How to make a slope for a flat roof. Flat roof slope: how to calculate and correctly install? Roof slope degree-percentage ratio

Since the flat roof used to cover office buildings, industrial facilities and residential buildings does not have slopes, increased demands are placed on the quality of waterproofing. 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 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

Minimum slope flat roofing 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 large area roof roll 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 necessary for the formation roofing pie, costs increase only due to 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:

Granules large size(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 is required concrete base roofs.

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 newly created roofs. In order to pitch the roof with concrete mixtures, special equipment and highly qualified workers are required. Two types are used concrete mixtures:

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 wages of highly skilled workers and the high cost of polymers, and the second is the large weight of concrete, which increases the load on the base of the roof.

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 poured 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:

Executed according to building regulations the slope protects the upper floors from leaks and extends its service life.

Video instruction

Stagnant puddles of rain or melt water are the merciless enemy of flat roofs. With stubborn persistence, they destroy the coating and components of the roofing pie. To ensure that atmospheric negativity does not create threats, it is necessary to provide and carry out protective measures. The most effective and affordable method is to form slopes that facilitate the rapid outflow of water.

In the name of long service roof and underneath building structure you need to know how to slope a flat roof. In order to create the most effective protection You should familiarize yourself with the applicable options for its design.

The slope of the plane is necessary so that, under the influence of standard gravitational forces, water is transported by gravity to the drainage points. It is required so that the surface is freed from rain and melt water, all year round threatening internal and external components roofing structure.

The list of risk factors associated with water stagnation includes:

Damage and rupture of coating. A phenomenon characteristic of periods of fluctuations of positive and subzero temperatures, for sharp frosts. During the process of crystallization, water noticeably increases in volume, which leads to peeling of the mineral protective coating on bitumen roofs. Due to the violation of the protective layer, the material becomes vulnerable to UV radiation. On membrane and self-leveling roofs, due to alternating freezing and thawing of water, a network of small cracks appears.
Excessive stress on waterproofing carpet. The difference in temperatures outside the building, inside and inside the structure creates unnecessary stress on the coating. Around stagnant puddles, the state of tension intensifies, resulting in ruptures and cracks.
Deflection of a thin load-bearing base. A typical example is roofing with profiled sheets, on which the accumulation of sediment can cause deformation and subsequent rupture of the coating.
Humidification of thermal insulation. Microscopic cracks undetected by the naked eye will let water into the body of the roofing system, which may not happen if the water is drained at a brisk pace. An equal problem on roofs with poor-quality seams. Wet insulation loses half of its insulating properties and gains weight. Weighting is very undesirable for roofing systems, arranged on corrugated sheets.
Origin of vegetation. Dust accumulated on a flat roof, coupled with stagnant water, is an excellent environment for wind-blown plant seeds to take root and flourish. Not all roofing coverings are able to withstand life-loving roots invading them.

Flat roofs built from heavy-duty materials are not afraid of horror stories from the above list, but they are creepy expensive materials. Someday, when the hearts of their manufacturers tremble with sympathy for the average consumer and the price tag becomes more humane, the need for constructing means for draining water from a flat surface will probably disappear.

However, for now, the method of preventing damage and premature aging is to install slopes, thanks to which currents of melt and rainwater independently move to water intake gutters and funnels or simply roll off the roof onto the ground.

Options for tilting a flat roof

Water will not drain spontaneously, without mechanical stimulation, from a flat surface. In order not to wait for it to evaporate or destroy the roof, it needs to create conditions for movement - i.e. incline. Guidelines for the installation of systems with bitumen and polymer coating The ideal slope angle for a flat roof is considered to be 1.5º; 1º-2º are considered acceptable, which in percentage gradation means from 1.7% to 3.4%, respectively.

It is possible to tilt the roof plane of a small household facility during the construction period. To do this, according to pre-made calculations, the difference in the height of the walls on which the two responsible sides of the slope will have to rest is set. This is a separate topic, suitable for buildings with an external organized and unorganized type.

