The optimal angle of inclination of the attic roof. The angle of the roof is the correct calculation. We choose the slope depending on the roofing material used

The reliability of the building and the comfort of living in it depend on the quality of roof construction. Its design is selected optimal for local operating conditions. Of particular importance is such a parameter as the slope of the roof, which will be discussed further.

The angle of the roof slope depends not only on its design and the features of the facade of the house, on the selected roofing material, but also on other factors. It is necessary, first of all, to take into account the climatic conditions of the area where the building is being erected. Where the amount of precipitation falling in winter is high, a large roof angle (within 45-60 degrees) is preferable: this contributes to better snow melting, which means reducing the load on the roof. It also becomes less likely that the surface of the floor will freeze due to compaction of snow covers.

If a building is being erected where weather with strong winds prevails, it is advisable to choose a minimum roof slope angle to reduce the windage of the structure. Otherwise, the structure is in danger of rapid destruction. Most often, the tilt range in this case is 9-20 degrees.

The greater the slope of the roof slope, the easier the snow cover comes off it.

But basically, the optimal roof slope angle is selected in average values, that is, from 20 to 45 degrees. It is suitable for almost any type of roofing material, for example, corrugated sheeting or metal tiles, which are very popular today.

In areas with a warm climate, where there are much more sunny days than cloudy ones, flat roofs will be more acceptable: their area is smaller than that of other types of structures, which means heating from the sun's rays will occur to a lesser extent. But such a structure should not be absolutely horizontal: the slope of a flat roof should be at least within 3-5 degrees. The minimum slope of the flat roof will ensure normal drainage of rain and melt moisture.

Types of roofing structures

Utility and utility buildings are often built with a pitched roof: it is easy to install and does not require large expenses. In fact, such a building has walls of different heights with a ceiling laid on them. The slope of the ceiling is selected within the range of 9-25 degrees, which is well suited for corrugated sheets and metal tiles. This design requires ventilation of the under-roof space.

But the most popular is the gable one: two planes located at an angle are connected along the ridge line. Other (end) planes are vertical and are called pediments. They may have doors to access a balcony or external staircase.

There are many options for roofing structures

Hip ceilings, the most popular representatives of which are hipped ones, are aesthetically very attractive. In such cases, especially in more complex structures, the slopes can be anything: it depends on the chosen design and the personal preferences of the developers. The advantage of hip roofs is that there are no restrictions on the use of roofing material.

A variant of the hip design is attic: the attic space is used as a living space, so the requirements for insulation are very high. The free space under the ceiling is formed due to the high angle of inclination of all slopes, in which the presence of roof windows should be provided.

Dependence of roof structure on floor material

Before choosing a roofing material, you should study its technical characteristics: this will help you optimally approach the issue and choose the most reliable one. In addition, there is a rule that determines the dependence of the slope angle on the roofing material used.

We list the main ones:

When choosing the slope value, you should take into account the strength characteristics of the roofing structure: the safety margin should be enough not only to withstand its own weight and the weight of the roofing material, but also for external loads (gusts of wind, snow). Also, the type of sheathing for laying most materials also depends on the slope of the slope: for small values of this parameter, either a continuous sheathing or with a small pitch (350-450 mm) is installed. When constructing any roof, especially a flat one, it is necessary to install a system of slopes and drainage. If the area is particularly large, additional drainage will be required.

Calculation of the angle of inclination

The design must meet the following requirements: be strong enough, provide reliable protection from precipitation, and have good thermal and sound insulation. It is also important that there is access for repairs and maintenance. How to calculate the angle of the roof so that all these conditions are met? Experts recommend using simple options for its construction, which include single-pitch, gable, hip (and half-hip), and attic.

Roofs can have a design of any complexity, with different slope angles

Single-pitch roofs are most convenient for verandas, outbuildings and outbuildings. The principle of creating a single-pitch roof is the same as other types: rafters and sheathing are installed, after which the roofing material is laid. The latter plays a decisive role: for corrugated sheeting an angle of 8-11 degrees is required (it is better to do 20), for metal tiles - at least 25, for slate and seam roofing - 35 degrees.

