Minimum roof slope for water drainage. The slope of a flat roof is minimum and maximum - what SNiP say. Disadvantages of a flat roof structure
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Choosing a roof slope only based on your aesthetic preferences would be somewhat reckless. Since the reliability and strength of the future structure largely depend on the correctly calculated value of the angle of inclination, taking into account the climatic features of the area. That is, the roof slope should be optimal from both a practical and aesthetic point of view.
The fact that ideally “flat” roofs simply cannot be beyond doubt. After all, rainwater must somehow be drained from it. Therefore, they make a slope to get at least a minimum slope flat roof.
It ensures the most efficient collection of rainwater from the surface of the roof covering and directs it either to the parapet or to the internal drains.
minimum roof angle
The minimum roof slope depends on many parameters, including the material waterproofing coating, the type of roof itself (standard or inverted), the number of waterproofing layers, and more.
Basic requirements that determine the slope of a flat roof: SNIP
What will be the minimum roof slope, depending various factors dictate special building regulations and norms.
The dependence of the roof slope angle on waterproofing is regulated by clause 4.3 of SP 17.13330 for 2011, according to which the slope of a flat roof varies in the range of 1.5–10%. Large angles (up to 24%) are performed extremely rarely, since the choice of material for waterproofing that would not slide to the base of the sloping roof when the temperature rises is very difficult.
On a note
The smallest slope for a flat roof is 1.5% or 1°.
As a rule, a roof with a low slope has a fairly large surface area and achieving its ideal value is very problematic. There will likely be areas where water will stagnate, which can cause wear on the roofing material or leaks. You can perform the slope geometry relatively accurately using a screed. It is also possible to use polystyrene concrete or foam concrete filling. To increase strength, a layer is already placed on top of the laid layer. thin layer durable concrete screed.
In turn, there is a specific connection between the steepness roofing structure and the number of layers of waterproofing. The larger it is, the water naturally leaves faster, which means that fewer waterproofing layers will be required (clause 5.5).
The inclination can be easily checked using a bucket of water. Water is poured onto the selected area; if the water flows almost completely to the funnel, then the slope of the flat roof is sufficient. A similar check can be carried out on the entire roof surface.
At the design stage, it is determined by calculation how many water intake funnels are required for a given roof, and already during construction, with the help of slopes, it is necessary to ensure unhindered outflow of water into the funnel from any point on the roof.
How to calculate the roof slope: which method is better
As you know, in addition to flat (sloping) structures, there are also pitched and high ones, and there are even more materials for roofing. In order to correctly navigate this diversity, according to SNiP, special tables and diagrams have been developed that reflect the relationship between the steepness of the slope and the type of roof.
The roof slope is determined by the following parameters:
- the type and amount of material intended for roofing;
- necessary protection from wind and moisture;
- ridge height for repairing an existing roof.
How to calculate the angle of inclination in degrees and percentages
Calculator for calculating roof slope
Using this calculator is extremely simple. In fact, any roof can be divided into ordinary gable roofs, the calculation of which is based on a triangle. It is on this position that the work of the calculator is based. The following parameters are used:
- H – the height of the ridge, that is, the leg right triangle;
- W – second leg, equal to half the width of the base;
- L is the length of the rafters, also known as the hypotenuse.
By substituting two known parameters, you can almost immediately determine the slope angle of a roof with similar characteristics. By the way, the third parameter is calculated automatically. Software calculator uses the properties of an isosceles triangle and the simplest trigonometric formulas.
Using a protractor
This device, which is also called an inclinometer, has a simple design: several slats with marked divisions and a pendulum. When making calculations, the main rail is placed perpendicular to the ridge. The pendulum pointer indicates the required angle on the division scale. As you can see, nothing complicated.
Formula for calculating roof slope
And finally, the required steepness of the slope can be calculated by yourself without using slope measuring instruments, mathematically. To do this you will need to know the value
- vertical height (H), measured from the highest point of the slope, usually the ridge, to the lowest point - the cornice;
- laying - the horizontal distance from the bottom to the projection of the top point of the slope.
The angle of inclination of the roof is calculated in degrees or percentages and indicated in the drawing by the letter “i”.
Mathematically, the percentage of roof slope is calculated as follows.
i = H: L, i.e. the roof slope angle is found from the ratio of the roof height to the pitch.
Then, in order to obtain the desired value as a percentage, the value of the resulting ratio is multiplied by 100. A special table of ratios helps to express the value of the slope in degrees.
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 standards and accounting climatic features in the region. The article provides a description of a flat roof, its advantages and features. It explains in detail why a flat roof is needed and how it is sloped. The information will be useful to all owners of plots planning to build a residential building, auxiliary or outbuildings.
