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What is the distance between the rafters of a gable roof. All about gable roofs: the optimal distance between the rafters. Dead load calculation

The distance between the rafters is one of key parameters, affecting the strength of the structure. Proper calculation of the installation pitch of the rafters allows you to build a roof that is resistant to high operating loads.

Roof loads and calculation of the rafter system

Development of a project for a single-pitched or gable roof starts with choosing a type rafter system, the angle of inclination of the slopes (roof height) and materials for constructing the structure. Calculation of the distance between the rafter legs is carried out taking into account the loads that the roof will experience during operation. Constant loads include:

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

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

weight of snow cover;

the weight of a person during roof maintenance and repair.

The pitch refers to the distance between the rafters of one slope. When calculating a single-pitch, gable or complex roof, we usually adhere to the following scheme:

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

The final result will allow you to determine at what distance the rafter legs should be placed. Determining the step cannot be extremely accurate, since it is necessary to take into account whole line additional factors, including the width of the insulation, installation features of the sheathing under different kinds roofing material. If a roof with a chimney is being designed, the pitch can be adjusted taking into account its location, so that you do not have to subsequently remove part of the rafters and install a supporting structure, such as a special rafter system.

Distance between rafters under slate

Slate is a traditional roofing material. Its advantages include characteristics such as resistance to external influences (excluding mechanical) and low cost. Slate allows you to create roofing, the repair of which can be reduced to replacing individual elements. Slate has heavy weight and requires the installation of a sufficiently powerful rafter system. Calculation of the distance at which it is necessary to place 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 a system under 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 sheathing is made of timber or boards with a cross-section of at least 30 mm. When calculating the rafter system for slate, you should read that this material has quite large restrictions on the choice of slope angle.

Rafters for metal tiles

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

The standard pitch of rafters for metal tiles is 600-900 mm. The cross-section of the elements can be 50-150 mm - this is enough to create a reliable frame for metal tiles. But if you plan to use insulation, the layer of which in areas with low winter temperatures should be 200 mm; for rafters under metal tiles, it is recommended to use 200x50 timber, so as not to install an additional system that holds the insulation. It is better to adjust the gap between the rafters for metal tiles to the width of the sheet or roll insulation.

Corrugated sheeting: rafters and sheathing

Corrugated sheeting is a lightweight and easy-to-use roofing material. Galvanized or coated with a decorative protective layer, corrugated sheets can be used for installing a pitched roof utility room or a garage, or for a gable roof of a residential building. How to calculate the distance required to install rafters under corrugated sheets?

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

Rafter system for soft roofing

Soft roofing includes bitumen and bitumen-polymer roll materials, roofing membranes, as well as soft tiles. Soft roofing is characterized by relatively low weight and the absence of the need to install a massive rafter structure.

The minimum distance between the rafter legs is 600 mm, the maximum is 1500 mm. When installing supports 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 sheathing should be. The choice of step is also influenced by the thickness of the material for the sheathing - the thicker the sheet of plywood or OSB, the larger the installation step of the rafter legs can be.

Ondulin: calculation of rafters

Ondulin (bitumen slate) is laid on a flat, continuous sheathing made of sheet material. This allows the roofing covering to successfully resist wind and snow loads. The sheathing for 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 pitched roof.

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

Sandwich panel roof

Sandwich roofing is most often erected on houses made of sip panels or hangar-type buildings. A special 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 top of the wall (or the distance between supporting structures pitched roof) allow the installation of a sandwich without additional supports.

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

Polycarbonate: construction of a supporting structure

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

Polycarbonate varies in weight depending on the thickness of the sheet. It is recommended to perform lathing under polycarbonate in increments of 600-800 mm. The lathing (wooden or metal) is mounted on rafters, which can be straight or arched. Typically, the gap between rafters for polycarbonate is from 1500 to 2300 mm. In order to correctly calculate at what distance it is better to lower the rafters, it is necessary to take into account the glazing area, the size and thickness of the sheets, and take into account that polycarbonate is attached with gaps for thermal expansion.

