snow, it is recommended to build a roof slope at a maximum angle of 35 ⁰ and place the roof in the “wind”. This reduces windage and leads to its self-cleaning.

Gable roof

Represents a structure assembled from rafters interconnected in the form of a triangle. The upper part, which rests on the ridge, and the lower part on the Mauerlats, located parallel to each other on opposite walls. In simple words, this is a roof consisting of two opposite slopes, connected by a ridge.

Double pitched roof structure, depending on its area, is mounted from separate rigid elements that enhance the strength of the roof. These include racks that support rafters, puffs that connect rafters to each other, jibs, girders, support beams, etc.

For a gable roof, often the rafters are mounted taking into account the insulation in increments of 0.9 - 1.2 m / p. In this case, the strength of the mounted structure will be the highest if the resulting triangle is isosceles. In regions with strong winds, it is recommended to mount the rafters with a slope of approximately 20⁰, and in snowy areas, the optimal angle should be 45⁰.

Although the gable roof is considered classic, it has several alternative "related" types.

mansard roof

For mansard roof, for the calculated parameter for determining the step between the rafters and their number, a load is taken in the range of 40-60 kg for every 1 m / p. rafters, and the maximum deflection from its length is 1/250. Usually, with a properly selected section, this distance along the centers of the rafters is, as for a gable roof, 0.6 - 1.2 m / p.

It should be noted that the average load on the attic is approximately 200 kg / m2. So, with the standard calculation of the section of the rafters, it is recommended to add a small percentage of the margin of safety.

hip roof

Among all roof structures, it is considered one of the most difficult . It's almost a hipped roof., while the rafters of the end slopes are attached with their upper ends to the corner bowstrings, and not to the ridge. Therefore, certain requirements may be imposed on this type of roof during construction. In this case, the rafters are installed similarly to a gable roof at a distance of 60 cm - 1.2 m / p.

Attic rooms under such a roof are made in rare cases, since its slopes “eat up” some area of ​​​​the attic room, especially in height.

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 step

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 the 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 pitch.

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).