The gable roof is the most popular design in private housing construction. truss system gable roof must provide a support platform for the installation of the roof. Properly calculated pitch of the rafters of a gable roof allows you to ensure the strength and stability of the structure to all external loads, create a durable and reliable roofing. This article discusses design features truss system, calculation and installation procedure. This information will allow you to correctly understand the methodology for creating a gable roof so that you do not ask unnecessary questions to workers during construction.
The distance between the rafters for a gable roof
Among people employed in the construction of a private or country house, there are constant discussions about the most successful roof design and the number supporting elements. In order to understand these opinions and take one side or another, it is necessary to consider general device roofs.
There are two types of rafter construction:
hanging.
Layered.
They are used on relatively small houses with a length of supporting elements of not more than 6 m. The structure consists of a number of truss trusses having the shape of an isosceles triangle. The trusses are installed on a strapping made of timber (Mauerlat), interconnected by batten strips. The bearing capacity of hanging rafters is relatively small, but the simplicity of design, economy and high speed of installation are their advantages. There are quite a few options for implementing hanging rafters, which is explained by the prevalence of small buildings that do not need a complex and massive roof structure.
Design layered truss system somewhat more difficult. Along the perimeter of the ceiling of the upper floor, a strong timber is laid - Mauerlat. Two (or more) vertical racks are installed along the longitudinal central axis, the height of which determines the angle of inclination of the slopes. A ridge run is installed between the posts, which runs along the entire length of the roof and serves as a reference line for rafter legs. Each of them has two points of support - at the bottom it is a Mauerlat, and at the top - a ridge run.
For education additional support, which excludes sagging of the supports, struts are used - inclined strips attached to the rafter legs at an angle close to a straight line and abutting in the lower part against the central lower bar - lying.
The step lag for the roof is the distance between two adjacent rafters. It is determined by the number of lags evenly distributed along the length of the longitudinal axis of the roof. The main supporting structures for the roof are rafters and lathing, forming inclined surfaces with a given geometry and area. The angle of inclination determines the wind and snow loads, and, with an increase in the angle, the wind load increases, and with a decrease, the snow load on the roof.
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What determines the pitch of the rafters
Consider the factors that determine the step between the rafters of a gable roof, in more detail. It must be immediately taken into account that the number of rafters determines the bearing capacity. Reducing their number complicates the installation of insulation, contributes to the sagging of the laths of the crate and the roof installed on them.
At the same time, too frequent placement of rafters also creates difficulties in the installation of insulation. It has to be adjusted in width, which creates waste, i.e. waste of material. Therefore, the size of the heat insulator is often used as a criterion for determining the pitch of the rafters. For example, many types mineral wool have a width of 60 cm, which is quite suitable for most designs of gable roofs.
In addition, the pitch of the rafters directly depends on their number. This is a calculated value, which is determined based on the bearing capacity of the supporting elements. The loads acting on the roofing, as well as the weight of the roofing itself, are quite large, so a stable and durable structure is needed to accept them. It should be borne in mind that the type of rafter system also matters, since layered rafters are much heavier than hanging rafters, they form a noticeable load on the walls and foundation of the house.
Wind and snow loads are external factors that affect the roof structure. Snow weight in winter period capable of pushing through or even breaking the roof if its design is not properly designed. The SNiP applications contain special data on the average annual amount of snow in different regions. In some of them, for each square meter accounts for up to half a ton of snow.
In addition to snow, wind creates serious loads. At the same time, if the snow load is static, then the wind effects are sudden and uneven. The wind can rise at any time of the year, both in winter and in summer, which makes us take it seriously. When choosing the angle of inclination, you should find out the strength and direction of the prevailing winds in the region, find out about the possibility of hurricane gusts. Available in SNiP applications.
All these factors determine the parameters of the truss system and the distance between the individual supports.
The dependence of the pitch of the rafters on the material of the roof
There are many types of roofing. Most of them are noticeably outdated and little used in modern construction. The most popular today are:
profiled sheet.
metal tile.
It should be noted that profiled sheet and corrugated board are one group of profiled coating. Some sources consider them to be different names for the same material, others separate them by wave height. The profiled sheet has a higher wave height, and the corrugated board is somewhat flatter. The first type can be used not only as a roof covering, but also as a material for the construction of fences, fences, metal garages, etc.
The corrugated board has a smaller wave and is intended for laying as a roof. Both materials have a common specific feature - profiling is performed only in the longitudinal direction, which expands their capabilities and allows you to make roofs for round roofs and canopies.
The step of the rafters of the gable roof under the corrugated board is selected taking into account this feature of the material. If the value is too high, it will be possible for the roof to sag between the rafters. In addition, there will be an excessive load on the battens, which may not be ready for it. An important parameter also becomes the area of the slope. Rafter step pitched roof under corrugated board is much less than that of a gable roof, since the length of the supporting elements and the magnitude of the load in it increase significantly and require an increased number of supports.
The metal tile looks like a canvas made of natural ceramic tiles. In all its operational qualities, it is very similar to corrugated board or profiled sheet, but in physical terms it has important feature- the presence of not only longitudinal, but also transverse waves. This allows you to slightly increase the step between the rafters of a gable roof under a metal tile, or be guided when choosing the size of a heat insulator.
When using slate or ondulin, the pitch of the rafters is taken according to the degree of rigidity of these materials. Alternatively, increase the density of the lathing, or install a solid version of thick plywood.
Method for calculating the distance between the rafters
There are two calculation options:
Engineering calculation using appropriate formulas and techniques.
Using online calculators, giving an answer after entering their own initial data.
