Calculate the roof slope. Roof slope: why is this parameter so important and how to calculate it correctly

The roof of the house must be reliable and beautiful, and this is possible with the correct determination of its angle of inclination for a given type of roofing material. How to calculate the roof slope angle is in the article.

Purpose of the under-roof space

Before calculating the angle of the roof, you need to decide how it will be used. attic space. If you plan to make it residential, the angle of inclination will have to be large - so that the room is more spacious and the ceilings are higher. The second way out is to make a broken line. Most often, such a roof is made of a gable roof, but it can also have four slopes. It’s just that in the second option the rafter system turns out to be very complicated and you simply cannot do without an experienced designer, and the majority prefer to do everything on their own, with their own hands.

When increasing the roof pitch there are a few things to remember:

This does not mean that low-slope roofs are better. They are cheaper in materials - smaller area roofs, but have their own nuances:

• They require snow retention measures to prevent avalanches.
• Instead of snow retainers, roof heating can be used to gradually melt snow and drain water in a timely manner.
• With a small slope, there is a high probability that moisture will flow into the joints. This entails enhanced waterproofing measures.

So roofs with a low slope are also not a gift. Conclusion: the angle of inclination of the roof must be calculated in such a way as to find a compromise between the aesthetic component (the house should look harmonious), practical (with a living space under the roof) and material (costs must be optimized).

Angle of inclination depending on roofing material

The roof on a house can have almost any shape - it can have low slopes, it can have almost vertical slopes. It is important to correctly calculate its parameters - cross-section rafter legs and the step of their installation. If you want to lay a certain type of roofing material on the roof, you need to take into account such an indicator as the maximum and minimum angle inclination for a given material.

The minimum angles are specified in GOST (see table above), but often manufacturers give their recommendations, so it is advisable to decide on a specific brand at the design stage.

More often, the angle of the roof slope is often determined based on how their neighbors are made. From a practical point of view, this is correct - the conditions of nearby houses are similar, and if the neighboring roofs are in good condition and do not leak, you can take their parameters as a basis. If there are no roofs in the neighborhood with the roofing material that you plan to use, you can start calculations with average values. They are shown in the following table.

Type of roofing material	Recommended tilt angle minimum/maximum	What slope of the slope is most often done
Roofing made of roofing felt with sprinkles	3°/30°	4°-10°
Two-layer tar paper	4°/50°	6°-12°
Zinc with double standing seams	3°/90°	5°-30°
4-groove tongue and groove tiles	18°/50°	22°-45°
Dutch tiles	40°/60°	45°
Regular ceramic tiles	20°/33°	22°
Corrugated sheeting and metal tiles	18°/35°	25°
Asbestos cement slate	5°/90°	30°
Artificial slate	20°/90°	25°-45°
Straw or reeds	45°/80°	60°-70°

As you can see, in the “how they do it” column, in most cases there is a significant range. So it is possible to vary appearance buildings even with the same roof. After all, in addition to its practical role, the roof is also a decoration. And when choosing the angle of its inclination, the aesthetic component plays an important role. This is easier to do in programs that make it possible to display an object in a three-dimensional image. If you use this technique, then calculate the angle of inclination of the roof in this case - select it from a certain range.

Influence of climatic factors

The angle of the roof is affected by the amount of snow that falls during the winter in a particular region. Wind loads are also taken into account during the design.

Everything is more or less simple. According to long-term observations, the entire territory of the Russian Federation is divided into zones with the same snow and wind load. These zones are mapped and shaded different colors, so it's easy to navigate. Using the map, determine the location of the house, find the zone, and use it to determine the value of the wind and snow load.

Calculation of snow loads

There are two numbers on the snow load map. The first is used when calculating the strength of a structure (our case), the second is used when determining the permissible deflection of beams. Once again: when calculating the angle of inclination of the roof, we use the first number.

The main task of calculating snow loads is to take into account the planned roof slope. The steeper the slope, the less snow can be retained on it; accordingly, a smaller cross-section of rafters or a larger pitch for their installation will be required. To take this parameter into account, correction factors are introduced:

• tilt angle less than 25° - coefficient 1;
• from 25° to 60° - 0.7;
• on roofs with a slope of more than 60°, snow loads are not taken into account - snow is not retained on them in sufficient quantities.

As we can see from the list of coefficients, the value changes only on roofs with a slope angle of 25° - 60°. For others, this action makes no sense. So, to determine the actual snow load on the planned roof, we take the value found on the map and multiply it by a coefficient.

For example, we calculate the snow load for a house in Nizhny Novgorod, the roof slope angle is 45°. According to the map, this is zone 4, with an average snow load of 240 kg/m2. A roof with such a slope requires adjustment - we multiply the found value by 0.7. We get 240 kg/m2 * 0.7 = 167 kg/m2. This is only part of calculating the roof angle.