Now we are much more interested in the formation of a slope equal at all points of the roof plane, mounted on load-bearing walls of equal height. Owners of country property often have to solve such problems and often do it themselves.

Leaning flat roof forms a barely noticeable relief with valleys and watersheds resembling ridge ridges pitched roofs. The essence of its formation is to regulate the flow of water.

The decrease in relief is always directed from the rising parts of the roof, including chimneys, skylights, roof aerators, etc., towards water intakes, which include drainage funnels with gutters. If two or more drain funnels are installed to drain water from a flat roof, then there must be a watershed between them, cutting the flow into different sides parts.

Stagnations along the parapets of flat roofs are eliminated by installing fillets. The design of a simple part is akin to floor plinth just no bulges. Along the line where the walls of a parapet or a standard wall with a flat roof meet, a block with a triangular cross-section is installed, which can be made by longitudinally splitting the block into two halves.

Instead of a split bar, a similar device made of basalt wool or expanded polystyrene. The fillet can be constructed directly on the site using concrete mortar.

To install a slope on a flat roof, the following practice-proven methods are used:

Application backfill thermal insulation : most often expanded clay or perlite, less often vermiculite. To create a ramp fill insulation The roof area is divided into segments. Guides are installed at the required angle, between which the material is poured. A screed of concrete mixture marked M150 is placed on top of the backfill. Concrete pouring must be reinforced with road mesh. Finishing layer concrete can be replaced by a dry screed made of plywood or sheets flat slate. The obviously labor-intensive method is not very accurate due to the inherent displacement of bulk particles. In addition, it is difficult to form a smooth increase in slope in this way.
Pouring light varieties of concrete– mixtures containing expanded clay, expanded polystyrene chips, perlite and similar fillers. It is carried out according to the traditional screed design, only the guides are installed at the required angle. The disadvantage of this method is weather restrictions, because... The screed cannot be poured when the thermometer readings are below zero. Dry concrete ramp there will be at least 28 days, during which the screed will need to be moistened and protected from rain and wind.
Installation of metal structures. They are made from PP profile 75×50×05 or similar material according to the size of the increase and decrease. The distances between structures are calculated depending on the upcoming load. Sheets of flat slate are laid on top of the formed relief. The disadvantages of the method lie in significant material costs and labor investments.
Construction of sheathing. It is used extremely rarely, because the application is unprofitable, and it is also too difficult to implement such insignificant slopes, but it is still mentioned among other methods.
Application of wedge-shaped thermal insulation boards, produced from basalt wool, foam glass, polystyrene foam, polystyrene foam specifically for making slopes on flat roofs and for creating an outflow of water from parapets.

The installation of slopes using wedge-shaped plates is leading due to its numerous impressive advantages. They were developed and introduced into the construction industry purposefully in order to eliminate the disadvantages of all the previously listed methods.

Wedge-shaped thermal insulation boards it is not without reason that they admit in the best possible way solving problems of drainage from a flat roof. This is the most convenient, cheapest and simple circuit, which does not require the performer to have in-depth skills and fundamental knowledge in the roofing business.

Wedge-shaped slabs are cut at the factory, which guarantees the accuracy of the result of the upcoming work. The material kit must be accompanied by practical installation instructions.

Advantages of using wedge-shaped slabs

Expanded polystyrene and mineral wool slabs for the formation of slopes have an equivalent set of advantages, these are:

Low weight, due to which the slope made of insulation creates the least load on load-bearing building structures.
Transportation to the installation site without the use of lifting construction equipment.
Independence of technology from weather conditions. The ability to carry out successful installation, despite unfavorable forecasts for builders.
Tangible relief and acceleration of actions to form inclined planes. No need to transfer finishing works due to the need to withstand technological interruptions. For example, wait 28 days for the cement-sand screed to gain the required hardness parameters.
Significant reduction in the cost of constructing slopes necessary and sufficient for the unhindered flow of rain and melt water.

