Roof of the house
The roof is constructive element The building, which is responsible for its protection from external factors. It must successfully withstand precipitation in the form of rain, hail, snow, heavy winds and destroying hurricanes. Correct slope of the roof plays a big role in the rapid removal from the roof of the water and the snow cover. In combination with a high-quality waterproofing, it provides excellent protection for the entire structure, including interior spaces.
From the competent slope of the roof will depend not only these indicators, but also its continued work and strength. How to correctly calculate, what factors to take into account, how to calculate it for roofs with different coatings - all these questions will be sanctified in this article.
On factors that affect the calculation of the angle of the roof slope
Roofs, as already written on our website, have different shapes and number of skates. They are one-, two- and four-sloped. The angle of the roof depends on the number of skates in your house.
Construction work on the installation of the roof may stop if you do not decide in advance what material you are going to make the finish coat and what angle of the roof. It must be remembered that these two concepts are closely intertwined, since the type of the proposed roofing material will be taken into account when calculating the slope angle of any pitched roof.
Let us dwell on the factors that are taken into account when calculating the angle of inclination of a roof.
For example, choosing the angle of inclination sill roof within 9-20 degrees, it will be necessary to take into account such factors as
- material of the finish coat;
- existing climatic conditions;
- functional purpose of the building.
In the case where the roof will have two or more stingrays, not only the above factors and the area in which the house is built will be taken into account. It will be necessary to consider for what purposes an attic space is arranged. If it is provided not for housing, but should be used to store temporarily unused items and items, then it is not necessary to arrange for these purposes a large room (we are talking about the height of the ceiling). When the owners plan to make a loft a living room in the form of an attic, then there is a need for a good roof with a significant slope.
In those regions where winds are not uncommon, minimal roof slope is made. Therefore, it does not have such a strong effect of the wind. Doing roofs without bias is also not recommended. Such coatings can be arranged in regions with a large number of sunny days and a low probability of precipitation.
Resistance to wind at a high roof is much greater than at low. However, with a very small bias, there is a possibility that the wind can tear off the finish coat. It turns out that with very steep roofs there is the same danger as with roofs without any slope. Therefore, it is recommended that the following roof slopes be selected - with gentle winds, it can have a value of 35 to 40 degrees, with strong winds, the optimal angle of the roof slope is 15-25 degrees.
In the area where precipitation falls in large numbers (we are talking about snowfalls, 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 the snow cover, as well as melt water and a lot of moisture during the rain.
Taking into account all the above, the value of the angle of the roof inclination is calculated, being guided by the range from 9 to 60 degrees. Designers, as a rule, make the appropriate calculations and usually stop at values that range from 20 degrees to 45 degrees.
Why is such an angle of inclination of the roof attractive? The fact that you can use any roofing material - metal, corrugated board, slate, etc. Nevertheless, each material for the finish coat has its own requirements, which are taken into account when constructing a roof structure.
- The use of deposited materials is most suitable when the roof has a slope of 0-25%. When the slope is 0-10%, then the material must be stacked in three layers. If the value of the angle of inclination is in the range of 10-25%, one layer can be dispensed with, but the material should be sprinkled.
- Asbestos cement corrugated sheets (slate) are covered with roofs having a roof slope of up to 28%.
- Tiles are used when the roof has a slope of at least 33%.
- The steel cover is laid on the roof with an inclination angle of less than 29%.
The material consumption directly depends on the slope of the roof. The bigger it is, the higher the flow of the finish material. Consequently, flat roof in this respect, it will cost less than a roof that has an angle of 45 degrees.
If you know the amount of roof slope, then calculate the amount necessary material is not difficult. The same can be said about the height of the roofing structure.
Let us dwell on each specific form roofing.
Roof from metal
If you compare with other roofing materials, the metal tile has considerable weight. Therefore, when constructing a roofing structure with the application of such a finish coat, all nuances should be considered and try to build it so that it has a minimum angle of the roof slope.
