Construction of any roof begins with a design that will help determine the amount of building materials needed (including insulation), the number, type of fasteners. Any attachment truss system depends on the type of roof, which can be one-two-chetyrehskatnoy, hip, hip or mixed type. Depending on where the bearing walls are located, rafters can be of two types.
Knots of fastening of rafter system.
They are installed in buildings where there is a central or middle bearing support (wall). Elements of this type can be in the form of boards 45-50 mm or bars, fixed in 2-3 points. One end rests on the ridge, the second - in the mauerlat. If it is assumed that the truss legs will have a length of up to 6.5 m, then a 3rd fastening point on the vertical support structure (usually in the form of an additional pole) is provided. To make the structure even more rigid, apply runs, as well as girders, struts. If the length of the slab exceeds 6-7 m, then it already makes sense to use metal trusses, beams. The type of fastener is chosen in accordance with the type of expected load. Fastening is carried out in the following ways.
Distance fastening of the truss system.
The distance construction implies the use of rigid fasteners along the whole gable. In this case, load bearing walls perceive the entire load (if there are supports, then they too). The tops of the installed "legs" abut each other. The bottom is attached to the power plate, which can be made, for example, in the form of a rigid frame fixed to the walls by means of anchor joints (brackets can be used). The basic techniques of attaching the "legs" to the mauerlat:
The unclad method does not imply rigid fasteners: the lower part of the rafter leg does not have additional stops and is mounted on "slide blocks". The upper parts are connected to each other through the lining. With this method of mounting rafters may have a small degree of rotation.
Attic from hanging rafters.
This is a structure in which the lower part of the rafter leg is located outside the roof (i.e., hangs). Hanging rafters are used in the absence of internal supports, and the entire truss system is “forced” to rest on the walls around the perimeter. The most common variant of the roof, where hanging rafters are used, is a triangular truss, often consisting of 7–12 m long rafter legs. They are installed with a slope, resting the lower end on the power plate. The upper end is attached to the ridge with a gash and reinforced with a crossbar - a special tie.
All methods are divided into a rigid and sliding mount. In the first case, torsion, bends, the possibility of turns between the elements entering the truss system are excluded. Rigid fastening is made:
Hinge (sliding) fixation is possible with the use of special fasteners, the design of which involves shifting the details of the truss system within certain limits. The rafter leg acts as a moving part, the mowerlat beam serves as the fixed part.
Sliding fastener installation is usually practiced in wooden structures; as a result, during shrinkage, the house gently “adjusts” to changes.
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