Important: despite the traditional thermal insulation qualities of materials, wedge-shaped slabs cannot replace the insulation layer. Elements of different thicknesses do not have equivalent thermal properties at all points. Therefore, the actual insulation layer is constructed and calculated separately. Its thickness has nothing to do with the upcoming installation of wedge-shaped slabs.

SNiP II-26-76 prescribes that work on installing the slope of the finishing coating of a flat roof should be carried out after laying the insulation, if thermal insulation was provided for in the project. If there was no need to insulate the roof plane, wedge-shaped slabs are laid on a base covered with steam or waterproofing.

Wedge-shaped thermal insulation is used in the construction of new roofs and when performing repairs and restoration work. With the help of lightweight, convenient slab modules, you can create literally any terrain to direct flows in a given direction.

How to make a slope with slabs?

Wedge slabs are supplied in kits that allow you to gracefully and quickly form slopes and counter-slopes on a flat roof. The sequence of laying the slope elements does not depend on what type of insulation they are made of. However, the composition of the slabs influences the design of the inclined planes.

For example, between the finishing polymer membrane and polystyrene foam or foam boards A layer of geotextile must be laid. Without a separating layer, the roof will blithely say goodbye to plasticizers and will certainly become unusable. But the finishing coating can be laid on basalt wool without fear, without using a separating layer, which will significantly reduce costs.

The polymer membrane is strictly prohibited from direct contact with bitumen and bitumen-polymer waterproofing. They can only coexist if the same separating layer is laid between them.

A geotextile backing is also required when laying slabs directly on a rough concrete surface, i.e. if they are used exclusively to form a slope on an uninsulated roof.

Marking of ramp elements

Within a single manufacturer, wedge-shaped slabs are produced according to general principle, regardless of the composition of the product. The elements are marked to facilitate the installation procedure and have identical dimensions.

The Russian manufacturer of building systems TechnoNikol, for example, offers sets of wedge-shaped slopes made of polystyrene foam and mineral wool. In both cases:

Plates marked with the letters A and B are intended for assembling slopes measuring 1.7%.
If the material is marked with the letters J and K, then it is used when constructing slopes of 3.4% and 4.2%.
Flat insulation boards with the letter C are used to gain height. Elements marked C can be laid both under the slope and on top of it.

More details on the diagrams:

The instructions from the material manufacturer usually contain a laying diagram with a visual representation of the sequence of arrangement of wedge-shaped slabs. The construction of one plane directed towards the drainage gutter, or two adjacent planes directed towards the drainage funnel, will not pose a serious problem for the home craftsman. Laying should begin from the lowest point of the roof and continue upward to the created watershed.

It is a slightly different matter if a complex terrain with several valleys and watershed ridges is being constructed. You will have to draw a plan and think through the course of action in advance. In plan, complex terrain usually looks like a collection of rhombuses and triangles. In such cases, laying starts from the edge of a rhombus or triangle and finishes the process in the center of the conventional figures.

The required height is achieved by means of a set of slabs with required thickness. When constructing a rhombus, it is as if divided into quarters, and a triangle into halves. Each segment is assembled separately, after which the actual trimming is done.

Rules for installing fasteners

Installation of wedge-shaped slabs on the base without preliminary thermal insulation is carried out using methods usually used or bitumen coating. In priority mechanical method fastening to the base, according to which the telescopic plates are fastened with self-tapping screws with a telescopic attachment.

The wedge-shaped parts made of mineral wool are fixed simultaneously with the main layer of insulation. It is recommended to install two fastening units on a slab measuring 600x1200mm. If both linear size the slabs are more than a meter long, 4 fastening points are required.

The wedge-shaped slope must be positioned so that its joints do not coincide with the joints of the underlying thermal insulation, i.e. the principle of seam spacing is observed both in relation to the multi-layer insulation system and in relation to the insulation layer with slope-forming material. If the elements of the thermal insulation slope are laid on the base without insulation, they are glued or simply loaded.

