The distance between the rafters under the ondulin. Installation of a truss system for a pitched roof

The truss structure is the fundamental element of a pitched roof. Incorrectly calculated distance between the rafters, incorrect calculation of the load on the erected system of beams, their incorrect installation, most likely, will lead to deformation and collapse. The stability of the truss system depends on:

1. from strength at the bottom, to the ridge at the top;
2. the validity of the drawing of the support for the rafters, taking into account the length of the span;
3. wood quality;
4. rafter steps.

Obviously, the main condition for the reliability of the roof structure is a correctly calculated distance between the rafters. You can figure out how to determine this value for a single-pitched, gable, hip roof.

What are span length calculations based on?

A competent design calculation, in which the pitch of all rafter legs is calculated according to the same principle for any type of roof, is based on such indicators:

1. type of roofing material (metal tile, slate, etc.);
2. distance (span) between adjacent supports;
3. the angle at which the legs of the rafter are attached.

• rafter weight;
• insulation weight;
• roof weight;
• crate weight;
• snow;
• wind;

the weight of a person or people who will subsequently be engaged in the repair, maintenance of the roof itself and the objects located on it.

Snow and wind are different values ​​for each region, you need to look for these indicators in the reference information of a particular area, region.

How to calculate truss gaps

The exact distance between the rafter legs is calculated using complex mathematical formulas, resistance materials, but many craftsmen cope with this task in their own way. After the calculation of the maximum load is carried out, the following actions should be performed:

• measure the length of the roof;
• divide the result by the span of the roof frame or the approximate step for installing the rafters, (the step of the rafters is the distance from one to the other leg of the rafter system, usually a standard value, approximately selected, is taken into account);
• add one to the result, round the resulting value;

After that, the length of the roof slope should be divided by the obtained value (the number of trusses) - the required step of the rafters will be obtained.

Calculation example. The slope has a length of 27m, the selected step is 0.8m.

27:0,8=33,75
33,75+1= 34,75
round = 35, The number 35 means that you need to put 35 rafters.

We determine the distance between the rafters: 27: 35 \u003d 0.8. That is, the leg is set one from the other at a distance of 80 cm.

The generally accepted standard is a value equal to 1 meter, a step of eighty, seventy, ninety cm can also be optimal. Obviously, the calculation procedure cannot be called accurate, because the type of roofing material is not taken into account.

Intervals between rafters used for different types of roofing materials

When calculating the step of the rafters, it is necessary to take into account the characteristics and dimensions of the roofing material. The most popular types of roofing are:

• corrugated board;
• ceramic tiles;
• metal tile;
• ondulin;
• slate.

These types of roofing are used for the installation of roofs of residential buildings, baths, outbuildings. For each type of roof and roof shape, single-pitched, double-pitched or otherwise, a certain gap between the rafters is used.

Decking

Decking is a modern durable material made of galvanized sheet formed into a specific profile. The material is lightweight and durable. When using it, the calculation of the distance between adjacent rafters is 60-90 centimeters. A greater distance is possible only if there is a large cross-section board that fastens the rafters. The crate for corrugated board is made from a board of thirty, mounted 50 cm apart, if the roof angle is 15 °, the corrugated board is laid on the crate, laid without gaps.

The step of the rafters under the corrugated board does not depend on its brand. So, C44, the heaviest material, is attached to a crate with a span of 30 cm, but the pitch of the rafters does not change.

Ceramic tile

The calculation of the pitch of the rafters for ceramic tiles, a heavy, expensive material, is somewhat different from others. For a material whose weight is large, only dried strong beams with a section of 50x150, 60x180 cm are used. The optimal distances between the rafters taken as standards are from 80 to 120 cm. The choice of interval depends on the slope and type of roof. The calculation must be made taking into account the length of the rafter beam. For the longest rafter, a minimum step is required, and vice versa, the short length of the rafter allows you to use a step of maximum width.

metal tile

Metal tile can be safely called the leader among all roofing materials. It is used for complex, hip, gable, hipped, pitched roofs. Its installation is much simpler than ceramic tiles. Metal tiles can be put on the old roof, ceramic tiles, slate can be replaced using the old step. The metal tile is 10 times smaller, therefore, beams of a smaller section of 50x150 are used, the step between the rafters is from 60-90 cm, standard values. It is especially convenient to insulate such a roof by including the width of the roll or sheet insulation in the calculation.