Calculation of wind loads

The effect of snow is easy to calculate - the more snow in the region, the greater the possible loads. Predicting wind behavior is much more difficult. You can only rely on the prevailing winds, the location of the house and its height. These data are taken into account using coefficients when calculating the roof slope angle.

The position of the house relative to the wind rose has great importance. If the house is located between more tall buildings, wind loads will be less than when it is located in open areas. All houses are divided into three groups according to the type of location:

• Zone "A". Houses located in open areas - in the steppe, desert, tundra, on the banks of rivers, lakes, seas, etc.
• Zone "B". The houses are located in wooded areas, in small towns and villages, with a wind barrier no more than 10 m high.
• Zone "B". Buildings located in densely built areas with a height of at least 25 m.

A house is considered to belong to a given zone if the specified environment is at a distance of at least 30 times the height of the house. For example, the height of the house is 3.3 meters. If at a distance of 99 meters (3.3 m * 30 = 99 m) there are only small one-story houses or trees, it is considered to belong to zone “B” (even if it is geographically located in a large city).

Depending on the zone, coefficients are introduced that take into account the height of the building (shown in the table). Then they are used when calculating the wind load on the roof of a house.

Building height	Zone "A"	Zone "B"	Zone "B"
less than 5 meters	0,75	0,5	0,4
from 5 m to 10 m	1,0	0,65	0,4
from 10 m to 20 m	1,25	0,85	0,55

For example, let's calculate the wind load for Nizhny Novgorod, cottage located in the private sector - belongs to group “B”. Using the map, we find the wind load zone - 1, the wind load for it is 32 kg/m 2. In the table we find the coefficient (for buildings below 5 meters), it is equal to 0.5. Multiply: 32 kg/m2 * 0.5 = 16 kg/m2.

But that is not all. We must also take into account the aerodynamic components of the wind (under certain conditions it tends to blow off the roof). Depending on the direction of the wind and its impact on the roof, it is divided into zones. Each of them has different loads. In principle, rafters can be installed in each zone different sizes, but they don’t do that - it’s unjustified. To simplify the calculations, it is recommended to take indicators from the most loaded zones G and H (see tables).

The found coefficients are applied to the wind load calculated above. If there are two coefficients - with a negative and a positive component, both values ​​are calculated, and then they are summed.

The found values ​​of wind and snow loads are the basis for calculating the cross-section of the rafter legs and the pitch of their installation, but not only. The total load (weight of the roof structure + snow + wind) should not exceed 300 kg/m2. If, after all the calculations, the amount you get is more, you need to either choose lighter roofing materials or reduce the angle of the roof.

The crowning achievement of building a house is always the roof, and what it will be like depends not only on the wishes of the homeowner, but also on how to calculate roof pitch angle.

Installing rafter legs usually does not cause difficulties if you have the necessary fasteners, however, when checking the angle at which the slopes will be laid, you can make a mistake if you do not know some of the subtleties. For example, a very high roof in an area with strong winds will be constantly subjected to heavy loads and will eventually be destroyed with a high degree of probability. Therefore, to avoid this, sometimes it is worth giving preference to a low roof that is not too spectacular, but stable. There are many such examples, but let’s consider the factors themselves that influence the height of the roof. What might she depend on?

As has already become clear, before calculating the angle of inclination of the roof, you first need to take into account climatic features region. So, for example, the sharper the gable roof, the worse it holds snow and the easier it flows off. rainwater. However, we already know what such a steep slope entails in a strong wind. In places where the sun is hot, it is better to build slopes with a minimal slope or do without them at all, that is, to make a flat roof surface, which receives and transmits heat more strongly, the larger its area. The latter increases in proportion to the steepness of the slope.

The flatter the roof, the higher the likelihood that strong gusts of wind and rain will drive moisture under the edges. roofing covering.

Among other things, you should consider how the space under the rafter system will be used - as an attic or as a residential attic. In the first case, the allowed distance to the skate is less than the average height of a person. In the second case, it is necessary that there be enough comfortable space for movement, that is, the clearance in the center of the room should be at least 2.5 meters and, preferably, at least one and a half meters at the lowest point of the ceiling. A significant impact on the angle of the roof slope can be exerted by the covering material, which can only be laid at a certain degree of slope.

The most important thing in any room is its effective area, that is, one that can be used for arranging furniture and moving, as well as for storing things. Sometimes it is difficult to use some areas of the space where the lowest point of the ceiling cladding is located. However, such places can be reserved for storing things by making built-in cabinets and cabinets there. Another thing is the free movement zone, its area directly depends on the height of the ridge, and therefore the angle of the roof.

