What should be the distance between the roof rafters. The distance between the rafters: the correct calculation

The reliability of the roof and its service life mainly depend on how correctly the calculations are made.

One of the most important parameters of the rafter system is how far apart the rafters are located.

After all, the distribution of the load on the frame depends precisely on this desired parameter.

If the calculation is made incorrectly, then deformation may occur and the roof will collapse.

Therefore, it is extremely important to perform an accurate calculation of the interval between the rafter legs when drawing up a roof project.

Basic provisions of the calculation

The pitch of the rafters is the distance from one rafter leg to the other.

In the construction of roofs of private houses, this value is 1 meter.

But this figure is approximate.

To get the exact size of the interval, it is necessary to calculate the bearing capacity of the truss system of the selected type.

To perform the correct calculation, the following scheme should be used:

• first you need to determine the length of the roof slope;
• now the resulting figure should be divided by the value of the approximately selected rafter step. If you previously chose its value of 1 meter, then you need to divide by 1. If you chose 0.8, then you should divide by 0.8, etc.;
• after that, one is added to the result obtained and the resulting value is rounded up. This action is necessary in order to get the exact number of rafters that will need to be installed on one slope;
• the total length of the slope must be divided by the number of rafter legs obtained in the previous calculation. And we get the exact distance between them.

To better understand everything, let's look at an example.

By measuring the length of the roof slope, we got 27.5 meters.

We choose a step of 1 meter to make it more convenient to count.

Further calculations will look like this:

Now we add the unit 27.5 m + 1 = 28.5 m.

We round up to the nearest value and get the number 29.

That is, 29 rafter legs must be installed on one slope of our roof.

Now we divide the length of the roof by their number: 27.5 / 29 \u003d 0.95 m.

So, in our case, the step of the rafter legs should be 0.95 meters.

This is a general calculation.

In which the peculiarity of a particular roofing material is not taken into account.

And he can significantly change this parameter.

When you know what kind of material you will use on the roof, some changes will have to be made to the calculation procedure.

Optimal and minimum value

The step is the unit of account.

After all, it depends, first of all, on the load on the roof frame and the section of the rafter legs.

You can take a thick board for their construction and make the interval between them 120 cm.

At this distance, the crate may begin to sag.

Yes, and how to lay the heater?

Indeed, for most materials, the width is 1 meter.

So they take an approximate step of 1 meter when calculating.

The minimum distance between the rafter legs is 70 cm.

And to obtain the optimal value for each material, it is necessary to perform a calculation.

Determining the pitch for a pitched roof

Shed roofing is the simplest.

Indeed, in the truss farm of such a roof there are only rafter legs.

There are no struts, racks, braces in its design.

Such a roof is usually arranged on garages, outbuildings, baths.

In order to determine the pitch of the rafters on a pitched roof, you can use the table:

As can be seen from the table, the rafter step depends on their length and cross section.

Distance between rafters for a gable roof

A gable roof is much more common than a shed roof.

And to explain such popularity is simple: the design is very simple, but for all its simplicity, the gable roof is distinguished by its reliability.

Its design is easy to adjust to any climatic conditions and any roofing material.

When calculating the pitch of the rafters of a gable roof, everything is performed according to the general calculation system (see above).

If the slopes have the same length, then it is enough to perform calculations for one slope.

If the slopes are of different lengths, then the calculation is performed for each slope.

It should be remembered that the limit values ​​for the pitch of the rafter legs are 70 and 120 cm.

Ondulin

If ondulin is used as a roofing material, then the rafter system is constructed from pine boards with a section of 50 x 200 mm, and the rafters should be located at a distance of at least 60 cm and not more than 90 cm from each other.

A crate of timber with a section of 40 x 50 mm is laid on top.

metal tile

Roofing from metal tiles is most often used in the construction of country houses.

Because this material is much lighter than ceramic or cement tiles.

Although in appearance it is very similar to her.

The light weight of the metal tile makes it possible to use boards of a smaller section when creating the rafter system, and to use thinner bars for the crate.

More about the counter-lattice under the metal tile.

About the hip roof with hanging rafters at the link. Also about the design of hanging rafters.

About the price of Viking metal tiles here. Specifications, photos, reviews.

Reducing the size of the elements of the rafter leg system, in turn, reduces the load on the walls of the building and its foundation.

During the construction of the rafter system under the metal tile, the rafters are mounted in increments of 60 - 95 cm.

The cross section of the material is 50 x 150 mm.

According to experts, if a heater having a thickness of 150 mm is placed between the rafters, then the most comfortable living conditions will be created in the attic.