If climatic conditions allow, it is better to make a roof with a slope of 45 degrees: this will allow you to neglect calculations related to the mass of snow. This is an almost ideal pitched roof: the angle of inclination will not complicate its installation and will facilitate maintenance (snow will not accumulate on its surface). But in this case, it will be necessary to strengthen the rafters and sheathing, since the wind pressure on the structure increases 5 times. It should also be taken into account that this will require high costs for materials - approximately 1.5 times.

Roofing material must be selected depending on the roof slope

As can be seen from the graph, each slope corresponds to a certain group of roofing waterproofing materials. There are 11 of them in total, with the inclined lines corresponding to the angle of inclination of the slope. The thick line indicates how the height of the ridge relates to ½ of its depth. It can be seen that the segment h is equal to half of the horizontal segment, designated by the fraction ½. The numbers at the tops of the semicircular scales correspond to the angle of inclination (in degrees), the vertical scale also indicates in percentage. When choosing any roof configuration, you should adhere to these recommendations and purchase roofing materials suitable for your chosen option.

In order to make it clear how the roof slope angle is calculated, we will give an example of calculating the smallest slope angle of a roof with tile waterproofing. On the graph we find a semicircular curve corresponding to this covering: this will be the curve indicated by the number 2. Tracing it to the point of intersection with the vertical scale, we find that the minimum slope of such a roof is 50%.

Taking into account the fact that the slope of the slope is the ratio of the height of the ridge to ½ of its depth, we calculate the slope. That is, with a ridge height h = 4 m and a slope equal to L = 15 m, the slope will be determined as h: (L/2) = 4: (15/2) = 0.53. To display it as a percentage, multiply the result by 100 and get 53%. This value of this parameter guarantees good drainage of rainwater. The minimum slope in the valley is 1%.

Features of calculating a gable roof

The gable roof is the most successful and common design. There are several reasons for this: high reliability, relative simplicity, low cost design. When constructing a roof, not everyone correctly chooses the optimal angle of inclination of a gable roof.

In areas of strong winds, it is necessary to calculate the gable roof so that its slope does not cause too strong wind loads. The greater the angle of inclination of the structure, the higher its windage.

You cannot reduce it to values less than 25 degrees: precipitation will be less easily removed from the roof, and dampness may appear in the under-roof space. Making it larger than 60 degrees is also not recommended: a strong impulse of faith can destroy the roof. The roof does not have to have symmetrical slopes: if you orient the building with a more gentle slope to the south, the roof will dry better after rain.

Conditions for using roofing materials depending on the slope angle

Useful attic area and drainage system

The usable area of the attic space depends on the roof structure: the greater the slope angle, the larger the area and vice versa (this is clearly shown in Figure 2). When constructing an attic, you have to make a compromise between the area that can be easily used, the cost of building a roof and the strength of the structure.

The method of removing precipitation can also be different. There are external or internal organized and unorganized - only external. The latter involves the installation of drainpipes and gutters, while wall and suspended systems are installed on roofs with a slope greater than 15%. The gutters are attached with a minimum slope of 3 degrees, their sides are made with a height of about 120 mm.

The usable area of the attic depends on the angle of the roof.

The distance between the pipes should be no more than 23 m. The cross-section of the pipe should ensure normal drainage of water and is selected depending on the area of the slope. External drains of an organized type are more suitable for areas with a warm climate. Internal gutters are used for cold climates. Such systems consist of a funnel for receiving water, a riser, an outlet and a discharge pipe. The main condition is that water drainage must be ensured at any air temperature.

Installing a roof is a very important task that requires the participation of highly qualified workers. Installation errors can cost home owners dearly. To avoid troubles, roofing work should be entrusted to specialists with sufficient experience: this will guarantee the reliability of the building and the comfort in it.

In civil low-rise construction, experienced builders call pitched structures 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. Pitched roofs are distinguished from flat roofs by the angle of inclination, which, according to building codes, 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.

The angle of inclination of the roof is a parameter for the engineering calculation of 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 waterproofing material used, 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 an engineering calculation that takes into account the climatic conditions of the area where construction is taking place, the characteristics of the roofing and the load-bearing capacity of the rafter frame. To ensure a reliable design, the following criteria must be taken into account:

Wind load. The steeper the roof, the stronger its sailing ability. Therefore, in regions with strong, gusty winds, flatter roofing structures are preferable. Although, on the other hand, the wind can tear off waterproofing material from low-slope slopes.
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.
Characteristics of the finishing coating. Each roofing covering has an optimal slope that must be taken into account when designing the structure.
Bearing capacity of the frame. The smaller the cross-section of the frame elements and the greater the 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 in central Russia is the high snow load characteristic of this area. Large amounts of snow falling in winter increase the pressure on the rafter system, leading to deformation 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:

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.
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.
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 can simply “slide” down when exposed to high temperatures.