The distance between the rafters of a gable and pitched roof

Find out what distance between the rafters needs to be made for a gable and shed roof. The maximum distance between rafters for metal tiles, ondulin and soft roofing.

Distance between rafters: principles and examples of calculating the pitch of a rafter system

The task of correctly calculating the distance between the rafters is a very important one. How seriously you begin to solve this problem will determine not only the reliability and durability of the roof, but also all subsequent work on it: laying insulation, installing roofing, installing additional elements. If you manipulate the pitch of the rafters under the roofing sheets, as many do, then it is not a fact that insulation will then fit between the rafters. If you focus only on insulation, the very first winter with its abundant Russian snow will crush the rafter system. That's why the whole point is to pick optimal step rafters for all slopes, and this is the skill we will teach you now.

What determines the pitch of the rafters?

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

1. Roof shape (gable, single-slope or multi-slope).
2. Roof angle.
3. Parameters of the timber used to make rafters (width, thickness).
4. The design of the rafter system (sloping, hanging or sliding).
5. The totality of all loads on the roof (weight of covering, 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 needs to be taken into account, which is exactly what this article is about.

Decorative rafters: 0% load

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

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 a purely aesthetic factor:

The illustration above shows that even such a building has its own pitch of rafters. After all, here it provides both the aesthetic factor and the rigidity of the structure itself. But they choose a step arbitrarily.

Functional rafters: detailed calculation

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

Point 1. Wall length and choice of rafter spacing

The first step in installing rafters on the roof of a residential building is usually chosen structurally based on the size of the building, although taking into account many other factors.

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

Point 2. The 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 a regular roof is 1 meter. But, if the area has a significant snow or wind load, 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 increase to a distance of 1.2 m-1.4 m.

Why is this 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 seems to bend around the slope of the roof, but at the same time trying to lift it. And at this moment forces arise in the roof that are ready to tear it off or overturn it - these are two windward sides and one lifting one.

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

This map of the average wind load will help you understand whether to make a high roof or a flat one:

The second point: in the Russian region, the standard roof of a house is constantly exposed to such atmospheric phenomena as snow. Here too, you need to take into account that the snow bag usually accumulates more on one side of the roof than on the other.

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

If you are building a house for the first time, then you won’t have to decide on your own worldview, but rather determine the average snow load for your area according to official data:

Point 3. The issue of insulation and standard width swear words

If you will be insulating the roof, then it is advisable to place the pitch of the rafters under standard sizes insulation slabs, which are 60, 80 cm and 120 cm.

Modern insulation materials are now 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. Quality and strength of the lumber used

It is also of great importance what kind of material you use to build the rafter system. So, for each type of wood there is its own normative documents, which concerns its load-bearing capacity:

Because For the manufacture of roof truss systems 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, you can derive a correction factor.

In addition, if the rafters have sections, notches or holes for bolts, in this place the load-bearing capacity of the beam must be calculated with a coefficient of 0.80.

Point 5. Distance between tie rods and floor beams

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

Point 6. Loads on rafters

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, the 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 capable of influencing the roof simultaneously at a certain moment, and therefore there is such a thing as critical value. This is exactly the load value at which the roof cannot withstand and becomes deformed.

Therefore, if a building is being built with significant spans, then steel roof trusses must be used. The fact is that there is no longer 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 trusses is calculated depending on the type of roof and the design of the roof itself.

Usually, a unified truss is installed 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.

Point 7. Weight of the rafter system and roofing pie

Do not forget that the main purpose of the rafters is to support the entire roof, and its weight is decisive:

Point 8. Ease of installation of roofing

The distance between the rafters is also influenced by factors such as the selected roofing covering. The higher the roof slope, the more roofing materials will be used in this case. And the heavier they are, the more often you will have to put rafters under them. But what about the continuous sheathing? 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 the edges need to be fixed directly into the rafter or sheathing, and it is important that they coincide. Otherwise, the work of covering the roof will easily turn into a living hell at altitude, believe me.