Ondulin

This type of soft roof is becoming more and more popular, lightweight, easy to install, strong and durable. Ondulin sheets are overlapped on a 40x50 crate made of coniferous boards (60 cm step).

The pitch of the rafter legs is from 60 to 90 cm. Beams are needed with a section of 50x150 or 50x200.

Slate

Slate is widely used to cover farm buildings, baths, houses, garages. Therefore, what should be the distance between the rafters when using this roofing material, many people know. The use of this particular material created a system of rafter pitch 60-80, battens 50x50. The crate is made of bars 50x50 or the thirtieth board, depending on the slope. For a sloping pitched roof, a batten pitch of 45 cm is used, for a gable roof - 65 cm.

How do the steps of the rafters of gable and shed roofs differ?

Each type of roof has its own strength. The pitch of the rafter beams depends on what margin of safety should be laid during the installation of a particular type of roof.

Shed roof structures, which are typical for simple household buildings, are made of beams mounted on walls. The distance between the roof rafters directly depends on their length. It is also important to take into account the cross section of the timber used, based on the fact that the longer the gap, the greater the load.

The gable system, which includes gable, tent, hip and other structures, is always mounted with thermal insulation. The standard step for such roofs is 1-1.2 meters. In each case, the calculation is carried out taking into account, as already mentioned, the weight of the roofing material and other things, SNiP 2.01.85 is taken as the basis, which considers all types of loads and impacts. The step is calculated according to the usual scheme given above. Be sure to take into account the angle of inclination. An angle of 45° allows the use of all types of roofing. With the same roof slopes, the pitch of one side is calculated.

Stick to the following tips:

• If a decision is made to independently arrange the roof, check the correctness of your calculations with specialists or, at worst, use the services of online calculators of construction companies.
• When determining the pitch of the rafters, remember about thermal insulation, any rolled or sheet insulation shrinks over time. Remember about ventilation holes, waterproofing.
• If the slope of the roof is 45° or more, the weight of the person is subtracted from the sum of the maximum load, which allows the use of fewer rafters (by 20%).
• Decide which type: layered or required for the selected roof geometry.
• Take your time with the choice of timber, it must be dry (residual moisture not more than 20%), made of coniferous wood.

When building a roof, the type of truss system is first chosen. This means that the rafters must be hanging or layered, or the entire rafter system will consist of both rafters, that is, combined. It is not difficult to calculate the distance between the rafters, knowing the magnitude of the loads that will act on the entire roof.

Loads are temporary and permanent. Permanent loads include:

• the weight of the materials of the truss system itself;
• weight of roofing material;
• the weight of the elements of the roofing cake, if the roof is insulated;
• the weight of the interior decoration of the attic ceiling.

Live loads include: the weight of the snow cover, the weight of a person during roofing work and maintenance of the roof during operation, wind load and the weight of possible water flows in summer.

What are the calculations based on?

The distance between the roof rafters is also calculated based on the selected material and the section of the rafters. All calculations are carried out at the design stage of the house by specialists of design organizations. To do this, they use reference documents and building codes and regulations governing a particular step of the rafters, the step of the crate and other calculated values.

When building a private house, rarely does anyone order a project where, based on calculations, it is recommended what distance between the rafters must be maintained. Most often, developers rely on the experience of the masters and trust them to conduct all the calculations on the spot. However, there are those who want to make the calculation of the truss system themselves and build a roof on their own.