The first method is only suitable for a professional roof system designer. For an unprepared person, it is extremely difficult to perform such calculations, since various specific data, coefficients, tabular values are needed, which are difficult to find and must be used correctly. Calculations obtained using online calculators are also not recommended for use in real construction, but as an option to refine or verify the results of calculations performed by specialized organizations.
Video description
In the video you can see what the step of the rafters should be:
Conclusion
In conclusion, it should be recalled that all design and calculation activities must be carried out by trained and specially trained specialists. The pitch of the rafters is an important and crucial value that determines the bearing capacity of the roof. The damage caused by the inability to take on existing loads is quite serious and can call into question the possibility of living in a house, so it is necessary to take this issue as seriously as possible.
The distance between the rafters is one of the key parameters that affect the strength of the structure. Competent calculation of the installation step of the rafters allows you to build a roof that is resistant to high operational loads.
Roof loads and rafter system calculation
The development of a single-pitched or dual-pitched roof project begins with the choice of the type of truss system, the angle of inclination of the slopes (roof height) and materials for the construction of the structure. The calculation of the distance between the rafter legs is carried out taking into account the loads that the roof will experience during operation. Permanent loads include:
- weight of materials from which it is made rafter system;
- roofing weight;
- weight of roofing cake materials (waterproofing, vapor barrier, insulation);
- the weight of the finishing elements of a residential attic or attic.
In addition to permanent loads, the roof also experiences temporary ones, which include:
A step is the distance between the rafters of one slope. When calculating a shed, gable or complex roof, the following scheme is usually followed:
- the length of the future roof slope is measured;
- the resulting value is divided by the optimal numerical value of the pitch of the rafters;
- one is added to the obtained value, the result is rounded off;
- the length of the roof slope is divided by the rounded result.
The final result will determine how far the rafter legs should be placed. The determination of the step cannot be extremely accurate, since it is necessary to take into account a number of additional factors, including the width of the insulation, the installation features of the crate under different kinds roofing material. If a roof with a chimney is being designed, the pitch can be adjusted according to its location so that it is not necessary to remove part of the rafter in the future and install a supporting structure, such as a special rafter system.
The distance between the rafters under the slate
Slate is a traditional roofing material. Its advantages include such characteristics as resistance to external influences (excluding mechanical ones) and low cost. Slate allows you to create a roofing, the repair of which can be reduced to replacement individual elements. Slate is heavy and requires the installation of a sufficiently powerful truss system. The calculation of the distance at which it is necessary to put the rafters under the slate is carried out taking into account the cross section of the beam for the manufacture of rafter legs.
The optimal solution is to install the system under the slate, in which the gap between the rafters must be at least 800 mm. In order for the slate structure to withstand not only the weight of the material, but also increased external loads, the crate is made of timber or boards with a cross section of at least 30 mm. When calculating the truss system for slate, it should be read that this material has rather large restrictions on the choice of the angle of inclination of the slopes.
Rafters for metal roofing
Metal tiles are actively used as a practical and aesthetic roofing material when arranging a shed, gable, hip or complex roof. The frame for the metal tile is built according to standard principles. To calculate at what distance it is better to place the rafters, it is necessary to take into account the loads and the angle of the roof. The metal tile is characterized by relatively low weight, so it can serve as a replacement for the old roofing of slate or ceramic tiles. In this case, the rafters do not need to be strengthened or the pitch of their installation changed.
The standard step of rafters for metal tiles is 600-900 mm. The cross section of the elements can be 50-150 mm - this is enough to create a reliable frame for a metal tile. But if it is planned to use insulation, the layer of which in areas with low winter temperatures should be 200 mm, it is recommended to use a 200x50 beam for rafters under metal tiles so as not to mount an additional system that holds the insulation. The gap between the rafters under the metal tile is best adjusted to the width of the sheet or roll heat insulator.
Decking: rafters and crate
The professional flooring belongs to easy and convenient roofing materials in application. Galvanized or coated with a decorative and protective layer, corrugated board can be used both for mounting a shed roof of a utility room or garage, and for a gable roof of a residential building. How to calculate the distance required to install the rafters under the corrugated board?
To ensure the necessary rigidity of the structure, it is enough to install the rafters under the corrugated board in increments of 600-900 mm. In this case, it is necessary to pay attention to the angle of the roof. The calculation shows that with high external loads, it is better to lay the corrugated board on the system with a minimum step. But if the distance between the rafters under the corrugated board is close to the maximum, and the angle of the roof slope is small, then the structure is strengthened by using a more frequent crate. In this case, the step of the crate under the corrugated board should be about 50 mm, the width of the elements should be at least 100 mm.
Rafter system for soft roofing
Soft roofing includes bituminous and bitumen-polymer roll materials, roofing membranes, as well as soft tiles. A soft roof is characterized by relatively low weight and no need to install a massive roof structure.
The minimum distance between the rafters is 600 mm, the maximum is 1500 mm. When installing a support under a soft roof, it is important to take into account the angle of inclination of the slopes: the smaller the angle, the smaller the distance between the supports for a continuous crate should be. The choice of step is also influenced by the thickness of the material for the crate - the thicker the sheet of plywood or OSB, the greater the installation step of the rafter legs can be.
Ondulin: calculation of rafters
Ondulin (bituminous slate) is laid on a flat continuous crate made of sheet material. This allows the roofing to successfully resist wind and snow loads. The crate under the ondulin rests on the rafters, which should be located in increments of 600 - 1000 mm, depending on the angle of inclination of the gable or shed roof.