Flat roof structure
A flat roof is a single sheet, not divided into separate sections, and has a certain slope to organize water flow. There are buildings of complex architecture, consisting of several departments with different levels of height. Each part usually has own roof, But general rules for each individual section are saved.
Flat roofs are traditional for architecture southern countries, but in northern regions are used primarily 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 design of flat roofs consists of a support system (rafters) forming an inclined plane with selected parameters. On top rafter system a flooring is created from boards on which the roofing sheet is attached. This design is simple, erected quickly enough and allows for the removal of moisture from the under-roof space.
The disadvantage is the use of wood, which is prone to warping, rotting and represents fire danger. Besides, wooden rafters have limited load-bearing capacity, requiring careful calculation to ensure compliance snow loads. A significant danger is posed by the influence of wind, strong gusts of which can rip off the roof, causing significant damage.
In order to increase strength and improve bearing capacity For flat roofs, a construction method has been developed in which the construction of the rafter system is abandoned, replacing it with a dense bulk layer - a slope. it is laid at a certain angle to the horizon, forming an inclined plane on which the roofing covering is laid. As a result, the roof of the upper floor becomes the supporting system, and the slope of the flat roof strengthens it and forms the required angle of inclination, optimal for the given conditions and materials.
Advantages of flat roofs
The main advantage of a flat roof is its simplicity and cost-effectiveness of construction. Such a surface is convenient and safe, allowing for maintenance or renovation work in optimal conditions. The surface area of such a roof is significantly less than that of pitched structures, which allows you to significantly save on roofing material.
An additional advantage of flat roofs is the convenience and ease of installation of various technical devices and equipment on them - satellite dishes, solar panels and so on. 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 effective, although it requires significant costs for the design and maintenance of the sites.
Slope for a flat roof: whim or technical necessity
Slope is a necessity caused by the abundance of rainfall. Rain or melt water must be able to be removed from the surface, otherwise the roofing will quickly deteriorate and fail. IN summer time stagnation of rainwater will provoke aggressive effects 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 begin to increase.
On our website you can get acquainted with the most . In the filters you can set the desired direction, the presence of gas, water, electricity and other communications.
To organize efficient water drainage, at least a minimum slope of the flat roof is required, allowing water to be removed from the roof by gravity. The best option roof problem solutions large area is the slope of a flat roof with bulk materials, forming a plane with the desired angle and simultaneously performing 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. SNiP contains SP 17.13330.2011, or, more simply, in the Code of Roofing Rules. It determines the standard values of the angle of inclination of the roofing covering depending on the roof structure, as well as the materials used. The values that the slope of a flat roof 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 different units:
In percentages.
Height to length ratio.
In degrees.
This abundance of units of measurement is caused by the specifics of construction work - checking the angle using a protractor on the site is much more difficult than measuring linear dimensions.
The situation is somewhat more complicated when constructing a roof with a large area. It is not always rational to make a slope in such conditions. The solution to the problem is the slope of the flat roof with internal drain, when the entire canvas is divided into relatively small areas With drainage funnels. Water entering them is discharged through a pipeline system into the storm sewer. This roof design is more complex and requires the creation of a system of drainage communications, but for large buildings this option is optimal.
In practice, the angles of inclination are much smaller and largely depend on local climatic conditions. Main factors influencing the choice are:
Snow amount in winter.
The power of the winds prevailing in this region.
The weight of snow is a significant load. It can be determined from the tables in the appendices of SNiP, which indicate the average annual values for different regions countries. The lower the angle, the less possibility of independent snow melting. At the same time, a large angle of inclination increases wind loads, dangerous because the roofing covering can be torn off from the supporting surface. The destruction that occurs in this case can lead to 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 adopted in accordance with them. If the roof structure consists of durable materials, capable of withstanding a static load from the weight of snow, they usually try to minimize wind effects that are dynamic in nature and unpredictable in direction.
How to calculate the slope of a flat roof
Specialized calculation of the angle of inclination is an extremely complex engineering task. The requirements of SNiP in this matter have a recommendatory value 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 be carried out by competent and experienced specialists.
Alternatively, you can use an online calculator, which are abundantly available on the Internet. It is recommended to duplicate the resulting value on another resource in order to compare the data and balance the results. It must be taken into account that online calculations have only advisory value and should not be used in the construction of critical structures.
Roofing materials for a flat roof depending on its slope angle
The choice of roofing material should primarily be determined by the angle of the roof. There are a lot options:
Roofs made from piece materials and corrugated sheets
Metal roofing.
Soft roof.
You can create a tilt angle by creating supporting structure the desired configuration or by filling the surface with an inclined layer of insulation. There are also specialized types of materials, for example, wedge-shaped insulation from the Technonikol company, the slope of the roof with which is created by laying slabs of a specific shape.
