Rafters of the attic - what features are waiting for us?
Looking at the attic roof, it is difficult to imagine the true complexity of the design of a system of inclined beams supporting its outer covering, a whole complex of waterproofing measures, steam protection and insulation for life support of the attic space. A high attic space, as a rule, is used as a dwelling and is called an attic.
Roof rafters must be interconnected, cut into mauerlat or tightened, have cut auxiliary elements( bolts, headstocks, struts and supports), additional fastenings with bolts, clamps or clamps. The choice of options for such fasteners depends on the characteristics of the prevailing load: tensile, compressive or bending.
The main operating forces aimed at the skeleton structure of the roof are caused by the weight of the rafters themselves, the crate reinforced on them, snow masses, wind and other loads. These are the factors of deformation for bending( considering the fixing of the legs of the trusses), therefore the above mentioned additional bolts, supports, struts, etc. are applied.elements.
Focusing on the design, the size of the elements, other factors, it is necessary to perform at least an elementary calculation of rafters attic. It is important not only to correctly select their section, but also the size of the fragment, taking into account the overhangs and ways of fastening, the support and fastening of each element, providing the necessary rigidity of the entire skeleton of the roof.
The calculation is based on the allowable deflection for the total length( no more than 1/250 parts, taking into account the load of 100 kg per square meter of the roof).
With a large overlapping area, it is important to correctly locate the Mauerlat( for waterproofing), preventing possible deflection of the entire roof( installation with an indentation from the edge of the wall and the use of special boarded "mare").It is equally important to correctly calculate and fix the whole of this construction to the walls of the building box. Special reinforced yokes made of steel wire or rope, braces, etc. are applied through one leg.
Roof rafters - structure of
structure As is well known, layered and suspended types of rafters are distinguished. The latter can have simple and complex constructions and are used in case of overlapping of large spans. The rafters of the attic roof belong to such a complex type. Taking into account the residential character of the attic space of the attic roofs, it is necessary to lay the insulation with the waterproofing across the entire area between the farms.
On top of the material, a layer of vapor barrier is required, with a transverse laying of sheets from the overhang upwards and ensuring their overlap with the next belt of at least ten centimeters. The material is sewn a lath providing ventilation between the roof and the insulating spacer. In the construction of the mansard farm, runs are used with the support on the posts, which transfer the weight load to the supporting wall.
Special struts and podbalki are used for heavy roofs, increased distances between racks etc. It is also desirable to provide wind bundles between runs. When constructing the roof of adjoining rooms and add-ons, their truss structures should not cut the main ones.
From the forces acting on the roof, it depends on how the rafters of the attic are connected by their own hands. Leg support for the Mauerlate belt is usually provided with special nests and spikes. It is allowed to use the Mauerlates from separate, fastened with each other, beams. For greater reliability, this fastening is performed on bolts of the appropriate length and diameter.
When making rafters from wood, the material is taken only of the highest grade, without knots and other defects. As already mentioned, the cross-section is chosen taking into account the length of the beam, the step between the trusses, the weight of the roofing material, the design loads per square meter of the roof. The condition of choice is the admissibility of the deflection at 1/250 of its length.
In case of using a material with a smaller cross-section, the provision of rigidity and strength is achieved by applying additional struts of logs of not less than fifteen centimeters of thickness. In this case, it makes sense to reduce the distance between the beams of the legs, use for Mauerlat material is not thinner than eighteen centimeters.
Installation of rafters in the attic - how not to confuse the sequence of actions?
Installation of rafters in the attic of is strictly one horizontally, with the same length of leg, hewn from the upper side. The task is facilitated by using a common template, prepared in advance in the required form and size. Work is conducted on a flat site, while the dimensions of boards, timber or logs should overlap the required length to account for possible errors in connection.
First, the edge farms are installed. On a tight cord or temporary board, installation and installation of intermediate ones with their exact alignment is carried out. The fitting ends are adjusted according to the cord or board. If the construction of the roof provides a crocheting farm( usually with hips), it is carried out by foot( natives) to the main rafters.
Leg clasps in the Mauerlat, all the important joints of the elements of beams, supports, girders, etc. are additionally strengthened by reinforced clamps, corners and clamps made of galvanized steel. Their fastening is performed on self-tapping screws. The next is the crate.
For wood lathing, materials of at least grade II, also without knots and edging, are used. It can be a board, a bar, a pole or a tes. The installation of the battens also depends on the materials of the roof and is carried out closely or sparingly, with the necessary ventilation between the heater and the roof.