Let's look at an example. Let’s say the width of the house is 9.5 meters. If you want space above your head within 3 meters, at least in the center of the room, then the angle between the slopes should be at least 35 degrees, since already at 30 the height of the ridge will be slightly more than 2.5 meters. However, it should be borne in mind that then the width of the space available for free movement (up to a two-meter ceiling level) will be slightly more than 3.5 meters. If you maintain the same height at the lowest points of the sloping ceiling, and at the same time make the roof angle 30 degrees, then the width of the room will be reduced to 2.4 meters. It will be most comfortable in an attic under a roof with an angle of more than 40 degrees, but it should be borne in mind that in such a structure, in comparison with a gentle slope (about 10 degrees), the wind load increases almost 5 times.

In general, the dependence of the roof inclination angle on the height of the ridge only facilitates the calculations of the rafter system.

Roof angle calculator

Choose any 2 known values, enter them.
The remaining values ​​will be calculated automatically.

However, for calculations you need to know the basics of geometry quite well. Most often, the cross-section of the roof structure on the side of the gables is a triangle, equilateral, isosceles, or another type. Accordingly, using the simplest formulas, you can calculate the length of any side and the angle adjacent to it, knowing the base and height. In this case, in addition to the measuring tape, we will need a Bradis table, since we will have to deal with tangents.

Prefabricated materials also do not tolerate steep slopes, for the simple reason that they can slide down under their own weight at the slightest prerequisite for this, such as a stormy gust of wind. However, the angle cannot be made too small, since in this case the mass of the roofing material will unnecessarily load the supporting structures, that is, rafters, sheathing and other elements. An angle of 22 degrees is considered optimal, which is sufficient to ensure that during rain, moisture flows freely and is not blown under the joints by the wind.

For corrugated sheeting and metal tiles, the minimum slope is 12 and 14 degrees, respectively, gentle enough for precipitation to drain from the roof without compromising its tightness at the joints. The steepness can increase to a greater extent without restrictions, however, taking into account the fact that a large roof area has a significant mass. Also, one should not forget about the wind load and high windage of roofs with an angle close to 45 degrees. The optimal tilt is about 27-30 degrees.

But at soft tiles, which consists of individual pieces of material of a standard size, the angle of the roof is related to the density of the sheathing. If the slopes are very flat, then the distance between the slats should be made as small as possible. This is due to the fact that snow masses can become an unbearable load for the coating. In the case where the steepness of the slopes is maintained within 30-40 degrees, the sheathing pitch is allowed to be larger, up to 45 centimeters.

In order for the roof of a building to fully perform all the functions assigned to it, it is necessary to take into account a number of parameters when creating it. One of the most important parameters of a roof is its slope, which ensures the removal of precipitation from its surface and affects the ability to withstand external loads. How to calculate the slope of the roof will be discussed in this article.

Determining the slope of the roof - what it depends on

To correctly calculate the roof slope, it is necessary to take into account several factors, among which the following stand out the most:

1. Wind loads. The slope of the slopes is greatly influenced by the wind. In order for the roof to be able to properly resist its impact, you need to choose the right angle. If the angles are too large, the load on them will be high, but an excessive decrease in the angle can also be dangerous - a flat roof can simply be torn off by a strong gust of wind.
2. Snow and rain loads. With snow, everything is quite simple - increasing the angle of inclination simplifies its descent from the roof surface. When the roof is tilted more than 45 degrees, snow will hardly linger on it. At a low angle of inclination of the roof, a snow bag may appear, which increases the load on the roof. The situation is the same with rainfall - if the angle of the roof is too low, then water can flow into the joints or even stagnate on the roof surface.

Based on these factors, you can calculate the angle of inclination of the slopes. In addition, before calculating the angle of two pitched roof, it is worth paying attention to the recommended indicators: for areas with strong winds, a slope of 15-20 degrees is suitable, and in other cases the optimal slope is 35-40 degrees. Of course, you need to understand that the calculation of a gable roof is individual, and choosing average indicators is simply undesirable.

Calculation methodology

When designing a roof, it is imperative to carry out a number of calculations, among which there should always be a calculation of the angle of inclination of the slopes. This parameter directly affects the roof structure: as the slope increases, the snow load decreases, but the impact of wind increases, therefore rafter system needs to be further strengthened. To arrange slopes at a large angle, you also need large quantity materials, which negatively affects construction costs.

Before you find out the degree of roof slope, you need to calculate the operational load on the roof, which requires two parameters:

• The total weight of the roof structure;
• Peak levels of snowfall typical for the region where construction is taking place.

A simplified calculation algorithm boils down to the following steps:

• First you need to determine the weight of one square meter roofing pie;
• The resulting value is multiplied by total area roofs;
• The mass of the roof is multiplied by a factor of 1.1.

An example of calculating the roof slope in degrees

To understand how to calculate the roof angle, it is worth considering the calculation process for specific example. For example, the following data will be taken: the sheathing has a thickness of 2.5 cm, one square meter of roofing weighs 15 kg, as thermal insulation material a 10 cm thick insulation is used, a square meter of which weighs 10 kg, and ondulin with a weight of 3 kg per square meter is used for the coating.

