Metal roofs are a practical and popular solution for the construction of private low-rise houses. This roofing material is characterized by high bearing capacity, resistance to mechanical damage to external environmental factors and heavy loads. The durability and reliability of the finish coating does not depend only on quality, these characteristics are influenced by the design of the roof, including the correctly chosen minimum slope. In this article we will tell you how to choose the right angle of inclination of the ramp and check it for compliance with the SNiP.
What is bias?
The slope of the roof - an important parameter of construction, which indicates the angle formed by the plane of overlap and roof slope. This indicator is expressed as a percentage or degrees. It is calculated as a result of dividing the height of the ridge by half the width of the building. The slope of the slope depends on the technical and operational properties of the material and is governed by the SNiP and manufacturer's instructions. It depends on him:
- The possibility of applying one or another type of roofing.
- Design, composition and cross section of the truss frame elements.
- The ability of the roof to effectively divert precipitation.
- The cost of roofing work.
- The weight of the roofing pie.
Note! If the slope of the roof of metal to increase from 22 degrees to 45 degrees, the area of the slope will be more by 20%, which will affect the cost of materials (finishing coating, waterproofing, insulation, wood), as well as the weight of the structure. Deciding on the optimal angle of inclination is necessary during the drafting of the project in order to correctly determine the load on the foundation.
Metal roofs are a relatively new constructive solution, therefore the technology of its installation and operation is not clearly regulated by the SNiP. Information on what should be the minimum slope of the roof provides the manufacturer, since this figure is directly dependent on the technical characteristics of the material itself. This indicator is calculated in accordance with the thickness, bearing capacity and method of laying the roof covering.
- According to SNiP, the minimum angle of inclination of the roof of a metal tile, if the length of the slope is 6 meters, must be at least 14 degrees.
- The allowable slope for the roof of metal is in the range of 14-45 degrees.
- The optimal angle of inclination, which ensures effective removal of precipitation with a smaller area of slopes, should be 22 degrees.
Important! The minimum roof slope of metal, which manufacturers allow, is 11 degrees. Some brands of material can be laid, even if the steepness of the slopes is 10 degrees. The reduction of this indicator allowed to achieve the use of new, smoother polymers and more durable steel for the production of roofing.
For a non-professional builder, it can be difficult to correctly select the minimum angle of inclination of the roof from metal tile. This indicator, in addition to the requirements of SNiP and manufacturer's recommendations, is influenced by other factors that also need to be taken into account. When choosing the slope of the slope is taken into account:
- Snow load in the construction region. To estimate the snow load on the roof of the metal, reference books take the average annual rainfall in the winter. The more snow falls in the region, the greater should be the minimum slope of the roof. Otherwise, the snow mass will accumulate on the surface of the slopes, creating an additional weight load that can collapse the structure.
- Wind load. This indicator also depends on the climatic conditions in the area where construction is underway. If the wind load is intense, then the angle of inclination of the roof should be minimal to reduce the windage of the slopes. Also taken into account is the probability of wind cataclysms, hurricanes, tornadoes.
Consider that the choice of steepness of slopes depends on the design of the roof. The optimum angle of inclination of the slopes of a single-sided metal roof is 20–30 degrees, and that of a dual-sided roof is 20–45 degrees.
Features roofs with a small slope
The minimum recommended angle of inclination of the roof made of metal is 14 degrees, however, experienced craftsmen can properly fit this type of roofing material, even if the slope of slopes is within 10-14 degrees. To increase the reliability of this design and reduce the risk of leakage, it is necessary to perform the following measures:
- Increase the frequency of battens and reduce the spacing between the rafters. To minimize the risk of roof collapse due to intense snow load, it is necessary to reinforce the roof frame of the structure and mount a partial or continuous crate.
- Zoom overlaps. Manufacturers recommend installing a metal overlay to do a horizontal overlap of 8 cm, and a vertical 10-15. To eliminate the possibility of leakage in structures with gentle slopes, you can increase the overlap at the joints of the sheets.
- Isolate joints. To prevent the penetration of melt and rain water between the joints of the sheets, you can treat the seams with silicone sealant, although this measure has a limited duration.
Experienced craftsmen argue that the easiest way to make a metal roof reliable is to follow the manufacturers recommendations and to strictly follow the recommended angle of inclination.