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

Determination of 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 rafter system: the weight of the rafter system, the snow cap, wind pressure. After you add all the loads together, be sure to multiply them by a factor of 1.1. So you will all count on unexpected favorable conditions, that is, provide an additional 10% percentage strength.

Now all you have to do is divide the total load by the planned number of rafters and see if each of them can cope with its task. If it seems that the structure will be frail, feel free to add 1-2 rafters to the total, and you will have peace of mind for your home.

You need to make calculations for destruction, i.e. for the full load acting on the roof. All these loads are determined by technical specifications materials and SNiPs.

The standard roof structure consists of rafters, lattice purlins, and each of these elements responds only to the load that puts pressure on it, and not on common roof generally. Those. Each individual rafter is subject to its own load, total, but divided by the number of rafter legs, and by changing the step of their location, you change the area where the load is collected on the rafters - reducing it or increasing it. And, if changing the pitch of the rafters is inconvenient for you, then work with the parameters of the cross-section of the rafter legs, and the overall load-bearing capacity of the roof will increase significantly:

When making 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 slopes up to 30 degrees, the rafters have so-called “bending elements”. Those. they work specifically for bending, and there are certain requirements for them. And the possibility of rafter deflection is calculated using 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 a roof with a warehouse slope of more than 30 degrees, which rafters are already considered “bending-compressed” elements. That is, they are affected not only evenly distributed load, which causes bending of the rafters, but also forces that are already acting along the axis of the rafters. Speaking in simple language, here the rafters not only bend a little under the weight of the roof, but are also compressed from the ridge to the mauerlat. In addition, the crossbar, which usually holds the two rafter legs, must also be checked for tension.

As you can see, even a person far from construction can handle 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 then all the work goes like clockwork!

Distance between rafters: what step should be between rafters

Detailed instructions on how to correctly calculate the distance between roof rafters different designs, taking into account the sum of the loads and the material used.

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

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

Distance for different roofing materials

Experts advise: when determining the pitch between the rafter supports, take into account the roofing material from which the roof of the gable roof will be created. Let's look at the most common roofing options suitable for private residential buildings.

1. Corrugated sheeting - for this roofing material, the digital distance we need is from 60 to 90 centimeters (if the pitch is increased to at least one meter, we will have to install additional transverse boards with large cross-section– 5 × 10 cm). In this case, under the corrugated sheeting you will need to install a sheathing, which will provide the ability to attach the required vertical components - a chimney, a ventilation system.
2. Ceramic tiles - roofing made from this material has enough heavy weight, therefore the load on the rafter system will be higher than when covering the roof with corrugated sheets. Accordingly, the distance that we calculate will be different: from 80 centimeters to 1 meter 30 centimeters. But in this option, the steepness of the roof slope is also taken into account (if the slope angle is 15 degrees, then the gap will be minimal - 80 cm, at 75 degrees - 130 cm).
3. Metal tiles - this roofing material is lighter than the previous one and is sold immediately in leaf form, therefore, the thickness of the components of the rafter system is reduced, and, consequently, the distance between the elements in it is reduced. For rafter material with a cross section of 15 × 5 centimeters, the gap should be selected from 60 centimeters to 95 centimeters. This distance will allow for high-quality insulation attic space(for this it is necessary to place the insulation material directly between the rafters). The peculiarity of installing a rafter structure under metal tiles is that the supports are installed on top of ridge run(usually they are installed on the side of the ridge beam). But in this case we should not forget about ventilation holes near the top roof.
4. Ondulin - this material is called “Euro slate”, and it is perfect for roofing private residential buildings. For the rafter structure under the ondulin, rafters from boards 5 × 20 centimeters are used, which provides a certain margin of safety (the rafter purlins are also taken into account). The distance between them rafter boards standard - from 60 to 90 centimeters, and the wooden beam for the sheathing should be a cross-section of 4 × 5 cm, with an interaxial step of 60 cm.
5. Slate is one of the most common roofing materials in our country; rafters for it should be selected with a cross-section of 5 × 10 / 5 × 150 centimeters. The distance between them will be in a slightly smaller range - 60-80 cm. The lathing is made of wooden beam has its own gap between the elements, which directly depends on the slope angle of the roof slope: for a small slope - from 45 cm, for a larger slope - from 60 cm.