Rafters for ondulin are made of timber with a section of 200 × 50 mm. When choosing at what distance to put the rafter legs for the structure under the ondulin, it is recommended to take into account the width of the insulation material in order to simplify its installation. This calculation allows you to reduce the financial costs of arranging the roof.
Sandwich panel roof
Sandwich roofing is most often erected on sip-panel houses or hangar-type buildings. A feature of the sandwich is its bending rigidity, which makes it possible to dispense with the installation of traditional rafters. Small spans from the ridge of a gable roof to the upper part of the wall (or the distance between the supporting structures of a shed roof) allow the installation of a sandwich without additional supports.
If the span exceeds 4 meters, additional girders must be installed. To install a sandwich roof on a residential building, a traditional truss system is often installed, but in this case the rafters can be positioned with a large step - they serve as a support for the girders. The distance between the rafter legs is selected based on the length of the available material for the runs and the length bearing walls. The technical parameters of the sandwich allow the roof to withstand high operating loads.
Polycarbonate: erection of the supporting structure
Polycarbonate in Lately actively used as a roofing material. First of all, polycarbonate is in demand in the construction of gazebos, sheds, winter gardens. The crate and truss system for polycarbonate can be made of wood or metal.
Polycarbonate varies in weight depending on the thickness of the sheet. The crate for polycarbonate is recommended to be done in increments of 600-800 mm. The crate (wooden or metal) is mounted on rafters, which can be straight or arched. Usually the gap between the rafters for polycarbonate is from 1500 to 2300 mm. In order to correctly calculate at what distance it is better to bleed the rafters, it is necessary to take into account the area of glazing, the dimensions 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 single-pitched roof
Find out what distance between the rafters you need to make for a gable and shed roof. The maximum distance between the rafters for metal tiles, ondulin and soft roofing.
The distance between the rafters: principles and examples of calculating the pitch of the truss system
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:
- The shape of the roof (gable, single-pitched or multi-pitched).
- Roof angle.
- The parameters of the timber that is used for the manufacture of rafters (width, thickness).
- The design of the truss system (layered, hanging or sliding).
- The totality of all loads on the roof (covering weight, atmospheric phenomena, etc.).
- 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.
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 to the rafter system small gazebo, hidden under the crowns of trees, have completely different requirements.
For example, if you are building a pergola in its classical sense, then it does not matter at all what exactly the distance between the rafters will be - this is already a purely aesthetic factor:
In the above illustration, it can be seen that even in such a building there is a step of rafters. After all, here it provides both an aesthetic factor and the rigidity of the structure itself. But the step is chosen arbitrarily.
Functional rafters: detailed calculation
We approach the main question: what distance should be between the roof rafters of a residential building? Here, be patient and carefully study all the nuances.
Item 1. Wall length and rafter spacing
First of all, the step of installing rafters on the roof of a residential building is usually chosen according to the structural size of the building, although taking into account many other factors.
For example, it is easiest to install rafters in increments of 1 meter, so for a wall 6 meters long, 7 rafters are installed as standard. At the same time, you can save money by placing them with a distance of 1 and 2 meters, and you get exactly 5 rafters. It can also be placed with a distance of 2 and 3 meters, but reinforced with a crate. But it is highly undesirable to make a step of rafters more than 2 meters.
Item 2. Influence of snow and wind loads on the shape of the roof
So, we settled on the fact that the average distance between the rafters of an ordinary roof is 1 meter. But, if there is a significant snow or wind load in the area, or the roof is more or less flat or simply heavy (for example, covered with clay tiles), then this distance must be reduced to 60-80 cm. But on a roof with a slope of more than 45 degrees, it can be even zoom to a distance of 1.2m-1.4m.
Why is it so important? Let's figure it out. The fact is that the air flow collides on its way with the wall under the roof of the building, and turbulence occurs there, after which the wind hits the eaves of the roof. It turns out that the wind flow, as it were, goes around the slope of the roof, but at the same time trying to raise it. And in the roof at this moment there are forces that are ready to rip or overturn it - these are two windward sides and one lifting.
There is another force that arises from wind pressure and acts perpendicular to the slope, trying to push the roof slope inwards. And the greater the angle of inclination of the roof slope, the more important are the safe wind forces and the less tangential. And the larger the angle of the slope, the less often you need to put rafters.
To understand whether you should make a high roof or a flat one, this map of the average wind load will help:
The second point: in the Russian region, such an atmospheric phenomenon as snow constantly affects the standard roof of a house. And here, too, you need to consider that the snow bag usually accumulates more on one side of the roof than on the other.
That is why in such places where such a bag is possible, it is necessary to insert paired rafter legs or make a continuous crate. The easiest way to determine such places is by the wind rose: single rafters are placed on the windward side, and paired rafters on the leeward side.
If you are building a house for the first time, then you will not find your own worldview, but determine the average snow load for your area according to official data:
Point 3. The issue of insulation and the standard width of mats
If you will insulate the roof, then it is advisable to put the step of the rafters under standard sizes insulation plates, and these 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:
- Static, which includes the weight of the rafter system itself, the weight of the roof, snow lying on the roof and additional elements.
- 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 can certain moment affect 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 technical specifications materials and SNiPam.