Note that polystyrene foam boards cannot be glued with bitumen glue containing a large amount of organic solvents. The material is not friendly with organic solvents and gasoline. Therefore, their proximity should be excluded.

It is recommended to glue polystyrene foam boards together during installation operations. double-sided tape so that they do not move due to careless touches. It is advisable to place a load on the assembled segment of a complex slope so that it maintains its location.

The type of fastener must correspond to the type of base to which the panels are fixed:

For installation on corrugated sheets, you will need Ø 4.8mm drill-tip screws.
For attachment to concrete screeds strength B-15 and cement-sand screeds M150 strength requires pointed roofing screws Ø 4.8 mm together with a polymer anchor sleeve.
For fixation on concrete bases of class B-25, it is necessary to stock up with drive-in anchors.

The size of the screws is selected taking into account the thickness of the layer so that the screw goes into the concrete by 5 cm, and beyond back side the corrugated sheet protruded by at least 1.5 cm. When installing a slope on old roofs being repaired with a bitumen coating, a disc category of fasteners is used. Age of the repaired bitumen roofing must be more than a year.

Using insulation fillets

A long piece made of basalt wool, triangular in cut, is used to redirect currents atmospheric water from the junctions of vertical and horizontal surfaces. They are laid along the line where the roof meets the parapet, adjacent wall, sides of skylights, chimneys, etc.

The material, cut with impeccable geometric precision, helps to increase the speed of work on arranging a flat roof. Laying fillets allows you to quickly create a smooth transition from a vertical surface to a horizontal plane.

Video tutorial on installing slopes

For those who want to know how to correctly make an ideal slope on a flat roof, this video will help you get acquainted with the specifics of the work in detail:

The list of options for installing slopes on a flat roof is quite rightly headed by wedge-shaped insulation slabs. They are designed to make work easier and significantly speed up processes. The wedge-shaped tilt copes with its assigned duties excellently.

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 climatic features terrain. 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, it should rainwater somehow be diverted from it. Therefore, a slope is made on them in order to obtain at least the minimum slope of a 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 on various factors, is dictated by special building rules and regulations.

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 of the roof 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 of a right triangle;
- W – second leg, equal to half base width;
- 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 the roof from similar characteristics. By the way, the third parameter is calculated automatically. Software The calculator uses the properties of an isosceles triangle and simple 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, to obtain the desired value as a percentage, the value of the resulting ratio is multiplied by 100. A special table of ratios helps express the slope value in degrees.

Every master must know that a perfectly flat roof simply cannot be. This is fraught negative consequences as for rafter system floors, and for the building underneath. That is why it is necessary to make at least the minimum slope of a flat roof. By the way, this is also regulated by SNiP clause 4.3 SP 17.13330. In the material below we will look in detail at why the slope of a flat roof is needed and how to calculate it correctly.

When erecting a roof covering, it is very important to understand that the roof is the main element of the house that takes the sedimentary impact. That is, the roof experiences wind load (in the case pitched design), as well as snow and rain. Moreover, according to SNiP, the load weight per m2 of roof in the event of precipitation in the form of snow is 180 kg. If the snow forms a snow crust, then this load will already be 400 kg/m2. In addition, it is worth understanding that the entire mass in the form of snow with spring melting must go somewhere, and not dry out naturally on the roofing. In particular, the need for a slope for a flat floor is determined by the following factors:

Stagnation of seasonal water on the roofing, which will destroy it over time under the influence of cycles of prolonged wetting and drying.
The pressure of a mass of sediment on the roof, which can lead to its destruction.
Negative effects on roofing materials from freeze-thaw cycles of water on the roof.
The accumulation of layers of dust on a roof covering, which over time forms a layer of soil in a moist, sedimentary environment. Plus, plant seeds, carried by the wind, fall onto fertile soil. And this is organic matter, which, when germinated, will destroy roofing materials.

Important: to avoid all of the above negative phenomena on a flat roof, perform a certain volume roofing works, which are called deflection. That is, they form a kind of minimum slope of a flat roof.