To ensure ventilation of the space where the insulation is laid, when installing the rafter system, holes will be drilled near the upper roof with a diameter of 12 mm.

The technology for manufacturing a truss system for metal tiles does not differ significantly from the technology for manufacturing a frame for other roofing materials.

Its only difference is the installation at the top.

The upper support is mounted not on the side of the ridge beam, but on the ridge run.

The presence of a free zone between the rafters allows the air to fully circulate under the flooring, which helps to protect against the formation of condensate.

Ceramic tiles

The design of the system for ceramic tiles has its own characteristics.

After all, clay is used to make such a roofing material.

And this is very heavy material.

If we compare metal and ceramic tiles, the latter weighs 10 times more.

Accordingly, the truss system is significantly different.

On 1 square meter of the roof surface there is a load of 40 - 60 kg, depending on the manufacturer and brand of the product.

The rafters for such a frame system are made from wood that has been dried for a long time.

Such wood should have a moisture content of no more than 15%.

A beam with a section of 50 x 150 or 60 x 180 mm is used.

So more reliable.

And the distance between the rafter legs can be 80 - 130 cm.

The exact value can be called if the angle of inclination of the slopes is known.

If the angle of inclination is 15 degrees, then the pitch of the rafters will be 80 cm.

And if the angle of inclination, for example, is 75 degrees, then the step can be larger - 130 cm.

More than 130 cm interval between the rafters do not.

Also, when calculating the pitch of the rafters, their length is taken into account.

The larger the dyne, the smaller the distance between them.

The shorter the rafter legs, the greater the distance can be.

If the angle of inclination is 45 degrees, then the roofer can safely move along the roof if the pitch of the rafters is 80 cm.

Decking

When creating a rafter system for corrugated board, the minimum distance between the rafter legs is 60 cm.

The maximum value is 90 cm.

If for some reason the pitch of the rafters was more than 90 cm, then it becomes necessary to install large cross-section boards.

The rafter legs themselves can have a section of 50 x 100 or 50 x 150 mm.

Slate

Despite the emergence of a large number of new roofing materials, asbestos-cement slate remains one of the most popular.

If it is planned to lay slate on the roof, then the rafters should have a section of 50 x 100 or 50 x 150 mm.

The distance between them is made not less than 60 and not more than 80 cm.

The crate is made from a bar having a section of 50 x 50 mm or a board with a section of 25 x 100 mm.

When constructing any building structure, it should be remembered that there are still unforeseen situations.

And, therefore, when calculating the sections of the rafters and the distance between them, it is necessary to provide for a margin of safety.

about the installation of the truss system.

Sergey Novozhilov is an expert in roofing materials with 9 years of practical experience in the field of engineering solutions in construction.

Source: http://ProRoofer.ru/montaz/stropilnye-sistemy/rasstoyanie-mezhdu-stropilami.html

The distance between the rafters of a gable roof and the pitch of the rafters

The quality and durability of the roof largely depend on the correct calculation of the pitch of the rafters. It affects the laying of insulation, the fastening of roofing material and the installation of additional parts.

Pay attention only to the requirements for the distance under the roofing sheets, then there may be problems with the insulation boards. And vice versa, adjusting the size of the insulation can make the frame too weak, and in winter there will be a threat of collapse.

The basics of determining the pitch of the rafters

As a rule, the pitch between the rafters depends on several factors. But usually the distance fluctuates between 0.6 and 1.2 meters. These figures are rounded, in practice the distance may differ by several centimeters downwards. For an accurate determination, the following calculations must be performed:

1. Determine the length of the slope by measuring along the eaves of the house. Suppose that it turned out 17.8 meters.
2. Divide the figure obtained by the planned step of the rafters. If it was decided that the distance between the beams would be 0.8 meters, then 17.8 / 0.8 = 22.25.
3. Further, we round the result up and add one: 23 + 1 = 24. At this stage, the number of rafters required is determined.
4. Now we calculate the distance between the axes of the beams. To do this, the length of the slope must be divided by the number of rafters: 17.8 / 24 \u003d 0.74 m.

So, you will determine the actual distance at which the rafters for a roof made of metal or some other material should stand.

Often, when planning a roof frame, specialized calculators are used. They enter basic data and get the finished result. Nevertheless, you should not completely trust the program, since only a person can take into account some conditions. When calculating, you can understand how the system works, what loads are acting. If necessary, adjustments are made to strengthen or facilitate the design. Self-calculation will help to more accurately determine the required pitch of the rafters of a gable and single-pitched roof.

Step calculation depending on the roofing material

For each coating, its own standards and dimensions are developed for the truss system. The main factors are the strength of the material, its weight and resistance to external loads. Consider the main types of coatings.

