The angle of inclination of the roof for the snow - optimal

In civilian low-rise construction, experienced builders call pitched structures the most common, rational, and economically viable type of roof. They can consist of one, two, three, or even four slopes, planes interlocking at one point, called the ridge. From flat roofs, pitched differs from the angle of inclination, which, according to building standards, must exceed 2.5 degrees. The choice of slope is an important stage in the creation of a project, on which strength, bearing capacity and durability of a structure depend. In this article we will tell you how to choose the right angle to ease the flow of snow in winter.

Angle determination

The angle of the roof - the parameter of engineering calculation of roofing structures, reflecting the ratio of the height of the ridge to the width of the base of the slope. Pitched roofs may have a slope of 2.5-80 degrees, however, the optimum range of values ​​of the angle of inclination is 20-450. The slope area, wind resistance and snow load depend on this parameter. In the literature there are the following terms:

• Minimum bias. The minimum angle of inclination in general for pitched roofs is 2.5 degrees, but depending on the waterproofing material used, this parameter may increase. Least of all is the minimum angle for rolled bitumen and membrane coatings, it is 2-4 degrees. The minimum allowable value for metal tile and corrugated is 11-12⁰, for ceramic tiles - 22⁰.
• Optimal. The best name is the most suitable roof slope in these climatic conditions when using a certain waterproofing material. The optimum angle of inclination provides an independent descent of snow, facilitating the maintenance of the roof.

Important! Roof slope can be expressed in degrees, as a percentage, or as an aspect ratio. To calculate this parameter of the roof structure, it is necessary to divide half the width of the facade by the height, and then multiply by 100 percent.

Criterias of choice

The choice of bias is based on engineering calculation, taking into account the climatic conditions of the area where the construction is being carried out, the characteristics of the roof covering and the bearing capacity of the truss frame. In order for the design to be reliable, the following criteria must be taken into account:

1. Wind load. The steeper the roof, the stronger its sailing ability. Therefore, in regions with strong, gusty winds, flatter roof structures are preferable. Although, on the other hand, a wind blown from low-angle slopes can tear off waterproofing material.
2. Snow load. The greater the snow load, the more covered the slopes make. The angle of the roof of 40-45 degrees provides an independent descent of snow from the surface of the roofing material.
3. Characteristics of the finishing coating. Each coating for the construction of the roof there is an optimal slope that must be considered when designing the structure.
4. Carrying capacity of the frame. The smaller the cross-section of the frame elements and the greater the distance between them, the higher the slope must be in order to withstand the snow load.

The optimal rate to facilitate the drift of snow

The limiting factor in choosing the angle of slope of the roof slopes in central Russia is the high snow load characteristic of this area. A large amount of snow falling in winter increases the pressure on the roof system, leading to deformations of the frame and roofing material of the structure. Experienced craftsmen believe that there is a steady correlation between slope and resistance to snow load:

1. If it is less than 30 degrees, then snow accumulates on the surface of the slopes. Snow drift and frost has a significant mass, due to which the load on the roof frame increases, reaching critical readings. However, part of the snow is blown away from the surface by the wind. If the angle of inclination of the roof is in this range, the snow holders are not installed on it, especially if the roofing material has a rough surface.
2. With a value of 45 degrees, the snow load on the surface of the slope reaches maximum values. Snow on such structures accumulates in large drifts, which lead to the collapse of the frame, if the roof is not periodically cleaned.
3. If the roof is 45 degrees or higher, then in calculations of the load on the rafter frame the weight of snow can be neglected, since the snow from the slopes slides off on its own, without lingering on the slope. To secure the operation of the roof, which has a large angle of inclination, snow-cutters are installed on it, cutting the layer of snow when it comes down on thinner plates that have lower speed and fall energy.

Please note! According to the construction climatology, the territory of Russia is divided into 8 climatic zones, each of which has its own average annual snow load. This reference value is used to calculate the slope of the roof, the thickness of the cross section of the truss frame and the choice of roofing.

Impact on the design

It is important that the change of the slope to facilitate the removal of snow strongly affects the design of the roof as a whole. Increasing the slope entails the following consequences:

• Increasing the weight of the roofing pie. The weight of 1 square meter of roofing pie with a slope of 50 degrees is 2-2.5 times higher than that of a roof with a slope of 2 degrees.
• Increase the area of ​​stingrays The steeper the roof, the greater the area of ​​its slopes, the greater the expense, and, consequently, the cost of the roofing material.
• Relief truss frame. In the absence of snow load, you can lighten the roof frame to save on wood.
• The inability to use roll materials. If the roof slope exceeds 40 degrees, it is not recommended to use bitumen and membrane rolled materials, as they can simply “slide” down under the influence of high temperature.

Experienced craftsmen note that the right choice helps to increase the service life of roofing structures, to facilitate the operation and maintenance of the roof in the conditions of the snowy Russian winters. Errors in the project associated with the wrong choice of the optimal angle lead to rafter deformations, sheathing collapse, and the pouring of atmospheric moisture into the interstitial space during slanting rain or during thaws.

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