Choice of the most suitable material is made by comparing local climatic conditions, construction parameters, capabilities and preferences of the owner. All these factors are equally important, but it is recommended to give priority in decision-making to representatives construction company with experience and specialized knowledge.
Video description
In the video you can see the construction of flat roofs:
Conclusion
In conclusion, it should be noted that the number of buildings with flat roofs has increased. The fashion for such architectural solutions, which came from Europe, requires the use of appropriate technologies and materials. Approaching construction using the usual standards common in Russia is irrational and impractical. For buildings with flat roofs, the creation of a special project is required, taking into account the climate, material properties, and hydrogeological conditions.
Since the flat roof used to cover office buildings, industrial facilities and residential buildings, has no slopes, the quality of waterproofing is subject to increased requirements. To avoid leaks, three to five layers of material are used, but a flat roof surface is not able to drain water as effectively as a pitched one. Because of this, areas where moisture accumulates are formed; they dry out only during the hottest periods of the year. The rest of the time, non-evaporating puddles are subjected to negative impact waterproofing layer, destroying it.
In addition, in places where moisture accumulates, particles of soil and dust settle, forming a kind of substrate. The wind carries seeds into this favorable environment and they germinate. Destroying the roofing pie. In order to organize the removal of excess moisture and its movement to drainage system lay the slope of the flat roof. So the name “flat” is just a figure of speech; in fact, its surface is located at a slight angle, invisible to the eye, without the use of a special geodetic instrument. What the slope should be and how it can be created, we will tell you in this article.
Building codes
The minimum slope of a flat roof is regulated by clause 4.3 of SP 17.1333, adopted and approved in 2011. It allows a roof surface inclination angle in the range of 1.5-10% or 1-6 degrees. That is, the smallest slope allowed by regulations is 1.5% or 1 degree, it creates conditions for the movement of water to drainpipes and gutters, prevents stagnation. Steeper angles are rarely used, since on a large roof area, rolled waterproofing materials slide down to the base.
The process of creating a slope is called flat roof slope. This task is performed in various ways using:
- Thermal insulating material;
- Backfill materials;
- Lightweight mixtures of concrete with backfill materials;
- Lightweight mixtures of concrete and polymers.
- Plastic panels
Important! The slope of the flat roof in use should not exceed 3 degrees, as increasing it reduces the safety of use.
Deflection with thermal insulating materials
The structure of any flat roof implies the presence of a layer of thermal insulating material. To set the angle of the roof surface, adjust the thickness of the insulation. To prevent slipping and maintain a given angle, it is fixed to the base of the roof with self-tapping screws. If the base of the roof is well cleaned, the insulation can be glued to it or special plastic supports can be used to hold the layers of thermal insulation together.
This method of deflection has advantages; it is good because:
- It is relatively cheap. Since insulation is already necessary to form the roofing pie, costs increase only through the purchase of glue or fasteners.
- Quite accurate. Using this method, you can accurately set an angle of 1-4 degrees, which is quite sufficient for effective drainage.
- A light weight. Unlike most other methods, sloping a flat roof using insulation does not require reinforcement of the base, since the thermal insulating agent, most often mineral wool or expanded polystyrene, has a low mass.
Deflection with backfill material
Creating a slope angle for a flat roof using backfill material begins with installation waterproofing material. This role is most often played by glass insulation; it is a modern one based on fiberglass, due to which it has increased tensile strength and a service life of more than 20 years. Expanded clay or perlite is poured onto the glass insulation so as to maintain the required slope angle. After this, the backfill material is covered with a polyethylene film arranged in overlapping strips and the remaining layers of the roofing cake are laid according to the design.
However, this method of creating a flat roof slope has disadvantages:
- Large granules (more than 20 mm) do not allow you to accurately maintain the specified angle and make it smooth.
- The backfill material cannot be rigidly fixed, which is why it moves over time. Moreover, this can happen even at the stage of forming the roofing pie, if the expanded clay is not poured with cement laitance. However, in this case, the time spent on drying increases.
- Backfilling is done almost by eye, so it is impossible to maintain the exact angle of inclination.
- Due to the large weight of the backfill material, reinforcement of the concrete roof base is required.
Sloping with concrete mixtures
To set the slope, you can use concrete-based mixtures. This method is not suitable for reconstruction or partial repair, it can only be used for created roofs. In order to pitch the roof with concrete mixtures, special equipment and highly qualified workers are required. Two types of concrete mixtures are used:
- With the addition of expanded clay and perlite, slag.
- With the addition of polymer materials.
This method has only two disadvantages: the high cost, which consists of the remuneration of highly qualified workers and the high cost of polymers, and the second - heavy weight concrete, increasing the load on the roof base.
