Roof slope angle for various conditions and roofing materials. Flat roof slope - building codes and recommendations Flat roof slope as a percentage of snip
Choosing the type of roof, determining the angle of inclination and other parameters of the roof is an important and responsible task that requires knowledge of the standards and taking into account the climatic features in the region. The article describes flat roof, its advantages and disadvantages. It explains in detail why it is needed and how the slope of a flat roof is made. The information will be useful to all owners of plots planning the construction of a residential building, auxiliary or outbuildings.
flat roof structure
A flat roof is a single sheet, not divided into separate sections, having a certain slope to organize the flow of water. There are buildings of complex architecture, consisting of several departments with different levels of height. Each part usually has its own roof, but general rules for each individual section are saved.
Flat roofs are traditional for the architecture of southern countries, but in the northern regions they are used mainly for non-residential buildings - utility or auxiliary. The reason for this attitude is the abundance of precipitation, which does not occur in such quantities in regions close to the equator.
The traditional device of flat roofs consists of a support system (rafters) that forms an inclined plane with selected parameters. On top of the rafter system, a flooring is created from boards, on which the roofing sheet is attached. This design is simple, built quickly enough and allows you to ensure the removal of moisture from the under-roof space.
The disadvantage is the use of wood, which has a tendency to warp, rot and present a fire hazard. In addition, wooden rafters have a limited load-bearing capacity, requiring careful calculation to match snow loads. A considerable danger is the impact of wind, strong gusts of which can tear off the roof, causing significant damage.
In order to increase the strength and increase the bearing capacity of flat roofs, a construction technique has been developed in which the construction of the truss system is abandoned, replacing it with a dense bulk layer - a slope. she fits under certain angle to the horizon, forming an inclined plane on which the roofing is laid. As a result support system the overlap of the upper floor becomes, and the slope of the flat roof strengthens it and forms the required angle of inclination, which is optimal for given conditions and materials.
Advantages of flat roofs
The main advantage of a flat roof is the simplicity and cost-effectiveness of construction. Such a surface is comfortable and safe, allows maintenance or repair work V optimal conditions. The surface area of such a roof is much smaller than that of pitched structures, which allows significant savings on roofing material.
An added advantage flat roofs is the convenience and ease of installation on them of various technical devices and equipment - satellite dishes, solar panels, etc. simplifies the repair and maintenance of equipment, which can be carried out at any time of the year.
There are flat roofs, the surface of which is equipped for lawns, swimming pools, recreation areas and other areas. In these cases, the use of the surface is most efficient, although it requires significant costs for the design and maintenance of the sites.
Slope for a flat roof: a whim or a technical necessity
Slope is a necessity that an abundance of precipitation causes. Rain or melt water must be able to be removed from the surface, otherwise the roofing will quickly collapse and fail. IN summer time stagnant rainwater will provoke an aggressive impact chemical elements and oxygen dissolved in the mass of sediments. IN winter time the presence of moisture is even more dangerous - when the temperature drops, it will freeze and begin to expand. The smallest cracks in the surface, where moisture penetrates, will increase.
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To organize the operational flow of water, at least a minimum slope of a flat roof is required, which allows water to be removed by gravity from the roof. The best option The solution to the problem for roofs of a large area is the slope of a flat roof with bulk-type materials, which forms a plane with the desired angle and simultaneously performs the functions of insulation and sound insulation.
Minimum and maximum slope of flat roofs according to SNiP
The angle of inclination of the roof is a value regulated by technical standards. In SNiP there is SP 17.13330.2011, or, more simply, in the Code of Roofing Rules. It defines the standard values of the angle of inclination roofing depending on the design of the roof, as well as the materials used. The values that the flat roof slope has are determined by SNiP in accordance with the surface properties of various roofing coverings. The degree of roughness of the metal sheet is much less than that of soft or wavy surfaces.
The slope is measured in various units:
In percentages.
Height to length ratio.
In degrees.
Such an abundance of units of measurement is caused by the specifics construction works- it is much more difficult to control the angle using a protractor on the site than to measure linear dimensions.
