What is the minimum slope of a flat roof? Calculation of the slope of a flat roof and materials Slope of a flat roof with internal drainage

During the construction of utility and industrial buildings it is necessary to do at least the minimum. Absolutely flat and flat roof ineffective as a water drainage solution. Precipitation linger on the roof, and over time, areas of stagnation appear that dry out only in extreme heat. From the outside, such a roof looks flat, as in the photo, but at the same time, the drainage efficiency increases, and accordingly, the service life of the roofing increases.

Why is it necessary to make an incline?

The formation of stagnation zones is harmful to the roofing material. IN cold season Every year, water constantly freezes and melts, because of this, the roofing material is destroyed, and all the conditions are created for corrosion to occur.

The percentage slope of a flat roof should be 1.7-7%.

Roof slope options

Sloping a flat roof can be done in the following ways:

using materials for insulation;
using expanded clay, perlite and other backfill materials;
using lightweight concrete mixtures based on backfill insulation;
using lightweight concrete mixtures based on polymer fillers.

Backfill materials are most often used, but tilting with their help has several disadvantages. This is, first of all, the displacement of the backfill material over time, due to which the angle of inclination changes. Such a deviation may become ineffective over time. In addition, the large size of the expanded clay unit (approximately 20 mm) does not allow creating a smooth slope.

Slope with application lightweight concrete is devoid of these shortcomings, but it cannot always be done. The structure has a significant mass, which creates a load on the flat roof. Therefore, degrading with concrete can only be done during the construction of a building or overhaul roofs.

If you need to correct the roof a little, then the slope of the flat roof can be made using special polymer materials, for example, extruded polystyrene.

Typically a flat roof consists of:

load-bearing structure;
leveling cement-sand screed;
layer vapor barrier materials;
layer of thermal insulation materials;
waterproofing from roofing roll material.

In addition to these layers, the flat roof must have water intake funnels if an internal drain is created. If the drainage system is external, install water inlet gutters that are attached either to external wall buildings, or under the roof. Naturally, it is necessary to calculate correctly.

If a profiled sheet of metal was used as the base, a structure made from a profiled sheet can also be used for waterproofing. A flat roof may have a different structure, but as a rule, general scheme remains the same.

Sloping with bulk materials

The slope using inexpensive backfill materials is done in the following way:

On hardware concrete base lay a layer of waterproofing material - glass insulation. This material is different for a long time service - up to 30 years.
Expanded clay is poured onto the glass insulation in accordance with the design. Large expanded clay granules do not make it possible to accurately measure the angle, so they have to be poured “by eye”.
Expanded clay is covered plastic film, laid overlapping. After this, the roof is made based on the design, and when creating each new layer, you need to control the angle.

Sloping a flat roof in this way is inconvenient for the reason that the angle of inclination cannot be accurately calculated, and besides, the displacement of expanded clay begins even when the screed is poured. This can be avoided by pouring expanded clay with cement laitance, but the drying time will be significantly increased. Plus, there is a load on the floor, as the weight of the flat roof increases significantly.

Incline with foam concrete

Instead of expanded clay and cement mortar, you can use foam concrete. First, a layer of foam concrete is poured onto the base in accordance with the angle of inclination, then a screed is made from foam fiber concrete. Lay on top of this waterproofing material.

This roofing has good thermal insulation and mechanical characteristics. But it also has disadvantages - the main one being high cost. It is also worth considering that it is unlikely that you will be able to lay out foam concrete yourself, so you will have to hire specialists.

Deflection with thermal insulation materials

The bend using thermal insulation materials is inexpensive and easy to perform. You can make a slope both during the construction of the roof and during repairs. The most profitable, based on financial costs and thermal insulation qualities, is the slope using polystyrene and mineral wool. An undoubted advantage is the low weight of these materials. When using them, there is no need to reinforce the roof.

Flat roof with slight slope, will be considered erected in accordance with building regulations and requirements. In this case, the correct bias will not be noticeable to the average person. If the standards are not followed, precipitation will certainly accumulate on the flat roof. You can learn more about the construction of a flat roof further from the article.

How is this roof constructed?

Installing a flat roof is not a difficult 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 bitumen mastics;
insulation: mineral wool, slabs, expanded clay bedding, concrete fills.

All components of the roofing cake are compiled taking into account the materials used.

