Any building needs reliable protection against adverse environmental influences. This refers to climate change, expressed in changes in wind strength and precipitation (snow, rain, hail). This protection is provided by the roof of the building, especially the pitched roof as the most effective. The reason is that the angle of the roof, using Earth's gravity, allows you to quickly remove precipitation from the roof without overloading its elements.
It is reasonable to assume that the roof with the greatest possible angle of inclination will be ideally self-cleaning. But it is worth making a simple drawing on paper to see what insurmountable problems appear in this case.
An increase in the angle of inclination of the roof carries higher and higher its ridge, and along with it, its construction and arrangement grows exponentially . The larger the roof area, the greater its windage, that is, the surface that is exposed to wind. For example, if you increase the angle of the roof by 34 degrees, from 11 to 45, the wind load on the roof increases fivefold. This automatically entails the strengthening of the roof structure. Finally, a large roof area means a greater consumption of materials. In sum, all this increases the cost of work at times.
The above numbers - 11 and 45 degrees - are not random. It is in this range that a compromise is sought between the need to protect the building from atmospheric precipitation and winds, on the one hand, and the structural features of the house, on the other. There are no universal recipes here, the calculation of the optimal angle at the design stage in each case must be performed separately.
Before calculating the angle of the roof, you need to know the value of the full load on the roof. It is composed of the mass of the roof per square meter and the maximum snow load in the region.
The mass of the roof is defined as the sum of the masses of all its components. As you know, a roofing "pie" is a coating, lathing and insulation. But at the same time, one must also take into account a certain mass reserve, for which it is necessary to multiply the resulting amount by a factor of 1.1.
Building normative documentation contains information on the regional maximum snow load indicator and its reduction factors taking into account the angle of the roof.
It will need to be changed if, as a result of the calculations, an excess of the maximum permissible value of the load on the roof is revealed. This change will entail a decrease in snow load. If such a measure did not lead to an acceptable outcome, the root of the problem should be sought in an imperfect roof design.
For each type of roofing materials has its own minimum angle of inclination of the roof. For example, tiles, slate and other materials from typesetting allow you to make a slope of 22 degrees. This angle of inclination of the roof prevents the accumulation of moisture in the joints. Three-layer roofing from rolled materials - 2-5 degrees, two-layer - 15 degrees. Decking - 12 degrees (at smaller angles, joints should be treated with sealant). Metal tile - at least 14, soft tile - 11 degrees.
When choosing the angle of the roof, you must always remember the load-bearing capacity of its structure, which allows you to resist any loads and external influences.
Thus, determining the angle of the roof is a crucial step. A mistake can not only cost material costs for emergency repairs, but also become a threat to the health and life of people living in the building.