In this case, they must first of all decide on the type of roof, choose which attic will be - heated residential or cold, since the type of truss system and the calculation of the distance between the rafters directly depend on these parameters

The distance between the rafters of a pitched roof

The calculation for a shed roof is the simplest. The rafter system does not provide for racks and braces - only the rafters themselves. Such a roof is most often equipped in utility rooms, garages, bathhouses, etc.

The step of the rafters of a shed roof is presented in the table below and depends on the section of the beam:

If the developer wants to independently calculate the loads on the truss system, it will be useful for him to familiarize himself with such documents as SNiP 2.01.85 "Loads and impacts" and "Changes from SNiP 2.01.85", where maps are laid for the climatic regions of Russia.

As a material for the construction of the truss system, coniferous wood is chosen, the humidity of which is 20-22%. Boards, beams and other types of lumber should be smooth without pilosity, rot, knots and blue.

All wooden elements should be treated with antiseptics and flame retardants to protect the wood from decay and fire. The material used, the length of the rafter legs and the cross section of the beam also affect the calculations (see table):

Approximate calculation

The step of the rafters is nothing but the distance between the rafter legs. As a rule, for residential private houses, this figure is 0.6-1.0 m.

The pitch of the rafters is influenced by a significant number of factors. The calculation of the required number of rafter legs is carried out in the following way:

• The length of the roof slope is measured. After that, the resulting value is divided by the selected step between the rafters.
• Then one is added to the resulting value and rounded up to get an integer. This is how the number of rafter legs required for a given length of one roof slope is obtained.
• After that, the entire length of the roof slope is divided by the resulting integer (the number of rafter legs) and as a result, the distance between the axes of the future rafters is obtained, which is called the rafter step.
• The axis should run in the center of the rafter. However, for different types of roofing, the pitch of the rafters may vary, and it also varies depending on the angle of the slope of the roof slope.

For example: the length of the roof slope is 16 meters, and the step between the rafters is 0.6 meters. Therefore, 16 / 0.6 + 1 \u003d 27.66 \u003d 28 meters (rafters are necessary for the slope device)

The greater the slope angle, i.e. the steeper the roof, the greater the pitch of the rafters. This is due to the fact that the load on steep roofs is not distributed over the entire roof plane, but is mostly transferred to the load-bearing walls.

Rafters for ceramic tiles

Ceramic tile is a material that has a decent weight. Therefore, for a tile roof, the cross section and length of the rafters should be calculated, given that one square meter of ceramics weighs almost ten times the weight of a metal tile.

• If in the design of the rafter system it is supposed to tighten the rafters, then its cross section should be increased.
• The rafters themselves must be made of dry healthy wood, their cross section must be 50x150 or 60x180 mm.
• The pitch of the rafters is done in the range of 0.8 -1.3 m for ceramic tiles, and its exact determination depends on the slope angle of the slopes.

The higher the roof, the wider the pitch of the rafters. For example, with a slope angle of 15 degrees, the pitch will be 80 cm, and if the slope angle rises to 75 degrees, the distance between the rafter legs will increase to 1.3 m.

Another circumstance affects the pitch of the rafters - this is the length of the rafter legs. The longer they are, the shorter their step. This is due to the fact that with the maximum length of the rafters, increased deflection loads are created. They can be reduced if you arrange a system of support posts, struts and other elements of the truss system, which take on part of the load from the rafters.

Rafters for a metal roof

The truss system for a metal tile is not much different from other truss structures. But due to the fact that it has a weight several times less than ceramic tiles, rafters and all other elements of the roof structure can be made with a smaller margin of safety, i.e., a smaller section. The difference in the weight of clay and metal tiles is about 35 kg per 1 m2.

The pitch of the rafters under the metal tile, as a rule, is 0.6-0.9 m. Metal tiles are widely used to cover country houses, in which attic rooms are often provided, so the roof is made insulated. The pitch of the rafters in such structures is adjusted to the dimensions of the insulation, which is inserted between the rafter legs.

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 standard values ​​can be determined from the Sheaves, and the calculated ones are derived on their basis separately for each structure.

At the same time, it is customary 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 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, especially in height.

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.