The calculation of the roof slope is carried out in accordance with the method described above. Substituting the available data leads to the following expression: (15+10+3)x1.1 = 30.8 kg/sq.m. The obtained value is quite acceptable - the average load on the roof of residential buildings is slightly less than 50 kg/sq.m. In addition, the formula contains a coefficient of 1.1, which slightly increases the actual weight of the roofing structure and makes it possible to subsequently replace the roofing covering with a heavier one.

How to find out the roof pitch

Between the slope roof slopes and snow load there is a direct relationship. If the roof slope angle is less than 25 degrees, then the snow load coefficient is 1, and at angles ranging from 25 to 60 degrees, then this coefficient increases to 1.25. A roof with a large slope will not be subject to snow loads at all, so they are not taken into account in the calculations.

To determine the angle of inclination of the roof, you need to use the Bradis table and a simple technique: the height of the roofing structure is divided by the length of the pediment divided by two, after which it remains to find the angle in the table that corresponds to the result obtained.

The height of the roof at the ridge is determined as follows:

• The first step is to calculate the width of the span;
• The resulting value is divided by 2;
• To calculate the height of the ridge, the result of the previous calculation is multiplied by a coefficient corresponding to a certain angle of inclination.

Using an example, the implementation of this calculation method looks like this: with a building width of 8 meters and a 25-degree roof slope, the calculated coefficient is 0.47. As a result of substituting the values, we obtain an expression of the following form: 4x0.47 = 1.88 m. The resulting value is the height of the roof corresponding to the available initial data.

Choosing a roof covering depending on the slope of the roof

There is a wide range of roofing materials on the market, so there is no choice suitable option there won't be any problems. Roof coverings differ in characteristics and application possibilities, and all their parameters must be studied before measuring the angle of the roof - only in this case will it be possible to create a reliable and efficient structure.

When choosing a roofing material, you should consider the following recommendations:

1. If the angle of inclination of the rafters is from 2.5 to 10 degrees, then coverings made of stone chips or gravel are best suited. In the first case, the top layer of coating has a thickness of 3-5 mm, and in the second - 10-15 mm.
2. When the slope is more than 10 degrees, the best option would be coarse-grained or roll materials, supplemented with bitumen waterproofing.
3. For the installation of pitched roofs with a slope angle of no more than 20 degrees, corrugated sheets or asbestos cement sheets are usually used. All seams and joints between roofing materials must be treated with sealant.
4. If the angle of the roof is within 20-60 degrees, then it is most often covered metal sheets. In this case, the joints of materials must be sealed.

Conclusion

Knowing how to find out the angle of inclination of a roof in degrees will significantly simplify the design process and allow you to create the most reliable design, which can well protect the building box from precipitation, wind and cold.

Roof slope

The slope of the roof slopes - what it depends on and how it is measured.

Such an important fact for the roof is its slope. Roof slope- this is the angle of inclination of the roof relative to the horizontal level. According to the angle of inclination of roof slopes there are low slope(sloping), average inclination And roofs with steep(highly inclined) stingrays.

Low slope roof that roof, the installation of which is carried out based on the smallest recommended angle of inclination of the slopes. So, each roofing has its own recommended minimum slope.

What does the slope of the roof depend on?

• From the ability of the roof to protect the structure from external factors and influences.
• From the wind- the greater the roof slope, the more value incident wind loads. With steep slopes, wind resistance decreases and windage increases. In regions and places with strong winds, it is recommended to use a minimum roof slope to reduce the load on bearing structures roofs.
• From roofing covering (material) - For each roofing material there is a minimum angle of inclination at which this material can be used.
• From architectural ideas, solutions, local traditions- so in different regions preference is given for one or another roof structure.
• From precipitation: snow loads and rainfall in the region. On roofs with a large slope, snow, dirt and leaves will not accumulate in large quantities.

What is the roof pitch angle measured in?

The designation of the roof slope on the drawings can be either in degrees or as a percentage. The roof slope is indicated by the Latin letter i.

In SNiP II-26-76, this value is indicated as a percentage (%). IN this moment There are no strict rules for indicating the size of the roof slope.

The unit of measurement for roof slope is degrees or percentages (%). Their ratios are shown in the table below.

Roof slope degree-percentage ratio

degrees % degrees % degrees % 1° 1,75% 16° 28,68% 31° 60,09% 2° 3,50% 17° 30,58% 32° 62,48% 3° 5,24% 18° 32,50% 33° 64,93% 4° 7,00% 19° 34,43% 34° 67,45% 5° 8,75% 20° 36,39% 35° 70,01% 6° 10,51% 21° 38,38% 36° 72,65% 7° 12,28% 22° 40,40% 37° 75,35% 8° 14,05% 23° 42,45% 38° 78,13% 9° 15,84% 24° 44,52% 39° 80,98% 10° 17,64% 25° 46,64% 40° 83,90% 11° 19,44% 26° 48,78% 41° 86,92% 12° 21,25% 27° 50,95% 42° 90,04% 13° 23,09% 28° 53,18% 43° 93,25% 14° 24,94% 29° 55,42% 44° 96,58% 15° 26,80% 30° 57,73% 45° 100%

You can convert the slope from percent to degrees and vice versa from degrees to percent using an online converter:

Slope converter - online calculator

from degrees to percentages and from percentages to degrees Go

Roof slope measurement

The slope angle is measured using an inclinometer or mathematically.