The situation is somewhat more complicated when building a roof with a large area. Making a bias in such conditions is not always rational. The solution to the issue is the slope of a flat roof with an internal drain, when the entire canvas is divided into relatively small areas with water funnels. Water, getting into them, is discharged through a system of pipelines to storm sewer. This roof design is more complicated and requires the creation of a system of drainage communications, but on large buildings this option is optimal.
In practice, the angles of inclination are much smaller and largely depend on local climatic conditions. Main factors that influence the choice are:
Amount of snow in winter.
The strength of the winds prevailing in this region.
The weight of the snow is a significant load. It can be determined from the tables in the annexes of SNiP, which indicate the average annual values for different regions of the country. The lower the angle, the less the possibility of independent descent of snow masses. At the same time, a large angle of inclination increases wind loads, dangerous in that the roofing can be torn off the supporting surface. The destruction that occurs in this case can lead to human casualties and threaten not only this building, but also all objects located nearby.
The choice of angle is based on the magnitude of the expected loads and is taken in accordance with them. If the roof structure consists of strong materials that can withstand the static load of the weight of snow, then usually try to minimize wind effects that are dynamic and unpredictable in direction.
How to calculate the slope of a flat roof
A specialized calculation of the angle of inclination is an extremely difficult engineering task. The requirements of SNiP in this matter are advisory and determine only the permissible limits for each type of roofing. For an unprepared person, performing such a calculation is inaccessible and even dangerous. It is necessary that the design is carried out by competent and experienced specialists.
Alternatively, you can use the online calculator, which is available in abundance on the Internet. The resulting value is recommended to be duplicated on another resource in order to compare the data and balance the results. It should be borne in mind that online calculations are only advisory and should not be used in the construction of critical structures.
Roofing materials for a flat roof, depending on the angle of its slope
The choice of roofing material in the first place should be determined by the angle of the roof. There is a mass options:
roofs from piece materials and corrugated sheets
metal roof.
Soft roof.
An angle of inclination can be formed by creating a supporting structure of the desired configuration or by filling the surface with an inclined layer of insulation. There are also specialized types of materials, for example, a wedge-shaped insulation from TechnoNIKOL, the roof slope with which is created by laying plates of a specific shape.
The choice of the most suitable material is made by comparing local climatic conditions, building parameters, the capabilities and preferences of the owner. All these factors are equally important, but it is recommended to give priority in decision-making to representatives of a construction company with experience and special knowledge.
Video description
In the video you can see the device of flat roofs:
Conclusion
In conclusion, it should be noted the increase in the number of buildings with a flat roof. Fashion for similar architectural solutions, which came from Europe, requires the use of appropriate technologies and materials. It is irrational and impractical to approach construction with the usual standards common in Russia. For buildings with flat roofs, a special project is required, taking into account the climate, material properties, and hydrogeological conditions.
When creating a roof, all details are taken into account. It is especially important to determine the slope of the surface, since not only depends on this appearance but also the durability of the structure. This indicator depends on many factors, including the climatic conditions of the area. In this case, it is taken into account that the roof provides protection from the impact environment, but she herself is exposed to all these negative factors. That is why it is important to calculate the slope of a flat roof even before construction begins.
The nuances of choosing a slope angle
To begin with, the effect of wind on the coating is considered. In regions with strong winds roofs with a slight slope are preferable. In this case, if there is a high roof, the likelihood that gusts of wind will tear off part of the material increases. To prevent this, it is necessary to make the truss system more massive, which causes an increase in the cost of installing the structure, and also negatively affects the weight of the entire structure. In areas where precipitation is especially frequent in winter, it is enough to make the roof slope within 45 °. This will provide a free slope of snow and eliminate the increase in the load on the roof surface.
In the event that there is little snow in winter, you can limit yourself to a low-slope roof, that is, the slope in this case will be minimal. According to SNiP, when creating such a design, it is recommended to use membrane materials to prevent leaks. When creating a flat surface, importance is also given to drainage, it is on it that the function of draining water and eliminating its accumulation on the surface is assigned. To reduce the impact sun rays you can use bituminous covers, green, sod or pebbles.
In regions where a harsh climate often prevails in winter, it is recommended to combine external and internal drainage. The latter will no longer be exposed to negative factors of nature.