Decking

The step of the rafters under the corrugated board can vary from 0.6 to 0.9 m. The final result depends on additional conditions, which we will discuss below. If for some reason the step should be larger, a transverse board with a large section is added. In this case, usually the rafters themselves are chosen with dimensions of 50x100 or 50x150 mm.

In addition to the rafters, a crate of 30x100 millimeters is used. The gap between the boards should be about 0.5 meters. It can be more, it all depends on the type of corrugated board and the height of the wave. Sheathing boards protruding beyond the boundaries of the eaves should have a thickness of 1.5 cm more than usual. This is done based on the need to mount ventilation, a chimney or a drain.

Ceramic tiles

The main difficulty in designing a roof frame for ceramic tiles is the large weight of the material for the roof. It is 10 times heavier than corrugated board and accounts for 40 to 60 kg per square meter.

Under such a coating, dry beams are used, with a moisture content of only 15%. Their cross section should be either 50x150 or 60x180 mm. With such indicators, the maximum allowable distance between the rafters can be 1.3 meters. The minimum allowable step through which rafters can be placed is 0.8 m. The roof slope affects the final decision: at 15 °, the step is 0.8 m, at 75 ° - 1.3 m.

The length of the rafter leg is also taken into account, the shorter it is, the larger the gap, and vice versa. In addition, if the slope is less than 45 °, and movement is planned on the surface, the beams are placed in increments of no more than 0.85 m.

The distance between the boards of the crate is selected so that each intersection of the tiles has its own base. The standard length of the material is 400 mm, and the amount of overlap during installation varies between 55 and 90 mm. It turns out that the distance between the central axes of the crate can be either 310 or 345 millimeters.

metal tile

In recent years, the question has been particularly acute: how to determine the distance between the rafters under the metal tile? It imitates more expensive ceramic material, but at the same time it has the positive properties of corrugated board. Installation of such a coating is simple and does not require large financial costs. All this makes the material attractive for the roofs of private houses.

The mass of metal tiles is less than ceramic, so a simpler frame is required. The section of the beams is reduced to 50x150 mm and the step between the crate is increased. The step of the rafters under the metal tile varies between 0.6 and 0.95 m.

Ondulin

The allowable step for covering from ondulin is 0.6-0.9 meters. The standard section of the rafters is 50x200 millimeters. Such dimensions will allow to withstand the load of the roofing pie on the gable roof.

On top of the counter-lattice, a crate of bars measuring 40x50 millimeters is attached. The pitch between the central axis is 600 mm.

Additional factors

When calculating the pitch of the rafters, attention is paid not only to the type of roofing. Many other points are taken into account, data on which can be found in reference books and SNiPs. Here are some of the factors:

1. Snow and wind loads. The more snow falls in winter and the stronger the winds blow, the smaller the distance between the beams should be. But, if you increase the angle of the roof slope over 45 °, then it is allowed to increase the pitch.
2. Choice of heater. To reduce the cost of insulation boards, it is recommended to take into account their standard sizes. They produce mats with a width of 600, 800 and 1200 mm. If this condition is neglected, then a large number of undercuts will appear, cold bridges and construction will be delayed.
3. lumber quality. It takes into account the type of wood, grade and section. As mentioned above, strength is affected by how well the beam was dried. When buying wood, pay attention to evenness and the presence of defects in the form of knots and traces of pests.
4. Floor beams and puffs. If you equip the attic floor under a gable roof, then the maximum distance between the rafters should be 0.75 meters.

The calculation of the distance between the beams for a gable and single-pitched roof is different. Even if he makes several slopes, for each it is necessary to make a calculation individually. This is especially true for buildings with different lengths of cornices.

Taking into account all these factors, it is possible to determine how far the rafters should be installed. Although all calculations can be done independently, since reference data is freely available, it is better to turn to professionals. They have experience in designing, they will quickly determine the required distance between the rafters. So, you will avoid possible mistakes and be sure of safety.

Source: https://build-experts.ru/shag-stropil/

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 relatively low 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 step 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 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 the 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.

Polycarbonate varies in weight depending on the thickness of the sheet. The crate for polycarbonate is recommended to be done in increments of 600-800 mm. The crate (wooden or metal) is mounted on rafters, which can be straight or arched.

Usually the gap between the rafters for polycarbonate is from 1500 to 2300 mm.

Source: http://krovlya-mp.ru/shag-stropil-dvuskatnoj-kryshi.html

The distance between the rafters: what step should be between the rafters

The task of correctly calculating the distance between the rafters is very responsible. Not only the reliability and durability of the roof, but also all subsequent work on it will depend on how seriously you begin to solve it: laying insulation, installing roofing, installing additional elements. If you manipulate the step of the rafters under the roof sheets, as many do, then it is not a fact that a heater will then enter between the rafters.