Inclinometer- this is a rail with a frame, between the slats of which there is an axis, a division scale and to which the pendulum is attached. When the staff is in a horizontal position, the scale shows zero degrees. To measure the slope of the roof slope, the inclinometer rod is held perpendicular to the ridge, that is, at a vertical level. On the inclinometer scale, the pendulum indicates the slope of a given roof slope in degrees. This method of measuring slope has become less relevant, since various geodetic instruments for measuring slopes have now appeared, as well as drip and electronic levels with inclinometers.

Mathematical calculation of slope

• Vertical height (H) from the top point of the slope (usually the ridge) to the level of the bottom (eaves)
• Laying (L) - horizontal distance from the bottom point of the slope to the top

Using mathematical calculation, the roof slope is found as follows:

The slope angle i is equal to the ratio of the roof height H to the foundation L

In order to express the value of the slope as a percentage, this ratio is multiplied by 100. Next, to find out the value of the slope in degrees, we translate using the table of ratios located above.

To make it clearer, let's look at an example:

Laying length 4.5 m, roof height 2.0 m.

The slope is: i = 2.0: 4.5 = 0.44 now multiply by × 100 = 44%. We translate given value according to the table in degrees and we get - 24°.

Roof slope table

Construction of the roof is an important final stage of building a house. The roof protects the house from aggressive influences environment, gives the building an aesthetic appearance.

Flat roofs predominate in multi-storey buildings; in private houses and cottages - pitched roofs. The angle of the roof is an important calculation indicator.

Types of roofs and their dependence on the angle of inclination

There are several types of roofs, depending on the roof structure:

• Shed roof- an inclined plane lying on walls of different heights.
• Gable roof– consists of two slopes, is reliable and simple.
• Hip roof– consists of 4 slopes with cut off tops.
• Hip roof– several isosceles triangles connected by vertices.

If the roof slope is more than 10°, then the roof is considered pitched.

What does the slope of the roof depend on?

• from the wind
• from the roofing
• from architectural ideas
• from precipitation ( snow and rain)

Roof slope is the angle of inclination of the roof relative to the horizon.

The slope indicator allows:

1. Pick up roofing material
2. Correctly calculate the number of snow holders

Knowing one of the values ​​​​from the table, you can find the remaining values.

Minimum slope for roofing materials (coatings)

Roof type	Minimum roof slope		in the ratio of the height of the slope to the foundation	in degrees	V %
	Roofs made of rolled bitumen materials: 3 and 4 layers (fused roofing)	0-3 0		up to 5%	until 1:20
Roofs made of rolled bitumen materials: 2-layer (fused roofing)	from	15
Seam roofing	from 4 0
Ondulin	5 0	1:11
Corrugated asbestos cement sheets (slate)	9 0	16	1:6
Ceramic tiles	11 0	1:6
Bituminous shingles	11 0	1:5
Metal tiles	14 0
Cement-sand tiles	34 0	67%	1:1,5
Wooden roof	39 0	80%	1:1.125

Example No. 1.

H = 2 m
I = 2.86 m

Let's calculate the roof angle (i): 2/2.86 = 0.699. This is 35° according to the table.

Example No. 2

The roof slope coefficient is 1.006. Find: degree of roof slope.

According to the table, this coefficient corresponds to a value of 6° degrees.

Calculation of roof slope angle

The roof is one of the essential elements any building. It is this that reliably protects the building from exposure negative factors environment, from precipitation.

Of course good design must be waterproof, provide high-quality drainage of atmospheric water, and also have high resistance to fire. At the same time, the roof must be convenient for repairs during its operation.

It should be remembered that the reliability and quality of the roof of your home will directly determine how long the building itself will last. Currently, many homeowners prefer a sloping roof.

I must say, this design has several obvious advantages. In addition, you should correctly calculate the angle of inclination of the roof.

Pros of a sloping roof

Simple structures, such as lean-to and gable roofs, hip or attic, have always been and remain the highest quality and reliable options. Without a doubt, the advantage of a sloping roof lies precisely in harmonious combination excellent quality and ease of execution.

This roof consists of base element roofs, as well as sheathing and rafters.

As for the roof, it serves to protect the building from exposure natural phenomena, snow and rain. The rafters, as well as the sheathing, support the entire structure and transfer the load to the walls.

Rice. 1 Calculate the angle of the roof

It should be noted that sloping roof protects the building from precipitation due to a certain slope of the roof.