Bend using panels
The most innovative way to set the angle of the roof is to use special plastic panels. They, like pieces of a children's puzzle, are assembled and placed on a pre-prepared base, and then filled with liquid rubber. Different thickness panels ensures the most accurate observance of the angle of inclination of the surface. But this method also has its own characteristics:
Monitoring the effectiveness of the deviation
To check whether the slope is done properly and whether water is effectively drained from the roof surface, use one of two methods:
The slope, made in accordance with building codes, protects upper floors from leaks and extends its service life.
Video instruction
When creating a roof, all details are taken into account. It is especially important to determine the slope of the surface, since not only 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 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 some of the material increases. To prevent this, it is necessary to make the rafter system more massive, which increases the cost of installing the structure, and also negatively affects the weight of the entire structure. In areas where precipitation falls especially frequently in winter, it is enough to make the roof slope within 45°. This will ensure free flow of snow and eliminate increased load on the roof surface.
If there is little snow falling 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 avoid leaks. When creating a flat surface, importance is also given to drainage; it is this that is entrusted with the function of draining water and preventing its accumulation on the surface. To reduce exposure to sunlight, you can use bitumen covers, green, turf or pebbles.
In regions where harsh climates often prevail in winter, it is recommended to combine external and internal drainage. The latter will no longer be affected negative factors nature.
The choice of materials depending on the angle of the slope
Each material has its own requirements for use. Rough surface the roof will prevent the drainage of gadflies, and a smooth roof will facilitate this. The design of the rafter system is also important. When creating a flat roof, it can be lighter, but designed to withstand heavy loads from water and snow. From a roof that has a slope, water rolls off faster and snow does not linger, but the roof itself must be more durable due to the complexity of the design. The type of rafters and the pitch of the sheathing are also influenced by the choice of roofing material.
The choice of roofing material should depend on the level of slope. To create high roofs, the range of roofing coverings is wider, and externally such buildings are particularly attractive. In order to perform correctly installation work on the roof, the following rules should be followed:
Slope angle measurement
For the correct selection of materials and design of the rafter system, it is important to calculate the angle of the slope. This action is performed using a protractor or by mathematical calculations and is expressed in degrees, percentages and ratios.
The simplest is 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 is converted into percentages using the table.
You can also calculate using 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 using a table to determine the slope and is also expressed as a percentage.
If you have a protractor, all actions consist of determining the angle and selecting materials to create the roof. Only after this can you do right choice, be sure to compare it with the requirements of SNiP.
Features of creating a low-slope roof
Most often, the slope of a flat roof is carried out using the following methods:
- backfill insulation, that is, perlin, expanded clay and others;
- concrete mixtures based on insulation materials;
- polymer materials and concrete mixtures based on them with the mandatory addition of fillers;
- use only insulating materials.
Each of the listed methods has its own advantages and disadvantages. Expanded clay and perlin can change position over time and disrupt the slope of the roof. As a result of this, the minimal slope after some time can become a flat roof. The size of the material also matters, since large components do not allow the slope to be made sufficiently uniform.
Concrete mixtures are especially often used for flat roofs. 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 rafter system. Considering this drawback, we can conclude that concrete mixtures can be used to create a flat roof at the construction stage or during overhaul. They are not suitable for partial repairs of flat roofs, as they cause additional stress.
According to SNiP, polymer materials are ideal for such work. Considering them a wide range of, they should be selected not only depending on the angle of the slope, but also take into account the features of the rafter system.
Regardless of how exactly the slope will be carried out, it is important to pay attention to the drainage system. These can be gutters, external catch basins and other systems. Calculate and select suitable option possible by assessing the material used, as well as the roofing requirements. On roofs with a slope of less than 10°, additional membrane materials should be used. They provide a reliable waterproofing coating.
In addition to drainage, ventilation is of no small importance when creating flat roofs. There is a dependence of the size of the roof space on the angle of the slope. The lower the slope, the greater the height of the ventilation gap.
Taking into account all the above requirements, it is possible to create a roof with a minimum slope angle, which will easily withstand the negative influence of natural factors and retain its qualities as much as possible.
Minimum slope of a flat roof, slope for a flat roof
Required minimum slope for a flat roof. Methods for slope of a flat roof and minimum roof slope according to SNiP
Flat roof slope according to SNiP
On a flat roof, which is erected according to the requirements building codes and rules, there is always a slight bias. If it is minimal, an inexperienced observer will not notice. But if there is no slope at all, it will be immediately visible. The fact is that in the absence of at least some inclination of the structure, rain or melt water will inevitably collect on it.