If you focus only on insulation, the very first winter with its abundant Russian snow will crush the truss system. That is why the whole point is to choose the optimal rafter pitch for all slopes, and now we will teach you this skill.

Here is a good video tutorial on how to independently calculate the distance between the rafters:

What determines the pitch of the rafters?

So, the distance between the rafters is determined by such important factors:

1. The shape of the roof (gable, single-pitched or multi-pitched).
2. Roof angle.
3. The parameters of the timber that is used for the manufacture of rafters (width, thickness).
4. The design of the truss system (layered, hanging or sliding).
5. The totality of all loads on the roof (covering weight, atmospheric phenomena, etc.).
6. Lathing material (20x100 or 50x50) and its parameters (solid, with gaps of 10 cm, 20 cm or solid plywood)

And each of these parameters must be taken into account, which is exactly what this article is about.

Online calculators vs. notebook and pencil

Today, there are many complex formulas for the correct calculation of the cross section of the rafters and the step of their installation. But remember that such formulas were at one time developed more in order to be able not only to ideally calculate the roof constructs, but to study the work of such elements.

For example, simple online programs that calculate the parameters of rafters are popular today. But ideally, if you can independently set specific tasks and calculate everything you need.

It is important to understand to the smallest detail what exactly happens in the truss system during operation, what kind of forces act on it and what loads. And a computer program cannot always take into account everything that the human brain notices.

Decorative rafters: 0% load

First of all, decide on the most important point: the type of roof and its purpose. The fact is that the roof of a residential building in winter can withstand a large cap of snow, a constant wind at a height and it is often insulated from the inside, but completely different requirements are imposed on the rafter system of a small gazebo hidden under the crowns of trees.

For example, if you are building a pergola in its classical sense, then it does not matter at all what exactly the distance between the rafters will be - this is already a purely aesthetic factor:

In the above illustration, it can be seen that even in such a building there is a step of rafters. After all, here it provides both an aesthetic factor and the rigidity of the structure itself. But the step is chosen arbitrarily.

Functional rafters: detailed calculation

We approach the main question: what distance should be between the roof rafters of a residential building? Here, be patient and carefully study all the nuances.

Item 1. Wall length and rafter spacing

First of all, the step of installing rafters on the roof of a residential building is usually chosen according to the structural size of the building, although taking into account many other factors.

For example, it is easiest to install rafters in increments of 1 meter, so for a wall 6 meters long, 7 rafters are installed as standard. At the same time, you can save money by placing them with a distance of 1 and 2 meters, and you get exactly 5 rafters. It can also be placed with a distance of 2 and 3 meters, but reinforced with a crate. But it is highly undesirable to make a step of rafters more than 2 meters.

Item 2. Influence of snow and wind loads on the shape of the roof

So, we settled on the fact that the average distance between the rafters of an ordinary roof is 1 meter. But, if there is a significant snow or wind load in the area, or the roof is more or less flat or simply heavy (for example, covered with clay tiles), then this distance must be reduced to 60-80 cm. But on a roof with a slope of more than 45 degrees, it can be even zoom to a distance of 1.2m-1.4m.

Why is it so important? Let's figure it out. The fact is that the air flow collides on its way with the wall under the roof of the building, and turbulence occurs there, after which the wind hits the eaves of the roof. It turns out that the wind flow, as it were, goes around the slope of the roof, but at the same time trying to raise it. And in the roof at this moment there are forces that are ready to rip or overturn it - these are two windward sides and one lifting.

There is another force that arises from wind pressure and acts perpendicular to the slope, trying to push the roof slope inwards. And the greater the angle of inclination of the roof slope, the more important are the safe wind forces and the less tangential. And the larger the angle of the slope, the less often you need to put rafters.

To understand whether you should make a high roof or a flat one, this map of the average wind load will help:

The second point: in the Russian region, such an atmospheric phenomenon as snow constantly affects the standard roof of a house. And here, too, you need to consider that the snow bag usually accumulates more on one side of the roof than on the other.

That is why in such places where such a bag is possible, it is necessary to insert paired rafter legs or make a continuous crate. The easiest way to determine such places is by the wind rose: single rafters are placed on the windward side, and paired rafters on the leeward side.

If you are building a house for the first time, then you will not find your own worldview, but determine the average snow load for your area according to official data:

Point 3. The issue of insulation and the standard width of mats

If you will insulate the roof, then it is advisable to set the pitch of the rafters under the standard dimensions of the insulation boards, which are 60, 80 cm and 120 cm.