Flat roof structure

As a rule, a flat roof has the following structure:

Base. Reinforced concrete floor slabs (for large high-rise buildings) or profile sheets can be chosen as the basis.
For a concrete base, a screed is formed from a cement-sand mixture.
Vapor barrier layer.
Insulation materials (plate or roll).
Waterproofing material.
Final roof covering.

Roofing materials for a flat roof depending on its slope angle

In order to avoid mistakes when choosing roofing material for a flat roof, it is necessary to take into account that coatings with a rough surface will delay the process of precipitation from the roof. In turn, smooth materials will facilitate their rapid removal towards the slope. At the same time, for arranging the rafter system and the pitch of the flat roof sheathing, the type of coating chosen should be taken into account. And the finishing coating itself must be selected taking into account the slope angle of the flat roof. So, according to the intensity of the slope of the flat roof, the covering materials can be as follows:

Minimum ramp slope. Here the best option There will be rolled material in the form of glass insulation or simple roofing felt. Can also be used membrane roofing. Thus, if the slope of a flat floor is only 2%, it must be laid with 2 to 5 layers of coating. The exception is flat roof slopes of 15°. In this case, you can lay 1-2 layers of material. The sheathing for such a low-slope roof should be continuous.
If the roof slope angle is 12°, then corrugated sheets can be used as a roofing material. And with an increase in the angle of inclination to 15°, metal tiles can also be laid. But in this case, the overlaps must be at least 20 cm, and all joints must be sealed as thoroughly as possible. The pitch of the sheathing for such roofing materials is made depending on the slope of the roof. The smaller it is, the smaller the step should be. And, conversely, the larger it is, the larger the board pitch is allowed.
Regarding ceramic tiles or asbestos cement sheets(slate), then according to SNiP for such materials the slope angle should be at least 22°. That is, they are not suitable for a flat roof.

Calculation of the slope angle of a flat roof

in order to change correct angle slope for a flat roof, you can use one of three methods:

Using a special online calculator program;
Use of a protractor device;
Use of mathematical calculations.

The results obtained can be expressed as percentages or degrees. Moreover, each percentage-degree pair has its own ratio.

For a private master more in a simple way there will be a calculation using mathematics. To do this, you will need to know the width of the roof and its height. Schematically, any roof always looks like a triangle. Thus, it is necessary to divide the height of the roof by half its width:

H: (W:2) x 100 = roof pitch angle

Multiply the resulting value by 100. The resulting result will be expressed as a percentage. It can be checked against the table above and converted to degrees.

If the master has a protractor, then with its help the roof slope angle is determined and the final roofing covering is selected according to SNiP. By the way, minimum slope flat roof can be 1.5% or 1°. At the same time, the optimal values for flat floors is the range of 1.5–10%. All of the above rules are regulated by SNiP clause 4.3 SP 17.13330.

Roof slope and materials for it

If the flat roof has a large area, then various rolled, bulk or tile materials can be used to form its slope angle. In particular, the following are used:

Insulation material. Mineral wool, expanded polystyrene, etc. Such materials are laid with a slope towards the drains and securely fixed in a given position.
Plastic panels. Radically new roofing material, which has an already specified angle of inclination. Such panels are assembled on the roof like puzzles and filled with a mixture of liquid rubber.
Polymers in concrete mix. Such options are often used for roof slopes. However, it is worth remembering that all such concrete mixtures are very high.
Concrete mixture filled with slag or expanded clay. This material fits very well and at the same time forms a thermal insulation layer. However, it also has a lot of weight.
Bulk insulation materials in the form of slag, expanded clay, etc. To fix them, the embankment is filled with cement laitance. Moreover, if you do not fill in bulk, then over time the slope of the roof will change. Loose materials can move from a given position and form a single, flat plane.

Important: leveling work on a large scale should only be carried out by specialists. And although this is quite expensive, the result is guaranteed to be productive.