Standardized slopes of pitched roofs. What is the minimum slope of a flat roof. Disadvantages of a flat roof structure

A flat roof with a slight slope will be deemed to have been erected in accordance with building codes and requirements. In this case, the correct bias will not be noticeable to the layman. If the standards are not observed, precipitation will surely accumulate on a flat roof. More information about the flat roofing device can be found later in the article.

How does such a roof work?

The device of a flat roof is not difficult. The basis for the structure can be reinforced concrete slabs or profiled metal sheets.

The flat roof layers are as follows:

cement-sand base or concrete;
vapor barrier materials using modern roll bases or bituminous mastics;
insulation: mineral wool, slabs, expanded clay bedding, concrete fill.

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

If it is a weldable 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 right technology, the construction process will take a maximum of two days. Load-bearing walls are of great importance when choosing the constituent components for the roof. Since they are mounted on beams, which can be either wood or steel.

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

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

The beams must be correctly selected and installed. Then the finishing coat is selected and installed. It should also have good performance properties. Of great importance for a flat roof is the stage of laying a vapor barrier and waterproofing.

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

The material must prevent the ingress of moisture.

A reinforced bitumen film based on fiberglass is often used as the first layer.
The second stage of installation is the laying of insulation, which is often used as expanded clay 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. Polymeric or bituminous materials are used as a basis for these works.

Specialists distinguish between flat roofs for heated houses, as well as roof options for utility rooms that are not heated. If there is no experience in the construction of roofs, then the construction associated with the installation of ceilings over a barn, gazebo, veranda will be a good experience.

Special skills are not required here, since for a roof of a small area it will be necessary to create a single slope in one direction.

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

Laying the flooring on the laid beams. The boards are covered with roofing material on top.
Roofing material is covered with insulation (expanded clay, slag).
Installation of the slope by leveling the insulation.
Installation of the screed over the insulation. The thickness of the screed is at least 2 cm.
The screed is additionally covered with 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 slope for?

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

traditional;
inversion.

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

The idea of an inverted roof is to protect the waterproofing, which can be laid loosely under the insulation. A vapor barrier is optional in this option.

In all flat roof options, it is important to create the correct slope. The correctness of the slope is associated with many parameters. The first important definition is wind action. In regions with frequent and strong winds, it is worth making a small angle of inclination. If the slope is incorrect, gusts of wind will simply tear off the roofing material. In addition, the rafter system and lathing will suffer.

The slope of a flat roof is necessary so that precipitation does not cause premature damage to roofing materials. It is clear that in the summer there may not be a problem with excessive moisture on the roof.

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

If there is sufficient moisture inside the materials, plants will germinate. On some improperly designed roofs, not only grass can be observed, but also trees, which will cause damage to the rafter system.

It also spoils the overall look of the building. Therefore, the procedure for deflecting the roof must necessarily be carried out, moreover, even at the initial stage of construction. Despite the fact that there seem to be a lot of activities to create a bias, the process is actually simple.

The calculations should take into account the materials that will be used in construction.

Payment

For professionals, let's say the calculation of the slope in degrees or percent. 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 calculation is carried out using trigonometric formulas. The value can also be found from the existing table, which has already been calculated by professionals.

The slope of the roof can be formed according to preliminary calculations that define the height difference between the walls. Two steep sides of the ramp 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 erected on walls equal in height.

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

Smaller slope angles are possible for plastic roofs. These can be membrane bases, ondulin, bituminous bases. The number of layers of the roofing cake will also affect the value of the slope. For a roof with two layers, an angle of inclination of 15 degrees must be provided.

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

Variants

If you have chosen bulk options (expanded clay) as the slope materials, then it is worth considering the features of this work scheme.

The concrete base of the roof will be better protected if a layer of glass insulating material is laid on it. It is a good waterproofing material. Expanded clay is poured over the waterproofing. At this stage, you need to create a slope. A layer of expanded clay is covered with a film material, while, if this layer is not a single one, the film is overlapped.
The next step is to apply a screed that includes sand and cement. A layer of bulk material is leveled with a screed. Next, a roofing cake is formed taking into account the existing project.
The slope from the profiled sheet of 6 meters should be equal to 12 degrees. At the same time, in order not to spend money on a sealant, it is enough to adhere to the recommended conditions for overlap. The choice of a roof slope from a profiled sheet is beneficial, first of all, from a financial point of view. This is the most economical and simplest way of roofing.