Experienced craftsmen note that the right choice helps to increase the service life of roofing structures and 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.

Video instruction

Roof of the house

A roof is a structural element of a building that is responsible for protecting it from external factors. It must successfully withstand precipitation in the form of rain, hail, snow, heavy winds and destructive hurricanes. The correct roof slope 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, but also its long-term operation and strength will depend on the correct slope of the roof. How to make the calculation correctly, what factors to take into account, how to calculate it for roofs with different coatings - all these questions will be discussed in this article.

About the factors influencing the calculation of the roof slope angle

Roofs, as already written on our website, have different shapes and number of slopes. They come in single, double and quadruple slopes. The angle of the roof depends on the number of slopes on your house.

Construction work on installing the roof may be suspended if you do not decide in advance what material you are going to use for the finishing coating and what angle of inclination of the roof. It must be remembered that these two concepts are closely intertwined, since the type of roofing material proposed 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 calculating the angle of inclination of the roof.

For example, when choosing the angle of inclination of a pitched roof within 9-20 degrees, you will need to take into account factors such as

finishing coating material;
existing climatic conditions;
functional purpose of the building.

In the case where the roof has 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 the purpose for which the attic space is being installed. If it is not intended for housing, but should be used to store temporarily unused things and objects, then you should not arrange a large room for these purposes (we are talking about the height of the ceiling). When the owners plan to turn the attic into a living space in the form of an attic, then the need arises to install a good roof with a significant slope.

In those regions where strong winds are not uncommon, the roof slope is minimal. Therefore, it is not subject to such strong wind influence. It is also not recommended to make roofs without a slope. Such coatings can be installed in regions with a large number of sunny days and a low probability of precipitation.

Wind resistance with a high roof is much greater than with a low one. However, with a very small slope, there is a possibility that the wind could tear off the finish. It turns out that with very steep roofs there is the same danger as with roofs that do not have a slope at all. It is therefore recommended to choose the following roof slopes - in light winds it can range from 35 to 40 degrees, in strong winds the optimal roof slope angle is 15-25 degrees.

In areas where precipitation occurs in large quantities (we are talking about snowfall, hail and rain), the angle of inclination can be increased to 60 degrees. It is the most suitable because it allows you to minimize the load on the roof from snow cover, as well as melt water and large amounts of moisture during rain.

Taking into account all of the above, the roof inclination angle is calculated based on the range from 9 to 60 degrees. Designers, as a rule, make appropriate calculations and usually settle on values that range from 20 degrees to 45.

Why is this roof angle attractive? The fact that you can use any roofing material - metal tiles, corrugated sheets, slate, etc. However, each finishing material has its own requirements, which are taken into account when constructing the roof structure.

The use of built-up 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 angle of inclination is in the range of 10-25%, you can get by with one layer, but the material must have a sprinkle.
Roofs with a roof slope of up to 28% are covered with asbestos-cement corrugated sheets (slate).
Tiles are used when the roof has a slope of at least 33%.
The steel covering is laid on the roof with a slope angle of less than 29%.

Material consumption directly depends on the roof slope. The larger it is, the greater the consumption of finishing material. As a result, a flat roof in this regard will cost less than a roof with a 45-degree slope.

If you know the roof slope, then calculating the amount of material required is not difficult. The same can be said about the height of the roof structure.

Let's look at each specific type of roofing.

Metal roofing

Compared to other roofing materials, metal tiles have considerable weight. Therefore, when constructing a roof structure using such a finishing coating, you should take into account all the nuances and try to build it so that it has a minimum roof slope angle.

This issue deserves special attention in areas with very strong winds. As you know, wind loads have a strong and negative impact on the roof. In this case, the calculation of the roof structure must be done especially carefully. When the angle of the roof is large, “swelling” of the roof may occur, which will lead to an increase in load, which will affect the entire structure. In turn, this can lead to premature failure of the roof.

Roofs that are covered with metal tiles must have a minimum slope angle of 22 degrees. Empirical data 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 melted snow or rain.

