Minimum roof slope

A modern roofing structure cannot be ideally flat, since anyway, precipitations that fall as snow or rain should be discharged from its surface. That is why when installing flat roofs, it is necessary to observe the rule of the so-called leveling, providing for a slight inclination of the flooring to one side. The presence of such a slope allows you to divert rainwater from the surface of the coating and collect it from the roof fence, where special drain holes are prepared for this purpose in advance. The minimum slope of the roof, as a rule, is chosen taking into account the following parameters of the mounted coating (and its performance is also taken into account):

• used roofing material;
• type of roof (classic or inversion);
• the number of waterproofing layers;
• average annual rainfall (snow load);
• wind loads on the structure.

SNiP requirements

The dependence of the angle of inclination on various factors is governed by special building codes and regulations (SNiP). Among the requirements for a flat roof slope of SNiP II-26-2010 Roofs, the following provisions are particularly important with regard to its dependence on the coating material:

• depending on the type of waterproofing used, the angle of inclination of the roof can vary from 1.5 to 10 ?;
• angles of greater magnitude (up to 2?) are chosen very rarely, due to the difficulty in selecting a soft coating that would not slip to the base of the roof at high air temperatures;
• the minimum slope of the so-called flat roof should be at least 1-1.5 ?.

Note! There is a definite relationship between the slope of the roof structure and the number of layers of waterproofing coating that are laid on it. The more significant this value is, the faster the precipitations will be removed from it, and, therefore, the number of waterproofing layers may be less.

Dependence on the structure of the roofing material

Roofing materials used to close the roof differ in their structure, according to which they have a more or less smooth surface. With an insufficiently smooth (rough) coating structure, the likelihood of water and snow retention on it is noticeably increased.

This is what determines the dependence of the minimum angle of inclination on the roofing material used. Next, we consider the specific values ​​of this indicator for different types of coatings.

Metal tile

The smallest angle of inclination of the slope in the arrangement of the roof of the tile is usually chosen not less than 15? (for some material models this value may be 14?). If necessary, reduce this figure, some manufacturers advise to handle the joints of metal sheets with a special waterproof sealant that retains its properties at low temperatures.

Note! If the slope is too gentle, precipitation will linger in certain places of the roof and leak into the joints during heavy rain. And this will lead to an additional load on the roof in those areas where they are delayed.

Partially get rid of this drawback is due to the use of samples of tiles with greater wave height.

Profulist

When using this type of roofing we consider the indicator should have a slightly lower value (as a rule, it is equal to 12?).

In the case of the manufacture of roofs from a professional sheet with a smaller bias when installing them, it is necessary to observe the so-called two-wave overlap, and at angles of the order of 15? and above it will be enough overlap of 20 cm. At the same time, with an increase in the angle of inclination, the pitch of the batten to be laid under the coating should also increase.

With a minimum angle of inclination of the roof (that is, when it is almost flat), a continuous crate should be used, which increases the load capacity of the supporting structure.

Soft roof

There are several types of soft roofs, differing in the material from which they are made:

1. Shingles. In case of using the so-called soft roof (shingles - in particular) as a coating, the lathing for it should be made in the form of a solid base made of plywood sheets (OSB). The minimum slope slope for this type of roofing is at least 11 ?.
2. Bituminous coatings. For soft coatings of this category, the minimum roof slope has the lowest value (its value, as a rule, does not exceed 2?). But at the same time, as noted earlier, you will need to increase the number of layers to be laid. In the case when for technical reasons it is not possible to lay more than 1-2 layers of bitumen material - you will have to increase this figure to 15 ?. The minimum angle of inclination of the coating made on the basis of ondulin, as a rule, does not exceed 6 ?. This roofing material is the most preferable for laying the roofs with a low angle of inclination of the slopes, but for its installation you will need a sheathing of a continuous type.
3. Clay tile (slate). When laying hard clay tiles or a classic slate sheet that has an uneven and snow-holding surface, the slope of the slopes should be at least 22 ?. At the same time, it is necessary to pay attention to the calculation of the system of rafters, which, due to the large weight of the material, will experience considerable loads. In addition, we should not forget about the additional loads on the rafters, which are possible with the accumulation of large amounts of snow on the roof, as well as with powerful gusts of wind in bad weather.

Taking into account all these factors, the requirements for the load capacity of the roofing system increase significantly.

Note! At production of a roof from a tile or slate covering with a tilt angle less than 22? you will have to recalculate the entire rafter system, since the loads on it in this case increase many times.

Sandwich panels

According to the requirements of the SNiP, the minimum slope of the sandwich panel flooring should be about 5? (provided that the coating is solid and does not have joints along the entire length). Immediately make a reservation that this indicator is valid only for cases when the roof does not provide built-in windows or other elements that violate the integrity of the solid coating.

In the presence of all of these violations of the integrity of the flooring the minimum angle of the roof of such a roof should be at least 7?

Even at the design stage of the future roofing system (and, in particular, when choosing a roof construction option with a certain angle of inclination) it is necessary to take into account the climatic features of your area. In the event that precipitation in your area falls quite often - the minimum indicator of the slope of the slope under the sandwich panel should be at least 40? But in areas with a small average annual precipitation, a slope of about 7–22? Is considered optimal.

Note! Before arranging roofs with large slopes of ramps, it is necessary to take into account the fact that in this case you need a greater amount of building material.

On the other hand, at a lower value of this indicator, water will accumulate on the roof, which over time can destroy the waterproofing seals of the panel joints. And in the offseason (with the onset of thaws and frosts) ice build-up of moisture accumulates, which can damage the protective layer of the sandwich panels, as well as their metallic sheath.

With a small slope of the roof (less than 7?) There is no need for additional mounting of panels on a frame basis of reinforced concrete, wood or metal. On the roof structures with a large angle of inclination additional fasteners are required.

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