Even if the surface of a flat roof is created perfectly flat, and, it would seem, there can be no talk of any puddles, the reality is different. Under the influence of the wind, solar radiation, rains of varying acidity, temperature changes, the roof becomes deformed over time, creating zones in which water or dirt brought by the wind can be retained. If there is a minimal slope, the chances that water or snow will linger on the roof for a long time are much less.
What's the point of slanting?
It would seem that sooner or later the snow lingering on the roof will melt, and the water will either dry up or the drainage system will cope with it. The experience that eventually resulted in the recommendations of the Building Code suggests the opposite. Water has the ability to destroy the roof structure in a variety of ways.
Firstly, water on the roof is not completely distilled, it chemical analysis will show the presence of dissolved oxygen and a whole range of substances that will actively destroy the roof material. Secondly, in the cold season, water can be changed several times a day. state of aggregation. Among other things, this is also a change in volume, which carries a powerful destructive force.
The slope of a flat roof is also necessary to prevent dust from accumulating on it. Many have seen vegetation on the roofs of residential and industrial buildings. It would seem, where do the grass and trees come from there? But the wind, water and sun do their job steadily. And plant roots, as is known, are capable of destroying even very strong materials.
How is slope measured and determined?
The parameters of a flat roof, the list of which includes the minimum slope, are regulated by the set of rules SP 17.13330.2011 SNiP II-26-76. A document so complex in notation is easier to distinguish by its name. It's called the Code of Rules for Roofing, or Theroofs in English.
The scope of the document is the design of roofs using rolled, bitumen and other roofing materials, several types of tiles, slate and tiles, galvanized steel and copper sheets, profiled sheets, aluminum, zinc-titanium and other structures.
Before considering the table available in the set of rules, it should be clarified that the slope of a flat roof can be measured either in degrees or as a percentage. There are also relative units of the 10/12 type, but they are rarely used.
Table regulating slope
In paragraph 4.3. of the above-mentioned set of rules contains a table that sets out the standards that determine the slope of a flat roof, that is, its minimum size. The values depend on the type of materials used to construct the roof, as well as on some other factors.
So, if the roof is made of roll materials or from bitumen-based mastics, it should be inclined in the range from 1° to 6° (1.5-10%), if gravel or other coarse substances are poured on top. If upper layer– foil, the slope of a flat roof varies from 1° to 16° (1.5-25%).
When using polymer roll materials, the slope should not exceed 1° (1.5%) without a protective layer and 2° (3%) with a protective layer.
Completely different values are provided for piece materials, metal sheets and concrete structures. For tiles and slates, the minimum slope of a flat roof is 12° (20%) to 22° (40%). Metal sheets can be placed at a minimum of 7° (12%), reinforced concrete trays - 3°-6° (5-10%).
The standards allow the use of significant slopes, but some additional requirements must be met.
How slopes are created
The process of creating roof slopes is usually called de-sloping. In this process they use:
- bulk materials, in particular perlite and expanded clay;
- lungs concrete compositions based on the same perlite and expanded clay;
- lightweight concrete compositions based on polymer materials;
- insulation materials.
What material will be used depends on the design of the building, the required slope and some other factors. For example, lightweight concrete in some cases may be too heavy, creating a significant load. On the other hand, when using bulk materials it is impossible to create a large angle. In general, different materials has its advantages, disadvantages and scope of application.
The slope of a flat roof will help protect the structure from premature destruction, significantly extend its service life and make maintenance easier.
Minimum slope of a flat roof according to SNiP
Slope of a flat roof according to SNiP A flat roof, which is erected in accordance with the requirements of building codes and regulations, always has a slight slope. If it is minimal, an inexperienced observer will not
What should be the slope of a flat roof + minimum slope as a percentage
There are many types of roofing, the most popular being flat. It has a number of advantages, such as: its installation will take less materials, ease and simplicity of installation and additional useful area.
Many people do not associate the phrase flat roof with a slope. Although this is far from true. Even the smoothest roof has its own slope, even if it is minimal.
At a minimum, this is necessary so that melt water and water after rain can easily flow into the installed funnels, which are part of the internal drainage system, or into the gutter of the external system.
In addition, on such a roof it is easy and simple to install additional, necessary equipment. To date, There are several types of flat roofs:
- Operated roof;
- Unused roof;
- Traditional roofs;
- Inversion roofs.
Flat roof slope - why is it needed?
The slope that should be on this type of roof is is approximately 1-5 degrees, if you neglect this, then water, both rain and melt, will accumulate, which in turn will damage the roof.
In summer, you may not encounter such a problem, since rainwater dries out under the rays of the sun. In winter and autumn, such water can freeze at night and melt during the day.
Puddles form, which ultimately leads to moisture gradually penetrates into the insulation. The essence of the mechanism is that moisture penetrates the waterproofing layer, which means that inevitable leaks occur.