This issue deserves special attention in areas with very strong winds. As you know, the load from the wind has a strong and negative impact on the roof. Calculation of the roof structure in this case must be done especially carefully. When the angle of the roof is large, a "swelling" of the roof can occur, which will cause an increase in the load, which will affect the entire structure. In turn, this can lead to premature destruction of the roof.
Roofs, which are covered with metal, should have a minimum value of the angle of inclination within 22 degrees. Empirical evidence suggests that due to this indicator, moisture accumulation at the joints of the roofing is prevented. There is their protection from undesirable seepage of water in the form of thawed snow or rain.
Important! The minimum roof slope, when there is such a need, can be at least 14 degrees. If the coating is used soft shingles, then the minimum value is reduced to 11 degrees. In this case, it would be correct to arrange an additional continuous crate.
Roofing made of corrugated board
About profiled sheeting, it is known that it takes the place of one of the most popular roofing materials. Everyone knows its advantages in the form of light weight and ease of installation. It is not difficult to mount profiled sheets on the roof.
Important! It should be noted that when installing such a roof, the requirements for a minimum angle of slope of the roof are more than 12 degrees (see the manufacturers recommendations).
Roofing with roll "soft" materials
When the roof is made of soft roofing, it is a roofing material, ondulin, polymer (membrane) roofing. When deciding how to calculate the angle of the roof, the following is taken into account:
- Number of covering layers. Depending on them, the angle of inclination of the roofing structure can be from 2 to 15 degrees.
- When covering in 2 layers it would be good to stop at the angle of the roof slope of 15 degrees. For a three-layer it is enough to have a slope within 2-5 degrees.
- Membrane coatings, which are optimal for any type of roof, including the most complex in its geometry, are laid on roofs having a slope of 2-5 degrees.
No 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. The atmospheric precipitation and their weight are temporary. They can be classified as wind, which exerts pressure on the roof structure and directly the finish coat. When constant loads are mentioned, then we are talking about the weight of the roofing structure itself and the material of the finish coat.
From the slope of the roof depends such a constructive element of the roof, as the crate - its type, step and design. For example, the lower the angle of inclination, the shorter the step of the crate in the roofing system. The minimum slope of the roof provides for the step of the crate, which is 35-45 centimeters.
One of the main questions is the question of the amount of material for the finish coat, which must be calculated and purchased. There is a tendency to see this: a larger roof slope requires more material consumption.
I would like to offer some practical tips that will be useful in selecting materials for the roof:
- with a slight slope of the roof (less than 10 degrees), the roof can be covered with a material that contains stone crumb or gravel (5 mm thickness for crumbs and 15 mm for gravel).
- when the angle of the roof slope is more than 10 degrees, then a basic waterproofing device is required from the bitumen. If roll materials are used, additional protection must be used. Such a coating, as a rule, is a color.
- roofing with such roofing material as corrugated board or asbestos cement sheets, provides for sealing of butt welds. Joints in this case are made double.
Calculate the angle of the roof
Calculation of the angle of inclination of the roof depends on the height of the ridge. What is the height of the roof in the ridge, depends on the functional purpose of the attic space.
When a full 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 height of the roof in the ridge is always as standard as 1.8 meters.
Sin A = a / b = 3 / 1.8 = 1.67
With the help of the Bradys table there is an approximate value that has a roof slope angle at a value of Sin A = 1.67 - this value is in the range of 58-59 degrees. You can stop at a maximum of 60 degrees, which will be our desired angle of inclination of the roof slope.
Whatever one may say, almost all private houses have pitched roof, which is not surprising, since they are easy to maintain, even though their device is more complicated than that of flat roofs. In order to make the roof properly, you need to calculate the minimum angle of the roof slope, and in order to calculate, you need to know what it depends on .
However, it is the angle of the roof slope and the sloping roofs differ from flat roofs. If the angle exceeds 10 degrees, then the roof is pitched.
In the event that the angle does not reach two and a half degrees, the roof is referred to as flat. There are roofs, the slope of which is more than 80 degrees, but they are very rare.
The angle of the roof depends on many factors, not only natural, but also on the properties of the roofing material used.
