Calculation of rafter pitch for various roofing materials. Interrafter distance: calculation technology What distance should be between the roof lags
The reliability of the roof and its service life mainly depend on how correctly the calculations are made.
One of the most important parameters of the rafter system is how far apart the rafters are located.
After all, the distribution of the load on the frame depends precisely on this desired parameter.
If the calculation is made incorrectly, then deformation may occur and the roof will collapse.
Therefore, it is extremely important to perform an accurate calculation of the interval between when drawing up a roof project.
Basic provisions of the calculation
The pitch of the rafters is the distance from one rafter leg to the other.
In the construction of roofs of private houses, this value is 1 meter.
But this figure is approximate.
To get the exact size of the interval, it is necessary to calculate the bearing capacity of the truss system of the selected type.
For execution correct calculation the following scheme should be used:
- first you need to determine the length of the roof slope;
- now the resulting figure should be divided by the value of the approximately selected rafter step. If you previously chose its value of 1 meter, then you need to divide by 1.
If 0.8 was chosen, then it should be divided by 0.8, etc.;
- after that, one is added to the result obtained and the resulting value is rounded up. This action is necessary in order to get the exact number of rafters that will need to be installed on one slope;
- the total length of the slope must be divided by the number of rafter legs obtained in the previous calculation. And we get the exact distance between them.
To better understand everything, let's look at an example.
By measuring the length of the roof slope, we got 27.5 meters.
We choose a step of 1 meter to make it more convenient to count.
Further calculations will look like this:
Now we add the unit 27.5 m + 1 = 28.5 m.
We round up to the nearest value and get the number 29.
That is, 29 rafter legs must be installed on one slope of our roof.
Now we divide the length of the roof by their number: 27.5 / 29 \u003d 0.95 m.
So, in our case, the step of the rafter legs should be 0.95 meters.
This is a general calculation.
In which the peculiarity of a particular roofing material is not taken into account.
And he can significantly change this parameter.
When you know what kind of material you will use on the roof, some changes will have to be made to the calculation procedure.
Optimal and minimum value
The step is the unit of account.
After all, it depends, first of all, on the load on the roof frame and the section of the rafter legs.
You can take a thick board for their construction and make the interval between them 120 cm.
At this distance, the crate may begin to sag.
Yes, and how to lay the heater?
Indeed, for most materials, the width is 1 meter.
So they take an approximate step of 1 meter when calculating.
The minimum distance between is 70 cm.
And to obtain the optimal value for each material, it is necessary to perform a calculation.
Determining the pitch for a pitched roof
Shed roofing is the simplest.
Indeed, in the truss farm of such a roof there are only rafter legs.
There are no struts, racks, braces in its design.
Such a roof is usually arranged on garages, outbuildings, baths.
In order to determine the pitch of the rafters on a pitched roof, you can use the table:
As can be seen from the table, rafter step depends on their length and cross section.
Distance between rafters for a gable roof
A gable roof is much more common than a shed roof.
And to explain such popularity is simple: the design is very simple, but for all its simplicity, the gable roof is distinguished by its reliability.
Its design is easy to adjust to any climatic conditions and any roofing material.
When calculating the pitch of the rafters of a gable roof, everything is performed according to the general calculation system (see above).
If the slopes have the same length, then it is enough to perform calculations for one slope.
If the slopes are of different lengths, then the calculation is performed for each slope.
It should be remembered that the limit values \u200b\u200bof 70 and 120 cm.
What is the step depending on the material of the roof
Ondulin
If ondulin is used as a roofing material, then rafter system It is constructed from pine boards with a section of 50 x 200 mm, and the rafters should be located at a distance of at least 60 cm and not more than 90 cm from each other.
A crate of timber with a section of 40 x 50 mm is laid on top.
metal tile
Metal roofing during construction country houses used most often.
Because this material is much lighter than ceramic or cement tiles.
Although according to appearance very similar to her.
A small one makes it possible to use boards of a smaller section when creating a truss system, and use thinner bars for the crate.
Reducing the size of the elements of the rafter leg system, in turn, reduces the load on the walls of the building and its foundation.
During the construction of the rafter system under the metal tile, the rafters are mounted in increments of 60 - 95 cm.
The cross section of the material is 50 x 150 mm.
According to experts, if a heater having a thickness of 150 mm is placed between the rafters, then the most comfortable living conditions will be created in the attic.