Modern heaters today are sold in standard widths, usually at the same standard rafter spacing. If you then take them and adjust them to existing parameters, then there will be a lot of waste, cracks, cold bridges and other problems.

Point 4. The quality and strength of the lumber used

Of great importance is also what kind of material you use to build the truss system. So, for each type of wood there is its own regulatory documentation, which concerns its bearing capacity:

Because for the manufacture of the roof truss system in Russia, pine and spruce are most often used, their bending strength and features of use have long been prescribed. If you use wood of other species, then you can display the correction factor.

In addition, if there are sections, cuts or bolt holes on the rafter, in this place it is necessary to calculate the bearing capacity of the bar with a factor of 0.80.

Item 5. Distance between puffs and floor beams

One more thing: if the roof is built with interconnected roof trusses, and their lower belt is used simultaneously as floor beams, then the distance between the trusses must be made within 60-75 cm to take into account the design of the future floor.

Item 6. Loads on truss nodes

So, here are the main loads that act on the roof truss system:

1. Static, which includes the weight of the rafter system itself, the weight of the roof, snow lying on the roof and additional elements.
2. Dynamic, which includes wind force, unexpected damage to the roof, the weight of a person and equipment for repairs, and similar factors.

And all these factors are able at a certain moment to act on the roof at the same time, and therefore there is such a thing as a critical value. This is exactly the value of the loads at which the roof does not withstand and deforms.

Therefore, if the building is being built with significant spans, then steel truss trusses are necessarily used. The fact is that there is no tension in such rods, and the entire load falls on the nodes - here they are affected by compressive and tensile forces. And the distance between such farms is calculated depending on the type of roof and the design of the roof itself.

Usually, a unified truss is placed with a span that is a multiple of six, and therefore a distance is made between the truss nodes that is a multiple of one and a half meters.

Item 7. Weight of the rafter system and roofing cake

Do not forget that the main purpose of the rafters is to hold the entire roof on itself, and its weight is crucial:

Point 8. Ease of installation of roofing

The distance between the rafters is also influenced by such a factor as the selected roofing. The higher the slope of the roof, the more roofing materials will be used. And the heavier they are, the more often you will have to put rafters under them. But what about a full slab? The fact of the matter is that it also has its own weight:

Each type of roof has its own optimal rafter pitch. After all, many standard sheets at the edges need to be fixed directly to the rafter or crate, and it is important that they match. Otherwise, roofing work will easily turn into a living hell at a height, believe me.

That is why, even before starting installation, it is necessary to make a layout, check everything several times. And to know some important subtleties for each type of coating.

Determining the totality of loads on the roof as a whole and the rafters separately

So, we have determined that, in addition to other design factors, a whole set of loads simultaneously acts on the roof truss system: the weight of the truss system, a snow cap, wind pressure. After you add all the loads together, be sure to multiply them by a factor of 1.1. So you all count on unexpected favorable conditions, that is, lay an additional 10% percent strength.

And now you just have to divide the total load by the planned number of rafters and see if each of them will cope with its task. If it seems that the design will be frail - feel free to add 1-2 rafters to the total, and you will be calm for your home.

You need to make a calculation for destruction, i.e. to the full load that acts on the roof. All these loads are determined by the technical characteristics of materials and SNiPs.

The standard roof structure is rafters, lattice runs, and each of these elements works only on the load that puts pressure on it, and not on the overall roof as a whole. Those.

each individual rafter has its own load, total, but divided by the number of rafter legs, and by changing the step of their location, you change the load collection area on the rafters - reducing it or increasing it.

And, if it is inconvenient for you to change the pitch of the rafters, then work with the parameters of the section of the rafter legs, and the total bearing capacity of the roof will increase significantly:

In this calculation, try to ensure that the longest rafter in your project is no more than six and a half meters, otherwise, splice along the length. Now let's explain in more detail.

So, on roofs with a slope of up to 30 degrees, the rafters are the so-called "bendable elements". Those. they work specifically for bending, and there are certain requirements for them.

And the possibility of deflection of the rafters is calculated according to a special formula, and if the result exceeds the norm, then the rafters are increased in height and a new calculation is made again.

But on the roof with a warehouse slope of more than 30 degrees, which rafters are already considered “bendable-compressed” elements. That is, they are affected not only by a uniformly distributed load, which causes the rafters to bend, but also by forces that are already acting along the axis of the rafter. In simple terms, here the rafters not only bend a little under the weight of the roof, but are also squeezed from the ridge to the Mauerlat. In addition, the crossbar, which usually holds back two rafter legs, must also be checked for tension.