- Wind. The more the roof slope is, the greater the wind load. When the angle is increased from 10 to 45 degrees, the load will increase by 5 times. True, if you make a small angle, the wind can break the sheets of the cover, falling under the joints.
- Snow and rain. With the increase in the slope of the roof slope, snow falls out better and water drains off. At the same time, it has long been known that the maximum snow load is observed at the slopes of 30 degrees. When a 45-degree ramp is installed, the snow is completely convergent, with smaller angles being simply blown away by the wind.
If the bias is small, the wind will try to drive the water under the joints, which determines the minimum roof slope. For example, for a tile the minimum angle is 22 degrees, for slate 30, for roll materials 5.
As a result, it turns out that with a large amount of precipitation it is better to make a ramp at least 45 degrees, if precipitation falls a little, then it will be enough 30 degrees.
As for the wind, the roof with 35-40 degrees will cope with normal wind conditions in the area, while in regions with strong winds it is 15-20 degrees.
12º - this is the minimum slope of the roof slopes
As mentioned before: all roof slopes have a suitable material for them. Let's look at the most common types of roofing materials:
All types of roofing are laid on the roof slope - the minimum angle of which corresponds to the material used and is supported by a structure that transfers the weight of the roof to the building. The supporting structure includes trusses and crates.
The slope of the roof from the metal tile should correspond to the permissible values, otherwise the roof can not successfully withstand the operational loads.
Technological features of metal
The high popularity of metal in private housing is due to its unique characteristics:
- Light weight (5-7 kg / m 2). This material allows you to equip the roof with complex geometric shapes, does not require additional reinforcement of the roofing system when changing the roofing, does not exert a high load on the building structure and foundation of the structure.
- Simple installation technology allows you to lay the roof covering to non-professionals, the work does not require special equipment.
- A wide range of color solutions makes it possible to select a shade of roofing that harmonizes with the overall appearance of the house.
- Metal tile, made of steel sheet with the thickness of 0,4 - 0,7 mm, is capable of withstanding significant loads due to the presence of the profile.
- The metal is reliably protected from corrosion due to galvanizing and an additional outer layer made of polymers with different physical and technical properties.
To modern roofing materials, high demands are placed on their functional and decorative parameters, since the roof should provide reliable protection of the building from external influences and aesthetically look.
Metal tiles attract consumers by combining durability, operational parameters and relatively affordable cost. However, the physical possibilities of this roofing cover impose some limitations on its application.
When choosing a metal roof during the design of a roof, one should take into account such a parameter as the minimum permissible angle of the ramp for mounting this type of coating.
From such an indicator as the minimum angle of inclination of the roof,:
- the possibility of using a roofing material;
- structural features of the rafter system;
- the ability to withstand the snow load characteristic of the region;
- the possibility of effectively (in full, in a short time) to remove sediments from the roof surface.
The minimum slope of the roof from the metal tile is quite low due to the rigidity of the profiled steel sheets, as well as low surface roughness, which is provided by a protective polymer coating. Such a roof is capable of successfully resisting falling precipitation.
Factors influencing the choice of the angle of inclination of rays
In fact, there are no unified angles for sloping the skates of a metal roof. The minimum slope of skates with this coating is affected by a number of factors that should be taken into account in the design process.
. This indicator is calculated based on the surface area of the roof, as well as the wind force characteristic of the construction region. In this case, it is necessary to take into account the possibility of wind disasters. The relevant information can be found in the special reference books.. In winter, snow accumulates on the roof slopes, and then slides down under the weight of its own weight. Roofs with a slight bias usually have to be cleaned to avoid damage to the truss structure under high snow loads. The steeper the roof - the faster the snow layers slip. The average amount of snowfall in the regions is contained in the reference books. Design roofing should be with a certain margin of strength to avoid deformation of the metal, if the amount of fallen snow significantly exceeds the average.