Before proceeding with the installation of a sloping (or, as it is also called, pitched) roof, it is necessary to accurately calculate the angle of inclination of the roof.

Even for those people who are not specialists in the field of roof construction, it is quite obvious: the smaller the angle of inclination, the more problems with tightness will subsequently arise.

And this absolutely does not depend on what building material you choose to cover your roof.

Factors that influence the choice of inclination angle

Of course, you should know what factors need to be taken into account when calculating the pitch of your roof. So, among the most important parameters are:

• Wind. It goes without saying that the roof will offer more wind resistance the higher the slope. However, too large an angle of inclination is quite dangerous for the roof. So, for example, when the angle increases from the minimum (11 degrees) to 45 degrees, the wind load increases five times. But on the other hand, when choosing a very small angle of inclination, another problem arises: with a strong gust of wind, the roof can simply be torn off;
• Snow and rain. It is quite obvious that snow melts better from a roof that has a large angle of inclination. So, if it is more than 45 degrees, complete snow rolling is ensured. And the higher the angle of inclination, the more airtight the beautiful roof of your roof will be. This is easy to explain: the fact is that when exposed to the roof, the wind usually drives atmospheric water under the joints of the roof. But the more you pitch the roof, the less likely it is that water will get under the joints of the roofing materials.

Based on these factors, it is necessary to calculate the angle of inclination of the roof. For areas with strong winds, experts recommend a roof slope of 15-20 degrees, and for areas with normal winds - about 35-40 degrees.

However, it should be remembered that the calculation of the roof slope angle must be done individually for each specific building.

It should also be emphasized that when making calculations, it is imperative to take into account the characteristics of not only the climate of the area, but also the design of the building itself.

Rice. 2 Shapes of pitched roofs

Calculation methods

It should be remembered that selecting the correct angle is a very important stage in the design of the future roof of the building. Typically, the roof slope ranges from 11 to 45 degrees; of course, there are exceptions.

If you increase the angle of inclination, the snow load on the roof decreases accordingly.

But at the same time, the higher the indicator, the stronger the impact of the wind. This leads to the fact that when constructing a roof, more durable Construction Materials, rafters and sheathing. This means that the future roof will cost you more.
roof slope calculation

Remember: the angle of inclination directly affects not only the quality, but also the quantity of material for roofing.

The larger the angle, the correspondingly big money the roof will cost.

A certain slope angle is given to the roof depending on the selected material, as well as climatic conditions. If there is a lot of precipitation in the area, the roof slope should be steeper.

The appropriate angle of inclination of the future roof can be determined taking into account the expected load. How to calculate the load? To do this, you need to take two indicators into account:

• Weight of the future structure;
• Snow load for a given area.

First of all, you need to take the weight per square meter of each roofing layer, and then add up the indicators for all layers. The next step: multiplying the resulting result by 1.1.

A clear example of such calculations

Let's assume the thickness of your sheathing is 2.5 centimeters, and 1 square meter will weigh 15 kilograms. You plan to lay insulation 10 centimeters thick: the weight of this material is about 10 kilograms per square meter.

You will also have to use Ondulin, weighing 3 kilograms per square meter.

So, our calculation: 15+10+3 * 1.1 = 30.8 kilograms per square meter. According to average indicators, for residential buildings the load on the roof usually does not exceed 50 kilograms per square meter.

It should be noted that for a number of coatings the permissible load is greatly overestimated, however, you do not need to neglect this.

Suppose you decide to change your roof in twenty years, and the roofing carpet will be heavier than before. In this case, the same reliability factor of 1.1 is required - it must be taken into account as a safety factor.

Finally, we will calculate the load from the roof’s own weight. Let's call it H1 for simplicity. It will be equal to:

H1 = 50kg/sq.m*1.1 = 55 kg/sq.m.

Learning to use the Bradis table

When it comes to snow load, the ratio will depend on what angle you choose for your roof. So, if the slope is less than 25 degrees, the coefficient is 1, and if it is from 25 to 60 degrees, then the coefficient is 1.25.

But if you choose a tilt angle of more than 60 degrees, you do not need to take into account the load from snow.

If you need to find the angle of inclination of the roof, use the Bradis mathematical table (tangent table).

The height at the ridge should be divided by? the length of the pediment, and using the corresponding value in the table, find the angle of inclination.

But in order to mathematically calculate the height of the ridge, you should calculate the width of the span of the house, divide this figure by two, and then multiply by relative size, which will be individual for a certain angle of inclination.

You can also use a square to determine the angle of inclination and height of the ridge.
calculation of roof slope.

Let's try to figure it out using a specific example. The width of the future building is 8 meters. Divide this value by two, we get 4 meters.

Fig.3 Dependence of roof slope angle on roofing material

We need to determine the height of the rafters if the roof slope is 25 degrees. So, we find in the corresponding table the indicator corresponding this angle slope: it is 0.47.

