How to build a roof of a country house with your own hands-3
When building a house from any material, wood, brick, etc. the bearing capacity of the outer walls is calculated as if by itself, and usually with a large (double or triple) margin. Of course, we will not consider “Japanese houses” made of rice paper and twigs, as well as cases when builders steal half of the building materials, after which the houses fall down in strong gusts of wind.
The classification of roofs by architectural design, by the level of thermal insulation and by shape can be found in the second publication of the series.
A roof cannot just be built without a preliminary calculation of the structure. The experience of "dacha neighbors" who built houses with the help of some "integrated teams" is not good. When building a solid country house, one cannot neglect the construction calculations that a professional designer must perform, otherwise, the operation of a roof erected “by eye” can turn into very big troubles.
truss structures
Consider pitched roofs, as the most common in suburban buildings. The basis of roofs, as already mentioned, are truss structures, and it is with their calculation that the whole process of roof construction begins.
For shed and gable roofs, layered rafters are almost always used, a schematic representation and constituent elements of which are presented below.
1 - Rafter leg
2 - Mauerlat
3 - Brace
4 - Rack
5 - Run
6 - Lezhen
7 - Spacer
8 - Tightening
The design of truss structures begins with the calculation of the truss legs of the distance between them. This distance is called "step". The cross section and pitch of the rafters are determined from the expected operational loads on the structures. This includes the own weight of the structure, the weight of the roof, wind and snow loads acting on the roof, as well as the angle of the roof.
Only a professional designer should deal with such calculations, however, in order to understand the numbers that appear in the basis of the calculations, we provide a table of the dependence of the length of the rafter legs, their thickness and the distance between the rafters.
In addition, there is an “iron” rule: layered rafters can be built without intermediate supports (racks) with a distance between the lower ends of the legs not exceeding 6 m. If one additional support is placed, the distance between them can be increased to 10-12 meters, and if there are two supports, then the distance increases to 15 meters. And only the designer can decide what configuration the truss structure should have, whether puffs, racks, etc. are needed.
Also, the designer can determine what waterproofing measures need to be applied to protect the entire building and roof,
For example, when using natural tiles as a roof and with a slope of 16 to 22 °, an additional layer of waterproofing is laid under the tiles.
With a slope of the roof slope from 10 to 16 °, a continuous crate is mounted under the roofing material, then a built-up roof is laid on it, which forms a continuous moisture-resistant layer.
To be continued