As you can see, even a person who is far from construction can cope with such calculations. The main thing is to take everything into account, be attentive and ready to spend a little more time on design, so that later all the work goes like clockwork!

When carrying out installation work, it is very important to correctly determine the pitch of the rafters under the metal tile. It is important to understand that it is quite difficult to make such calculations, and it is on how correctly everything will be done that the level of roof strength directly depends. Many experts argue that the operational life of not only the roof, but also the structure itself depends on the level of reliability of attaching the metal tile to the rafters. As a result of the fact that the metal tile has a rather large weight, the truss system must be strong. In addition, beginners will not be able to lay roofing material. In order to properly carry out installation work, it is recommended to responsibly approach the calculation of the step of the truss system.

The device of the truss system under the metal tile

Do-it-yourself rafter system for metal tiles is not as difficult to perform as it is to make the appropriate calculations. It is important to understand that the type of system used depends entirely on the type of roof. To date, the truss system for a gable roof under a metal tile is considered the most popular option. Such truss systems, as practice shows, are great for installing metal tiles on the roof of a dwelling. To equip the rafters, wooden blocks of different lengths are used - the choice, as a rule, directly depends on the length of the legs. Many experts recommend paying attention to the fact that it is necessary to choose the right angle of inclination, which can vary from 15 to 30 degrees - this value is considered optimal.

Calculation of the distance between the rafters for metal tiles

The step of the rafter under the metal tile is the distance from one rafter leg to the other, to put it differently, then this distance is called the step of the rafter system by roofers. This distance directly depends on the type of roofing chosen. As practice shows, for all roofing materials, including metal tiles, this size varies from 0.6 to 1.2 m. However, it is important to understand that it is best to carry out accurate distance calculations for each material separately - it must be individual approach.

Before proceeding with the installation work, it is necessary not only to determine the distance between the rafters, but also to understand how much material is required for the legs. To find out the pitch of the rafters of a gable roof under a metal tile or a shed, it is recommended to adhere to the following recommendations:

1. First of all, calculate the length of the roof slope from the metal tile. Measurements, as a rule, are carried out along the eaves of the roof.
2. After that, it is possible to choose an arbitrary step. It is important to take into account the fact that the step limits for metal tiles can vary from 0.6 to 1 m. For example, initially it became necessary to adhere to a distance of 0.8 m. The length of the slope should be divided by the chosen value for the step of the truss system. Let's say that the length of the slope is 12 m, it turns out that 12 / 0.8 and it turns out 15. After that, you need to add 1 to the resulting value. In the case when the number turns out to be fractional, then it should definitely be rounded up. Thus, it turns out 15+1=16. This value shows exactly how many rafter legs should be installed on the roof. Then you need to take the length of the slope and divide it by the resulting number of legs. It turns out that 12/16 and it turns out 0.75 m.

Many experts recommend entrusting these works to professionals, which will allow you to get the desired result in the future. It is important to understand that there is a high probability that mistakes will be made, which will ultimately negatively affect the finished roof structure.

Attention! As practice shows, such calculations can be used for any roofing materials.

Installation of rafters under the metal tile

Since the installation work is carried out at a great height, if necessary, it is possible to assemble the frame for the supporting truss system on the ground, and then lift and fix it on the roof. For these purposes, it is best to create a special template or scheme of the truss system for the metal tile from the boards, according to which the installation will be carried out.

The whole process is carried out in stages:

1. First of all, the boards are raised above the wall of the building, leveled and fixed with nails.
   
   
2. According to the project, the boards must be aligned at a certain angle of inclination, after which all elements are securely fixed.
   
   
3. Ultimately, a structure should be obtained that, in appearance and shape, resembles a truss system. Manufacturing must be carried out taking into account the calculations made.
   
   
4. Then you need to lower the template to the ground and install all the finishing elements.

Do not forget about the installation of supporting elements, namely, Mauerlat. Laying is carried out on load-bearing walls in a longitudinal position. As fasteners, special studs or wire rods are used.

The next step is the installation of the ridge run, which is used as a supporting part for all roofs. For work, you will need to use a beam or a hewn log. In cases where the length of the slope does not exceed 6 m, then additional supporting elements can be dispensed with.

When the installation of all elements has come to an end, you can proceed with the installation and further installation work on the arrangement of the truss system according to the attached template.

Mauerlat can be fixed in several ways:

• rigid connection- in this case, a beam or corners should be used, nails and staples are used much less often, a feature is the fact that it will be necessary to additionally tie the rafters to the wall, using anchors for this purpose;
• sliding way- in such cases, an articulated connection must be created, it can be done by joining the elements with cuts.