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

Before installing the rafter system, the question arises at what step to install the floor beams. Correctly calculating the distance between the rafters means preventing subsequent deformation or even destruction of the roof frame. After reading the article to the end, readers will learn what the distance between the rafters should be for different types of roofing and how to make the calculation correctly.

Even at the design stage of a wooden house, all load calculations must be made. This also applies to the rafter system. This is especially important in wooden house construction, since the top link is often used instead of a Mauerlat. It is difficult to correct errors in such a design later. For correct calculation There is a method for determining the distance between beams.

The span of the roof frame for the construction of a house made of timber typically exceeds 1 m, and the smallest permissible value this is 60 cm, such indicators are indicated in GOSTs (see figure). You can correctly calculate the length of the rafters and their pitch using the following option:

Using a tape measure, the length of the roof slope is measured, the result is divided by the pitch size of the roof frame. For example, if the distance between the rafters is 1 m, then you need to divide by 1, if 70 cm, then by 0.7. The resulting figure is added to 1 and rounded to the nearest more. This way you can determine the number of beams for one roof slope.

You need to divide the length of the future slope by the result obtained. The result will be the distance between each rafter.

For example, consider a roof whose slope is 25.5 m and in increments of 0.6 m. You need to calculate the following indicators: 25.5:0.6=42.5, to 42.5+1=43.5. We round this figure to the nearest larger integer, we get 44. This is the number of rafter beams per 1 slope of the future roof.

Now we calculate the span between the rafters: 25.5:44 = 0.58 m. It turns out that you need to install the legs of the frame after 58 cm. This way you can easily calculate the pitch of any roof frame, single or complex, without taking into account the roof. But professionals recommend their calculations for a certain type of roof.

Rafter pitch depending on material

Since each forging material has its own characteristics and features. Among the most common are:

1. Profiled sheeting. It has different thicknesses and tropezoidal curve shapes. Costs from 120 rubles.
2. Ceramic tiles. Expensive material from 670 rubles. Has 12 color options.
3. Metal tiles. It's more cheap material unlike ceramic and costs from 320 rubles.
4. Ondulin. A soft roof insulates the house from rain, hail, etc. Costs from 340 rubles.
5. Slate. Most economical option from 90 rub.

We will consider the step size for the most common types of coverage below.

Spacing of rafter beams under corrugated sheeting

The distance between the roof beams depends on the size of the sheet that the corrugated sheet has. The pitch of the roof frame beams under the corrugated sheeting is standardly taken to be no less than 60 cm and no more than 90 cm.

If this distance is greater, then boards with a larger cross-section are attached between the rafter beams. The cross-section of the rafter legs under the corrugated sheet is selected 50x100 or 150 mm.

The most important thing to consider when planning to attach corrugated sheeting is the sheathing. It is made from boards with a cross-section of 30x100mm; it must be mounted with a span of 50 cm. It depends on the brand and thickness of the corrugated sheeting and the slope of the roof.

So, a 15º roof, grade C 10 corrugated sheeting is mounted on a continuous sheathing, C 21 corrugated sheeting is mounted on the sheathing with a span of 30 cm. The largest corrugated board C 44 is mounted on the sheathing in increments of 50 cm to 1 m. In this case, before attaching the sheathing, you need to consider the free space chimney passage, ventilation hood and so on.