There are also options for materials that will add maximum comfort not only to the builder, but also to the owners, since they will not create hassle during operation. Such materials include TechnoNicol products. It is the largest manufacturer of roofing materials recognized as reliable and efficient all over the world.

If the traditional method of deflectoring with bulk materials is not suitable, modern methods can be considered.

These methods are worth considering as backfill insulation can:

to shift, which threatens to violate the deviation;
do not provide a smooth transition;
do not ensure the accuracy of work at subzero temperatures.

To ensure the accuracy of the slope, you can consider ready-made insulation boards with the existing slope. Boards can 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 thermal insulation.

Plates are stacked under:

roof covering;
waterproofing layer.

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

A flat roof has advantages over a pitched roof in its ability to withstand the challenges of bad weather.

The sails of a flat roof are significantly less, so it can withstand high wind loads.

But on a flat roof, a roof is laid, which is conventionally called flat, because it necessarily has a slope.

Why is there a slope on a flat roof?

The roof absorbs all environmental influences and is designed to protect the building from them.

In addition to the wind, precipitation also brings serious tests.

It is part of the function of the roof so that moisture does not linger, but flows down to the drainpipes.

Properly organized water drainage significantly extends the life of the roof.

A flat roof, no matter what materials it is made of, will not withstand moisture if water lingers on it, especially in the cold months of the year.

The processes of turning water into ice and thawing will erode the layers of the roof.

In stagnant puddles, dust settles on the surface over time, the wind brings plant seeds, which promotes their germination.

So grass, bushes and even trees appear on the roof, which, with their root system, finally destroy the covering material.

To prevent these negative phenomena, a slope is made on a flat surface, and this process is called a slope.

Minimum roof pitch

The slope is a value that indicates at what angle the roof line is in relation to the base; it can be measured with a geodetic instrument with an inclinometer.

Each type of roofing materials has the smallest and largest values of the roof slope allowed by the norms.

The data of these values are collected in a graph by which it is easy to determine which roofing coverings correspond to which values of the roof slopes.

In the same graph, you can convert the percentage value to degrees and vice versa.

There are tables of such translation.

If you divide the height of the roof by the width, divided by two (the projection of the slope) and multiply the result by one hundred, you get the slope value as a percentage.

The slope is determined by the climatic conditions of the region, the purpose of the building, the type of coverage.

The angle to which the roof should be tilted is calculated at the design stage.

SNiP II-26-2010 “Roofs” defines its minimum value for roofs made of roll materials and mastics from 1.5% (1 o) and up to 10% (6 o).

For operated roofs, its minimum value is in the range of 1.5% ÷ 3% or 1 o ÷ 2 o.

The graph of the mutual conversion of percentages and degrees, expressing the slope and the correspondence of the roofing material to it, is shown below.

Flat roof structure

The basis for a flat roof can be a reinforced concrete floor slab or metal profile sheets.

A flat roof consists of layers:

cement-sand screed, if the base is concrete;
vapor barrier using roll materials or bituminous mastics;
insulation: mineral wool mats, expanded polystyrene plates, expanded clay bedding, concrete mixtures;
waterproofing: several layers of rolled material.

If fusion materials are used for a flat roof, then there will be slightly different components of the roofing pie.

In the building, where the project provides for an internal drain, there will be funnels for the catchment in the roof device.

Materials used for deflection

Bulk insulation

Expanded clay, perlite, slag and other bulk insulation are used to plan the slope on a flat roof.

The peculiarities of these materials, namely the fact that they are free-flowing, create some difficulties.

The minimum slope may be violated over time and the insulation will take a horizontal level.

In addition, if large granules are present, it will be difficult to create a slight slope.

Sometimes, when using bulk insulation, a screed is made on top of it, which makes the roof heavier.

Glass insulation is used as waterproofing.

Concrete mix

Concrete mixtures with fillers of slag, expanded clay, perlite can be used as a heater.