During operation, the step distance of the truss system must be observed.

When choosing a rafter pitch for a metal tile, you should pay attention that the distance should not be less than the minimum allowable value and more than the maximum allowable value, that is, it can vary from 0.6 m to 1.2 m.

If it was decided to choose a distance from 0.6 to 1 m, then the length of the rafters in this case should not be more than 6 m. In the event that it is reduced, it is allowed to make a run up to 1.2 m.

If the legs of the truss system are installed more often than after 0.6 m, then this will only contribute to a significant weighting of the roof and, as a rule, an increase in costs. If necessary, the distance can be 1.2 m, but it is important to understand that in this case the level of bearing capacity will be significantly reduced, which will negatively affect the structure of the metal tile.

If necessary, you can increase the level of strength, then for this you will need to perform a continuous crate of wood boards. In such situations, the step can vary from 0.2 to 0.3 m. This option is used extremely rarely, since its implementation requires much more investment.

An interval of 1.2 m is almost never used during installation work. This is due to the fact that despite the rather high level of strength, the metal tile will begin to sag under the weight of snow in the winter or with strong gusts of wind.

An important value is the cross section of the timber used for arranging the truss system. It depends on him what distance will be chosen. The best option is the choice of wooden bars with a cross section of 150 * 150 mm, while the crate can be installed at intervals of 4 to 7 cm. In this case, it is recommended to take into account the step of the transverse wave.

Conclusion

The pitch of the rafters under the metal tile can only be determined after the appropriate calculations have been made. It is important to understand that if the distance is quite small, this can significantly increase the material consumption and project budget, and if the distance is made too large, then the roofing material will begin to sag during operation, which will lead to deformation of the metal tile.

As you know, the roof of any building is its upper part, which can combine protective and decorative functions. It protects the roof mainly from atmospheric precipitation getting inside the building from above, at the same time, with its appearance, material and color of the roof, it can emphasize the architectural features of the building.

The wooden beams that make up the rigid roof frame are called rafters; the selected roofing material is already mounted directly on them.

As buildings carry different functional contents (for example, residential buildings or industrial and technological buildings), so the roofs of various buildings differ from each other. Their shape can directly depend on climatic conditions: on the wind load or the amount of snowfall. It is difficult to clean the roof from the latter if its slope is 30 0 or less, and the large "sail" of a high roof can be a serious problem with wind gusts of more than 18 m / s.

Among the huge variety of roofs, most usually consists of a roof and a set of building structures that hold this roof.

One of the main elements of these structures are, as a rule, wooden beams, on which the roofing is mounted. These beams are called rafters or trusses. They are also the stiffening elements that determine the mechanical strength of the roof, as well as those guides that determine the angle of inclination of the roofing.

The rafters can be located either from one to the other outer wall of the building, with a certain slope, or from the center (ridge) of the roof to the outer wall. According to the first method, single-pitched roofs are arranged, according to the second - gable roofs.

It can be assumed that the closer these truss trusses are located to each other, the more reliable the base for roofing will be.

However, the excessive use of materials makes the structure heavier and leads to higher construction costs. Therefore, the question of how to install rafters is one of the fundamental when designing a roof.

There are two types of rafters: the so-called "hanging", resting with their ends only on the outer load-bearing walls, and those that rest with one of their ends on the inner load-bearing wall of the building or the inner column. Farms of the latter type are called "layered".

Proper placement and fastening of these elements of the building is the basis for the fact that its upper part is not deformed under the influence of possible loads.

How to properly install rafters

General provisions

When designing the roof of a building, determining the number of trusses and the distance between them, they must take into account the required section of the beam used for the construction of the rafters, determine its material and the optimal length of the rafter. Usually, a bar made of coniferous trees is used for the device of rafters, with a section of 50x150 mm (considered the most used) or more.

The length of the trusses directly depends on the size of the building box, the type of roof, and also on its height. The cross section of the timber used and the distance between the rafters determine the strength of the supporting structure for the roof. The distance between the axes of adjacent trusses is called and calculated when designing the roof. In practice, the applied pitch can take a value from 600 to 2000 mm. The specified step is interconnected with the length of the trusses: the shorter they are, the greater the distance between them can be installed.

There is a generalized method for calculating the specified distance. It lies in the fact that the table determines the preliminary step of the rafters. Having then measured the length of the roof overhang of one slope along the lower edge, the resulting distance must be divided by the step determined from the table. The result obtained and the unit added to it, after rounding up, will correspond to the number of rafters required for one slope of the projected roof.