We multiply half the width of our building by this relative value. We get the following calculation: 4*0.47=1.88. Accordingly, in this situation we will need to raise the rafters to a height of 1.88 meters.

Rice. 4 Roofing system diagram

The choice of roofing material depending on the angle of inclination

It should be emphasized that all materials for roofing are combined into separate groups: according to their physical properties, technical characteristics, as well as price parameters.

• In the event that the slope of the roof is very small, ranging from 2.5 to 10 degrees, coatings made of stone chips (coarse-grained) and gravel are usually used. The top coating layer is 10-15 millimeters for gravel, 3-5 millimeters for stone chips.
• If the roof slope is 10 degrees or more, and basic bitumen waterproofing was used, it is necessary to make a top layer of coarse-grained material. If the indicator is the same, and the material chosen is a film roll, then it will be necessary to use a special painting layer for protection.
• In the event that the roof angle is up to 20 degrees, and the covering itself is made of metal corrugated sheets, or asbestos cement sheets, you should definitely seal all joints. Is it worth choosing metal tiles?

At angles up to 60 degrees, it is necessary to seal the joints of roofing sheets made of copper or steel. In this case, the joints must certainly be double.

Taking into account all the listed parameters and making the correct calculations, it is possible to design reliable roof, which will last for a year or a dozen years.

Metal roofs are a practical and popular solution for the construction of private low-rise houses. This roofing material is characterized by high load-bearing capacity and resistance to mechanical damage. external factors environment and intensive loads. The durability and reliability of the finishing coating depend not only on the quality; these characteristics are influenced by the design of the roof, including the correctly selected minimum slope. In this article we will tell you how to choose the right slope angle and check it for compliance with SNiP.

The roof slope is an important design parameter, which indicates the angle formed by the floor plane and the roof slope.

1. This indicator is expressed as a percentage or degrees. It is calculated as the result of dividing the height of the ridge by half the width of the building. The angle of inclination of the slope depends on the technical and operational properties of the material and is regulated by SNiP and the manufacturer’s instructions. It depends on:
2. Possibility of using one or another type of roofing covering.
3. Design, composition and cross-section of rafter frame elements.
4. The ability of a roof to effectively drain precipitation.
5. Cost of roofing work.

Weight of the roofing pie.

Note! If the slope of a metal tile roof is increased from 22 degrees to 45 degrees, the area of ​​the slope will increase by 20%, which will affect the cost of materials (finish coating, waterproofing, insulation, wood), as well as the weight of the structure. It is necessary to decide on the optimal angle of inclination during the preparation of the project in order to correctly determine the load on the foundation.

Optimal values Metal roofs are relatively new constructive solution

• , therefore, the technology of its installation and operation is not clearly regulated by SNiP. Information on what the minimum roof slope should be is provided by the manufacturer, since this indicator directly depends on the technical characteristics of the material itself.
• This indicator is calculated in accordance with the thickness, load-bearing capacity and method of laying the roofing.
• The optimal angle of inclination, which ensures effective removal of precipitation with less impact on the slopes, should be 22 degrees.

Important! The minimum slope of a metal tile roof allowed by manufacturers is 11 degrees. Some brands of material can be laid even if the slope is 10 degrees steep. A reduction in this indicator was achieved by the use of new, smoother polymers and more durable steel for the production of roofing.

Slope selection

It can be difficult for a non-professional builder to correctly select the minimum angle of inclination of a metal tile roof. In addition to SNiP requirements and manufacturer’s recommendations, this indicator is influenced by other factors that also need to be taken into account.

When choosing the steepness of the slope, the following are taken into account: Please note that the choice of slope slope depends on the roof design. Optimal slope angle pitched roof

from metal tiles is 20-30 degrees, and gable tiles - 20-45 degrees.

Features of roofs with a small slope

1. The minimum recommended angle of inclination of a metal tile roof is 14 degrees, however, experienced craftsmen can install this type of roofing material efficiently, even if the slope of the slopes is within 10-14 degrees. To increase the reliability of such a design and reduce the risk of leaks, the following measures must be taken:
2. Increase the frequency of the sheathing slats and reduce the pitch between the rafters. To minimize the risk of roof collapse due to intense snow load, it is necessary to strengthen the rafter frame of the structure and install frequent or continuous sheathing.
3. Increase overlaps. Manufacturers recommend when installing metal tiles to make a horizontal overlap of 8 cm, and a vertical overlap of 10-15. To eliminate the possibility of leakage in structures with gentle slopes, you can increase the overlap at the joints of the sheets. Insulate joints. To prevent the penetration of melt and rain water between the joints of the sheets, you can treat the seams silicone sealant

, although this measure has a limited duration. Experienced craftsmen

claim that the easiest way to make a roof made of metal profiles reliable is to follow the manufacturers’ recommendations and strictly adhere to the recommended angle of inclination.