Due to the fact that this material is heavier than other heaters, it is used during construction or if major repairs are being made.

Concrete mixes are not suitable for partial repairs.

To carry out the work, qualified workers and special equipment will be required, which will increase the cost of construction.

Polymer materials as filler

Resin-filled concrete is a good option for sloping flat roofs.

The disadvantage is that the weight of concrete, albeit lightweight, is much greater than other insulation materials.

And, as in the previous case, the involvement of specialists increases the cost of work.

Plastic panels

The modern way is to use plastic panels with an individually set angle of inclination.

The panels are assembled on the roof like puzzles, filled with liquid rubber.

The disadvantage of this method is the high cost of the material.

Insulating materials

One of the most popular ways to ensure the slope of a flat roof is to use insulation: mineral wool and styrene foam boards.

Such materials are economical, easily attached to the base with mastics or adhesives.

Create minimal slope

The slope of the roof is created at the time of laying the insulation.

The way the slope is formed depends on the type of insulation chosen.

If the material is free-flowing, pour it in, setting the required angle.

For fixing, it is poured with cement milk.

Specialists will perform the slope from foam concrete; this method cannot be done without them.

When using thermal insulation materials, to create a given slope, either thermal insulation plates made with a slope are used, or plastic supports that can be adjusted are used.

The main task of the diversion is to ensure the unhindered movement of water to the drainage funnels anywhere on the roof.

If you check - pour out a bucket of water, it should go away without delay.

Qualitatively performed work on the sloping of the roof will significantly extend its service life.

Video about the device of a flat roof.

Sergey Novozhilov is an expert in roofing materials with 9 years of practical experience in the field of engineering solutions in construction.

A perfectly flat roof cannot be by definition. Otherwise, it will accumulate rain and melt water, which will lead to its early deterioration. Therefore, according to generally accepted standards, a flat roof has a slope of 1 to 11.5 degrees. At the same time, the average value fluctuates in the region of 1-5 degrees, which in practice is 1.5 centimeters or more of the slope per meter.

How to calculate the angle of inclination

In order to find out the angle of inclination of the roof, you must:

Know the height of the parapet.
Know the thickness of the roofing cake.
Know the exact location of the funnel.

As an example, let's take a parapet height of 500 mm; the thickness of the roofing cake without taking into account the slope layer is 250 mm, while 50 mm of the parapet should remain on top, above the roof plane; the 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 5 meters away, which means that for these 5 meters we need to go to zero: 200/5 = 40. Thus, the roof slope will be 4 centimeters per meter, or 4%. With a minimum value of 1.5%, this is a sufficient level.

If you consider such a slope to be too large, it can be reduced to a minimum - 1.5%. This means that if from the funnel to the parapet is 5 meters, 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 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 the slope so that the water flows evenly over the entire roof area.
Formation of kerchiefs... 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.

Markup

To conveniently mark the future screed, you will need a laser level. The laser is aimed at an acceptable level of the thickness of the parapet, in our case it is 200 mm, and a line is drawn around the perimeter of the entire roof with a construction pencil. In the absence of a laser level, you can use a conventional or hydraulic one. Then we find the thickness of the parapet in one place and, placing a level, draw a line around the entire perimeter. You can check that the line does not crawl up or down using the hydraulic level.

Further, a lace is pulled from the parapet to the funnel. Beacons can be placed along the lace, so it will be more convenient to work. If the deflection occurs with the help of the formation of kerchiefs, the lace is necessarily pulled along their border.

Roof sloping with polystyrene concrete

Polystyrene concrete is a type of lightweight concrete made from cement, water, mineral filler and all kinds of additional additives. In order to make it heavier, it is permissible to add sand. To produce polystyrene concrete at home, you will need:

Concrete mixer. Specialists use a special unit that allows concrete to be pumped through a hose directly to the roof.
Cement 500 brands.
Polystyrene chips. Manufactured from defective polystyrene boards.
Water.
Liquid soap.
Sand.

It is made from the calculation: 2 shovels of cement, a shovel of sand, 5 ten-liter buckets of polystyrene okroshka, 50 grams of liquid soap, water, until the mixture reaches the desired consistency. The concrete should not be runny or too dry.

