One of the important stages of any construction is the construction of the roof of the building, the basis of which is the installation of the truss system. From how correctly chosen step rafters, i.e. the distance between them, will be completely dependent uniform distribution of the weight of the roof on the frame, the reliability of the roof and the duration of its operation as a whole. In the event of any minor calculation error, damage and collapse of the entire roof may occur.
The device truss system.
The rafter system includes the following components:
Farmhouses consist of a deadbolt, base, rafter legs, fasteners and fasteners. Rafter legs are the beams located along the slopes, the lower ends of which are connected with the power plate, and the upper - with the purlins.
The rafters pitch is the exact distance between two trusses.
Fixing units for the truss system.
To get the exact value specified, you first need to know the values of some important values for this.
It is right to make all calculations for the roofing system at the design stage of the house. Such a responsible business can be carried out by yourself or entrust it to specialists The more accurate the calculations, the stronger will be the foundation for the roof.
In order to correctly perform all the required calculations, including the step size of the rafters, you need to know:
One of the indicators that must be taken into account when calculating the rafter step is considered to be permanent and temporary loads. These include:
Perform the calculation of the truss system.
It should be noted that these data are taken in special tables developed by scientists, depending on the climatic zones, for different territorial regions.
The angle of the slope can be determined by knowing the length of the wall of the house and the height of the roof. The steeper the roof, the greater the distance between the rafters, since the load on such roofs will be transmitted mainly to the load-bearing walls. By making further calculations, the length of the rafters is easily calculated. Most often they have standard values: 4 and 6 m.
Softwood is well suited for roofing systems. Timber must be of high quality, no knots, rot. Before work, all wooden elements must be treated with antiseptic special compounds.
The step of the rafters will depend on the type of roof, i.e., on the functional features and its shape. The size of a simple and complex roof will be different.
How the type of roofing will affect the rafter step should be considered in more detail.
After making all the necessary measurements, it is possible to make a constructive calculation of the step of the rafters. Based on practice, this indicator is in the range from 0.6 to 1.0 m.
Table for calculating the distance between the rafters.
To independently perform this calculation, you need to adhere to the following technology:
It should be noted that this calculation is made in the center of future rafters. However, the calculations can not be considered accurate and constant. In each case, the construction of the roof of the house takes into account the angle of the slope of the roof, and features of the selected roofing material, and other indicators. In this regard, it is necessary to consider the features of the choice of rafters pitch for the most common roofing materials: metal and ceramic tiles, corrugated board, slate and ondulin.
The step of the rafters under the metal tile.
Metal tile as a roofing coating is extremely common in both urban and suburban construction.The construction of the roof truss system using metal tiles will differ little from the general scheme. However, due to the fact that this building material has a small weight, rafters and other elements of the system can be taken smaller section, i.e. with a smaller margin of safety. The distance between the rafters when using metal tiles is 60-95 cm. Performing all works on the installation of the roof made of metal is much easier than from other roofing materials. A feature of the lathing of this material is that the board near the eaves should be about 1.5 cm thicker than the rest. Usually the section of the rafters of metal tile is 50x150 mm.
Ceramic tile is a roofing material of considerable weight, which is 10 times the weight of metal tile. In this regard, it is necessary to more thoroughly approach the calculation of the roof truss system. The cross section of the rafters should be slightly increased - up to 60x180 mm. The average distance between the rafters to cover the ceramic tiles is set in the range of 0.8-1.3 m. The angle of incline of the slopes is necessarily taken into account: the distance between the rafters is made larger, the higher the roof.
The length of the trusses in this case will have a strong influence on the result. The distance between the rafters decreases with increasing their length . With their long length, increased loads may appear on the deflection, which can be significantly reduced by additionally installing a system of struts, props and other elements.
Table for calculating the length of the rafters, the pitch between them and the beam section.
The most common roofing material is slate. This is due to its low cost, ease of installation, the possibility of replacement when damaged individual elements of the roof.
The characteristics of a batten for slate are its thinned type, consisting of any type of board or bar, but with a mandatory cross section of at least 30 mm. This is necessary for proper and high-quality distribution of the weight of slate on the batten.
The optimum distance between the rafters when combining the load from the weight of slate sheets should be 80 cm. One should constantly take care of the safety of the truss system, which may be due to various unforeseen circumstances. Otherwise, its establishment under the slate roof is no different from other options.
Now you should pay attention to some features when installing the roof system for roofing materials such as sheeting and ondulin.
The weight of professional flooring and ondulin is much lighter than that of ceramic tiles or slate, so the technology of installing rafters for these materials is almost the same as the installation of metal tiles. The distance between the rafters for the roof of corrugated is 60-90 cm, and of the ondulin - 60-100 cm.
If you need to increase the distance between the rafter legs, you need to strengthen the system design with transverse sheathing elements.
The device for crates for corrugated flooring is very similar to the device for crates of metal tiles. It is important to remember that in this case the last board should be somewhat thicker than all the others.
A special feature of the installation of a batten for an ondulin should be considered the need for its continuous type for high-quality resistance to various loads. In some cases, it is possible to use a thinned type of crate, but then the step between the rafters should be no more than 30 cm.
Thus, being able to make all the necessary measurements, knowing the basics of installing the truss system for the main materials for the roof (tiles, corrugated, slate and ondulin), you can correctly calculate the distance between the rafters.
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