To ensure ventilation of the space where the insulation is laid, when installing the rafter system, holes will be drilled near the upper roof with a diameter of 12 mm.
The technology for manufacturing a truss system for metal tiles does not differ significantly from the technology for manufacturing a frame for other roofing materials.
Its only difference is the installation at the top.
The upper support is mounted not on the side of the ridge beam, but on the ridge run.
The presence of a free zone between the rafters allows the air to fully circulate under the flooring, which helps to protect against the formation of condensate.
Ceramic tiles
The design of the system for ceramic tiles has its own characteristics.
After all, clay is used to make such a roofing material.
And this is very heavy material.
If we compare metal and ceramic tiles, the latter weighs 10 times more.
Accordingly, the truss system is significantly different.
For 1 square meter the roof surface has a load of 40 - 60 kg, depending on the manufacturer and brand of the product.
The rafters for such a frame system are made from wood that has been dried for a long time.
Such wood should have a moisture content of no more than 15%.
A beam with a section of 50 x 150 or 60 x 180 mm is used.
So more reliable.
And the distance between can be 80 - 130 cm.
The exact value can be called if the angle of inclination of the slopes is known.
If the angle of inclination is 15 degrees, then the pitch of the rafters will be 80 cm.
And if the angle of inclination, for example, is 75 degrees, then the step can be larger - 130 cm.
More than 130 cm interval between the rafters do not.
Also, when calculating the pitch of the rafters, their length is taken into account.
The larger the dyne, the smaller the distance between them.
The shorter the rafter legs, the greater the distance can be.
If the angle of inclination is 45 degrees, then the roofer can safely move along the roof if the pitch of the rafters is 80 cm.
Decking
When creating a truss system for corrugated board minimum distance between is 60 cm.
The maximum value is 90 cm.
If for some reason the pitch of the rafters was more than 90 cm, then it becomes necessary to install cross boards large section.
The rafter legs themselves can have a section of 50 x 100 or 50 x 150 mm.
Slate
Despite the appearance a large number new roofing materials, asbestos-cement slate remains one of the most popular.
If it is planned to lay slate on the roof, then the rafters should have a section of 50 x 100 or 50 x 150 mm.
The distance between them is made not less than 60 and not more than 80 cm.
The crate is made from a bar having a section of 50 x 50 mm or a board with a section of 25 x 100 mm.
When constructing any building structure, it should be remembered that there are still unforeseen situations.
And, therefore, at and distances between them, it is necessary to provide a margin of safety.
Video about the installation of the truss system.
It is pointless to argue about the importance of the roof for any building. It is not for nothing that over a dozen different types of roofs have been invented in the history of mankind, 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 dimensions.
Before starting the construction process top design at home, you should perform a calculation by determining the optimal distance between the rafters.
Gable roof rafter pitch
The most widespread in our country are gable roofs. They are a structure that has two parallel planes, with an angle of inclination relative to the horizon from 20 to 50 degrees.
With an insufficient slope of the gable roof in snowy areas, there is a danger of accumulation of large snow masses, which can lead to the destruction of the structure. An increase in the slope angle in regions with a predominance of strong winds is also fraught with a high load and the risk of breaking not only the roof, but the entire structure as a whole.
Mansard roof truss system
Most private houses have an exploited 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. Typically, stingrays mansard roof broken lines with a varying angle of inclination. For their installation, a double truss system is used.
The steepness of the lower slopes of the mansard roof significantly exceeds the slope of their upper extensions. The plane load perceived by them is not great. Thanks to this, the rafters in the lower part can be installed with a maximum pitch. The upper ridge slopes are recommended to be mounted with a reduced gap from each other.
Rafters in a shed roof
For outbuildings and some private houses, roofs with one slope are used. Due to the limitation of the angle of inclination, they are high pressure. Experts recommend for rafters shed roof use lumber of increased cross-section, with a minimum step setting 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. With a small slope, this characteristic has great importance. Roofing material for such roofs is best chosen with a minimum dead weight, which will reduce the bending load.
Hip roof truss system
The hip roof truss system is considered the most difficult in construction. This type is called four-pitched, since the roof is formed not only by side, but also by additional end slopes, where the installation of rafters is carried out not on the ridge, but on the corner bowstrings. This places special demands on the organization of the roof frame.