The order of work is as follows:

Creation of roof markings. Use beams or beacons. Please note that the timber must subsequently be removed on time. That is, when one section is flooded and the solution has already frozen, the timber is removed so that it does not interfere with the flooding of the neighboring section. The lace in this case is a weak helper. Concrete will make it wet and sag.
To create a flat roof slope, the resulting mixture must be delivered upstairs. We advise you to take care of the creation of the winch in advance. This will make it easier to lift the concrete. Better yet, initially bring all the material onto the roof, and also deliver a concrete mixer there. This will greatly simplify the work of deflection.
Polystyrene concrete is pulled together by beacons using a rule. It is advisable to leave as few irregularities as possible, subsequently insulation will be laid on the concrete. The solution hardens in a day, and it is already possible to move freely through it.
Insulation is laid along the slope-forming layer, and then everything is fixed with a cement-sand screed, for which a reinforcing mesh is necessarily laid. The screed is approximately 6 centimeters thick.

Polystyrene concrete is used both on reinforced concrete bases and on bases made of profiled sheets.

The advantages of this material include:

Inexpensive cost.

Disadvantages:

The complexity of installation, provided that the work is done independently.

Expansion of expanded clay

The creation of a minimum slope of a flat roof is permissible when using expanded clay. It is obtained by firing clay shale. Expanded clay is laid both on a base made of reinforced concrete slabs or corrugated board, and on a heater.

The order of work is as follows:

Creation of roof markings. To do this, you can use a wooden bar, a metal profile or just a lace. It is more convenient to work with a bar and a profile, but closer to the end of the work they need to be obtained, and the resulting pits should be leveled. This is not necessary when using laces.
Backfill of expanded clay. To facilitate this process, you can order a manipulator that will deliver expanded clay directly to the roof. Otherwise, the material will have to be worn by hand for a very long time.
Beacon alignment. Align using a rule. For convenience, you can make a wooden rule with a handle, according to the principle of a rake, only instead of teeth - an even, wide bar. 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 a good drainage of water.
To fix expanded clay in the desired position, it is poured with cement milk. Prepared from cement and water, with the calculation of 200 kg of cement per 1 cubic meter of expanded clay. The consistency of the milk must be sufficient for it to spill to the ground, but at the same time, it must not be allowed to flood.

Fixing expanded clay is not necessary, but desirable, since during the installation of the roof, you will often have to walk on it, violating the created level.

Removing the markings. If a timber was used, or a metal profile, the depressions are filled up.
Next, you need to fully fix the slope with a cement-sand screed, about 6 centimeters thick. As in the previous case, a reinforcing mesh must be laid for it.

Advantages of expanded clay:

Low cost. Even lower than when using polystyrene concrete.
Convenience of creating a flat roof slope according to SNiP. Expanded clay is light, it is convenient to take it apart, you do not need to remove the excess from the roof. The only problem is to deliver the material to the roof.
Good thermal insulation characteristics.

Cement milk, like other fixing solutions, is not able to ensure 100% preservation of the expanded clay level.
If it rains during the installation process, this can become a big problem. You cannot expel moisture from under the expanded clay, which means you have to wait until everything dries out.

Expansion of expanded clay concrete

Another popular material for creating a flat roof slope according to SNiP is expanded clay concrete.

To prepare it you will need:

Cement
Sand
Expanded clay

It is made according to the proportions: one shovel of cement, two shovels of sand, three shovels of expanded clay. Water is added until the solution reaches the required consistency.

The order of work is exactly the same as in the case of polystyrene concrete:

Markup.
Delivery of mortar to the roof.
Stretching by level.
Laying insulation and forming a fixing screed.

Advantages of expanded clay concrete:

Low cost. Comparable to polystyrene concrete.
Good thermal insulation.

Very difficult installation when carrying out work on your own. The main problem is the delivery of concrete to the roof.

Deflection with insulation

A wedge-shaped insulation is produced especially for flat roofs. It is made in the form of mineral wool and extruded polystyrene foam.

There are three main elements used to create a base slope:

Type A slabs creating a slight slope.
Type B slabs complementary to A slabs.
Additional plates required for raising the height.