Video instruction In civil low-rise construction, experienced builders call the most common, rational and economically feasible type of roof. They can consist of one, two, three or even four slopes, planes that meet at one point, called the ridge. From flat roofs pitched ones are distinguished by an angle of inclination, which, according to building regulations must exceed 2.5 degrees. The choice of slope is an important stage in creating a project, on which the strength, load-bearing capacity and durability of the structure depend. In this article we will tell you how to choose the right angle of inclination to facilitate snow melting in winter.

Roof angle - engineering calculation parameter roofing structures, reflecting the ratio of the height of the ridge to the width of the base of the slope. Pitched roofs can have a slope of 2.5-80 degrees, however, the optimal range of slope angles is 20-450. The area of ​​the slopes, wind resistance and snow load depend on this parameter. The following terms are found in the specialized literature:

• Minimum slope. The minimum tilt angle in general is 2.5 degrees, but depending on the type used waterproofing material this parameter may increase. The minimum angle for roll bitumen and membrane coatings is the smallest; it is 2-4 degrees. The minimum permissible value for metal tiles and corrugated sheets is 11-12 0, for ceramic tiles - 22 0.
• Optimal. Optimal is the most suitable roof slope in given climatic conditions when using a certain waterproofing material. The optimal angle of inclination ensures that snow melts off independently, making roof maintenance easier.

Important! The slope of a roof can be expressed as degrees, as a percentage, or as an aspect ratio. To calculate this parameter of the roof structure, it is necessary to divide half the width of the facade by the height, and then multiply by 100 percent.

Criterias of choice

The choice of slope is based on engineering calculations, taking into account climatic conditions areas where construction is taking place, roofing characteristics and bearing capacity rafter frame.

1. To ensure a reliable design, the following criteria must be taken into account:
2. Snow load. The greater the snow load, the more covered the slopes become. A roof inclination angle of 40-45 degrees ensures that snow will melt off the surface of the roofing material on its own.
3. Characteristics of the finishing coating. Each roofing covering has optimal slope, which must be taken into account when designing the structure.
4. Bearing capacity of the frame. The smaller the cross-section of the frame elements and longer distance between them, the higher the slope must be to withstand the snow load.

Optimal indicator for facilitating snow melting

The limiting factor when choosing the angle of inclination of roof slopes is middle lane Russia is characterized by a high snow load, characteristic of this area. A large number of snow falling in winter increases pressure on the rafter system, leading to deformations of the frame and roofing material of the structure. Experienced craftsmen believe that there is a strong correlation between slope and resistance to snow load:

1. If it is less than 30 degrees, then snow accumulates on the surface of the slopes. Snow drifts and ice have a significant mass, due to which the load on the rafter frame increases, reaching critical levels. However, some of the snow is blown away from the surface by the wind. If the angle of the roof is in this range, then snow guards are not installed on it, especially if the roofing material has a rough surface.
2. At a value of 0 degrees (i.e. for flat roofs), the snow load on the surface reaches its maximum values. Snow on such structures accumulates into large drifts, which lead to the collapse of the frame if the roof is not periodically cleaned.
3. If the roof is 45 degrees or higher, then in calculating the load on the rafter frame the weight of the snow can be neglected, since the snow slides off the slopes on its own without stopping on the slope. To ensure safe operation of a roof with a large angle of inclination, snow cutters are installed on it, cutting the layer of snow as it descends into thinner plates that have a lower speed and fall energy.

Please note! According to construction climatology, the territory of Russia is divided into 8 climatic zones, each of which has its own average annual snow load. This reference value is used to calculate the roof slope, the section thickness of the rafter frame elements and the selection of roofing.

Impact on design

It is important that changing the slope to facilitate snow melting greatly affects the roof structure as a whole. An increase in slope has the following consequences:

• Increase in weight of the roofing pie. The weight of 1 square meter of a roofing pie with a slope of 50 degrees is 2-2.5 times higher than that of a roof with a slope of 2 degrees.
• Increasing the area of ​​the slopes. The steeper the roof, the larger the area of ​​its slopes, the greater the consumption, and, consequently, the cost of the roofing material.
• Lightening the rafter frame. In the absence of a snow load, you can lighten the roof frame to save on wood.
• Inability to use roll materials. If the roof slope exceeds 40 degrees, it is not recommended to use bitumen and membrane roll materials, as they are subject to high temperature they can simply “slide” down.

Experienced craftsmen note that right choice helps to increase the service life of roofing structures, facilitate the operation and maintenance of the roof in snowy Russian winters. Errors in the design associated with the incorrect choice of the optimal angle lead to deformation of the rafters, collapse of the sheathing, and the pouring of atmospheric moisture into the joint space during slanting rain or during thaws.

claim that the easiest way to make a roof made of metal profiles reliable is to follow the manufacturers’ recommendations and strictly adhere to the recommended angle of inclination.