The choice of materials depending on the angle of the slope
Each material has its own requirements for use. The rough surface of the roof will prevent the removal of the gadfly, and the smooth one will contribute to this. Equally important is the design of the truss system. When creating a flat roof, it can be lighter, but designed for a powerful load from water and snow. From a roof with a slope, water rolls off faster, and snow does not linger, but it itself must be more durable due to the complexity of the design. The choice of roofing material also affects the type of rafters and the step of the crate.
The choice of material for the roof should be based on the level of slope. To create high roofs, the range of roofing is wider, and outwardly such buildings are particularly attractive. In order to properly perform installation work on the roof, you must adhere to the following rules:
Grade Angle Measurement
For the correct choice of materials and the design of the truss system, it is important to calculate the angle of the slope. This action is performed using a goniometer or by mathematical calculations and is expressed in degrees, percentages and the ratio of indicators.
The simplest is the mathematical calculation. To do this, you need to know the width of the blood and its height. Using trigonometric formulas, the angle is calculated in the form of cosine, sine or tangent. The result obtained using the table is converted into percentages.
It can also be calculated by another method. To do this, divide the height of the future roof by half the width of the room, and multiply the result by one hundred. The result is compared against the table to determine the slope and it is also expressed as a percentage.
In the presence of a goniometer, all actions consist in determining the angle and selecting materials to create a roof. Only then can you do right choice, be sure to compare it with the requirements of SNiP.
Features of creating a low-slope roof
The most common flat roof slope is carried out using the following methods:
- backfill insulation, that is, perlin, expanded clay and others;
- concrete mixtures based on heaters;
- polymer materials and concrete mixtures based on them with the obligatory addition of fillers;
- using only insulating materials.
Each of the above methods has its own advantages and disadvantages. Expanded clay and perlin can change position over time and break the slope of the roof. As a result of this, the minimum slope after a while can become a flat roof. The size of the material also matters, since large components do not allow the slope to be sufficiently uniform.
For a flat roof, concrete mixtures are especially often used. The main disadvantage of these materials is their weight. That is, it is necessary to calculate the additional load when developing the design of the truss system. Considering this shortcoming, it can be concluded that concrete mixtures can be used to create a flat roof at the construction stage or during overhaul. They are not suitable for partial repair of a flat roof, as they cause additional stress.
According to SNiP, polymeric materials are ideal for such work. Given their wide range, they should be chosen not only depending on the angle of the slope, but also take into account the features of the truss system.
A flat roof with a slight slope will be considered built in accordance with building codes and requirements. In this case, the correct bias will not be noticeable to the layman. In case of non-compliance with the standards on a flat roof, precipitation will certainly accumulate. You can read more about the device of a flat roof in the article below.
How is this roof made?
The device of a flat roof is a simple task. The basis for the design can be reinforced concrete slabs or professional metal sheets.
The layers of a flat roof are as follows:
- cement-sand base or concrete;
- vapor barrier materials using modern roll bases or bituminous mastics;
- insulation: mineral wool, slabs, expanded clay bedding, concrete pouring.
All components of the roofing pie are made taking into account the materials used.
If it is a built-up base, then the surface is mounted with one type of material.
A flat roof is simple in configuration, but its construction technologies are quite diverse. If you correctly decide on the technology, the construction process will take a maximum of two days. Of great importance when choosing the constituent components for the roof are bearing walls. Since beams are mounted on them, which can be either made of wood or steel.
At the same time, it is these details that transfer the load from the roof to the walls and the base of the house:
- flat roof beams support the weight of the remaining floors;
- weight of people serving structures;
- atmospheric loads accumulating on the roof.
Beams must be correctly selected and installed. Then the finishing coating is selected and installed. It should also have good performance properties. Equally important for a flat roof is the stage of laying vapor barrier and waterproofing.
According to the rules, the vapor barrier is laid on the surface first.
The material must prevent the ingress of moisture.
- As the first layer, a reinforced bitumen film is often used, based on fiberglass.
- The second stage of installation is the laying of insulation, which is often used for flat roofs expanded clay. If a flat roof fails heavy weight, then options for polymer insulation are considered.
- The third stage is the installation of waterproofing. As a basis for these works, polymeric or bituminous materials are used.