The standard roof structure is rafters, lattice runs, and each of these elements works only on the load that puts pressure on it, and not on the overall roof as a whole. Those. each individual rafter has its own load, total, but divided by the number of rafter legs, and by changing the step of their location, you change the load collection area on the rafters - reducing it or increasing it. And, if it is inconvenient for you to change the pitch of the rafters, then work with the parameters of the section of the rafter legs, and the total bearing capacity of the roof will increase significantly:
In this calculation, try to ensure that the longest rafter in your project is no more than six and a half meters, otherwise, splice along the length. Now let's explain in more detail. So, on roofs with a slope of up to 30 degrees, the rafters are the so-called "bendable elements". Those. they work specifically for bending, and there are certain requirements for them. And the possibility of deflection of the rafters is calculated according to a special formula, and if the result exceeds the norm, then the rafters are increased in height and a new calculation is made again.
But on the roof with a warehouse slope of more than 30 degrees, which rafters are already considered “bendable-compressed” elements. That is, they are affected not only by a uniformly distributed load, which causes the rafters to bend, but also by forces that are already acting along the axis of the rafter. In simple terms, here the rafters not only bend a little under the weight of the roof, but are also squeezed from the ridge to the Mauerlat. In addition, the crossbar, which usually holds back two rafter legs, must also be checked for tension.
As you can see, even a person who is far from construction can cope with such calculations. The main thing is to take everything into account, be attentive and ready to spend a little more time on design, so that later all the work goes like clockwork!
The distance between the rafters: what step should be between the rafters
Detailed instructions on how to correctly calculate the distance between roof rafters different designs, taking into account the amount of loads and the material used.
truss system, undoubtedly, is the most important structural element of any pitched roof. The consequence of its improper installation can be not only the deformation of the roof, requiring expensive repairs, but also the complete collapse of the roof on the head of an insolvent builder.
The following four main factors influence the stability of the truss system to various loads:
- fastening strength rafters to the ridge and Mauerlat;
- correct calculation of the supporting structure for rafters, depending on the length of the span;
- choice roofing material;
- step between the rafters.
The topic of this article is the choice of material and pitch between the rafters, taking into account the intended type of roof.
What are the calculations based on?
When making calculations, four main indicators are taken into account:
The most important is the calculation of the maximum roof load, consisting of:
- rafter weights,
- crate weight,
- weight of roofing material and insulation,
- snow load (reference information unique to each region),
- wind load (also reference information),
- person's weight (if repair or cleaning is necessary, 175 kg/sq.m).
To carry out accurate calculations, experts use special formulas from strength of materials, but when building a private one, you can use approximate recommendations.
Method for calculating the distance between the rafters
Accurate Distance Calculation between rafters is based on the results of a preliminary calculation of the maximum allowable step. To make this calculation, the total load, the roof structure and the material used on the rafter legs are taken into account.
Method for calculating the step of the roof frame:
- Measure the length of the roof from end to end.
- Received distance divided by the maximum step size.
- The resulting value is rounded up to a larger integer.. This is the number of inter-rafter spans.
- Divide the total length of the roof by the number of spans. This is the required rafter step size.
- Add one to the number of spans.This is the required number of rafters.
For some types of roofing material it is desirable to use fixed distances between the rafters, in which case an additional rafter with a non-standard pitch is installed on one of the ends of the roof.
Rafter leg step depending on the material
Can be increased as the strength of the material from which they are made increases. Most often, for each roofing material, the step of the rafters required for it and the permissible sections of the rafter legs, taking into account the load, are indicated.
These recommendations are regional character and are applicable to the central strip of Russia and more southern regions. Before developing a drawing, you should definitely check the level of wind pressure and snow cover in your region, and adjust the pitch and / or cross section of the rafters.
In those regions where the snow load significantly exceeds the wind load, the use of roofs with a slope is recommended. 35 – 45 degrees.
truss system in private houses, it is most often made of logs with a diameter 12 - 22 cm, beam/board thickness 40 – 100 mm and width 150 - 220 mm. When calculating, it is possible to allow the use instead of logs of a certain diameter of bars of the same width, thickness 100 mm.
Rafter structure for corrugated board
Roof structure for ceramic tiles
Ceramic tiles has significant differences from other types of roofing materials, which must be taken into account when designing a truss systems for it:
- 5 to 10 times the weight resulting in doubling the weight of the entire roof. This leads to the need to use the frequent step ( 0.6-0.8 meters) and increased by 25% cross-sectional area of the rafters.
- Fine-grained nature of the material. Increases the requirements for the accuracy of the installation of the transverse battens. The step of the sheathing beam, the permissible sections and installation angles are always indicated in the instructions for each specific tile model.
There are models of tiles designed for installation at an angle. 12 - 60 degrees, ordinary models are recommended to be mounted at an angle 20 - 45 degrees. For crates most often use timber 50x50 mm.
Roof structure for metal roofing
metal tile essentially a less rigid and lighter decorative option corrugated board, so the requirements for the rafter system, in particular for the recommended sections of the rafter legs, are largely the same.
A feature of the truss structure under the metal tile can be called a significant reduction in the pitch of the crate, which should be equal to the length of the longitudinal wave (30 cm for most species). This leads to the need to reduce the distance between the rafters. up to 0.6 - 1 m, to reduce the cost of lumber for the crate. The angle of the roof slope is selected from 22 to 45 degrees.
Rafter structure for ondulin
Ondulin- slate based on fiberglass and bitumen, produced by only one manufacturer and has unified technological installation standards:
- permissible mounting angle - 5 - 45 degrees;
- distance between rafters - 60 cm at a slope angle of up to 15 degrees, up to 90 cm - at an angle of more than 15 degrees;
- crate - solid plywood on a slope up to 10 degrees, board 30x100 mm step by step 45 cm on the slope 10 - 15 degrees, beam 40x50 mm step by step 60 cm on the slope above 15 degrees.