Under hip roof the attic is not often arranged. This is due to the small angle of inclination of the rafters and the roof as a whole. In the case of an increase in the angle of the slopes to the horizon, the distance between the rafters is increased, with a decrease, vice versa. An additional aspect of the calculation is the roofing material used.
The dependence of the pitch of the rafters on the roofing material
In addition to variable snow and wind loads, a constant (static) one also acts on the roof, the force of which depends on the roofing material used. It's no secret that different kinds roofs have their own weight, which can differ by 10 or more times.
The right choice of material affects not only the top, but also all other parts of the structure of a residential building and other buildings. Not without reason, when designing the foundation, it is necessary to decide in advance on the choice of the roof.
Roofing from profiled sheet
Currently, one of the most common roofing materials is a profiled sheet, which is produced galvanized or with subsequent polymer coated. To distinctive features profiled sheet will include the following parameters:
- High corrosion resistance;
- As a result, a long (more than 15 years) service life;
- Easy installation even without the necessary qualification;
- Small sheet weight (weight 1 m 2 is 4-5 kg).
Since this roofing material does not exert a high load on the truss system, the distance between the elements is chosen as much as possible for a particular angle of inclination. In addition, the profiled sheet does not require high strength characteristics from the roof lathing. All this together allows minimizing the total load on the foundation and walls.
Roofing from a metal tile
The second common type of steel roofing materials is metal tiles. This type of profiled sheet, which successfully imitates natural clay material, but with a lower mass (10 or more). A feature of the rafters under the metal tile is the smaller section size.
When choosing at what distance to install the rafters, first of all, you should be guided by the dynamic load. Like a profiled sheet, a metal tile is not demanding on the size of the rafter legs and is well mounted on a crate made of an inch coniferous board. All this makes a metal roof low-cost.
Rafter system for ondulin
In the 21st century, corrugated sheet materials were replaced by a more durable and lightweight analogue - ondulin. Among others - the most lightweight material. The weight of the sheet does not exceed 6 kg.
The small thickness of ondulin sheets at slope angles of less than 15 ° requires the construction of a continuous crate of plywood sheets, for example, which will require an appropriate rafter pitch. This should be taken into account in the calculations.
slate roof
Not so long ago, a wavy material from an asbestos-cement mixture, called slate, was widespread. High mass and fragility are the main disadvantages, however, even today he finds his fans in the construction of various outbuildings.
A high mass, comparable to the weight of a clay tile, will not allow the use of the same truss system as under a metal tile. Building codes defined minimum angle slate roof slope of 22 degrees or more. Otherwise, the load from the material itself and the truss system with the crate exceeds the permissible parameters. The step of the inclined bars, as well as their cross section, are selected individually in each case.
Polycarbonate roof
AT last years Increasingly, on the roofs of verandas and gazebos, artificial polymer material- polycarbonate. Produced in two versions - monolithic and honeycomb. The first in its properties is similar to ordinary quartz glass, but significantly exceeds it in strength. The second one has less mechanical properties, but high thermal insulation and light transmission.
Cellular polycarbonate is standardly much lighter than a monolithic counterpart. It is used as a roof without the use of lathing, provided that the step does not exceed ½ of the width of the sheet of material. The high strength of the monolithic analogue also makes it possible 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 under a soft roof
The original pattern can be obtained through the use of soft roofing materials, which are spread with an adhesive layer. They are installed on a continuous crate made of plywood or OSB. The step of the rafters should allow you to fix the sheets, so it is chosen as a multiple of ½ of the width. On condition standard sizes plywood 1520x1520 mm, the center distance between the rafters will be: 1520: 3 = 506 mm.
Rafter step 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 plates with dimensions of 600x1000mm. These parameters are used as starting points.
Rafter pitch calculation scheme
By building codes the pitch of the roof rafters is in the range of 0.6 - 1 meter. Its final calculation is performed according to a simple formula, depending on the total length of the roof. For the calculation, you must perform the following list of actions:
- determine how much distance should be between the rafters for your specific building conditions. According to the reference book, the magnitude of wind and snow loads in the area is determined.
- the length of the roof is divided by the desired distance by adding one. The result will be equal to the number of rafter legs that are installed on one roof slope. If the value is not an integer, it is rounded off.
- the length of the roof is divided by the number of rafters calculated above, we get the final step in meters.