Spacing of rafter beams for ceramic tiles

The specifics of installing a rafter system for laying ceramic tiles are related to the weight of this roof. Ceramic tiles are made from clay, and this roofing weighs 9-10 times more than metal tiles. The calculation of the load on the rafter system for ceramic tiles is 40-60 kg/m2.

Beams for the roof truss system for ceramic tiles are made only from dried material. The cross section is suitable 50x150 or 60x180 mm. The standard distance between the rafters for a tile roof is 80-120 cm. The span depends on the slope of the roof. At an angle of 15º, the span between the rafters is 80 cm, at 750 every 1 m 30 cm.

When calculating the step, you need to take into account the length of the beam. Taking maximum length the distance between the rafters is minimal. And, on the contrary, with a minimum length of rafters, the pitch is maximum.

When laying ceramic tiles, it is important to consider that you will need to walk on the roof. The maximum safe step of the rafter legs for such movement is 80 cm.

It is important when laying ceramic tiles to calculate the span of the sheathing. This distance is directly related to the size of the roofing material. A standard sheet of tiles is 40 cm long. Laying occurs with an overlap of 50 to 90 mm. When calculating the sheathing pitch, the overlap size is subtracted from the length of the tiles. The result is a pitch of 305-345 mm.

For a pitched roof for the construction of a house made of profiled timber, it is not difficult to make calculations. If the roof has a complex, multi-pitched shape, then each distance between the rafters is calculated separately per sheathing step. Having secured the cord to opposite side The roof slope can be easily marked with rows.

Features of the roof frame for metal tiles

Metal tiles are used more often than ceramic or corrugated sheets. Externally, the roof resembles ceramic tiles, but unlike it, it is easier to install and lighter.

Metal tiles weigh from 35 kg/m2 of roofing. This makes it possible to lighten the rafter structure and use beams of smaller cross-section. The step between the rafter legs of the roof frame increases and is equal to 60 to 90 cm. The beam is used with a section of 50x150 mm.

To create a ventilated space, holes with a diameter of 12-13 mm are drilled in the beams under the roof.

The design of the roof frame for metal tiles is not much different from corrugated sheets or ceramic tiles. But there is a small peculiarity: the support from above is attached to the ridge girder from above, and not from the side as in other cases. This will create a ventilated gap under the metal tiles, which will prevent the accumulation of condensation.

Features of rafter legs for ondulin

Ondulin is soft roof used for the construction of a house made of laminated veneer lumber or other material. Ondulin is produced in the form of sheets; it looks like painted slate, but is lightweight. This material is great for wooden houses both low-rise and large.

Rafter beams under ondulin are placed with a distance of at least 60 cm, maximum 90 cm. For the rafter system, timber from coniferous species wood with a section of 50x150 or 50x200 mm. A smaller cross-section will not provide sufficient strength to the rafter purlins.

The sheathing on the rafters is made of material with a cross-section of 40x50 mm in increments of 60 cm. This is quite enough for fastening sheets of ondulin with an overlap of 30 cm. Ondulin is fastened with special nails, which are sold as a set.

Features of the slate rafter system

Slate is rarely used for roofing modern houses. But in dacha construction and household This material is irreplaceable in buildings. He has low cost and easy to install.

Slate rafters

Slate rafter legs are used with a section of 50x100 or 50x150 mm. The fastening spacing between the rafters is no less than 60 cm and no more than 80 cm.

The slate lathing is made from 50x50 mm bars or 30x100 mm wide boards. The sheathing is laid in steps depending on the slope of the roof. For a steep pitched roof it is 45 cm. The consumption is 4 bars per 1 sheet of slate. For a flat pitched or gable roof 63-65 cm, the consumption is reduced to 4 bars per sheet.

The pitch of the rafter system under slate differs in the roof structure. For households It is not uncommon for buildings to have a shed roof installed.

Feature of the size between the rafter beams on a single-pitched and gable roof

Whether a safety margin is needed during installation depends on the shape of the roof. And the distance between the rafter beams directly depends on this.

