If strong winds are a frequent visitor in your region, it is recommended to set the minimum roof slope when building roofs. This is due to the fact that with an increase in the angle of inclination of the slopes, the "sail" increases. Consequently, the load on the supporting structures of the roof increases. Further on this in more detail.
A low-slope roof is a roof, the installation of which was carried out on the basis of the smallest recommended angle of inclination of the slopes. Each roofing material has its own minimum slope.
What is a roof pitch? This is the angle of the roof to the horizon. What is it for? Any person can tell that the greater the slope, the faster the water will drain from this surface.
Therefore, on a roof with a large slope angle, snow, dirt, water and leaves will not linger.In addition, the designs of such roofs are simpler, almost any roofing materials can be used for covering, and the roof itself looks much more interesting. And what affects the angle of inclination?
What determines the slope of the roof?
No one will argue that the main function of the roof is to protect the structure from external factors.
That is, the roof must be waterproof, reliable and durable. Therefore, it is necessary to approach the choice of design and roofing materials with all responsibility.
And here the angle of inclination of the roof will play an important role, and it depends on the following factors:
- Wind. The higher the roof, the higher the “sail”, the resistance to wind. Low-slope roofs are used in the construction of buildings in areas where there are strong winds.
- Precipitation. The rate of water runoff on low-slope roofs is much lower than on high roofs. Consequently, dirt and leaves can linger on them, especially if materials with a rough surface were used for coating.
- Roofing materials. For each roofing there is a minimum angle of inclination at which this material can be used.
- Traditions. In each region, preference is given to one or another roof design. And this factor should also be taken into account.
For your information! Progress does not stand still. There are new roofing materials that can solve many problems. Architects can create projects that will not only fulfill the wishes of customers, but will also comply with all the norms and traditions for the region.
How is slope angle measured?
The slope of the roof is measured in degrees or percent. Their ratio is shown in the table in Figure 2.The slope angle is measured using an inclinometer or a mathematical method.
An inclinometer is a rail with a frame, between the bars of which there is an axis to which a pendulum + division scale is attached. If the staff is in a horizontal position, the scale will read zero.
To determine the angle of the roof, the rail is held perpendicular to the ridge. On the scale, the pendulum will show the slope of the given roof in degrees.
Mathematically, this value is found as follows. What is the angle of inclination of the slope - the ratio between the height of the ridge and half the laying of the roof (the width of the building divided by two). .
To get the value as a percentage, we multiply the resulting number by 100. Further, if you need to find out the value of the slope in degrees, we translate it according to the table. To make it clearer, let's look at an example.
The width of the building is 7 m, the height of the ridge is 0.6 m. We get: 0.6: (7/2) \u003d 0.17, now we multiply 0.17x100 \u003d 17%. We look at the table: 17% \u003d 10 degrees. That is, the angle of inclination of the roof will be 10 degrees.
The designation of the roof slope in the drawings can be either in degrees or as a percentage. The slope is indicated by the English letter "i".
Some may indicate in ppm, but they say this is not very convenient.
In SNiP II-26-76, this value is indicated as a percentage. That is, to whom it is convenient, at the moment there are no strict rules on this matter.
Now consider the minimum value of the roof slope angle for the most common roofing materials.
Minimum roof pitch for roofing materials:
- membrane coatings.Can be used for roofs of any design. The minimum slope is 2 degrees.
- Roll materials. When laying 3 or more layers, the minimum angle will be 2-5 degrees. If you plan to lay two layers or less, the angle will be 15 degrees.
- Ondulin - 6 degrees.
- Soft tiles. It can be used at an angle of inclination of 11 degrees, but at the same time the material is laid on a continuous crate.
- Decking. The minimum angle of inclination will be 12 degrees, but it is recommended to additionally coat the joints with sealants.
- Metal tile - 14 degrees.
- Slate, tiles. So that moisture does not linger on the roof and does not seep into the roof at the junction, the minimum angle of inclination should be 22 degrees.
Dealt with the materials. Now we list some points that should be taken into account when building roofs with a small slope.
Namely:
- Properly equip the drainage system. It can be internal (water receivers are located on the roof itself and the slope is made in their direction) and external (water flow outside the roof, along the gutters).
- At roof pitch less than recommended by 10, a waterproof lower roof should be installed.
- The less roof pitch angle, the larger the under-roof ventilation gap.
- If the roof slope is less than 10 degrees, ventilation should be from slope to slope.
- If bituminous tiles are used as roofing, and roof pitch is 6 degrees, experts recommend waterproofing membranes throughout the base of the roof.
From all of the above, we can conclude: the minimum roof slope is not a single value for all roofs.For each roofing, this value is different, but under certain conditions it can be reduced.
But the use of materials, with slopes less than recommended, significantly increases the cost of roof construction, although this is not always justified aesthetically.
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