Experts distinguish between flat roofs for heated houses, as well as roof options for unheated utility rooms. If there is no experience in the construction of roofs, then the construction associated with the installation of ceilings over a barn, gazebo, veranda will be a good experience.
It does not require special skills, since for a roof of a small area it will be necessary to create a single slope in one direction.
A flat roof for a house will require thoroughness and division of work into stages.
- Laying flooring on laid beams. Boards on top are covered with roofing material.
- The roofing material is covered with insulation (expanded clay, slag).
- Mounting the slope by leveling the insulation.
- Mounting the screed over the insulation. The thickness of the screed is at least 2 cm.
- The screed is additionally covered roll material or treated with a primer.
According to the regulations, the slope of a flat roof is calculated as a percentage. Next, we consider in more detail the calculation technology
What is slope for?
In addition to operated and non-operated types of roofs, there are two more options:
- traditional;
- inversion.
Traditional roofing maintains the order of the layers of the roofing pie when the waterproofing is laid on top of the thermal insulation. However, in this case, loads and constant pressure quickly disable the waterproofing layer, all other layers also suffer.
The idea of an inverted roof is to protect the waterproofing, which fits freely under the insulation. A vapor barrier device is optional in this variant.
In any type of flat roof, it is important to create the correct slope. The correctness of the slope is associated with many parameters. The first important definition is the effect of the wind. In regions with frequent and strong winds, it is worth making a small angle of inclination. With the wrong large slope, gusts of wind will simply tear off the roofing material. In addition, it will suffer rafter system and crate.
The slope of a flat roof is needed so that precipitation does not cause premature damage to roofing materials. It is clear that in the summer period there may not be a problem with excessive moisture on the roof.
However, the danger is that in winter and autumn, the moisture accumulated from snow and rain will thaw during the day and freeze at night. This will lead to the fact that moisture will gradually penetrate into the insulation or waterproofing, and leaks will occur. In addition, dust will get into the materials, which carries the seeds of various herbs.
If there is enough moisture inside the materials, the plants will germinate. On some improperly designed roofs, not only grass can be observed, but also trees that will cause damage to the truss system.
It also spoils the general appearance of the entire building. Therefore, the procedure for flattening the roof must be carried out, and even on initial stage construction. Despite the fact that there seem to be a lot of steps to create a slope, the process is actually simple.
The calculations should take into account the materials that will be used in construction.
Calculation
For professionals, let's calculate the slope in degrees or percentages. The drawing will help determine the correct size. To create it, you need to know the height of the roof, as well as its width. Direct mathematical calculation is carried out using trigonometric formulas. The value can also be found from the existing table, which has already been calculated by professionals.
The slope of the roof can be formed according to pre-made calculations, which define the wall height difference. Two sheer sides of the ramp will rest on these walls. You can also form a slope on an equal footing at all points of the roof plane.
That is, the beams are initially erected on walls of equal height.
The calculation is permissible on the basis of the information specified for specific building materials. For example, for a corrugated roof, the minimum possible slope according to SNiP is less than 12 degrees. For a metal roof, it is worth increasing the figure to 15 degrees. In this case, both those and other sheets must be treated with a sealant.
Smaller angles of inclination are possible for roofs made of artificial materials. These can be membrane bases, ondulin, bituminous bases. The number of layers of the roofing cake will also affect the amount of slope. For a roof that includes two layers, an angle of inclination of 15 degrees should be provided.
If the roof covering is soft tiles, then 11 degrees is enough for a slope. But when laying soft tiles it is worth considering a continuous crate. Consider the options for laying some types of materials in more detail.
Options
If you have chosen bulk options (expanded clay) as demolition materials, then it is worth considering the features of this scheme of work.
- The concrete base of the roof will be better protected if a layer of glass isolator is laid on it. this one good waterproofing material. Expanded clay is poured over the waterproofing. At this stage, you need to create a slope. The expanded clay layer is covered with a film material, and if this layer is not a single one, the film is overlapped.
- The next step is to apply a screed, including sand and cement. The layer of bulk material is leveled with a screed. Further formed roofing cake taking into account the existing project.
