The roof is a structural element of the building, which is responsible for its protection from external factors. It must successfully resist atmospheric precipitation in the form of rain, hail, snow, heavy winds and destructive hurricanes. The correct slope of the roof plays a big role in quickly removing water and snow from the roof. In combination with high-quality waterproofing, it provides excellent protection for the entire structure, including the interior.
Not only these indicators will depend on a competent slope of the roof, but also its long-term work and strength. How to make the calculation correctly, what factors to consider, how to calculate it for roofs with different coatings - all these issues will be covered in this article.
Content
About factors influencing the calculation of the angle of the roof slope
Roofs, as already written on our website, have a different shape and number of slopes. They are single, double and four-slope. The angle of the roof depends on the number of slopes on your house.
Construction work on the installation of the roof can be suspended if you do not decide in advance which material you are going to make the top coat from and what the angle of the roof. It must be remembered that these two concepts are closely intertwined, since the type of the proposed roofing material will be taken into account when calculating the angle of inclination of any pitched roof.
Let us dwell on the factors that are taken into account when doing the calculation of the angle of the roof.
For example, choosing a slope roof angle of 9-20 degrees, you will need to take into account factors such as
- topcoat material;
- existing climatic conditions;
- functional purpose of the building.
In the case when the roof will have two or more slopes, then not only the above factors and the area in which the house will be built will be taken into account. It will be necessary to take into account for what purposes an attic room is arranged. If it is not intended for housing, but should be used to store temporarily unused things and objects, then you should not arrange for these purposes a large room (we are talking about the height of the ceiling). When the owners plan to make a loft in the form of an attic from the attic, then there is a need for a good roof with a significant slope.
In those regions where strong winds are not uncommon, they make minimal roof slopes. Therefore, it does not have such a strong impact of the wind. Making roofs without a slope is also not recommended. Such coatings can be arranged in regions with a large number of sunny days and a low probability of precipitation.
Resistance to wind with a high roof is much greater than with a low. However, with a very small slope, there is a possibility that the wind can disrupt the finish. It turns out that with very steep roofs there is the same danger as with roofs that have absolutely no slope. Therefore, it is recommended that you choose the following slopes of the roofs - with light winds it can have a value from 35 to 40 degrees, with strong winds the optimal angle of the roof slope is 15-25 degrees.
In the area where precipitation falls in large quantities (we are talking about snowfalls, hail and rain), the angle of inclination can be increased to 60 degrees. It is most suitable because it allows you to minimize the load on the roof from the snow cover, as well as melt water and a lot of moisture during rain.
Taking into account all of the above, the value of the angle of inclination of the roof is calculated, focusing on a range from 9 to 60 degrees. Designers, as a rule, make the appropriate calculations and usually stop at values that range from 20 degrees to 45.
What is attractive with such a roof angle? The fact that you can use any roofing material - metal, corrugated board, slate, etc. However, each finishing material is distinguished by its requirements, which are taken into account when constructing the roof structure.
- The use of surfaced materials is most suitable when the roof has a slope of 0-25%. When the slope is 0-10%, the material must be laid in three layers. If the value of the angle of inclination is in the range of 10-25%, you can do with one layer, but the material should be sprinkled.
- Asbestos-cement corrugated sheets (slate) cover roofs with a roof slope of up to 28%.
- The tile is used when the roof has a slope of at least 33%.
- The steel coating is laid on the roof with an inclination angle of less than 29%.
Material consumption directly depends on the slope of the roof. The larger it is, the greater the consumption of finishing material. As a result, a flat roof in this respect will cost less than a roof having a tilt angle of 45 degrees.
If you know the value of the slope of the roof, then calculate the amount of required material is not difficult. The same can be said about the height of the roof structure.
Let us dwell on each specific type of roofing.
Roofing
When compared with other roofing materials, the metal tile has considerable weight. Therefore, when constructing a roof structure using such a topcoat, you should take into account all the nuances and try to build it so that it has a minimum angle of the roof slope.