If this 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 choose the technology correctly, the construction process will take a maximum of two days. Great importance when choosing components for the roof, they have load-bearing walls. Since beams are mounted on them, which can be made of either wood or steel.

Moreover, it is these parts that transfer the load from the roof to the walls and foundation of the house:

flat roof beams support the weight of the remaining floors;
weight of people servicing the structure;
atmospheric loads accumulating on the roof.

Beams must be correctly selected and installed. Then select and install finishing coating. It must also have good performance properties. The stage of laying vapor barrier and waterproofing is of no small importance for a flat roof.

According to the rules, the vapor barrier is laid on the surface first.

The material must prevent moisture from entering.

A reinforced bitumen film based on fiberglass is often used as the first layer.
The second stage of installation is laying insulation, which is often used for flat roofs. If a flat roof cannot withstand a lot of weight, then options for polymer insulation are considered.
The third stage is the installation of waterproofing. Polymer or bitumen materials are used as the basis for these works.

Experts distinguish between flat roofs for heated houses, as well as roof options for unheated utility rooms. If you have no experience in constructing roofs, then construction related to the installation of floors over a barn, gazebo, or veranda will be a good experience.

No special skills are required here, since for the roof small area you will need to create a single slope in one direction.

A flat roof for a house will require care and division of work into stages.

Laying the flooring on the laid beams. The boards are covered with roofing felt on top.
Ruberoid is covered with insulation (expanded clay, slag).
Installation of the slope by leveling the insulation.
Installation of screed on top of 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 standards, the slope of a flat roof is calculated as a percentage. Next, let's take a closer look at the calculation technology

What is the tilt for?

In addition to exploited and unexploited types of roofs, there are two more options:

traditional;
inversion

Traditional roofing maintains the order of the layers of the roofing pie when waterproofing is laid on top of thermal insulation. However, in this case, loads and constant pressure quickly damage the waterproofing layer, and all other layers also suffer.

Idea inversion roof consists of protecting the waterproofing, which is laid freely under the insulation. A vapor barrier device is optional in this option.

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 wind. In regions with frequent and strong winds, it is worth making a small tilt angle. If the slope is incorrect, gusts of wind will simply tear off the roofing material. In addition, the rafter system and sheathing will suffer.

The slope of a flat roof is needed to prevent precipitation from causing premature damage. roofing materials. It is clear that in summer period There may not be a problem with excessive moisture on the roof.

However, the danger is that in winter and autumn periods moisture accumulated from snow and rain will thaw during the day and freeze at night. This will lead to moisture gradually penetrating into the insulation or waterproofing, and leaks will occur. In addition, dust that carries seeds of various herbs will get into the materials.

If there is sufficient moisture inside the materials, the plants will germinate. Some improperly designed roofs may contain not only grass, but also trees, which can cause damage. rafter system.

It also spoils general form the entire building. Therefore, the procedure for tilting the roof must be carried out, and even at initial stage construction. Despite the fact that there seems 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, it is acceptable to calculate the slope in degrees or percentages. The drawing will help determine the correct value. To create it, you need to know the height of the roof, as well as its width. Direct mathematical calculations are carried out using trigonometric formulas. The value can also be found from the existing table, which has already been calculated by professionals.

The roof slope can be formed according to preliminary calculations, which set the difference in height between the walls. The two steep sides of the slope will rest on these walls. It is possible to form a slope equally at all points of the roof plane.

That is, the beams are initially installed on walls of equal height.

The calculation is permissible based on the information specified for specific building materials. For example, for a roof made of corrugated sheets, the minimum possible slope according to SNiP is less than 12 degrees. For a metal roof, it is worth increasing the indicator to 15 degrees. In this case, both sheets must be treated with sealant.

Smaller slope angles are possible for roofs made of artificial materials. These can be membrane bases, ondulin, bitumen bases. The amount of slope will also be influenced by the number of layers of the roofing cake. For a roof consisting of two layers, a slope angle of 15 degrees must be provided.

If the roof covering is soft tiles, then 11 degrees is enough for the slope. But when laying soft tiles It is worth considering the continuous sheathing. Consider the options for laying some types of materials in more detail.

Options

If you have chosen bulk options (expanded clay) as the slope materials, then you should take into account the features of this work scheme.