- Razklonka from a profiled sheet of 6 meters should be equal to 12 degrees. At the same time, in order not to spend money on sealant, it is enough to adhere to the recommended conditions for overlapping. The choice of a roof slope from a profiled sheet is beneficial, first of all, from a financial point of view. This is the most economical and easiest way to install a roof.
There are also options for materials that will add maximum comfort not only to the builder, but also to the owners, since they will not create trouble during operation. Such materials include the products of TechnoNikol. It is the largest manufacturer of roofing materials, recognized as reliable and efficient throughout the world.
If the traditional method of spreading with bulk materials is not suitable, modern methods can be considered.
These methods are worth considering, as bulk insulation can:
- move, which threatens to break the ramp;
- not ensure a smooth transition;
- not ensure the accuracy of work at sub-zero temperatures.
To ensure the accuracy of the slope, you can consider ready-made insulation boards with an existing slope. Plates may include mineral wool or styrofoam. An economical and reliable method is the use of polystyrene. The process of working with plates coincides with the stages of the thermal insulation device.
Plates are laid under:
- roofing;
- waterproofing layer.
To fix the plates, self-tapping screws or glue are enough.
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 the roof slopes there are low-slope(sloping), medium 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 for each roofing there is a recommended minimum slope.
What determines the slope of the roof
- From the ability of the roof to protect the structure from external factors and influences.
- From the wind- the greater the slope of the roof, the greater the value of the attributable wind loads. With steep slopes, wind resistance decreases, and windage increases. In regions and places with strong winds, it is recommended to apply a minimum roof slope to reduce the load on the roof's load-bearing structures.
- From roofing (material) - Each roofing material has its own minimum angle slope at which the material can be used.
- From architectural ideas, solutions, local traditions- so in different regions preferred for a particular roof structure.
- From atmospheric precipitation: snow loads and rainfall in the region. On roofs with a large slope, snow, dirt and leaves will not accumulate in huge quantities.
What is the roof pitch measured in?
The designation of the roof slope in the drawings can be either in degrees or as a percentage. The slope of the roof is indicated by the Latin letter i.
In SNiP II-26-76, this value is indicated as a percentage (%). Currently does not exist strict rules according to the designation of the size of the roof slope.
The unit of measure for roof slope is degrees or percentages (%). Their ratio is 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 the online converter:
Roof pitch 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 a pendulum is fixed. When the rail is in a horizontal position, the scale shows zero degrees. To measure the slope of the roof slope, the inclinometer rail is held perpendicular to the ridge, that is, at a vertical level. On the scale of the inclinometer, the pendulum indicates the slope of a given roof slope in degrees. This method of measuring the slope has become less relevant, since now there are various geodetic instruments for measuring slopes, as well as drip and electronic levels with inclinometers.
Mathematical calculation of the slope
- Vertical Height (H) from the top of the slope (usually the ridge) to the level of the bottom (cornice)
- Foundation ( L ) - horizontal distance from the bottom of the slope to the top
Using a mathematical calculation, the value of the slope of the roof is found as follows:
The angle of the slope of the slope i is equal to the ratio of the height of the roof H to the laying L
i \u003d H : L
In order to express the slope value as a percentage, this ratio is multiplied by 100. Further, to find out the slope value in degrees, we translate according to the ratio table above.
To make it clearer, let's look at an example:
Let it be:
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 this value according to the table into degrees and get - 24 °.
Minimum slope for roofing materials (coverings)
| Roof type | Minimum roof pitch | ||
|---|---|---|---|
| in degrees | V % | in the ratio of the height of the slope to the laying | |
| Roofs made of rolled bituminous materials: 3 and 4 layers (welded roofing) | 0-3° | up to 5% | until 1:20 |
| Roofs made of rolled bituminous materials: 2-layer (welded roofing) | from | 15 | |
| seam roof | from 4° | ||
| Ondulin | 5° | 1:11 | |
| Wavy asbestos cement sheets (slate) | 9° | 16 | 1:6 |
| Ceramic tiles | 11° | 1:6 | |
| bituminous tiles | 11° | 1:5 | |
| metal tile | 14° | ||
| Cement-sand tiles | 34° | 67% | |
| wooden roof | 39° | 80% | 1:1.125 |