Single-pitch rafter system

A pitched roof is more durable and easier to assemble. The thickness of the rafters is selected depending on the type of wood, its strength and the specifics of a particular structure. The step between them can be 60-140 cm. The distance also takes into account whether the structure will be insulated. If yes, then the step should correspond to the width of the insulation.

The thickness of the rafter beams must be calculated depending on the roof slope. For a slight slope of 15-20º, you can use material with a cross section of 50x100 mm. For a steep slope of 45º, stronger ones with a section of 50x150 mm are needed.

Gable rafter system

If you do not calculate the pitch of the frame of a pitched or other type of roof correctly, the roof may move away, and the beams will sag and bend due to the weight of the structure. In this case simple repairs If you can't do it, you'll have to redo the entire structure. Therefore, it is so important to correctly calculate the distance between the legs of the rafters, depending on the roofing material used: corrugated sheeting, ceramic or metal tiles, ondulin or slate, etc.

There is no point in arguing about the importance of a roof for any building. It is not for nothing that over the entire history of mankind, more than a dozen different types of roofs have been invented, from simple to quite complex in design and construction. An important element When planning the construction of a roof, there is a step between the rafters - strong bars that are the basis of the structure. This will be discussed in this article.

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

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

Before starting the process of erecting the upper structure of the house, you should perform a calculation, determining the optimal distance between the rafters.

Gable roof rafter spacing

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

If the roof slope is insufficient gable roof in snowy areas there is a danger of large snow masses accumulating, which can lead to structural failure. An increase in the angle of the slopes in regions with a predominance of strong winds is also fraught with high loads and the danger of breaking not only the roof, but the entire structure as a whole.

Mansard roof rafter system

Most private houses have a usable under-roof space called an attic. This design is characterized by an increased height of the slope, which is caused by the need to create a living space of a comfortable height. As a rule, stingrays mansard roof broken lines with varying slope angles. For their installation, a double rafter system is used.

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

Rafters in a pitched roof

For outbuildings and some private houses, roofs with one slope are used. Due to the limitation of the angle of inclination, they are exposed to high pressure. Experts recommend using lumber with a larger cross-section for the rafters of a pitched roof, setting a minimum spacing from each other.

When calculating the distances at which roof beams are installed, Special attention should be given to the magnitude of the snow load in a particular area. At a small slope this characteristic has great importance. It is better to choose roofing material for such roofs with a minimum dead weight, which will reduce the bending load.

Hip roof rafter system

The hip roof rafter system is considered the most complex in construction. This type is called hipped, since the roof is formed not only by side, but also by additional end slopes, where the rafters are installed not on the ridge, but on the corner strings. This places special demands on the organization of the roof frame.

Under hip roof An attic is not often installed. This is due to the small angle of inclination of the rafters and the roof as a whole. If the angle of the slopes to the horizon increases, the distance between the rafters increases; if it decreases, vice versa. An additional aspect The calculation is also made by the roofing material used.

Dependence of rafter pitch on roofing material

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

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

Corrugated sheet roofing

Currently, one of the most common roofing materials is profiled sheet, produced galvanized or with subsequent polymer coating. TO distinctive features profiled sheet will include the following parameters:

1. High corrosion resistance;
2. As a result, a long (more than 15 years) service life;
3. Easy installation even without the necessary qualifications;
4. Low leaf mass (weight of 1 m2 is 4-5 kg).

Since this roofing material does not place a high load on the rafter system, the distance between the elements is selected as much as possible for a particular angle of inclination. In addition, the profiled sheet does not require high strength characteristics from the roof sheathing. All this together allows us to minimize the overall load on the foundation and walls.

Metal roofing

The second common type of steel roofing materials is metal tiles. This type of profiled sheet successfully imitates natural clay material, but with less weight (10 or more). A special feature of rafters for metal tiles is their smaller cross-sectional size.

