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The slope of the roof



The slope of the roof is a defining aspect for the final appearance of the roof. It represents the inclination angle of the slope and the value directly influences the type of material to be used for the coating. It is generally measured in degrees, which represents the angle made by the horizontal plane with the slope line, or in percentages, which represents the height reached by the coating in 100 meters.

Types of sloping roofs

Depending on the slope, the roofs are divided in several kinds: flat roofs with a slope of less than 5 degrees; low-pitched roofs with a slope of less than 15 degrees; medium-pitched roofs – having the degree of inclination between 15 and 45 degrees; steep roofs with a slope bigger than 45 degrees. Medium and steep roofs are also called high roofs.

When mentioning the minimum slope of the roof, reference is made to the minimum pitch recommended by the manufacturer under which the material used for the coating can no longer have the protective role against water infiltration, or will require additional safety measures.

The maximum roof slope can be considered vertical 90 °. The manufacturer of the material to be used for the covering shall specify, where necessary, for which slope values ​​additional measures are required to ensure its stability and strength.

The roof slopes can be continuous, straight or in different angles, with slope breaking or curves.


For flat roofs an impermeable covering is to be used due to the fact that it does not allow the water to infiltrate into their structure. For high roofs waterproof coating is used. Under wind pressure, it allows a small amount of rainfall to enter into their structure. It does not damage the structure because it will naturally evaporate in a short time. Waterproof roofs require a suitable ventilation system.


The frame is the resistance structure of the pitched roofs and their common element, regardless of their inclination. It is very important to choose the materials to be used for covering the house from the planning phase, because, depending on the materials, the dimensions of the frame and the slope of the roof will be determined. Depending on the material chosen for covering, the building contractor will decide the necessary details in order to achieve the desired solution. The structure and the slope of the roof must be designed to resist under the load and the weight of the roof.

Here are some examples: The minimum slope for ceramic tiles is 11 degrees , respectively25%; in the case of ceramic tiles and concrete tiles, the minimum slope is 15 degrees, 35%; for the fiber-cement boards, the minimum slope is between 8 degrees, respectively 18% and 27 degrees, respectively 60%; for corrugated fiber-cement boards, plastic and bituminous boards, the minimum slope is 5.4 degrees, 12%; the minimum slope of the slate plates is between 8 degrees, 18% and 27 degrees, 60%; for flat boards or scale slates, the minimum slope is 3 degrees, 7%; for corrugated sheets, 4.5 degrees, respectively 10%; for the bituminous shingle the minimum slope is 9 degrees, 20%.

The slope of the roof is also important when it comes to ways of protection against environmental factors. When determining the slope it is also recommended to consider the climate in the area where the construction is located.

Calculating the slope

To calculate the roof slope, you should measure the height of the wall at the beginning of the slope. At a distance of one meter from the wall, the height under the ceiling is measured, and from this sum you subtract the first number. The result will be the percentage of the slope.

Correspondences between percentages and degrees: 10% = 5 °; 20% = 11 °; 30% = 16 °; 40% = 21.5 °; 50% = 26.5 °; 60% = 31 °; 70% = 35 °; 80% = 38 °; 90% = 42 °; 100% = 45 °; 110% = 47.5 °; 120% = 50 °; 130% = 52.5 °; 140% = 54.5 °; 150% = 56 °; 160% = 58 °; 170% = 59.5 °; 180% = 61 °; 190% = 62 [deg.].



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