The concrete base of the roof will be better protected if a layer of glass insulation is laid on it. This is a good waterproofing material. Expanded clay is poured over the waterproofing. At this stage it is necessary to create a slope. The expanded clay layer is covered with a film material, and if this layer is not uniform, the film is overlapped.
The next step is to apply a screed containing sand and cement. The layer of bulk material is leveled with a screed. Next is formed roofing pie taking into account the existing project.
The slope of a 6-meter profiled sheet should be 12 degrees. At the same time, in order not to spend money on sealant, it is enough to adhere to the recommended conditions for overlap. Choosing a roof slope made from corrugated sheets is beneficial, first of all, from a financial point of view. This is the most economical and simplest way to install a roof.

There are also options for materials that will maximize comfort not only for the builder, but also for the owners, since they will not create hassle during operation. Such materials include TechnoNikol products. This largest producer roofing materials recognized as reliable and effective around the world.

If traditional way Leveling devices using bulk materials are not suitable; modern methods can be considered.

These methods are worth considering because backfill insulation can:

shift, which threatens to disrupt the deviation;
fail to ensure a smooth transition;
cannot ensure the accuracy of work at sub-zero temperatures.

To ensure the accuracy of the slope, you can consider ready-made insulation boards with the existing slope. The boards may include mineral wool or expanded polystyrene. An economical and reliable method is the use of polystyrene. The process of working with slabs coincides with the stages of installing thermal insulation.

The slabs are laid under:

roofing;
waterproofing layer.

Self-tapping screws or glue are enough to fix the plates.

It has a number of advantages, such as: its installation will require less materials, ease and simplicity of installation and additional usable territory.

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.

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 under the rays of the sun rainwater dries out. 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 into the 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.

Flat roof

In essence, it is a cake made of several layers:

Direct basis, which is reinforced concrete slabs that have a certain wave height;
, which can be made from different materials, such as bitumen, or rolled materials;
Next layer -, 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 making a small angle of inclination.

CAREFULLY!

If you make a strong slope of a flat roof, then the wind can tear out roofing sheets. It is important to note that the angle of the roof dictates the necessary conditions for the rafter system, as well as for all components of the roof, namely: rafters, sheathing pitch.

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 , then her minimum slope must be at least 12 degrees(according to SNiP). If the roof is made of, 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 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;
Having covered the roof, 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.

Despite the fact that a flat roof is called flat, it still needs a slope. The minimum slope for a flat roof is 1 degree or 1.7%.

In the instructions for using bitumen and polymer coatings for deviation it is indicated that optimal angle the tilt 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 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 inclination angle. This option is faster, but in terms of accuracy they are both correct.

Minimum slope

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 scheme according to which it is necessary to carry out such a procedure:

First of all, on the concrete base itself, 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 .

Remember that when laying each layer, you need to ensure that the previously prepared angle of inclination is maintained.

ATTENTION!

If you are worried that the expanded clay will move when you start laying sand-cement screed on top of it, you can fill it with cement laitance. But it is worth understanding that because of it, the structure becomes heavier.

If you want to create minimum angle slope, and the roof area is not particularly large, then sand-cement mortar will be enough.

Bulk material

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, most 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 and during roof installation.

Thermal insulation material

Foam concrete

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, 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 in this case It’s worth turning to professionals.

If the roof has minimum slope, then it is important to note that in this case, needs to be installed correct systems drain. The slope itself is done exclusively to the side (funnel, gutter);
If your roof is bitumen, you should make 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).

zero cycle

Greetings, my dear readers.

Although the roof is called flat, this does not mean that it must be made absolutely level horizontally. All roofs must have a slope. It is necessary so that storm and melt water can flow freely into funnels with internal drainage or gutters with an external drainage system.

Let's figure out what the slope of a flat roof should be and how to arrange it.

Why do you need a slope on a flat roof?

In the warm season of the year, rainwater, if the roof is properly waterproofed, quickly or slowly evaporates from it. However, in cold period water puddles constantly freeze and thaw. As a result, the roof covering begins to collapse, and the liquid begins to penetrate into the thermal insulation material.

With a slight slope of the flat roof, moisture stagnates on it and penetrates under the waterproofing layer. This provokes its leakage into the premises of the building.
Dust and soil particles blown by the wind accumulate in permanent water puddles. He delivers the seeds there different plants. They successfully take root in this favorable environment. Therefore, it is not uncommon to find roofs with grass and moss growing on them. Their roots gradually destroy the roof cladding.