The choice of the minimum slope of the projected roof is affected by the presence of heating pipes, as well as the thermal insulation of the house itself and the roofing cake. If the roof is not sufficiently insulated, significant heat losses occur through the roof. This means that the snow falling on it, thaws and accumulates more slowly, as the moisture flows down. Providing additional thermal insulation of the roof made according to the project, it is possible to reduce heat loss, but snow on the roof will accumulate more actively. If the slope was calculated before the thermal insulation, then it is likely that the roofing will not be able to withstand the increased snow loads.
The number of factors influencing the choice of bias includes the amount of rainwater. It is best if the skates are at an angle of at least 22 degrees. A roof made of metal with a smaller slope is required to be mounted using a sealant, which will help prevent moisture from seeping into the roofing cake at the junctions.
Also take into account the shape of the roof. The recommended angle of inclination of a saddle roof is 20 - 30 degrees, gable - 20-45 degrees.
Minimum angle of inclination of skates
According to the requirements of SNiP, if the length of the ramp is 6 meters, the minimum allowable angle of the roof slope from the metal roof is 14 degrees. This parameter is calculated based on the average strength of the material, its ability to withstand high loads. However, when designing a roofing system, you should pay attention to the recommendations of the manufacturer of the selected roofing material.
In most cases, manufacturers indicate that the minimum slope for metal should be 12 degrees. Some companies produce material suitable for mounting on roofs with a slope of stingrays of 11 degrees. Change of this parameter to a smaller side became possible due to the improvement technical specifications a number of models of metal: it has increased rigidity and is equipped with a smoother and slippery coating.
It is worth noting that a metal roof with a minimum angle of inclination can be used only in certain climatic conditions, that is, in regions where there is not a lot of rain and snow. A small angle of slope allows the roof to withstand wind loads very well, but it significantly increases snow loads, since snow does not slip under its own weight.
Roofing of metal with a minimum angle of inclination is most relevant in the area, which is characterized by a large number of sunny days per year. Such a roof has a smaller area, due to which it is heated much less, and this favorably affects the microclimate inside the house. The minimum angle of inclination makes it possible to save money on materials for erecting the roofing system and laying the roofing cake, as they are required less than when building a steeper roof.
Metal roof with the minimum angle of slope of the skates is a practical and economical option for southern regions with a small amount of average annual precipitation.
If the slope for the metal tile is less than that indicated by the manufacturer, this will result in the roof covering not being able to provide a reliable protection of the building against moisture. In addition, in regions with heavy snowfall, there is a risk of collapse of such a metal roof.
Choosing the optimal roof slope
The larger the angle of the ramp, the larger the total surface area of the roof. The roof with steeper slopes does not hold snow and water on its surface, precipitation effectively slides down. But the high roof increases sailing, in addition, when building it requires more material for the truss system and the roof.
The higher and steeper the roof, the more expensive it will cost to build it and the installation is more difficult.
It is necessary to take into account that due to high sails of high roofs, metal roofs with a large angle of inclination are not recommended to be built in regions with strong winds, since they can not withstand mechanical stress.
The slope of a roof made of metal tiles affects its ability to withstand loads. To increase the strength of the roof with a slight slope may need a more frequent crate, which will not only strengthen truss system, but also increase the reliability of the roofing.
Despite the fact that there are no definite restrictions in the use of metal roofing for pointed roofs, this material is not very suitable for covering such roofs. If the angle of the ramp exceeds 45 degrees, the sheets of metal can slip down under their own weight. To avoid this, when mounting the sheets, it is necessary to provide additional fixing points for the material to the crate.
+14In civil low-rise construction, the most common, rational and economically expedient kind of roof experienced builders call sloping structures. They can consist of one, two, three or even four rays, planes that close at one point, called a ridge. From flat roofs pitched features an angle of inclination, which according to building codes should exceed 2.5 degrees. The choice of bias is an important stage in the design of the project, on which the strength, bearing capacity and durability of the structure depend. In this article, we will tell you how to correctly choose the angle of inclination in order to facilitate the gathering of snow in the winter.