Important! The minimum roof slope, when such a need exists, can be at least 14 degrees. If soft tiles are used as a covering, then the minimum value is reduced to 11 degrees. In this case, it would be correct to arrange additional continuous sheathing.

Corrugated roofing

It is known about corrugated sheeting that it occupies the place of one of the most popular roofing materials. Everyone knows its advantages in the form of low weight and ease of installation. Fastening profiled sheets to the roof is not difficult.

Important! It should be taken into account that when installing such a roof, the requirements for the minimum roof slope angle are more than 12 degrees (you should look at the manufacturers' recommendations).

Roofing using rolled “soft” materials

When the roof is made from soft types of roofing, we are talking about roofing felt, ondulin, polymer (membrane) roofing. When deciding how to calculate the roof pitch, consider the following:

Number of covering 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 one, it is enough to have a slope within 2-5 degrees.
Membrane coverings, which are optimal for any type of roof, including the most complex in its geometry, are placed on roofs that have 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 include precipitation and its weight. These include wind, which puts pressure on the roof structure and the finishing coating itself. When constant loads are mentioned, we are talking about the weight of the roofing structure itself and the finishing coating material.

A structural element of the roof such as sheathing—its type, pitch, and design—depends on the slope of the roof. For example, the lower the angle of inclination, the shorter the pitch of the sheathing in the roofing system should be. The minimum roof slope requires a sheathing pitch of 35-45 centimeters.

One of the main questions is the amount of material for the finishing coating that needs to be calculated and purchased. The following trend can be seen here - a larger roof slope requires more material consumption.

I would like to offer some practical tips that will be useful when selecting roofing materials:

with a slight roof slope (less than 10 degrees), the roof can be covered with a material containing stone chips or gravel (5 mm thick for chips and 15 mm for gravel).
when the roof slope angle is more than 10 degrees, then a basic bitumen waterproofing device will be required. When using rolled materials, additional protection must be applied. This coating is usually a paint.
covering the roof with roofing material such as corrugated sheets or asbestos cement sheets provides for sealing the butt seams. The joints in this case are made double.

We calculate the angle of inclination of the roof

Calculation of the roof slope angle depends on the height of the ridge. How high the roof at the ridge will be depends on the functional purpose of the attic space.

When a full-fledged attic room is made from the attic, the angle of inclination is calculated as follows:

For example, the end of the roof (the width of the pediment) is 6 meters. This figure is divided in half (6:2=3). The standard roof height at the ridge is always 1.8 meters.

Sin A=a/b=3/1.8=1.67

Using the Bradis table, an approximate value is found for the angle of inclination of the roof with a value of Sin A = 1.67 - this value is in the range of 58-59 degrees. You can stop at the maximum value of 60 degrees, which will become our desired angle of inclination of the roof slope.

Every potential homeowner should know how to calculate the angle of inclination of the roof of a country house or cottage, because not only the cost of roofing material and construction work, but also the safety of living itself depends on the angle of inclination. The correct geometry of the roof allows you to save on building materials and create a structure that prevents the accumulation of snow caps and ice blocks on the roof, the collapse of which can damage both the structure and household members. Therefore, in this article we will present methods for calculating the optimal angle of inclination of the slope.

There are four main types of roofs that can be used in residential buildings. The lean-to option is suitable for an extension or outbuilding, but does not look at all on the main building. The only real advantage of this type is the minimal consumption of roofing material, but there may be problems with safety. Almost all fallen snow is retained on the flat slope, so such roofs are cleaned manually by climbing onto the slope.

A gable roof does not require the construction of a complex frame

The gable version, built on the basis of two slopes, allows you to create a safe roof from which snow caps of any thickness will come off. In addition, a gable roof looks very presentable and does not require the construction of a complex frame. The hip version and its derivatives are a hipped structure with a complex frame and relatively low consumption of roofing material. Not all specialists are capable of building such a structure - the abundance of joints (especially in the attic or half-hip version) requires more skill and time to assemble the roof. After all, in case of an error, it will flow, flooding a residential building.

The multi-gable option is a multi-slope structure of complex shape. This option can only be built by experienced roofers. A multi-gable roof requires more building materials and time, making this the most expensive option available. Moreover, a complicated form (such a roof has five or more slopes) can both decorate and overload the exterior of a home, creating a feeling of excessive complexity, which causes a feeling of irritation in people with delicate architectural taste.