The order of work is as follows:

Marking is not needed, therefore, after laying the vapor barrier film, they go directly to the installation of the plates. They start from the lowest point, type A slabs are laid in the first row.
Type B slabs are laid behind the first row.
Then add additional plates, 40 mm thick, are laid and plates A.
New additional 40 mm thick slabs and B slabs. These operations are repeated until the parapet is reached. In this case, the flat roof has a slope of 1.7%.
If necessary, mechanical fasteners use special dowels "mushrooms". Average consumption - two dowels per sheet.
On top of this slope, another layer of insulation is laid to evenly distribute the load.

To create a counterclone along the resulting gutter, use:

J slabs
Plates K
Additional slabs

The counterclone is made in the form of a rhombus, with sequential laying of sheets J and Pa parallel to its lines.

Simple and quick installation.

The high cost of wedge-shaped insulation.

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

When erecting a roof slab, it is very important to understand that the roof is the main link of the house that absorbs the sedimentary impact. That is, the roof is subjected to wind load (in the case of a pitched structure), as well as snow and rain loads. Moreover, according to SNiP, the weight of the load per m2 of the roof in case of precipitation in the form of snow is 180 kg. If the snow forms a stale snow crust, then this load will already be 400 kg / m2. In addition, it should be understood that the entire mass in the form of snow with spring melting should go somewhere, and not dry out naturally on the roofing. In particular, the need for a slope for a flat floor is due to the following factors:

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

Important: in order to avoid all of the listed negative phenomena on a flat roof, a certain amount of roofing work is performed, which is called a slope. That is, they form a kind of minimum slope of a flat roof.

Flat roof structure

Typically, a flat roof has the following structure:

Base. Reinforced concrete floor slabs (for large high-rise buildings) or profile sheets can be selected as a basis.
For a concrete base, a screed is formed from a cement-sand mixture.
Vapor barrier layer.
Insulating materials (slab or roll).
Waterproofing material.
Finishing roofing.

Roofing materials for a flat roof, depending on the angle of its slope

In order to avoid mistakes when choosing a roofing material for a flat roof, it must be borne in mind that coatings with a rough surface will delay the process of precipitation from the roof. In turn, smooth materials will help them quickly move towards the slope. In this case, for the arrangement of the rafter system and the pitch of the lathing of the flat roof, the type of the selected coating should be taken into account. And the topcoat itself must be selected already adjusted for the slope angle of a flat roof. So, according to the intensity of the slope of a flat roof, the materials for covering can be as follows:

The minimum slope of the slope. Here, the best option would be rolled material in the form of glass insulation or simple roofing material. Membrane roofing can also be used. Thus, if the slope of a flat slab is only 2%, then it is necessary to lay from 2 to 5 layers of coating. The exception is 15 ° slopes of flat roofs. In this case, you can lay 1-2 layers of material. The lathing for such a low-slope roof should be solid.
If the slope angle of the roof is 12 °, then a profiled sheet can be used as a roofing material. And with an increase in the angle of inclination up to 15 °, metal tiles can also be laid. But in this case, the overlaps should be at least 20 cm, and all joints must be sealed as carefully as possible. The step of the lathing 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 pitch of the boards is allowed.
As for ceramic tiles or asbestos-cement sheets (slate), then according to SNiP for such materials, the slope angle must be at least 22 °. That is, they are not suitable for a flat roof.

Calculation of the slope angle of a flat roof

To change the correct slope angle for a flat roof, you can use one of three methods:

Using a special online calculator program;
The use of a protractor device;
Using 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, an easier way would be to calculate with the help of 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 of its width:

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

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

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

Roof slope and materials for it

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

Insulating 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... A radically new roofing material that has a predetermined 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 sloping. However, it is worth remembering that all such concrete mixes are very high.
Concrete mix filled with slag or expanded clay... This material fits very well and at the same time forms a heat-insulating layer. However, it also carries a lot of weight.
Bulk insulation materials in the form of slag, expanded clay, etc. To fix them, the embankment is poured with cement milk. Moreover, if you do not fill in bulk, then over time, the slope of the roof will change. Loose ones can move out of a given position and form a single flat plane.