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. Therefore, we advise you to make all the calculations manually.

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.

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 structurally according to the 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 load-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!

The roofs of modern private houses can have a different configuration. The most popular type of roofing is gable. The owners of suburban areas consider reliability, rather attractive appearance and economy to be the undoubted advantages of such a roof. The design of this type of roof is extremely simple, and therefore it will not be difficult to build it, including with your own hands.

Lightweight and durable sheet materials are what a gable roof is most often sheathed with. Decking, for example, is just perfect for such a design. The roof of this variety protects the interior space of the house well, lasts a long time and is inexpensive. Of course, the procedure for erecting a truss system under corrugated board, as well as under any other material, has some of its own characteristics.

Where to begin

How is a gable roof assembled? under the corrugated board it will turn out to be reliable, and the roof itself will be neat only if a detailed design project is first drawn up. When developing the latter, you need:

determine the angle of inclination of the slopes;

determine the type of materials needed for construction;

make detailed drawings of the frame indicating the method of connecting all nodes.

If all these operations are performed without errors, you will end up with a solid gable roof. The truss system for corrugated board, a drawing of which can be made using, for example, special software on a computer, will last as long as possible.

Load calculation

This step when drafting a roof should not be skipped in any case. Properly performed calculations are a guarantee that in the end you will get a durable gable roof. The rafter system for corrugated board (a photo of the assembly of such a frame can be seen below) is mounted taking into account the following parameters:

the weight of all used for materials;

The values ​​of the last two indicators can be found in special tables developed specifically for each specific region.

All figures obtained as a result of calculations must be added and multiplied by a reliability factor of 1.1. Having performed the calculation of the gable roof truss system in this way, it will be possible to determine, first of all, the type of materials necessary for assembly. Also, taking into account the final load indicator, the optimal angle of the roof frame supports is chosen.

Ramp angle

In addition to the load, when choosing this indicator, the features of the roofing material itself should also be taken into account. The angle of inclination of the slopes can be any, but not less than 12 degrees. If you make the roof more gentle, in the future it will leak. At the same time, the sheets themselves will begin to sag under the weight of snow in winter. That is, the roof will have to be constantly repaired. And this, of course, additional costs.

In Central Russia, taking into account wind and snow loads, it is almost universally allowed to build roofs with a slope angle of 30-45 degrees. This option is ideal for corrugated board. In the southern regions, the angle of inclination of the roof slopes of houses may be smaller, and in the northern regions, on the contrary, it may be larger.

Among other things, when choosing a method for installing rafters, it is worth considering how exactly the attic will be used in the future. If it is supposed to be insulated and equipped for living quarters, it is better to make the slopes more abruptly. But of course, in this case, the construction of the roof will cost a little more, since you will have to use more materials.

What to build from

From what specific materials can such a gable roof be built? with their own hands, which, in any case, is a responsible matter, should, of course, be as reliable as possible. But one of the advantages of corrugated board is that it is light in weight. Therefore, it is not necessary to use any special, very durable, materials for assembling the frame for it. For rafters, such a roof is quite suitable for a standard beam of 150x100 mm. It is advisable to use lumber of a larger section only if the attic is supposed to be used as a living space. Rafters for such a roof are usually made of timber 200x100 mm.

The crate can be assembled from edged boards 30x100-150 mm. Too wide lumber in this case cannot be used. After a while, such boards will simply dry out and become very warped, which will have an extremely negative effect on the reliability of the roof. Under the Mauerlat, it is better to take a thicker beam - 200x150 mm.

Step between structural elements

Too often, frame supports under light metal sheets are also not necessary. The optimal distance between the rafters of a gable roof for corrugated board is 60-80 cm. As for the crate, the step between its elements is selected taking into account the variety of sheets used. So, for a thick material of 0.6-0.7 mm with a profile height of 3.5 cm, boards can be packed at a distance of up to 1.5 m from each other.