To stop all these problems and increase the service life of the roofing pie, it is necessary to slope the roof. It is formed at the stage of roof construction.

Slope value for flat roof

The slope indicates the angle at which the roof plane is located relative to the base. It is calculated using a geodetic instrument - an inclinometer. All types roofing coverings There are minimum and maximum roof slopes in degrees defined by standards.

These values are collected in a published chart. It is very easy to find out which material is optimal for the design slope of the roof. Looking at this graph, it is possible to convert the percentage parameter into degrees and vice versa.

This can also be done manually. To do this, you need to divide the height of the roof by the width divided by 2 (this is the projection of the slope). If you multiply the result by 100, you will find out the roof slope as a percentage.

The slope of a flat roof is determined:

climatic features of the area;
purpose of the building;
type of roofing material.

The angle at which a flat roof must be tilted is determined during its design. SNiP No. II-26/76 “Roofs” indicates its minimum and maximum value:

for flat roofs with cladding made of roll and membrane coatings, polymer and bitumen mastics, the angle of inclination should be from 1.5% (1˚) to 10% (6˚).
for operating and inversion structures, the slope can be from 1.5% (1˚) to 3% (2˚).

Methods for creating minimal slopes on a flat roof

The slope of a flat roof can be done using such materials:

bulk substances (blast furnace slag, expanded clay granules, perlite sand);
lightweight concrete with the above fillers;
polymer concrete mixtures;
thermal insulation boards and mats.

It is worth warning that bulk materials have several disadvantages:

Over time, this layer shifts. In this case, the structure of the slope is disrupted. This creates obstacles for water drainage.
The excessively large diameter (approximately 1.5–2 cm) of expanded clay particles does not make it possible to form a smooth slope.

A ramp made of light concrete mixture does not have such disadvantages. But it cannot always be used. This design has significant weight.

This creates unnecessary pressure on the roof base. Apply concrete mortar to create slopes on the roof, it is possible at the stage of its construction or during major repairs.

To arrange the slope, you can use the following types of thermal insulation materials:

EPPS (extruded polystyrene foam);
dense basalt wool in slabs;
sprayed polyurethane;
lightweight gas and foam concrete.

Creating slopes using bulk materials

The algorithm for arranging a ramp made of expanded clay is as follows:

Photo	Stage of work
	Step 1 On reinforced concrete floor or roll waterproofing is laid on the load-bearing corrugated sheet of a flat roof. This can be waterproofing, glass insulation. These materials reliably insulate the roof from moisture and have a long service life (about 30 years).
	Step 2 The thickness of the bedding should be at least 10 cm. The slopes on the roof are formed from this layer.
	Step 3 Then a second layer of waterproofing is placed on the fill. This may be a polyethylene film. Its panels are overlapped by 10 cm, and the joints are sealed with tape.
	Step 4 After this, the film is filled with a leveling screed. It can consist of concrete or sand-cement mortar.
	Step 5 Lastly, the roof covering is laid. This is done so that the resulting slope is maintained.

To prevent the expanded clay bedding from moving when laying concrete, it is advisable to fix it with cement laitance. But it should be remembered that then the roofing pie will become heavier and the load on the base will increase.

When you need to arrange minimal slopes on flat roof at small area its surface, they can be made with sand-cement mortar.

Use of insulating materials

Now the use of insulation is the least expensive and labor-intensive method of forming slopes on a flat roof. Thermal insulators are inexpensive and weigh little.

The best option- use polystyrene foam or stone wool for bending:

To set the design slope angle, slabs of insulating material are fixed to the roof slab with self-tapping screws or dowels.
Sometimes the heat insulator is glued to the base bitumen mastic or special glue. It should be taken into account that the reliability of the adhesion of surfaces must exceed the tensile strength of the insulation.

Formation of slopes using foam concrete

Foamed concrete mixtures are made on special equipment. Experienced specialists should lay the slope of them:

First, they apply a layer of foam-fiber-concrete mortar to the roof slab using a pump and form slopes from it.
When the screed dries, it is covered with rolled roofing.

With this method of forming a slope, the roof is durable, reliably heat- and waterproofed.

Conclusion

To give a minimal slope to a flat roof, you can use different ways. The main thing is to choose its angle correctly. In this case, the water will flow into the drainage system without obstacles.

If you still have any questions, you can ask x in the comments. Therefore, I say goodbye and success to you in your endeavors.

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