Slope and slope angle for a metal roof

The metal tile is considered one of the most convenient and popular roofing materials. Featuring a high bearing capacity, strength, ease of installation, metal tiles are little subject to mechanical stress. When planning the layout of the material, it is necessary to calculate the correct slope for the metal tile and observe the technological details of installation. Then the roof will serve for a long time and will not require an early renewal.

What is a slope, the optimal slope angle

The slope of the roof is an important defining structure, formed by the angle cut off by the floor plane and the roof slope. The indicator is expressed as a percentage or degrees, calculated by dividing the height of the ridge by 1/2 of the width of the building. The angle of inclination of a roof made of metal tiles is regulated by SNiP and the supplier's instructions. The indicator depends on factors such as:

1. Roof covering application.
2. The ability of the roof to effectively remove natural precipitation, withstand winds and other climatic phenomena.
3. Roofing price.
4. The mass of the roofing cake.

A fairly new coating, metal tile, is not so strictly regulated by standards. Therefore, the manufacturer himself often advises the minimum angle indicator, based on the technical characteristics of the product. The calculation is made according to the thickness of the sheet, the bearing capacity of the base and the method of laying the roofing. However, there are optimal values ​​that you should rely on:

• With a slope of 6 meters in length, the minimum slope according to SNiP must be at least 14 °.
• The permissible slope of the roof of metal tiles should be in the range of 14-45 °.
• The optimal value of the angle is 22°, this indicator is sufficient for the normal removal of precipitation with a slope area of ​​​​less than 6 meters.

The choice of the roof slope is not always simple, therefore, based on the indicators of SNiP, one should take into account the following recommendations for the equipped slope slope:

1. The level of snow load in the construction region. To determine the indicator, you need to take information from the directory and calculate the average annual amount in the winter. The thicker the snow cover, the greater the level of slope, otherwise the snow mass will linger on the roof, which will lead to deformation of the sheets.
2. Wind load - the indicator also depends on the characteristics of the region. At the maximum intensity of wind flows, the angle of inclination is small, which reduces the windage of the slopes.

Advice! The number of hurricanes, tornadoes and other natural disasters is also taken into account. The information is taken from reference books.

Features of metal roofs with a small slope

The lowest slope angle is 14 °, but experienced roofers lay materials when calculating an angle of 10-14 °. And to ensure the reliability of the roofing carpet and reduce the risk of leaks, the following actions are performed:

• The frequency of the laths in the crate increases by reducing the inter-rafter step.
• The rafter system is strengthened by means of a frequent or continuous crate.
• Significantly increase the number of overlaps! Despite the recommendations of manufacturers for a horizontal overlap of 8 cm, a vertical overlap of 10-15 cm, the overlap increases by the width of the wave. Thanks to this method, the strength of the roofing carpet increases and the risk of leaks on the roof of a small slope is eliminated.
• Carefully seal the joints with a silicone-based sealant.

Advice! All measures taken are temporary, so a visual inspection of the roof once a year will not hurt.

Determination of the roof slope by geometric dimensions or in degrees

The formula for calculating the steepness of the slope for a roof made of metal by size, for example, for a gable roof, is calculated using the following formula: I = H / (1/2L), where:

• I - the desired angle for the metal tile;
• H - the distance from the border of the ceiling to the ridge, that is, an indicator of the height of the rafter structure;
• L - dimensions of the width of the building.

To find the percentage, the resulting index i is multiplied by 100. And for the expression in degrees, you should use the trigonometric function or find the value in the corresponding table:

Important! This type of calculation is suitable for single, double-pitched roofs. For a single-slope, the entire span length is taken into account. In the case of arranging a roofing carpet with an asymmetrical slope, the roof angle is calculated from the distance from the projection point of the ridge element to the ceiling for each slope separately.

The optimal angle for a roof with complex structural elements is taken into account by the correction factor for the projection in the horizontal direction:

• Roof angle 1: 12 (7°) - K = 1.014;
• 1:10 (8°) = 1.020;
• 1:8 (10°) = 1.031;
• 1:6 (13°) = 1.054;
• 1:5 (15°) = 1.077;
• 1:4 (18°) = 1.118;
• 1:3 (22°) = 1.202;
• 1:2 (30°) = 1.410.

Criteria for choosing the angle of inclination

When calculating the angle of inclination of a roof for a metal tile, you need to know that a small steepness has its advantages:

1. economical consumption of materials;
2. reduction in the weight mass of the roofing carpet, the sheet windage index, which minimizes the risk of defects during heavy winds;
3. convenience and simplicity of arranging drainage systems.

But there are also disadvantages, if the slope of the roof is minimal, then:

1. it is necessary to seal the joints as much as possible, since the almost complete absence of a drain increases the possibility of moisture penetration through the attachment points;
2. it will be necessary to remove snow blockages on the roof more often so that the metal tile is not subjected to increased load;
3. the need to equip a powerful crate will require a calculation of the bearing capacity of the base and complicate the fastening of roofing elements;
4. under a flat roof, it is not always possible to equip spacious residential / non-residential premises.

But if the slope of the roof is large, for example, 45 °, then, despite the free melting of the snow cover, the mass of the coating is increased, due to which the sheets simply slide off. The way out is to strengthen the fasteners and strict adherence to the installation technology of the roofing carpet. In addition, when the angle of inclination of the metal roof is too steep, the consumption of roofing material increases, as with the arrangement of curly slopes.

In order not to calculate which angle will be better, take as a basis the recommendations of experienced roofers: for shed roofs it is 20-30 °, for gable roofs - 25-45 °. And a little advice: when arranging the lathing with frequent steps, a kind of shock-absorbing cushion is obtained that strengthens the roofing carpet. Knowing the calculation formula, it is easy to calculate different options for the steepness of the slopes and decide which angle to give preference to, depending on weather, climatic conditions and the financial component: whatever one may say, material consumption is less on roofs with a minimum slope.