Given the low weight of the material, the cross section of the rafter legs is selected based on the same recommendations as for corrugated board.
Rafter construction under a covering from slate
Slate- traditional, rather rigid and heavy roofing material, fragile, but resistant to constant loads. Such properties change the recommendations for the optimal design of the truss system towards the use of more durable elements and increasing the step between them:
- Due to low tightness, it is undesirable to use slate roofs with a slope angle of less than 22 degrees. If it is necessary to install such a roof, you can use the recommendations for installing an ondulin as an instruction, adjusted for the universal batten pitch - 55 cm.
- Permissible angle for installing rafters under slate - up to 60 degrees.
- The installation step is selected from 0.8 to 1.5 m, depending on the section of the rafter leg, the load and the presence of the crate material.
- The material for the rafters is selected with a slightly larger section than for light roofs. For the most popular move 1.2 m a bar is taken with a section from 75x150 to 100x200 mm, depending on the length of the span between the supports.
- Material for the crate selected in accordance with the distance between the rafters - timber 50x50 mm up to 1.2 m, timber 60x60 mm - 1.2 m and more.
- Lathing step is selected in such a way that each sheet lies on three bars, and has an overlap on 15 cm with neighboring. Considering the standard sheet length 1.75 m, step is used 80 cm.
Rafters for single-pitched and double-pitched roofs
What is the distance of the rafters for a pitched roof? shed roof does not require a complex truss structure. The rafters are laid from wall to wall, most often without the use of a Mauerlat, directly on the crown.
No extra ribs stiffness sets the maximum slope angle - 30 degrees and allowable span length - less than 6 m(for wooden rafters). The optimal angle 15 - 20 degrees.
Such roofs usually not subject to wind loads, but require protection from precipitation. In regions where wind pressure is comparable to snow load, correct installation shed roof "downwind" can lead to self-cleaning of the roof.
gable roof
is a system of parallel triangles interconnected by a Mauerlat and a ridge. There are many elements for firmly fastening the sides of the triangle to each other and transferring loads from the rafter legs to the walls - racks, ties, jibs, support beams, and so on.
The step between the rafters of a gable roof is made taking into account the size of the heat insulator that is laid between them. Approximate step between rafter legs 1-1.2 meters
Rigid Triangle Strength increases as its shape approaches isosceles, therefore, with an increase in the slope angle up to 60 degrees you can expand the step between the rafters.
However, this will also lead to an increase in material consumption and to a multiple increase in the windage of the roof. The optimal slope angle for snowy regions is 45 degrees, for windy - 20 degrees.
Distance between rafters roofs attic type determines how much of the load falls on each element. When designing hip roofing step rafters should be between 60 cm and 1 m.
- The correct fastening of the rafters is no less important than the correct calculation of the structure. Front self-assembly the roof is worth taking a lesson from an experienced carpenter and reading educational literature.
- When choosing a rafter pitch, do not forget about thermal insulation. All types of insulation can shrink a little, so you can buy them by approximate size. The most commonly produced sizes are 60, 80, 100, 120 cm.
- For roofs with a slope of 45 degrees or more, the weight of a person on the roof can be ignored. This removes 175 kilograms of design load per square meter and allows you to put rafters on average 20% less often.
- Snow and wind load in Russian regions can be found by regulatory documents - maps in the application F To .
- There are many online roof calculators on the web., capable of, if not correctly calculating all the nuances, then at least advise on the selection of the correct section for the rafters.
A shed type of roof is rarely seen in private housing construction. Although, according to some, this is in vain, because the installation of a shed roof is much easier than the installation of a gable roof. On the other hand, such a roof design will not be able to keep the heat in the room so well. That is why shed roofing is most often used to build a garage, country house or barn.
True, if the work on thermal insulation is correctly performed, then the structure may well be warm. In this case, under a pitched roof, living room. Let's look at the advantages of a shed roof, what types of truss systems exist, how the design is calculated. In addition, we will consider how to install this type of roof.
Pros and cons of a shed roof for a house
Beginners in the construction business will be delighted that such a shed construction is quite simple and can be done by hand. True, it is impossible to call the work the easiest, but with detailed instruction a pitched roof will be created. But before considering the design features of the roof, you need to find out its features and advantages. They characterize this type of roof.
Advantages of a pitched roof:
- Profitability. For the device of the roof, a lot of building materials are not needed, on which the bulk of the funds are spent.
- The simplicity of the truss system and the shed structure as a whole. The best thing for beginners. Installation will be easier than with a gable roof.
- The building will have a small weight. This means that there is less load on the walls and foundation.
- Thanks to this shape, a shed roof perfectly resists wind loads, as well as the weight of snow that accumulates on the surface.
- The angle of inclination is very different, depending on the needs. It varies from 5° to 45°.
- If you make the angle of a shed roof small, then it can be used for various purposes. For example, if this is a barn, then install a tank for heating the liquid. If this is a living space, then on a shed roof you can equip a great place to relax. Alternatively, install solar panels as alternative source nutrition.
- The versatility of a one-slope building. It is covered with almost any material available on the market. It all depends on the operating conditions and the chosen angle of inclination.
Despite all its advantages, a shed roof has its drawbacks. This is not surprising, since nothing is perfect, but it is better to know about the cons and use them profitably.
Cons of a shed roof:
- The first concerns insulation. There is no more space with an air gap under the structure, so the issue of insulation should be taken more seriously. If you do not make thermal insulation of the structure, then in summer the attic will be too hot, and in winter, on the contrary, it will be supercooled. In either case, the temperature (high or low) will be transmitted to the house. Correct calculations and high-quality insulation will help eliminate this;
- when creating a ceiling immediately under the roof, made at a slight angle, the house will not have an upper air gap and an attic. And in this case, living space cannot be organized;
- due to a slight slope, which reaches from 5 to 10 °, snow and moisture will accumulate on a shed surface.