The angle of the roof slope is the engineering calculation parameter roofing structures, reflecting the ratio of the height of the ridge to the width of the base of the ramp. Pitched roofs can have a slope of 2.5-80 degrees, however, the optimal range of values of the angle of inclination is 20-450. From this parameter depends the area of skates, wind resistance and snow load. In the literature there are the following terms:
- Minimal bias. The minimum inclination angle for the whole is 2.5 degrees, but depending on the used waterproofing material this parameter can be increased. The lowest minimum angle for roll bitumen and membrane coatings, it is 2-4 degrees. The minimum allowable value for metal and corrugated board is 11-12 0, for ceramic tiles - 22 0.
- Optimal. Optimum is called the most suitable roof slope in these climatic conditions when using a certain waterproofing material. Optimum angle of inclination ensures independent snow-falling, facilitating maintenance of the roof.
Important! The roof slope can be expressed in degrees, as a percentage or as a ratio of sides. To calculate this parameter of the roofing structure, it is necessary to divide half the width of the facade to the height, and then multiply by 100 percent.
Criterias of choice
The choice of the deviation is based on engineering calculations that take into account the climatic conditions of the zone where the construction is being carried out, the characteristics of the roofing and the load-carrying capacity of the rafter frame. To make the structure reliable, the following criteria must be taken into account:
- Wind load. The steeper the roof, the stronger its sailing ability. Therefore, in regions with a strong, gusty wind, more gentle roofing designs are preferable. Although on the other hand, with a low-slope ramp the wind can tear off the waterproofing material.
- Snow load. The more snow loads, the more covered the skates are. The angle of the roof's inclination is 40-45 degrees, which allows independent snow-fall from the surface of the roofing material.
- Characteristics of the finish coat. Each roof covering has an optimal slope, which 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 steepness must be in order to withstand the snow load.
Optimal indicator to facilitate the loss of snow
The limiting factor in choosing the angle of inclination of roof rajids in the central strip of Russia is the high snow load characteristic for this area. A large amount of snow falling in the winter period increases the pressure on the rafter system, leading to deformations of the carcass and the roofing material of the structure. Experienced masters believe that there is a stable correlation between slope and resistance to snow load:
- If it is less than 30 degrees, there is accumulation of snow on the surface of the rays. Snow and sediments have a significant mass, due to which the load on the rafter frame is increased, reaching critical values. However, some of the snow is blown off the surface by wind. If the angle of inclination of the roof is in this range, snow floaters are not installed on it, especially if roofing material has a rough surface.
- At a value of 45 degrees, the snow load on the surface of the ramp reaches its maximum values. Snow on such structures accumulates in large drifts, which lead to collapse of the frame, if the roof is not periodically cleaned.
- If the roof is 45 degrees or higher, then in calculations of the load on the rafter frame, the weight of the snow can be neglected, since the snow slides off from the skates independently, without lingering on the slope. To ensure the operation of the roof, which has a large angle of inclination, it installs snow cuts that cut a layer of snow upon descending to thinner plates having lower velocity and energy of incidence.
Keep in mind! According to construction climatology, the territory of Russia is divided into 8 climatic zones, each of which corresponds to its average annual snow load. This reference value is used to calculate the slope of the roof, the thickness of the section of the elements of the rafter frame and the choice of roofing.
Influence on construction
It is important that a change in the slope to facilitate the loss of snow greatly affects the design of the roof as a whole. The increase in steepness entails the following consequences:
- Increase the weight of the roofing pie. The weight of 1 square meter of roofing pie with a slope of 50 degrees is 2-2.5 times higher than roofing with a slope of 2 degrees.
- Increase in the area of skates. The steeper the roof, the larger the area of its skates, the greater the flow, and, consequently, the cost of the roofing material.
- Relief of the rafter frame. In the absence of snow load, it is possible to facilitate 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 bituminous and membrane roll materials, as they can simply "slide down" under the influence of heat.
Experienced masters note that right choice helps to increase the service life of roofing structures, to facilitate operation and maintenance of the roof in conditions of snowy Russian winters. Errors in the project associated with improper selection of the optimal angle lead to deformations of the rafters, crumbling of the crate, flooding of atmospheric moisture into the inter-seam space during oblique rain or during thawing.