When choosing at what distance to install the rafters, you should first of all be guided by the dynamic load. Like corrugated sheets, metal tiles are not demanding on the size of the rafters and can be easily mounted on a sheathing made of one-inch softwood boards. All this makes metal roofing low-cost.

Rafter system for ondulin

In the 21st century, wavy ones are replacing sheet materials a more durable and lighter analog has arrived - ondulin. Among others, it is the lightest material. The weight of the sheet does not exceed 6 kg.

The small thickness of ondulin sheets with slope angles less than 15° requires the construction of a continuous sheathing made of plywood sheets, for example, which will require an appropriate pitch of the rafters. This should be taken into account when making calculations.

Slate roofing

Not so long ago, wide use had a corrugated asbestos-cement mixture material called slate. High mass and fragility are the main disadvantages, however, even today it finds its fans in the construction of various outbuildings.

The high mass, comparable to the weight of clay tiles, will not allow the use of the same rafter system as for metal tiles. Building codes determine the minimum slope angle of a slate roof to be 22 degrees or more. Otherwise, the load from the material itself and the rafter system with sheathing exceeds the permissible parameters. The pitch of the inclined beams, as well as their cross-section, are selected individually in each specific case.

Polycarbonate on the roof

IN last years Increasingly, artificial polymer material - polycarbonate - has begun to be used on the roofs of verandas and gazebos. Available in two versions - monolithic and cellular. The first is similar in properties to ordinary quartz glass, but significantly exceeds it in strength. The second has smaller mechanical properties, but with high thermal insulation and light transmittance.

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

Thematic material:

Rafters for soft roofing

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

Rafter spacing for insulation

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

Scheme for calculating rafter pitch

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

1. determine what distance should be between the rafters for your specific construction conditions. The reference book determines the magnitude of wind and snow loads in the area.
2. The length of the roof is divided by the desired distance, adding one. The result obtained will be equal to the number of rafter legs that are installed on one roof slope. If the value is not a whole number, it is rounded.
3. The length of the roof is divided by the number of rafters calculated above, we get the final pitch in meters.

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

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

As you can see, the calculation technology is not complicated, but it is only approximate diagram. Taking into account many of the other parameters mentioned above can make certain adjustments.

The task of correctly calculating the distance between the rafters is a very important one. How seriously you begin to solve this problem will determine not only the reliability and durability of the roof, but also all subsequent work on it: laying insulation, installing roofing, installing additional elements. If you manipulate the pitch of the rafters under the roofing sheets, as many do, then it is not a fact that insulation will then fit between the rafters.

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

What determines the pitch of the rafters?

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

1. Roof shape (gable, single-slope or multi-slope).
2. Roof angle.
3. Parameters of the timber used to make rafters (width, thickness).
4. The design of the rafter system (sloping, hanging or sliding).
5. The totality of all loads on the roof (weight of covering, 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 needs to be taken into account, which is exactly what this article is about.

Online calculators vs. notepad and pencil

To correctly calculate the cross-section of rafters and the step of their installation, today there are many complex formulas. But remember that such formulas were at one time developed more so that it would be possible not so much to perfectly calculate roof structures, but to study the operation of such elements.

For example, today simple online programs are popular that do a good job of calculating rafter parameters. But it’s ideal if you can set specific tasks yourself and calculate everything you need. It is important to understand down to the smallest detail what exactly happens in the rafter system during operation, what exact forces are exerted on it and what loads. A computer program cannot always take into account everything that he notices human brain. Therefore, we advise you to make all 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 in winter the roof of a residential building can withstand a large cap of snow, a constant wind at altitude, and it is often insulated from the inside, but completely different requirements are placed on the rafter system of a small gazebo hidden under the treetops.

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 a purely aesthetic factor:

The illustration above shows that even such a building has its own pitch of rafters. After all, here it provides both the aesthetic factor and the rigidity of the structure itself. But they choose a step arbitrarily.