But this is not the only problem. In addition, puddles on the roof can contain dust, which eventually settles to the bottom. Seeds of various herbs and plants can fall into this puddle and germinate there.
Often on the streets you can find houses with grass or thin trees on their roofs. It is logical that this spoils the roof and also spoils the aesthetic appearance of the entire building.
To avoid such a nuisance, and thereby extend the life of your roof, it is necessary to carry out the roof tilting procedure. Such complex manipulation is carried out at the time of construction itself.
The process itself is quite complex and includes many different structured activities. The purpose of this procedure is to ensure that the roof itself acquires the required slope.
But before you start pitching the roof, you need to find out what a flat roof consists of.
In essence, it is a cake made of several layers:
- Direct basis, which is reinforced concrete slabs that have a certain wave height;
- Vapor barrier, which can be made from different materials, such as bitumen, or roll materials;
- Next layer - insulation, which can be made of mineral wool or other durable material.
The components of such a pie can be changed if the builder wants to make the entire roof using new building materials. It is worth understanding that such a procedure as slope, carried out immediately at the time of laying the insulation.
It is important that in addition to these main layers of the roof, there must also be water intake funnels or gutters.
The angle of the roof slope is very important, and it depends on many parameters. The first thing you should pay attention to is the wind exposure. If you live in an area where there are frequent strong winds, then it is worth doing small angle tilt
Obviously, the steeper the slope of the roof itself, the faster the outflow of water.
Slope in percent
Minimum angle and calculation of roof slope
The minimum slope angle can be determined based on the materials of the roof itself:
- If the roof is made of corrugated sheets, then her minimum slope must be at least 12 degrees(according to SNiP). If the roof is made of metal tiles, the angle increases to 15 degrees. It is important to understand that the cracks in the material and other joints must be treated with a special sealant - frost-resistant/water-resistant. If the angle of inclination is 15 degrees, then the sheets of material should be overlapped by about 200mm, if the angle is smaller, then the overlap should increase;
- The minimum slope angle may be in cases where if the roof of your house is made of artificial materials . These, in turn, include membrane coatings, ondulin, and bitumen-based materials. It is logical that by the magnitude of the slope angle, The number of layers of the roof also affects. If, for example, the roofing is carried out in two layers. then a tilt angle of 15 degrees is quite sufficient;
- Covering the roof soft tiles, it is worth understanding that 11 degrees of inclination angle is quite enough, but in this case you need to make a continuous type of sheathing.
Such a process as the slope of a flat roof, made from such materials:
- Extruded polystyrene (technoNIKOL);
- Wool, both mineral and glass/basalt based;
- Polyurethane foam;
- Foam concrete;
- Foam glass;
- Various types of backfill materials.
Each of the materials has its pros and cons. And before you start work, it is worth correctly calculating the angle of inclination. In fact, this calculation is quite easy to carry out; for this you need to use a protractor, or use fairly simple mathematical formulas.
In the instructions for using bitumen and polymer coatings for tilting, it is indicated that the optimal tilt angle should be 1.5 degrees. A tilt of 1-2 degrees is acceptable.
Everything is very simple here. You need to know the height of the roof and its width. Next, simple trigonometric formulas will help you calculate the immediate angle (sine, cosine, tangent). And from the existing table, which was calculated earlier, you can find out the value as a percentage.
There is another way to calculate - the value of the roof height must be divided by half the width, and the result already obtained must be multiplied by one hundred, after which, in the table, you can find out the percentage value of the future angle of inclination. This option is faster, but in terms of accuracy they are both correct.
Sloping a flat roof using bulk materials
If you decide that the tilting procedure will be carried out using bulk materials, then the first thing worth noting is the diagram according to which such a procedure must be carried out:
- First of all, on its own concrete base, it is necessary to lay a layer of glass insulation. This material not only has a long service life (30-35 years), but also has high waterproofing performance;
- Further, it is necessary to pour the main material on it - expanded clay. But at the same time, everyone needs to create the right bias;
- Necessarily you need to cover a layer of expanded clay with a special plastic film . It is important to note that it must be overlapped;
- Further, it is necessary to apply the prepared sand-cement screed, doing it smoothly, slowly. Its essence is to level the layer of expanded expanded clay;
- After these events you can begin shape the roofing “pie”, according to the developed project.
Remember that when laying each layer, you need to ensure that the previously prepared angle of inclination is maintained.
If you want to create a minimum angle of inclination, and the roof area is not particularly large, then a sand-cement mortar will be enough.
Thermal insulation materials
One more good material, for roof slope are thermal insulation materials. Experts say that this is the most affordable option.
Its advantage is that it is quite light and quite cheap, which plays a very important role in construction. Mineral wool, the best material. The process diagram is quite simple.