Despite all the obvious disadvantages, a shed roof is ideal option to create a garage and other buildings on the site.
Calculation of the construction of a single-pitched roof
This is the first stage before the installation of the truss system. It is recommended to draw up a detailed plan or drawing, which will be guided by when working. To create this schema, you need to highlight the following data:
- the total width of the roof construction, as well as the length of the spans that is formed between the bearing walls;
- slope angle, desired or obtained;
- the length of the single-pitched roof;
- selected roofing material;
- what is the height and width of the load-bearing walls.
Note! When a shed roof is created for a barn, garage, or country house, you can simply raise the front wall of the structure above the back.
As a result, the angle of the slope will depend on the height of the rise. The second option involves the creation of supports, on which the run will fit. The second way allows you to save building materials.
For drawings, you need to know the following nuances:
The drawing of the future shed roof should have all the necessary information about the elements. The dimensions, distances between them, fastening features, etc. are indicated. Below is an example of such a drawing of a pitched roof.
Choosing the corner of a shed roof
The angle of the slope is chosen taking into account the fact that the resulting roof forms a triangle, one corner of which will always be right. The legs are the floor beams and the gable part of the building, and the rafters serve as the hypotenuse. This is clearly seen in this diagram.
The designations are as follows:
- Lc - the length of the rafter used;
- Lbc - our leg, indicating the height of the pediment from the floor beam to the roof plane;
- Lsd - the width of the building;
- A - the selected or desired angle of a pitched roof.
Given the basic values, it is possible to calculate all the parameters of a single-slope structure. There is a formula for this. The first is used when the width of the building and the planned height of the pediment are taken as the basis. In this case, the formula is:
When you have decided on the angle of the shed roof, then you need to calculate the future height of the gable. For this, the formula is:
In this case, the length of the roof rafter legs is calculated as follows:
Note! This length of the rafters does not take into account the canopy from the rear or the facade of the room.
Many criteria influence the choice of slope angle. The main one is the choice of roofing material. Each of them is recommended to buy for a particular angle of inclination. Here are recommendations for popular roofing materials:
- For the installation of corrugated board, the slope must be at least 8 °.
- When using metal tiles, you will need to make a roof with an angle of inclination of 30 °.
- For a slate device, indicators from 20 ° to 30 ° are needed.
- As for rolled roofing materials (roofing material, shingles and soft roof), then the angle of inclination should be 5-7 °, not less.
Advice! A roof without a heating system in an area where there is a lot of snow in winter, ideal solution there will be a single-pitched roof with a slope of 40 °, despite the roofing material. So all precipitation will quickly descend from it.
Varieties of the truss system of a shed roof
There are three options for creating a truss system. The choice of design depends on the size of the room and its type.
Now that we have dealt with the design of the truss system and learned its types, we can consider the process of creating a shed roof.
Installation work on the creation of a pitched roof
Having on hand the drawings and the selected type of system, you can get to work. You will also need the appropriate tools and lumber. The installation of the truss system is performed as follows:
- For safety, the building should be covered with beams. They are placed on the wall. To extend their service life, roofing material is glued to the wall. It will protect the beams from moisture and decay. You need to position the floor sticks in the same way as the rafters. Fastening pitch -500-800 mm.
- Mauerlat is laid on top of the beams. This is a massive beam that will serve as a support. It fits on the back bottom wall of the building.
- To safely move around the roof, flooring is laid on the floor beams from wooden planks. He is temporary.
- Now you need to build a gable wall. It is made from the same material as the building itself. You can use lighter material. For example, if the walls are brick, then the pediment rises by means of bars or boards.
- Floor beams must be covered with waterproofing and walled into the wall. The pediment rises to the chosen height, according to the drawings.
- On the finished pediment, you can fix the Mauerlat. It turns out that two Mauerlat are parallel to each other.
- Markings are applied to the lower wall for attaching the rafter legs. The fastening elements themselves are fixed.
- To firmly fix the rafter, based on the drawings, grooves are cut on it. This a good option mounts. The grooves are in two places, top and bottom, to enter the Mauerlat. There are other methods of fixing the rafter leg, as shown in this photo.
- After that, the legs are fixed with special corners and fasteners. From above, at the pediment, the legs are screwed rigidly. But the lower part is made depending on the chosen truss system of a pitched roof. It can be rigidly fixed or made sliding.
- There is a certain sequence of inserting rafter legs. First, the extreme elements of the truss system are mounted. A cord is stretched between them, serving as a guide and level for subsequent rafters. Do not forget that the step of the rafters corresponds to the step of the floor beams.
- The rafters that are already installed are connected to the floor beams through racks, struts and other elements to give them stability. We talked about them above. Fixation is carried out with metal corners and staples.
Tip! If you want to lengthen the rafters and bring them out of the wall, then “fillies” are attached to the bars. So you can protect the adjacent part of the structure from precipitation.
- When the construction of a shed roof is ready, you can begin to insulate and create a roofing pie.
The photo shows what layers the correct insulated shed roof should consist of.
Insulating material is laid between the rafters. He has to hold on tight there. After that, a counter-lattice for ventilation is made on top. Fits on the counter-lattice waterproofing film. It protects the insulation from moisture, which can ruin it.