For example, with a slope of 30 degrees, the maximum distance between the rafters of a gable roof under a metal tile is 0.6 measure. The length is assumed to be 16 meters. Consequently:
- 16:0,6+1=27,66;
- rounding the result, we get 28 rafters per slope;
- 16:28 \u003d 0.57 meters - the center gap of the rafter legs for these specific conditions.
As you can see, the calculation technology is not complicated, but this is just an approximate scheme. Taking into account many other parameters mentioned above can make certain adjustments.
The service life and final reliability of the roof are in the correct preparatory work, to which the correctly chosen distance between the rafters can be attributed. It is from this element of the supporting frame that the distribution of the load on the supporting frame directly depends, an error in the calculations of which can lead to deformation and collapse of the entire roof. So, the calculation of the total distance between the truss elements is one of the most important tasks in planning and calculating the load-bearing house.
Basic calculation technology
Rafter pitch is the exact distance between two legs of one truss truss. Most often, in private construction, the distance between the legs is about one meter, but the exact figures should come from a detailed calculation of the bearing capacity of the selected type of roofing system. In order to independently perform such a calculation, you must adhere to the following scheme of actions:
- Having measured the eaves of the roof structure, it is necessary to determine the total length of the roof slope.
- The resulting value must be divided by the selected and the most optimal step rafters. In other words, if exactly one m is chosen in the rafters, then the length of the slope must be divided by this unit of measurement.
- One is added to the result, after which you can round the finished value. It is this method that allows you to determine the number of roof trusses on one roof slope.
- Now it’s worth dividing the length of the roof slope by the resulting number of trusses, which will allow you to determine the pitch of the rafters.
It is worth recalling that this way miscalculation of such a building element as the pitch of the rafters cannot be considered extremely accurate, because in such calculations it is necessary to take into account the features of the selected roofing material, which can be a problem in the absence of proper experience in this matter. It is for this reason that methods will be described below that will allow you to choose the right rafter pitch for popular roofing materials.
Ceramic tiles and rafter installation
The main feature of the manufacture and installation of the truss carrier system under the tiles ceramic type consists in the extremely large weight of the roofing material, which in its totality is tens of times greater than the weight of any roofing material.
As a rule, this type and size of roofing material provides for up to 60 kg per square m of the truss bearing system. All this becomes the reason for the use of only dry lumber on the roof, which eliminates the possibility of further deformation during drying and pressure.
When using a wooden beam on the roof, the cross section of which is 150x50 mm, the step between can vary from 70 to 120 cm.
In addition, the distance between rafter legs may also depend on the overall slope of the roof.
Do not forget about the length of the rafter-type legs themselves. The longer this length is, the smaller the distance should be between the legs of the rafters, otherwise the supporting frame of the roof will be deprived of maximum strength and stability.
Experts recommend using no more than 80 centimeters of pitch between trusses if the roof slope is up to 45 degrees. Special attention should be paid to the lathing system when using ceramic roofing material on the roof.
To determine such a step, it is necessary to take into account the characteristics of each individual element of the roofing material, namely each tile. In order to perform the correct calculation of the crate step for such material, it is necessary to subtract the length of the bottom row and the distance between the last bar and the row of battens.
As a rule, all varieties of such roofing material have a length of no more than 40 cm. When laying the tiles, they are overlapped, which takes up to 9 cm from the bottom row. In other words, the correct step in this calculation is from 31 to 35 cm.
Metal tiles and laying methods
As a rule, the use of metal tiles in private construction is considered the most common, for which there are a number of reasons and positive characteristics of this roofing material on the roof.
If we compare such a roofing type material with the one described above, then several striking differences can be noted, each of which can be safely considered a positive feature of the material. First, it is worth recalling the simplicity and speed of installation of such material, which is made in a sheet type, allowing you to cover a significant area of \u200b\u200bthe roof at a time.
The second feature of metal roof tiles can be considered the extremely low weight of the material, which has a positive effect on installation, work on the roof and the load on the supporting frame of the roofing system.
This feature can be considered the most important, because it is responsible for the lower costs of labor and time in organizing the truss carrier system. When using this roofing material, the pitch of the rafter bearing legs is from 60 to 95 cm, because the reduced weight and size of the roof does not require high load resistance parameters.
With such indicators, it is worth using thermal insulation material, whose thickness is not less than 15 cm, which fits between the rafters. When organizing, the thickness of the insulating material should or may be greater, because this is necessary for arranging a residential floor in the attic. This also affects such an element as the thickness of the material that is used to make the rafter load-bearing legs.