And if you choose based on the simplicity of the design and the calculations carried out, the volume of building materials used and the presentability of the exterior, then the best option would be a gable roof with two slopes. It is this design that we will consider when trying to understand how to calculate the angle of inclination of the roof for a country house or cottage.

Before calculating the optimal roof geometry, you should become familiar with roof design to understand the process and terminology involved. This will not take much time, since the option we have chosen consists of 7 original elements:

1. Mauerlat – logs at the base of the frame, which are laid on a load-bearing wall.
2. Ridge - the upper edge of the roof. In our case, this is not exactly a detail, but a place where the roof slopes meet.
3. Beams - beams under the ridge of the roof, laid at the same level as the mauerlat.
4. Racks - a vertical beam connecting the bed and the ridge girder (beam under the top edge).
5. Rafters - beams resting on the Mauerlat and ridge girder of the roof.
6. Lathing - alternating longitudinal slats laid on top of the rafters and forming the basis of the frame for the roof slope.
7. Strut - a beam laid at right angles to the rafters and stretched to the point where the post and the beam meet.

At the base of the frame there are logs that are placed on load-bearing walls (mauerlat)

The total number of elements depends on their functional purpose. For example, there is always one bed near the roof, and at least two for the mauerlat. The number of rafters is always paired and equal to the number of struts. Well, the number of racks is determined by dividing the sum of the rafters by two. After all, there is only one stand for each pair of rafter legs. And now about the most important thing - the roof angles we calculate are formed by the plane of the base (horizontal) and the line of the rafters laid at an angle to the mauerlat.

Technically, the slope of the roof can vary from 0 to 90 degrees. In the first case, we will get a flat roof, and in the second, a pitched roof (the second slope should be less than 90°).

Snow load is an important factor in determining the roof pitch

The geometry of the roof with two slopes and angles differs from the limit values, but cannot be any; the possible value of the slope of the rafters is determined under the influence of the following factors:

Wind and snow load. The correct slope should help save on frame construction. After all, the higher the load, the more rafters, racks and struts will be needed.
Type of roofing. Each type of structural roofing material imposes restrictions on the minimum and maximum value of the calculated angle.
Cost of building materials - the lower the slope, the cheaper the structure. After all, if the roof slope is zero, then the area of the slope is equal to the dimensions of the roofing. And as the slope increases, the area of the slope also increases. And if you have chosen an expensive building material, then the correct slope will help you save on its purchase.
The dimensions of the structure itself - the height of the ridge should correspond to the distance between the mauerlats. Otherwise, you will get distorted proportions and ruin the aesthetics of the house’s exterior.

Moreover, all the factors mentioned above are interrelated, so they are considered only as a whole when calculating the optimal roof geometry. How to do it? We will talk about this below in the text.

The optimal angle of inclination of a gable roof should not lead to an increase in snow and wind loads, distort the exterior of the house and force the purchase of more roofing and building materials. Therefore, to determine its value, we will sequentially move through all the mentioned parameters, selecting the optimal size for each of them. After which we will calculate the slope based on the average value and acceptable limits for the roofing material.

The most optimal angle of inclination of a gable roof is about 37 degrees

For wind loads, the optimal slope is 0 degrees. In this case, it does not add height to the building. Therefore, all multi-storey buildings have a flat roof. In addition, a zero slope gives a minimum slope area. In this case, it is equal to the area of the ceiling (ceiling or floor). For snow loads, the optimal angle is 60 degrees. Roofs with such angles do not accumulate snow on the slopes, which makes it possible to ignore the snow load as such. As a result, the average slope in snow and wind is 30 degrees ((0+60)/2). This value lies beyond the threshold value (25 degrees), which allows reducing the calculated snow load by 30 percent and does not increase the wind load.

The optimal exterior gives the ratio of the height of the rack and the distance between the mauerlat and the floor in the proportions of 3:4 or 1:1 (in the case of an exploited roof). That is, the tangent of the slope angle in this case will be equal to 0.75 (3/4) or 1.0 (1/1), which corresponds to angles of 37 and 45 degrees. The average angle for the exterior and wind/snow load is 37.5 degrees ((30+45)/2), which corresponds to the optimal proportion of 3:4 (the ratio between the height of the ridge and half the width of the building on the gable side).