As for the crate for laying roofing material, it is selected depending on what kind of roofing material it will be. For example, a solid crate of boards or plywood is needed when installing soft tiles and other rolled materials. If metal tiles, corrugated board, slate, ondulin and other types of hard roofing are used, then the crate is done in a row. The step depends on the roofing material.
And in order to protect the insulation from the inside of a shed roof, you need to sheathe it vapor barrier film. Now we can say that the shed roof is completely ready.
Note! If a shed roof is made for a barn or other non-residential structure, then it is not necessary to insulate it. It is better to spend them for another purpose.
Conclusion
Creating a roof, whether it is a gable or single-pitched, is a dangerous, time-consuming and responsible process. That is why caution is required and strict adherence to the instructions for creating a structure. Only then can the best result be achieved.
The shed truss system came to us from the USA and Europe. Residents using it noted reliability and cheapness, so the popularity of this type spread very quickly. Despite the fact that a small amount of wood was required for the construction of one slope, few people dared to build such a construction. The fact is that most developers considered such a system too simple for residential buildings, while the other part simply did not know how to build it to prove the opposite. In this article I will try to explain to you how to easily and quickly create such systems and correctly select the pitch of the rafters of a pitched roof.
Basis of calculation
Despite its simplicity, one slope must meet all the installation rules. After all, if serious mistakes are made at the same time, then the roofing will deform, which will inevitably entail not only leaks, but also the collapse of the entire roof.
To achieve maximum stability of the roofing system, it is necessary to pay attention to four components:
- Reliability of fastening of the rafter legs to the support beam and ridge;
- Proper selection of auxiliary parts for the truss system;
- Durable lumber and auxiliary elements;
- Rafter step.
Do not think that by observing only four points you will achieve the most stable design. To do this, you will have to use all known methods and technologies.
Calculation values
You can’t perform calculations without knowing certain indicators, right? Therefore, before starting, you need to make sure that you have four basic values.
In addition to all these indicators, the main task of any project is to calculate the maximum allowable load on the roof. It includes quite a lot of values, and here is a list of elements whose mass is especially important in the calculation:
- rafter legs
- crate
- roofing cake
If you are far from the construction industry, then you will have to remember that the calculation of the maximum roof load consists of two parts. The first one takes into account all the materials used, and the second one contains the snow load of your region. Its meaning is written in a special reference book, which you can easily find on the net.
But even on this, the indicators will not be accurate, because you forgot about the wind load and the weight of the worker himself, who will conduct installation work and subsequent maintenance (repair, cleaning).
When developing a project by a construction organization, they use complex formulas of strength of materials, so if you don’t want to bother with this, you can use the recommendations of experienced people.
How to calculate the required distance between the rafters
The distance between the rafters of a shed roof largely depends on the previously calculated maximum possible step. To determine this value, you will need to have a total load value, roof parameters and data on the wood of the rafter legs.
You can calculate the optimal step of the rafter leg using the following method:
- First of all, you need to find the total length of the roof. This value must include any ends and overhangs;
- The resulting value is divided by the maximum allowable distance between the rafters;
- The answer is rounded up. This number will indicate the number of spans;
- Next, we take the value of the length of the roof and divide it into spans. So you will find the optimal step;
- And to find the number of rafter legs, you need to add one to the spans.
This rule works for the vast majority of roofs, but there are those that cannot be calculated in this way. If you have just such a case, then you will have to acquire an additional rafter on one of the ends. 
Rafter system depending on the roofing
It's no secret that the greater the mass of the roofing, the greater the number of rafter legs must be installed. Most manufacturers of this material in the instructions for their product indicate the optimal number of rafters and their dimensions.
You should not blindly trust these instructions, only if you do not live in the central strip of Russia, because they were written specifically for this territory. Before developing a drawing, it is necessary to carefully study the prevailing winds and draw a kind of rose, which will be a guide for future construction.
It is worth noting that in regions of the country where a large amount of precipitation in the form of snow falls, it is best to create steep roofs with a slope of 35-45 degrees. This will provide fast natural gathering snow cover from the surface.
In most cases, the truss system of private houses is created from logs with a diameter of 12 to 22 centimeters, timber or boards with thicknesses from 40 to 100 and widths from 150 to 220 millimeters.
Rafter system for corrugated board
Roofing corrugated board is a fairly light material and at the same time has good strength characteristics. Therefore, as rafter legs, you can use lumber of a small section, but with a frequent step: 0.6 - 1.2 meters. The roof slope should be at a slope of 12 to 45 degrees.
The required section can be selected based on the span distance between the supports. If the distance is about 3 meters, then the section can be taken 40x150 millimeters, at 4 meters this value increases to 50x180 millimeters, and at 6 meters it is necessary to use lumber whose section is 60x200 millimeters.
By the way, the crate in this matter also plays an important role. In the case when the rafter step is a decent value, you will have to use wider boards. For example, for a step of 0.6 meters, elements with a section of 25x100 millimeters will be needed, and for 1.2 meters - 40x100.
The crate for corrugated board is arranged discharged method, and the step of its elements should be 50-80 centimeters. However, these values \u200b\u200bmay go beyond due to the characteristics of the roofing itself. You can also find tips on how to arrange these parts in the instructions that came with the purchased material.
Rafter system for ceramic tiles
Ceramic tiles are a unique roofing material. It is made of clay, which makes this material very heavy. Designed truss systems in without fail must follow the following requirements:
In the roofing sphere, there are only 3 types of crates. One of them can be arranged at an angle of 12-60 degrees, and the other two at an angle of 20-45 degrees. As elements of the crate for clay tiles, you can most often see a beam with a section of 50x50 millimeters.