All this indicates the absence of significant differences in the truss system under metal tiles on the roof. This roofing material provides standard knowledge about the construction of truss and roofing systems, which is simply necessary to install. The main difference of such a system may be the fastening of the upper type support to the ridge run, and not through the ridge type beam itself.
The free space at the top of the system, obtained through the installation of rafter legs, is ideal for ventilation of the entire under-roof space, which is often covered with condensate in metal roofing material.
In the event that changes are made to the roof of the old wooden house, it is necessary to completely remove the Mauerlat, replacing it with a common crown of the upper type. In such a crown, it is necessary to put marks and make selections with the desired step, into which the elements of the rafter bearing legs will be installed. This allows you to more accurately calculate the pitch of the rafter bearing legs and install them.
Decking and determining the distance between the racks
When using a roofing material such as corrugated board, the calculation the right step rafter load-bearing legs is 60-90 cm, which practically coincides with all the types of structures and roofing materials described.
If necessary, put more distance between the elements of the rafter legs, it is necessary to insure the transverse elements of the crate with a greater thickness and cross section. This will strengthen all load-bearing structure which will extend the life of the entire roof. The step between is about 50 centimeters, when using a board that is at least 10 centimeters in size.
When it comes to such a moment as calculating the crate on the truss system, then do not forget that the last board should be 1.5 centimeters thicker than all the other elements of the system. Before installing the elements of the crate, it is worth remembering the presence of a chimney and a special system that should be on each roof. This will save time on the calculation and alteration of the truss system, and the crate as a whole.
Ondulin and construction installation methods
As in the cases described above, ondulin provides for the calculation of the pitch of the rafter bearing legs from 60 to 100 cm, which makes such sizes standard when using the most popular roofing materials.
The truss trusses themselves are made of lumber with a section of 200x50 millimeters, which is quite enough to ensure that the strength and reliability of the truss system are at the maximum level, and it is easy to install them. It is immediately worth noting the fact that the described roofing material needs a continuous lathing system, which will allow the material to qualitatively resist the loads from snow thicknesses, as well as solar exposure.
In some cases, you can also use a thinned type of crate, the calculation of which is quite simple, if used for this. wooden beam, the step between the elements of which is no more than 30 cm. As a rule, this option is more expensive than necessary for the installation of a continuous crate. In other words, it is irrelevant to use the thinned type of system in this case.
Slate and truss structure under it
As a rule, slate coating is considered the most common in our country. The reason for this indicator can be considered the extremely low cost of the material, the simplicity and speed of installation, as well as the possibility of replacing individual sheets in case of damage to individual sections of the roof.
The distance between the rafters for this type of roof should be 80 cm. It is this distance that is considered the most optimal solution when combined load from the weight of slate sheets.
The crate in such a system needs a thinned type using a board or timber of any type, but of a certain section, which should not be less than 30 mm. Such a thickness of a board or timber is needed for high-quality and correct distribution of weight from the roofing material itself, as well as from winter precipitation.
Do not forget about the constant margin of safety when organizing the truss system, which may be required in case of unforeseen circumstances associated with mechanical loads and bad weather. All other features of the truss and crate system do not have any special differences from the options listed above. In other words, for all other types of coatings, we determine the distance in the same way as for the above roof.
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
Development of a single-slope or gable roof begins with the choice of the type of truss system, the angle of inclination of the slopes (roof height) and materials for the construction of the structure. The calculation of the distance between the rafter legs is carried out taking into account the loads that the roof will experience during operation. Permanent loads include:
- the weight of the materials from which the truss system is made;
- roofing weight;
- weight of roofing cake materials (waterproofing, vapor barrier, insulation);
- the weight of the finishing elements of a residential attic or attic.
In addition to permanent loads, the roof also experiences temporary ones, which include:
A step is the distance between the rafters of one slope. When calculating a shed, gable or complex roof, the following scheme is usually followed:
- the length of the future roof slope is measured;
- the resulting value is divided by the optimal numerical value of the pitch of the rafters;
- one is added to the obtained value, the result is rounded off;
- the length of the roof slope is divided by the rounded result.
The final result will determine how far the rafter legs should be placed. The determination of the step cannot be extremely accurate, since it is necessary to take into account a number of additional factors, including the width of the insulation, the particular installation of the crate for various types of roofing material. If a roof with a chimney is being designed, the pitch can be adjusted according to its location so that it is not necessary to remove part of the rafter in the future and install a supporting structure, such as a special rafter system.