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

Point 1. Wall length and choice of rafter spacing

The first step in installing rafters on the roof of a residential building is usually chosen structurally based on the size of the building, although taking into account many other factors.

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

Point 2. The 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 a regular roof is 1 meter. But, if the area has a significant snow or wind load, 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 increase to a distance of 1.2 m-1.4 m.

Why is this 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 seems to bend around the slope of the roof, but at the same time trying to lift it. And at this moment forces arise in the roof that are ready to tear it off or overturn it - these are two windward sides and one lifting one.

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

This map of the average wind load will help you understand whether to make a high roof or a flat one:

The second point: in the Russian region, the standard roof of a house is constantly exposed to such atmospheric phenomena as snow. Here too, you need to take into account that the snow bag usually accumulates more on one side of the roof than on the other.

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

If you are building a house for the first time, then you won’t have to decide on your own worldview, but rather determine the average snow load for your area according to official data:

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

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

Modern insulation materials are now 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. Quality and strength of the lumber used

It is also of great importance what kind of material you use to build the rafter system. Thus, for each type of wood there is its own regulatory documentation that concerns its load-bearing capacity:

Because For the manufacture of roof truss systems 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, you can derive a correction factor.

In addition, if the rafters have sections, notches or holes for bolts, in this place the load-bearing capacity of the beam must be calculated with a coefficient of 0.80.

Point 5. Distance between tie rods and floor beams

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

Point 6. Loads on rafters

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, the 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 capable of influencing the roof simultaneously at a certain moment, and therefore there is such a thing as critical value. This is exactly the load value at which the roof cannot withstand and becomes deformed.

Therefore, if a building is being built with significant spans, then steel roof trusses must be used. The fact is that there is no longer 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 trusses is calculated depending on the type of roof and the design of the roof itself.

Usually, a unified truss is installed 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.

Point 7. Weight of the rafter system and roofing pie

Do not forget that the main purpose of the rafters is to support the entire roof, and its weight is decisive:

Point 8. Ease of installation of roofing

The distance between the rafters is also influenced by factors such as the selected roofing covering. The higher the roof slope, 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 the continuous sheathing? 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 fastened directly into the rafters or sheathing, and it is important that they coincide. Otherwise, the work of covering the roof will easily turn into a living hell at altitude, believe me.

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

Determination of 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 rafter system: the weight of the rafter system, the snow cap, wind pressure. After you add all the loads together, be sure to multiply them by a factor of 1.1. So you will all count on unexpected favorable conditions, that is, provide an additional 10% percentage strength.

Now all you have to do is divide the total load by the planned number of rafters and see if each of them can cope with its task. If it seems that the structure will be frail, feel free to add 1-2 rafters to the total, and you will have peace of mind for your home.

You need to make calculations for destruction, i.e. for the full load acting on the roof. All these loads are determined according to the technical characteristics of the materials and SNiPs.

The standard roof structure consists of rafters and lattice purlins, and each of these elements responds only to the load that puts pressure on it, and not on the roof as a whole. Those. Each individual rafter is subject to its own load, total, but divided by the number of rafter legs, and by changing the step of their location, you change the area where the load is collected on the rafters - reducing it or increasing it. And, if changing the pitch of the rafters is inconvenient for you, then work with the parameters of the cross-section of the rafter legs, and the overall load-bearing capacity of the roof will increase significantly:

When making 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 slopes up to 30 degrees, the rafters have so-called “bending elements”. Those. they work specifically for bending, and there are certain requirements for them. And the possibility of rafter deflection is calculated using 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 a roof with a warehouse slope of more than 30 degrees, which rafters are already considered “bending-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 rafters. In simple terms, here the rafters not only bend a little under the weight of the roof, but are also compressed from the ridge to the mauerlat. In addition, the crossbar, which usually holds the two rafter legs, must also be checked for tension.

As you can see, even a person far from construction can handle 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 then all the work goes like clockwork!