The exact distance between the axes of the "legs" of neighboring farms will be obtained by dividing the length of one roof slope by the number of rafters calculated for it.

In this way, it is possible to determine at what minimum distance the rafters can be installed so that the roof supporting structure meets the design load requirements.

However, this method does not take into account possible additional loads on the structure associated with the use of various types of roofing, from slate to ondulin. Does not take into account the need to organize free space between trusses to accommodate sheets or slabs of roofing insulation used.

In the case when it is planned to use insulating agents, the width of which is known to be the width of the canvases or panels, you can immediately determine at what distance the rafters should be installed. It is recommended in such cases to equate the step to the width of the insulation, minus 1.5 to 2 mm.

Recommendations for choosing a rafter pitch for different roofing

For corrugated roofing, the pitch is selected in the range from 600 to 900 mm. At the same time, the beam is recommended with an optimal section - 50x150 mm.

A heavy roof made of ceramic tiles is characterized by an increased load on the rafters, about 60 - 70 kg / m 2. The step is recommended in the range from 800 to 1300 mm. Moreover, it can increase in proportion to the increase in the angle of inclination of the roof. For example, the distance between trusses should be no more than 800 mm if the angle of inclination of the roof does not exceed 15 0. By increasing the specified angle to 70 0 the step can be increased to the maximum. The cross section of the timber for such a roof is recommended from 50x150 to 60x180 mm.

The device of the supporting structure of the roofing for metal tiles is not much different from the standard one. The material, in comparison with ceramics, is almost twice as light: the load per 1 m 2 does not exceed 30 kg. A bar with dimensions of 50x150 mm is recommended for use. Some features of fastening the upper ends of the rafters are associated with the provision of ventilation of the metal roof to prevent condensation.

Slate roofing is the optimal solution for numerous buildings, despite the fact that this material is recognized as harmful and banned for use in European countries.
Recommendations for the installation of rafters for corrugated slate roofing are typical: they are placed in intervals from 600 to 800 mm, they can be 50x100 or 50x150 mm.

For roofing from ondulin, it is proposed to perform according to the recommendations in force for slate roofing. The modern innovative material ondulin looks like slate, but it is five times lighter than the last one.

The determination of the inter-rafter distance for multi-pitched (tented) roofs is made separately for each slope. For buildings in which the “box” is assembled from logs or timber, the lower end of the rafters is attached directly to the upper part of the outer load-bearing wall, and not to a special timber laid along the perimeter of the upper part of the building (Mauerlat). This installation method makes the price of an error especially high when determining the pitch of the rafters, since it can be very difficult to eliminate such an error.

Bearing truss structure for a mansard roof

For such roofs, the supporting structures for the roof are usually made of timber. The pitch of the rafters for a slope no longer than 15 m can be selected in the range from 800 to 1000 mm. For attics with slopes longer than 15 m, it is recommended to use metal rafters.

It should be noted that for all types of roofs, when determining the pitch of the rafters, the presence of existing vertical structural elements of the building passing through the attic and roof should be taken into account. These elements include chimneys and air ducts. If the design point of the truss installation coincides with the passage of the existing pipe or other building elements that cannot be transferred to another part of the attic, the rafter placement plan should be changed accordingly.

If for some reason it is not advisable to change the specified plan, it is recommended that the rafter, which coincides in place with the building element, be arranged so that it is interrupted at the place where the pipe passes. Moreover, the ends of this truss, cut off before and after the passed pipe, must rest on the corresponding jumpers connecting adjacent rafters.

It must be borne in mind that the nodes of such an "interception" of the truss should be performed with the necessary reliability and quality, which allows it to correspond to the calculated reliability of the supporting structure of the roofing.

It should be noted that the installation of rafters is part of a whole complex of very serious and very important construction work on the roof of a building. As a structural element of the load-bearing roofing system of a building, rafters are specified in the roof project plan, which reflects the results of calculations of various possible loads.

Such calculations should take into account all kinds of factors that affect the designed structure in the complex:

• necessary and sufficient height and slope of the roof;
• optimal material for roofing;
• the parameters of its placement on the required crate and the total weight of the roofing;
• the necessary bearing capacity of the truss structure in general and the corresponding parameters of the rafters in particular;
• method of attaching the roof to the walls of the building and the condition of the walls.

And other equally important data, without taking into account which the constructed building and its roof may not withstand various loads.

Therefore, in order not to have distressing consequences as a result of inept actions, it is better to entrust issues related to the design and construction of buildings to professional specialists with the necessary experience and knowledge. At least in the part that concerns the calculation of the load on the truss structures.

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 estimate point 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 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 relatively low 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 step 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 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 the 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.