The construction of the truss system of the building begins with the installation of the Mauerlat. This structural element is a timber beam with a section of 100x100 or 100x150 mm and performs the functions of evenly distributing the loads transmitted by the entire roof onto the walls.
In fact, the mauerlat is the foundation for the rafter legs and provides high rigidity to the entire truss system with minimal consumption of building materials. It should not be forgotten that the installation of this element is carried out only on a surface insulated with two layers of waterproofing cushioning material (roofing felt, roofing felt, bipolycrin).
Mauerlat should be laid on a concrete belt with its internal reinforcement with steel meshes. At the first stage, it is necessary to lay out the timber along the walls, observing strict horizontality, which is checked using a hydraulic level. After completing all the required measurements, the Mauerlat must be firmly fixed to the wall surface. There are several ways to do this, and the most reliable of them is fastening with anchor bolts to a reinforced concrete belt, because the further construction of the truss system fully depends on the correct installation of the Mauerlat.
The next stage of the work is the installation of rafters, which are made of softwood timber with a section of 50x150 or 50x200 mm. The cross section of the beam fully depends on the type of roofing material used to cover the roof, the optimal values of snow and wind loads, as well as the distance (step) through which they are installed. To ensure a reliable and durable fastening of the rafters on the Mauerlat, their lower ends must be cut accordingly. Next, the lower ends of the rafters are fastened to the Mauerlat, and the upper parts of the rafters are joined at the desired angle. They cut the top of the rafter legs in such a way that when connected they fit snugly together, forming a reliable knot, they are fastened with nails and wooden lining on both sides. Further, the preparation of the rafter legs is carried out already on the ground, having previously performed all the relevant measurements on the installed pair of rafters.
The rafter system is further installed in the following order: first of all, the rafters are installed in the area of the gables of the building, it is necessary to pull the cord between them and continue installing the remaining rafters with the step specified by the project and checking the verticality of the installation
using a plumb line or building level. The device of the truss system requires a clear regulation of the rafter legs in height (a stretched cord serves as a guide) in order to avoid problems in the future when installing the crate. During installationrafter legs, their temporary jointing is performed. With a large distance between the main walls of the building, it is necessary to install a puff, that is, a structural element connecting one pair of rafter legs. A 50x75 mm beam or a 30x150 mm edged board is used as a puff.