It is necessary to attach the material to the base itself, using self-tapping screws or dowels. Some prefer sheets of such cotton wool to be glued to a previously cleaned base, special glue. This process can be performed both during repairs and during roof installation.
A good material that can be used to slope a flat roof is foam concrete. It is immediately worth noting that this procedure must be carried out using special equipment.
A layer of foam concrete is poured onto the base itself, but at the same time the angle of inclination is noted, and only after make a special screed from foam fiber concrete. Next, it is important to apply waterproofing material.
A huge advantage of this tilt option is high thermal insulation rate, as well as other mechanical characteristics . For example, strength and durability.
Speaking of minuses, there are some here too, or rather one. This is the price. She's tall enough. And again, it will not be possible to carry out such a procedure on your own. Therefore, in this case it is worth turning to professionals.
- If the roof has a minimum slope, then it is important to note that in this case, needs to be installed correct systems drain. The slope itself is made exclusively towards the drain (funnel, gutter);
- If your roof is bitumen shingles, it is worth making the slope angle less than 6 degrees, while The bottom layer of waterproofing must be made of membrane materials;
- It is important to know that with small slope angles, it is necessary to ventilate the under-roof space itself, what does all the stingrays have to do with it. The thickness of the gap also depends on the value of the angle (the larger the angle, the smaller the thickness and vice versa).
Flat roof slope: minimum roof slope as a percentage, with TechnoNIKOL according to SNiP
In this article you will learn what the minimum slope of a flat roof should be, what is the correct slope with TechnoNIKOL material according to SNiP.
Flat roof slope
Perfect flat roof cannot be by definition. Otherwise, it will accumulate rain and melt water, which will lead to rapid wear. Therefore, according to generally accepted standards, a flat roof has a slope of 1 to 11.5 degrees. Moreover, the average value fluctuates around 1-5 degrees, which in practice amounts to 1.5 or more centimeters of slope per meter.
How to calculate the angle of inclination
In order to find out the angle of the roof, you need to:
- Know the height of the parapet.
- Know the thickness of the roofing pie.
- Know the exact location of the water inlet.
As an example, let's take a parapet height of 500 mm; the thickness of the roofing pie, excluding the slope formation layer, is 250 mm, while 50 mm of the parapet should remain on top, above the roof plane; the water intake funnel is located 5 meters from one of the parapets. Thus, 500–250–50=200 is the thickness of the slope-forming material at the parapet. The funnel is located 5 meters away, which means that within these 5 meters we need to reach zero: 200/5=40. Thus, the roof slope will be 4 centimeters per meter or 4%. At minimum value 1.5% is a sufficient level.
If you consider this slope to be too large, it can be reduced to a minimum of 1.5%. This means that if there are 5 meters from the funnel to the parapet, and we rise by 1.5 centimeters every meter, then the thickness of the slope-forming layer at the parapet will be 5 * 1.5 + 2 = 9.5 centimeters.
Provided that the water intake funnel is located not outside, but inside the roof, there are two options for organizing the slope:
- Formation of a circular system. That is, make a slope so that water flows evenly over the entire roof area.
- Formation of scarves. Draw the roof from the funnel like an envelope. So, improvised gutters are created.
Note that when two or more water intake funnels are located, the roof slope is organized exclusively according to the second option.
To make it convenient to mark the future screed, you will need a laser level. The laser is aimed at an acceptable level of parapet thickness, in our case it is 200 mm, and a line is drawn along the perimeter of the entire roof with a construction pencil. In the absence of a laser level, you can use a regular or hydraulic level. Then we find the thickness of the parapet in one place and, placing a level, draw a line along the entire perimeter. You can check that the line does not creep up or down using a hydraulic level.
Next, a string is stretched from the parapet to the funnel. You can set beacons along the cord, so it will be more convenient to work. If the deflection occurs through the formation of scarves, the lace must be pulled along their border.
Roof slope with polystyrene concrete
Polystyrene concrete is a type lightweight concrete, made from cement, water, mineral filler and all kinds of additional additives. To add weight, sand may be added. To produce polystyrene concrete at home, you will need:
- Concrete mixer. Specialists use a special unit that allows concrete to be supplied through a hose directly to the roof.
- Cement 500 grade.
- Polystyrene chips. Made from defective polystyrene boards.
- Water.
- Liquid soap.
- Sand.
Made from the calculation: 2 shovels of cement, a shovel of sand, 5 ten-liter buckets of polystyrene okroshka, 50 grams liquid soap, water, until the mixture reaches the desired consistency. The concrete should not be liquid or too dry.
The work order is as follows:
- Creating markings on the roof. Use timber or beacons. Please note that the timber must subsequently be removed on time. That is, when one area is poured and the solution has already hardened, the timber is removed so that it does not interfere with the pouring neighboring plot. The lace in this case is a weak helper. The concrete will make it wet and sag.
