The choice of roofing material does not practically affect the quality parameters of the roof. The main thing when creating a floor is a structure consisting of a batten and a rafter. These parts of the roof are the basis on which the roof is mounted. The service life of this entire complex depends on the quality parameters of the truss system, therefore, during construction, they should be given special attention. In order to properly select the desired construction of roof systems, it is necessary to learn more in detail the principles of their work and their typical components.
Diagram of the roof truss system.
The structural elements of the roof that transmit the main loads from its weight and various atmospheric influences on the walls of the house or internal supports (if they are in the project) are called rafters. They are made of the following materials:
Typically, wood is used in construction. Beam joints are overlapped or end-to-end. For the complete calculation of these elements for bending and torsion, there are special techniques and reference books, with the help of which they determine the dimensions and sections of wooden beams so that the truss structure created meets all building standards and withstands design loads:
Scheme of nasled and hanging trusses.
Some of these loads are related to roofing, and those that are associated with weight gain (snow) have a direct effect on rafters.
To reduce the effect of snowfall, roofs are made with steep slopes (more than 27 degrees), and the distance between the rafters themselves is reduced.
The influence of the wind on the roof of the house is enormous - when it encounters a building, it creates high and low pressure zones near the walls, and its tearing force is able to tear off part of the roof or blow it up. To minimize these phenomena, the base of the roof should be airtight, and its individual elements have additional attachments to the base.
All materials used in the construction of a house tend to stretch when the temperature rises and to compress when it is lowered. To avoid deforming the roof or its destruction, they should be selected with approximately the same coefficient of thermal expansion.
Layout of roof types.
Water vapor that accumulates inside a building can adversely affect wooden or metal rafters and other structural elements. To partially eliminate this problem, apply special vapor barrier film materials.
To protect against microorganisms or insects, wooden rafters are impregnated with special antiseptic compounds.
Based on the above requirements, in order for the truss system of a building under construction to withstand all loads, the distance between the individual beams is chosen within 0.35-1.1 m.
There are the following types of similar structures:
Consider both of these constructions in more detail.
The use of overlay truss systems is carried out during the erection of the roof of buildings with a central supporting wall or pillars in the form of the main supporting elements. In this case, the rafter beams rest on the walls of the house, and the middle part of this system - on the supporting wall or pillars.
When using rafter beams for a hanging construction, it is necessary to take into account that they have two reference points located on the walls of the house.
The scheme of fastening the rafters to the power plate.
The rafters of this system are subject to bending and compression, and the horizontal (tearing) force is transmitted to the walls of the building. To reduce it, a so-called wooden or metal tie is made, connecting the roof beams. During the construction of the attic, it is installed near the base, and in other cases it is slightly higher.
It must be remembered that the steeper the slope of the roof, the smaller the distance between the rafters themselves should be. This will reduce the load on the supporting walls of the house during heavy snowfalls.
The types of roofs used are of the following type:
Shed roofs are used in the construction of residential buildings is very rare. Mostly they are used in the construction of commercial buildings, terraces, etc. This type of roof is made on walls of different heights. Slope should be located on the windward side of the building. The roof can cover the whole house or be part of a complex roof. In the construction of a shed roof is used on the gutter system.
If the size of a country house or cottage is small (for example, 5 x 5 m), then a gable roof overlap is used. Two sloping platforms and 2 gables are formed - this design allows the use of lightweight materials for the roof. It is easy to install, and to create it can be used as an on-wall truss system, and hanging type.
Scheme of types of connection rafters.
If the roof consists of 2 trapezoids and the associated triangular ramps, then it is called hip. This is one of the most difficult types of roofs, which are used in the construction of houses in areas with very high wind loads.
Polycline roofs have many edges and junctions, and under them are usually built attic floors, which makes it necessary to take into account in the construction budget additional costs for their insulation. Rafters in such roofs can be covered with finishing materials or left visible. Mnogochiptsovye designs have the following advantages:
The disadvantage of this design is the increased labor intensity of the work.
The selection of the type and elements of the rafters is carried out taking into account the following parameters:
There are a number of standard schemes when designing a gable roof of a building with different distances between supporting walls (pillars):
The following units are used as elements of such structures:
After the final determination with a constructive solution, all the main components of the system are calculated and their plan is made for the construction of a roof of the chosen type.
For them, they use well-dried wooden bars with dimensions that were obtained in the calculation. Of these, right on the construction site, trusses are manufactured according to plan and lifted to the installation site with the help of a crane. When assembling sections of wooden trusses, they can be treated with special compounds.
Finished farms are installed at the calculated distance from each other. When a large area of the roof section is assembled from several raised parts, which simplifies installation.
Approximate list of the necessary materials and tools in the design and manufacture of the truss system:
The correctness and reliability of the functioning of the roof of the erected building and the comfort of the future residents of this house largely depend on how correctly the calculation and manufacture of the truss system is made.
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