For a standard H grade corrugated board, the crate pitch is usually 60-70 cm. The same distance is suitable for CH material. A thin sheet C is mounted on a crate stuffed in 10 cm increments or knocked down with a solid sheet of 12 mm plywood or OSB sheets.

How a gable roof is assembled. Rafter system for corrugated board

The roof frame of the house is mounted in a few steps:

Mauerlat is installed;

rafters are mounted;

if necessary, a heater is installed;

the rafters are covered with a waterproofing;

crate is stuffed.

Mauerlat installation

They begin to assemble such a structure as a gable roof made of corrugated board, with their own hands from the installation of this particular element. Mauerlat is mounted on top of the building box. As a basis for a rafter system, this element is used only on brick, monolithic or block walls. In cobbled and chopped, its role is played by the upper crown. Fasten the timber to the walls using anchor bolts. You can also use steel dowels, galvanized wire from 5 mm thick or staples.



Ways of fastening rafters

The supports themselves can be attached to the Mauerlat in two ways. For brick, block and monolithic houses, rigid fixation technology is used. In this case, they are attached to the Mauerlat using galvanized steel corners and self-tapping screws or a “knot” of three nails (one in the upper plane, two on the sides).

On chopped and cobbled walls, the rafters are fixed using a sliding method. The fact is that such houses for the first time after construction give a strong shrinkage. Therefore, a rigidly fixed roof frame in the future can simply lead. With the sliding method of installing the rafters, special fixing elements, “sleds”, are used, which ensure the mobility of the supports in a small range.

How to install

The support elements of the frame must be mounted correctly. In this case, you get a neat symmetrical gable roof. The rafter system for corrugated board, as well as for any other material, must be assembled using a template. In this case, all legs will have the same length. For gable roofs from corrugated board, they can use both simple straight rafters (with an edge cut at the required angle), and a variant with landing nests under the Mauerlat. Between themselves at the top of the frame supports are usually fixed by means of special thick steel plates.

The end trusses are always installed first. Further, a cord is pulled between their highest points. Then, focusing on it, intermediate farms are installed. On large roofs, a ridge run on supports is pre-mounted between the extreme paired rafters. The latter are securely fixed on the floor beams.

Installation of insulation and waterproofing

If the attic is supposed to be made residential, it will, of course, have to be insulated during the construction of the roof. On corrugated roofs, mineral wool is most often used for this purpose. As a support under it, from the side of the attic, a wire is pulled onto the rafters. The mats themselves are installed by surprise.

The waterproofing agent on the rafters is sewn with a slight sag (2 cm). It is impossible to stretch the film strongly. Otherwise, when the frame moves, it can simply break. The waterproofing strips are mounted horizontally from the bottom up with an overlap of at least 10-15 cm.



Lathing installation

Support boards for corrugated boards are fixed to the rafters with nails with a diameter of about 3-3.5 mm. The length of the fasteners in this case should exceed the thickness of the fixed elements themselves twice. The assembly starts from the eaves. Boards should be fastened to each rafter with two nails. The last two rows at the ridge are stuffed without a gap.

After the crate is assembled, you can proceed to sheathing the frame with the corrugated board itself. At the final stage, the gables of the roof are upholstered with a board.

What you need to know

Wood is a material that is very easy to process and at the same time quite durable. That is why the do-it-yourself truss system of a gable roof is most often assembled from timber and boards. However, unfortunately, lumber cannot boast of too long a service life. Sooner or later, as the roof of the building begins to dry out or rot. Therefore, before assembling it, the timber and boards must be treated with special compounds that increase their moisture resistance.

Another disadvantage of wood is flammability. To minimize the risk of fire, the lumber used to build the frame of the building should, among other things, be carefully treated with a fire retardant.



This is how the gable roof is assembled. The rafter system for corrugated board, as you can see, is mounted elementarily. Nevertheless, the installation of a roof frame is a very responsible matter. If any technologies are violated, the owners of the house will subsequently have problems with leaks, the need to replace individual elements, etc. Therefore, it is worthwhile to approach the assembly of the roof truss system with maximum responsibility.