The distance between the rafters under the slate
Slate is a traditional roofing material. Its advantages include such characteristics as resistance to external influences (excluding mechanical ones) and low cost. Slate allows you to create a roofing, the repair of which can be reduced to the replacement of individual elements. Slate is heavy and requires the installation of a sufficiently powerful truss system. The calculation of the distance at which it is necessary to put the rafters under the slate is carried out taking into account the cross section of the beam for the manufacture of rafter legs.
The optimal solution is to install the system under the slate, in which the gap between the rafters must be at least 800 mm. In order for the slate structure to withstand not only the weight of the material, but also increased external loads, the crate is made of timber or boards with a cross section of at least 30 mm. When calculating the truss system for slate, it should be read that this material has rather large restrictions on the choice of the angle of inclination of the slopes.
Rafters for metal roofing
Metal tiles are actively used as a practical and aesthetic roofing material when arranging a shed, gable, hip or complex roof. The frame for the metal tile is built according to standard principles. To calculate at what distance it is better to place the rafters, it is necessary to take into account the loads and the angle of the roof. The metal tile is characterized by a relatively small weight, so it can serve as a replacement for the old roofing from 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 the support under 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 big step- they act as a support for the runs. The distance between the rafter legs is selected based on the length of the available material for the runs and the length bearing walls. Technical specifications sandwich allow the roof to withstand high operating loads.
Polycarbonate: erection of the supporting structure
Polycarbonate has recently been actively used as a roofing material. First of all, polycarbonate is in demand in the construction of gazebos, sheds, winter gardens. The crate and truss system for polycarbonate can be made of wood or metal.
The roof frame must be reliable and durable. But without well-conducted calculations, this is difficult to achieve. In the process of carrying out the calculations, it is determined at what distance to put the rafters on the roof.
What can lead to an incorrect or inaccurate calculation of the loads that the truss structure will undergo? To the most negative consequences, starting from the deformation of the rafter legs and damage to the roof covering and ending with the collapse of the base of the roof frame. Therefore, when designing buildings, the list of mandatory calculations contains data on what should be the distance between the roof rafters. There is a certain technique that allows you to calculate this value.
Method for calculating the distance between the rafters
The distance between the rafters on the roof is called the pitch of the rafters. As a rule, the step of the rafters in the roof structure usually exceeds one meter, and the minimum gap varies within 60 centimeters.
Calculation required amount rafters for a roof of a certain length and the pitch of the rafters are produced as follows:
Roof structure for metal roofing
During the construction of suburban private real estate, metal roofing can be found most often. This roofing material is similar to the flooring made of clay tiles, but in comparison with it has a number of advantages. Sheet metal tiles are easy to install, so you can build a roof in more short time, the truss system for metal tiles is also not complicated.
Metal tiles are lighter than ceramic products, the difference in weight sometimes reaches 35 kilograms per square meter, depending on the thickness of the products (read also: ""). Due to a significant reduction in the weight of the roofing, it becomes possible to reduce the thickness of the elements of the rafter structure and the cross-sectional dimensions of the lathing bars, and increase the installation step of the rafters.
Under the metal-tiled coating, the rafter legs are mounted with a distance of 600 to 950 millimeters, while the cross section of the construction material is 150 by 50 millimeters. According to experts, in this case, if a heater 150 millimeters thick is placed between the rafters, then such thermal insulation will create comfortable conditions for staying in the attic room. At the same time, for greater reliability, it is advisable to choose a 200 mm insulation.
When installing rafters, to ensure ventilation of the space that is filled with insulation, holes with a diameter of 10-12 millimeters are drilled in the rafters near the upper roof.
The technology for creating a truss system for metal tiles does not differ significantly from structures for other types of roofing materials. The only feature is that at the rafters, the upper support is mounted on the ridge run from above, and not on the side of the ridge beam. The presence of a free zone between the rafters ensures air circulation under the roofing, and this, due to the use of metal material, reduces the risk of condensation.
Shed roof truss system, main advantages and characteristics ").
The distance between the rafters of a gable roof is made taking into account the size of the heat insulator that is laid between them. An approximate step between the rafter legs is 1-1.2 meters (read: ""). Rafters regulate the size of the roof overhang.