Rafters for metal tiles
Due to the fact that metal sheets have a much smaller thickness, you do not have to arrange a serious truss system. Therefore, you can safely follow the advice and recommendations of roofing material manufacturers.
It is worth saying a few words about the only nuance that will allow you to save some lumber. So, it lies in the fact that the minimum step of the crate can be increased to 1 meter. This is due to the dimensions of the sheet material. When a metal tile is tripled, then, as a rule, it is supported by a crate in only a few places, and with a rafter pitch of 0.6 meters, it is impossible to create an “economical” crate, so you have to change it along with the rafter system. 
Rafter structure for ondulin
Today, ondulin has given way to more modern coatings, but despite this, developers whose roofs were laid with asbestos slate began to look at this material as a profitable alternative. It is made on the basis of bitumen and fiberglass, has a low weight and high quality.
The truss system for ondulin must comply with the following parameters:
- The slope of the slope should be in the range from 5 to 45 degrees;
- With a small slope, the step of the rafter legs should be minimal: 0.6 meters, and with a steeper roof, this distance increases to 0.9 meters;
- With a sloping roof, say up to 10 degrees, it is necessary to arrange a continuous crate. To do this, it is best to use moisture-resistant plywood, OSB boards or edged board with a section of 30x100 or timber 40x50 millimeters.
As for the section of the rafter legs themselves, it is selected according to the same rules as for corrugated board.
Rafter system for corrugated asbestos-cement sheets (slate)
Surprisingly, everyone knows the roofing material called "slate", because the vast majority of private houses are covered with this particular product. Due to its rigidity and components, this material has a fairly solid weight, so it is necessary to follow the recommendations for the construction of the truss system so that it does not collapse even before the start of operation.
- The low tightness of the finished plane does not allow the use of slate with a slope of less than 22 degrees, this will lead to leaks. If you cannot find any recommendations for the installation of asbestos-cement sheets (which is unlikely), then you can always use the instructions that came with ondulin;
- The maximum possible slope of the rafters at slate roof- less than 60 degrees;
- The optimal step of the rafter legs lies in the range from 0.8 to 1.5 meters. Here everything will depend on the load and cross-section of lumber;
- As a rule, a wooden system for slate requires a slightly larger section of the legs than with a light roof. An example is the situation when the pitch of the rafters is 1.2 meters. For the rafters, you will have to take a bar with a section of 75x150 or 100x200;
- As for the crate, its elements will also differ from the step of the rafter legs. If it is up to 1.2 meters, then a bar of 50x50 millimeters will do, and with a larger step - 60x60 millimeters;
- The step of the crate beam should be selected so that one sheet is supported by 3 elements. The slate should extend beyond the edges by 15 centimeters on both sides. For example, if we consider the standard dimensions of an asbestos-cement sheet (175 centimeters), then we can use a crate step of 80 centimeters.
It is probably worth remembering that asbestos is harmful substance
, therefore, when working with a material that contains its particles, safety precautions must be observed. Which states that the worker must wear personal protective equipment. 
Rafter system of one and two slopes
Recently, the shed roof is gaining more and more sympathy. It is understandable, because materials are only getting more expensive, and you want to save money. Due to the simple design, this can be done. The rafter system of one slope is quite primitive. To do this, you just need to put the beams on the crown and secure. Of course, do not forget about the insulating material.
The maximum slope of a shed roof can be 30 degrees, and the span is 6 meters (this rule applies to lumber). by the most optimal slope 15-20 degrees is considered. At this angle, the wind load will not cause much harm, but the snow cover will cause some inconvenience. The solution to this problem can be to place your building "downwind", which will allow it to remove snow mass from the roof naturally.
An alternative option for a single-pitched roof is a double-pitched one. It is a number of rectangles connected together with a Mauerlat and a ridge. It is worth noting one interesting fact. When the shape of a triangle approaches an isosceles one, its rigidity increases. In this regard, with a roof slope of up to 60 degrees, it is possible to expand the step between the rafter legs.
But do not flirt with calculations, because this can lead to an increase in windage and lumber consumption. The most optimal ramp slope for gable system- 45 degrees.
If you decide to build a roof yourself, then you will certainly need some tips that will not only make your work easier, but also increase the operational period of your roof as a whole.
- Calculating the structure correctly is not an easy task, but even if it is done correctly, it can be broken if it is incorrectly fastened. Therefore, mounting the rafter legs in their places, do the work with all responsibility. To improve your skills, you can read information on the network, or invite a knowledgeable person to the facility;
- The step of the rafter legs should not affect the thermal insulation in any way. It is worth remembering that the plates can vary slightly in size. Take advantage of this and push them as tightly as possible. In a hardware store, there are standard sizes of insulation boards of 60, 80, 100 and 120 centimeters;
- For most roofs with a slope of less than 45 degrees, it is necessary to include the weight of the worker in the calculation. As for sharper roofs, this is not necessary, therefore, it is possible to reduce the pitch of the rafter legs by 20%;
- Take advantage modern technologies and calculate your roof with online calculators. All you need is to enter the exact parameters;
- Regulatory documents regarding wind and snow load you can find on the net or from the craftsmen at the construction site;
- Any wood used for construction purposes should be dried as much as possible. This will avoid its deformation in the future.
The roof of a building is one of the most important elements of the entire building. If you start saving on a roofing pie, then soon you will face costly repairs that will affect not only this site, but the entire building as a whole. Therefore, if you want to get the maximum operating period from your comfort, then you should not use low-quality materials.