- To create a slope for a flat roof, the resulting mixture must be delivered to the top. We advise you to take care of creating a winch in advance. This will make lifting the concrete easier. Even better, initially bring all the material onto the roof, and also deliver a concrete mixer there. This will greatly simplify the leveling work.
- Polystyrene concrete is pulled together along the beacons using a rule. It is advisable to leave as few irregularities as possible; subsequently, insulation will be laid over the concrete. The solution hardens within a day, and you can now move freely on it.
- Insulation is laid over the slope-forming layer, and then everything is fixed cement-sand screed, for which reinforcement mesh must be laid. The thickness of the screed is approximately 6 centimeters.
The advantages of this material include:
- Inexpensive cost.
- Difficult to install if you do the work yourself.
Deflection with expanded clay
Creating a minimum slope of a flat roof is permissible when using expanded clay. It is obtained by burning clay shale. Expanded clay is laid on a base made of reinforced concrete slabs or corrugated sheeting, and for insulation.
The work order is as follows:
- Creating markings on the roof. For this you can use wooden beam, metal profile or just a lace. It is more convenient to work with timber and profiles, but closer to the end of the work they need to be taken out and the resulting holes should be leveled. When using laces, this is not necessary.
- Expanded clay backfill. To facilitate this process, you can order a manipulator that will deliver expanded clay directly to the roof. Otherwise, you will have to carry the material by hand for a very long time.
- Alignment by beacons. Align using a rule. For convenience, you can make a wooden rule with a handle, similar to the principle of a rake, only instead of teeth there is a flat, wide beam. Expanded clay is pulled from the parapet towards the funnel. If there is too much material, it can be stretched to the edges of the parapet to ensure good stock water.
- To fix the expanded clay in the desired position, it is watered with cement laitance. Prepared from cement and water, with the calculation of 200 kg of cement per 1 cubic meter expanded clay. The consistency of the milk should be sufficient for it to spill down to the base, but at the same time it should not be allowed to flood.
Fixing the expanded clay is not necessary, but is desirable, since during the installation of the roof you will often have to walk on it, violating the created level.
- Removing markings. If timber or metal profiles were used, the depressions are filled.
- Next, you need to fully fix the slope with a cement-sand screed, approximately 6 centimeters thick. Just as in the previous case, reinforcement mesh must be laid for it.
- Low cost. Even lower than when using polystyrene concrete.
- Convenience of creating a slope of a flat roof according to SNiP. Expanded clay is lightweight, it is convenient to take it apart, there is no need to remove excess from the roof. The only problem is delivering the material to the roof.
- Good thermal insulation characteristics.
- Cement laitance, like other fixing solutions, is not able to 100% ensure the preservation of the expanded clay level.
- If it rains during installation, this can become a big problem. You can’t get moisture out from under expanded clay, which means you have to wait until everything dries.
Inclination with expanded clay concrete
Another popular material for creating a slope of a flat roof according to SNiP is expanded clay concrete.
To prepare it you will need:
It is made according to the proportion: one shovel of cement, two shovels of sand, three shovels of expanded clay. Water is added until the solution reaches the required consistency.
The procedure is exactly the same as in the case of polystyrene concrete:
- Marking.
- Delivery of solution to the roof.
- Level stretching.
- Laying insulation and forming a fixing screed.
- Low cost. Comparable to polystyrene concrete.
- Good thermal insulation.
- Very difficult installation if you do the work yourself. The main problem is delivering concrete to the roof.
Angle with insulation
To create the main slope, three main elements are used:
- Type A slabs creating a slight slope.
- Type B slabs complementary to A slabs.
- Additional slabs required to raise the height.
The work order is as follows:
- Marking is not needed, so after installation vapor barrier film proceed immediately to installing the slabs. Start from the lowest point, laying type A slabs first row.
- Type B slabs are laid behind the first row.
- Then additional slabs with a thickness of 40 mm are laid and slabs A are placed on them.
- Again, additional 40 mm thick slabs and slabs B. These operations are repeated until the parapet is reached. At the same time, the flat roof has a slope of 1.7%.
- If mechanical fastening is necessary, special “mushroom” dowels are used. Average consumption– two dowels per sheet.
- Another layer of insulation is laid on top of this slope to evenly distribute the load.
To create a counterslope according to the resulting gutter use:
The counter-clone is made in the form of a diamond, with sequential laying of sheets J and K parallel to its lines.
- High cost of wedge-shaped insulation.
Slope of a flat roof: what is the minimum slope according to generally accepted standards?
What is the minimum slope for a flat roof according to generally accepted standards? Flat roof slope in percentage and SNiP.