That is, the optimal slope angle should be as close as possible to 37 degrees. Moreover, in snowy regions it can be brought closer to 45 or even 50°, and in the southern regions it can be reduced to 30°. After all, snow and wind loads, even in central Russia, have a ratio of 4:1. On average, about 200-210 kilograms of snow or the equivalent of 35-40 kilograms of wind presses per square meter of roofing structure. Therefore, counteracting snow in our latitudes will be more relevant.

From the point of view of roofing materials, an angle of 37° allows the use of such varieties as two-layer roofing felt (roofing felt), galvanized seams, tongue-and-groove tiles, and slate when arranging the roof.

As you can see, at this angle you can choose a material to suit every taste and budget. From the standpoint of rational use of space, this angle is also beneficial in that an attic arranged inside the roof will provide at least 4 square meters of usable area for each meter of ridge length, and the area of the external covering will fluctuate within 13 m2 per meter of ridge length. That is, 37° will also be beneficial from an economic point of view.

If strong winds are a frequent visitor in your region, it is recommended to set the minimum roof slope when constructing roofs. This is due to the fact that as the angle of inclination of the slopes increases, the windage increases. Consequently, the load on the load-bearing roof structures increases. More on this later.

A low-slope roof is a roof, the installation of which was carried out based on the smallest recommended angle of inclination of the slopes. Each roofing material has its own minimum slope.

What is roof slope? This is the angle of the roof to the horizon. What is it for? Anyone can tell that the greater the slope, the faster the water will drain from that surface.

Consequently, snow, dirt, water and leaves will not linger on a roof with a large slope angle. 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. What affects the angle of inclination?

What does the slope of the roof depend on?

No one will argue that the main functions of the roof are 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 the roof will play an important role, and it depends on the following factors:

Wind. The higher the roof, the higher the windage and wind resistance. Low-slope roofs are used in the construction of buildings in areas where there are strong winds.
Precipitation. The rate of water drainage on low-slope roofs is significantly lower than on high roofs. Consequently, dirt and leaves can become trapped on them, especially if materials with a rough surface were used for the coating.
Roofing materials. Each roofing covering has its own 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. New roofing materials are emerging that can solve many problems. Architects can create projects that can not only realize the wishes of customers, but will also comply with all norms and traditions for a given region.

What is the slope angle measured in?

The roof slope is measured in degrees or percentage. Their ratio is shown in the table in Figure 2. The slope angle is measured using an inclinometer or mathematically.

An inclinometer is a rack with a frame, between the slats 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 batten is held perpendicular to the ridge. On the scale, the pendulum will show what the slope of this roof is in degrees.

Mathematically, this value is found as follows. What is the slope angle - the ratio between the height of the ridge and half the roof pitch (the width of the building divided by two).

To get the percentage value, multiply the resulting number by 100. Next, if you need to find out the value of the slope in degrees, we translate it using 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) = 0.17, now we multiply 0.17x100 = 17%. We look at the table: 17% = 10 degrees. That is, the angle of inclination of the roof will be 10 degrees.

The designation of the roof slope on 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, as it is convenient for anyone, at the moment there are no strict rules on this matter.

Now let's look at the minimum roof pitch angle for the most common roofing materials.

Minimum roof pitch for roofing materials:

Membrane coatings. Can be used for roofs of any design. Minimum slope 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. Can be used at a tilt angle of 11 degrees, but in this case the material is laid on a continuous sheathing.
Profiled sheeting. The minimum tilt angle will be 12 degrees, but it is recommended to additionally coat the joints with sealants.
Metal tiles - 14 degrees.
Slate, tiles. To ensure that moisture does not linger on the roof and does not seep into the roof at the joints, the minimum angle of inclination should be 22 degrees.

We've sorted out the materials. Now we list some points that should be taken into account when building roofs with a low 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 drains outside the roof, through gutters).
If it is less than the recommended value by 10 0, a waterproof lower roof should be installed.
The smaller the number, 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 shingles are used as a roof covering, and the temperature is 6 degrees, experts recommend waterproofing membranes along the entire base of the roof.

From all of the above, we can conclude: the minimum roof slope is not the same value for all roofs. This value is different for each roofing covering, but under certain conditions it can also be reduced.

But the use of materials with slopes less than recommended significantly increases the cost of constructing a roof, although aesthetically this is not always justified.