The construction of the roof truss system begins with the installation of the Mauerlat. This structural element is a bar made of wood with a cross-section of 100x100 or 100x150 mm and performs the functions of uniform distribution of roof loadings on the walls. As a matter of fact, Mauerlat is the foundation for rafter legs and provides high rigidity to the entire rafter system with minimal consumption of building materials. Do not forget that the installation of this element is only on the surface, isolated by two layers of waterproofing cushioning material (roofing felt, ruberoid, bipolikrin).
Laying the Mauerlat should be done on a concrete belt with its internal reinforcement with steel mesh. At the first stage, it is necessary to spread the beam along the walls, observing strict horizontality, which is checked with the help of a hydraulic level. After completing all the required measurements, the Mauerlatt must be firmly fixed on the wall surface. For this, there are several ways, and the most reliable of them is considered fastening with anchor bolts to the reinforced concrete belt, because the further construction of the truss system depends entirely on the correct installation of the Mauerlat.
The next stage of the work is the installation of rafters, which are made from a beam of coniferous wood with a cross section of 50x150 or 50x200 mm. The cross-section of the beam depends entirely on the type of roofing material used to cover the roof, the optimal values of snow and wind loads, as well as the distance (pitch) through which they are installed. To ensure a reliable and strong fastening of the rafters on the Mauerlate, their lower ends must be cut in the appropriate manner. Further, the lower ends of the rafters are fastened to the Mauerlat, and the upper parts of the rafters are joined at the right angle. Cut the top of the rafter legs in such a way that when they join tightly they come to each other, forming a reliable knot, they are fastened with nails and wooden patches on both sides. Further, the preparation of the rafters is made already on the ground, having previously performed all the relevant measurements on the installed pair of rafters.
The construction of the rafter system is then carried out in the following order: first the rafters are installed in the area of the pediments of the building, it is necessary to pull the cord between them and continue the installation of the remaining rafters with the specified step and alignment of the installation Using a plumb or construction level. The construction of the rafter system requires a precise regulation of the rafter legs in height (the tension cord serves as a guide), in order to avoid problems with the installation of the crate in the future. In the process of installing the rafter legs, their time alignment is performed. With a large distance between the building's walls, it is necessary to install the tightening, that is, the structural element that connects one pair of rafter legs. As a tightening, a bar of dimensions 50x75 mm or an edging board 30x150 mm is used.