What are rafters? This is a pitched roof system consisting of sloping beams, vertical struts and struts. A common geometric shape design, providing maximum stability, is a triangle. By the form, these structures are divided into hanging and slashed. They have both advantages and disadvantages.
The device truss system.
The elements of the rafters rest on the walls of the building, and the middle part - on the piping of an intermediate value, which naturally assumes the construction of a house with a middle wall, or it is arranged from pillars in the attic.
Such rafters can be installed in their own houses, where the attic space does not exceed the width of 6.5 m. And additional supports will allow it to be increased. The advantage of this type is the ease of construction.
The ends of the rafters rest on the mauerlat, a support element made around the perimeter. In this role is the upper crown of the house, made of timber or logs. It can be carried out around the perimeter of the house or just under the rafters. If the house is built of brick, then the support bar must be hidden by brick masonry. Between the two textures laid out a layer of waterproofing, which today is a great many.
The design of the hanging trusses should be designed for light structures, for the "legs" working in compression can "burst" the walls. Rafters in this case are strapped on the bottom, mounting metal or wooden tightening structure. If the harness is located above the base, it should be even safer.
If it is supposed to make spans of more than 8 m, then a rack with struts is mounted in the structure of the rafters. In this and their main advantage is the ability to overlap a large distance of spans.
In order to assemble the upper ends of the truss structure, a ridge run is done. It is mandatory for the device of any roof, which implies a pitched version.
To correctly calculate material consumption and safety of installation, and then roof operation, craftsmen must find out many different factors that precede the work. The main will be the definition of temporary and permanent loads on the rafter system.
Subsidies of hanging and slant rafters.
To constant loads include the specific weight of the house and the roof construction as a whole. Masters or designers of a typical house project will not forget to take into account the climatic conditions of the region, and, relying on them, will choose the type of roof and, accordingly, the construction of the rafters. There are special tables for this, according to which the “formula” of the optimal solution will be found.
Approximate cross-section for wooden elements of the roof frame should be adjusted to the following dimensions:
The list is incomplete, more covering information can be found in the passports of the proposed buildings and depending on the roof construction on an individual project.
The necessary actions to be taken before the installation of the truss system include the following:
The load on the rafters.
The arrangement of the roof can be carried out with the use of many technologies, but the essence of the truss system is the same - to position the bars along the perimeter ends and make the appropriate strapping.
After all the precautions taken with the wooden elements, check the base of the roof for moisture protection. If necessary, a second layer of roofing felt or other insulator is laid on the upper crowns. Either the mauerlat is coated with bitumen mastic and fixed to the walls with steel anchors.
Rifle mounting scheme.
Then the ridge girder is set, which, in accordance with the design of the roof, should divide the truss system in half. Subsequently, when the roof covering is finished with finishing materials, the girder will become a certain mark for the installation of the ridge.
After that, the installation of the rafters begins at the edges, that is, at the opposite ends of the house. This is done in order to check the parallelism of the edges of the beam with a tension cord. If this does not happen, we can talk about the violation of the technology of wall construction. Zapily at the ends of the beam is done strictly diagonally, so that the fit to the mauerlat and ridge beam is ideal. To further strengthen the reliability of attachment, you can resort to using metal plates or corners.
Then, making sure that the extreme legs meet the requirement, the middle rafters are attached, and also checked for discrepancies.
To the mauerlat, the truss system is attracted by a twist of 6 mm wire.
Table selection section for rafter legs.
This is done quite toughly, for no discrepancies with the power plate are permissible. The clip is carried out by corners or plates.
The step of installing the rafters is determined by the length of the wooden elements - the thicker and longer the bar, the greater the step. For example, for a timber section of 100 * 250 mm, a distance of 2150 mm from the neighboring one will be required.
Bends and contractions in the structure are inevitable, therefore, in addition to rigid fastening, you need to make a harness. It is carried out with the same materials, from below or at the ridge run. The more reliable the harness is, the less chance there is for the roof to fall apart. Especially it will be unpleasant when the house becomes residential. By the way, strong piping, overlapped with fastening from bolts, can serve as an additional overlap for arranging the attic.
Types of roof systems.
Also, the installation technology of the truss system includes a horizontal scramble - tamping the beam strictly parallel to the power plate. This element works with the occurrence of loads on the roof - snow, as well as with unaccounted factors of subsidence of the foundation, i.e. emergency version.
The installation process of the truss system can be accelerated if you make in advance the preparation of trusses right there on the roof. But such a technology can afford only the masters who deal with the construction of roofs is not the first time.
Do not rush to make a system of rafters with your own hands - everything must be verified carefully, because the roof is the most important element of the house. A lot of work is needed on the calculation and formulas regarding the material for the rafters. If this is taken carelessly, you should not expect durability from your own home.
And the roof can go away from alterations in case of unsuccessful installation. Both literally and figuratively. Therefore, if the master is able to make a simple gazebo, this does not mean that he will be able to build a truss system, but the gods do not burn the pots - it’s worth trying.
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