This issue deserves special attention in areas with very strong winds. As you know, the load from the wind has a strong and negative effect on the roof. The calculation of the roof structure in this case must be done especially carefully. When the angle of inclination of the roof is large, “bloating” of the roof can occur, which will entail an increase in load, which will affect the entire structure. In turn, this can lead to premature destruction of the roof.
Roofs that are covered with metal should have a minimum angle of inclination within 22 degrees. Empirical evidence suggests that this indicator prevents the accumulation of moisture at the joints of the roofing. They are protected from unwanted seepage of water in the form of thawed snow or rain.
Important! The minimum slope of the roof, when there is such a need, can be at least 14 degrees. If soft tiles are used as a coating, then the minimum value is reduced to 11 degrees. In this case, it would be correct to arrange an additional continuous crate.
Roofing
It is known about corrugated board that it takes the place of one of the most popular roofing materials. Everyone knows its advantages in the form of low weight and ease of installation. Mounting profiled sheets on the roof is not difficult.
Important! It should be noted that when installing such a roof, the requirements for the minimum angle of the roof slope are more than 12 degrees (you should look at the recommendations of the manufacturers).
Roofing using rolled “soft” materials
When the roof is made of soft types of roofing, then we are talking about roofing material, ondulin, polymer (membrane) roofing. When deciding how to calculate the angle of the roof, the following is taken into account:
- The number of coating layers. Depending on them, the angle of inclination of the roof structure can be from 2 to 15 degrees.
- When covering in 2 layers, it would be good to stop at a roof angle of 15 degrees.For a three-layer layer, it is quite enough to have a slope within 2-5 degrees.
- Membrane coatings that are optimal for any type of roof, including the most difficult in its geometry, are placed on roofs with a slope of 2-5 degrees.
Without a doubt, the angle of the roof will be chosen by the owner of the building. He must take into account that the roof is designed for temporary and permanent loads. Temporary are precipitation and their weight. These include wind, which exerts pressure on the roof structure and the topcoat itself. When constant loads are mentioned, then we are talking about the weight of the roof structure itself and the finish material.
Such a structural element of the roof as a crate depends on the inclination of the roof - its type, pitch and design. For example, the lower the angle of inclination, the shorter the pitch of the crate in the roofing system should be. The minimum slope of the roof provides for the step of the crate, which is 35-45 centimeters.
One of the main issues is the question of the amount of material for the finish coating, which must be calculated and purchased. This trend is observed here - a greater slope of the roof requires a greater consumption of material.
I would like to offer some practical tips that will be useful when selecting material for the roof:
- with a small slope of the roof (less than 10 degrees), the roof can be covered with material containing stone crumb or gravel (5 mm thick for crumb and 15 mm for gravel).
- when the angle of the roof slope is more than 10 degrees, then a basic waterproofing device from bitumen will be required. In the case of roll materials, additional protection is necessary. Such a coating, as a rule, is a color.
- covering the roof with such roofing material as corrugated board or asbestos cement sheets provides for sealing of butt joints. Joints in this case are doubled.
We calculate the angle of the roof
The calculation of the angle of the roof depends on the height of the ridge. How high the roof will be in the ridge depends on the functional purpose of the attic space.
When a full attic is made from the attic, the angle of inclination is calculated as follows:
For example, the end face of the roof (width of the pediment) is 6 meters. This figure is divided in half (6: 2 = 3). The height of the roof in the ridge is always 1.8 meters as standard.
Next, we determine the sine of the angle, which, according to the geometry in a right-angled triangle, is equal to the ratio of the adjacent leg to the opposite leg. The sine, according to the formula, is equal to:
Sin A = a / b = 3 / 1.8 = 1.67
Using the Bradis table, an approximate value is found that has a roof tilt angle with a value of Sin A = 1.67 - this value is in the range of 58-59 degrees. You can stop at a maximum value of 60 degrees, which will become our desired angle of inclination of the roof slope.
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