Important: Only specialists should carry out work on large-scale expansion. And although it is quite costly, the result will be guaranteed to be productive.

Choosing the type of roof, determining the angle of inclination and other parameters of the roof is an important and responsible task that requires knowledge of the standards and taking into account the climatic features in the region. The article provides a description of a flat roof, its advantages and features. It explains in detail what it is for and how the slope of a flat roof is made. The information will be useful to all land owners planning the construction of a residential building, auxiliary or outbuildings.

Source horoshidom.ru

Flat roof structure

A flat roof is a single sheet, not divided into separate sections, with a certain slope for organizing water flow. There are buildings of complex architecture, consisting of several departments with different heights. Each part usually has its own roof, but the general rules for each individual site remain the same.

Flat roofs are traditional for the architecture of the southern countries, but in the northern regions they are used mainly for non-residential buildings - economic or auxiliary. The reason for this attitude is the abundance of precipitation, which cannot be found in such quantities in regions close to the equator.

Source folksland.net

The traditional flat roof structure consists of a support system (rafters) forming an inclined plane with selected parameters. On top of the rafter system, a plank flooring is created, on which the roofing sheet is attached. This design is simple, erected quickly enough and allows moisture to be removed from the under-roof space.

The disadvantage is the use of wood, which has a tendency to warp, rotting and is a fire hazard. In addition, timber rafters have a limited load-bearing capacity, which requires careful calculation to match the snow load. A considerable danger is the effect of the wind, strong gusts of which can tear off the roof, causing significant damage.

Source odome.kz

In order to increase the strength and increase the bearing capacity of flat roofs, a construction technique has been developed, in which the construction of a 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 is laid. As a result, the overlap of the upper floor becomes the support system, and the slope of the flat roof strengthens it and forms the required angle of inclination, which is optimal for the given conditions and materials.

Source krovlikom.ru

Advantages of flat roofs

The main advantage of a flat roof is the simplicity and cost-effectiveness of construction. Such a surface is comfortable and safe, and allows for maintenance or repair work in optimal conditions. The surface area of such a roof is significantly less than that of pitched structures, which allows significant savings on roofing material.

An additional advantage of flat roofs is the convenience and simplicity of installing various technical devices and equipment on them - satellite dishes, solar panels, etc. simplifies the repair and maintenance of equipment, which can be carried out at any time of the year.

Source ivd.ru

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 sites.

Source archilovers.com

Slope for a flat roof: a whim or a technical necessity

The 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, stagnant rainwater will provoke aggressive effects of chemical elements and oxygen dissolved in the mass of precipitation. In winter, 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.

Source blues-dev.ru

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To organize an operational water flow, at least a minimum slope of a flat roof is required, which allows water to be removed by gravity from the roof. The best solution to the problem for large roofs is to slope the 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. In SNiP there is a joint venture 17.13330.2011, or, more simply, in the Code of rules for roofing. It defines the standard values for the angle of inclination of the roof covering, depending on the structure of the roof, as well as the materials used. The values that the slope of a flat roof has, SNiP determines in accordance with the surface properties of various roofing coatings. The roughness of the metal sheet is much less than that of soft or wavy surfaces.

The slope is measured in various units:

In percentages.

Height to length ratio.

In degrees.

Source kak-sdelat-kryshu.ru

Such an abundance of units of measurement is caused by the specifics of construction work - it is much more difficult to control the angle using a protractor on the site than to measure linear dimensions.

The situation is somewhat more complicated when building a roof with a large area. Making a bias in such conditions is not always rational. The solution to the issue is the slope of a flat roof with an internal drain, when the entire canvas is divided into relatively small areas with gutters. Water entering them is discharged through the pipeline system into the storm sewer. Such a roof structure is more complicated and requires the creation of a drainage system, but on large buildings this option is optimal.

Source blues-dev.ru

In practice, the tilt angles are much smaller and largely depend on local climatic conditions. The main factors influencing the choice are:

Snow amount in winter.

The strength of the winds prevailing in the region.

The weight of the snow is significant. It can be determined by the tables in the SNiP annexes, where the average annual values for different regions of the country are indicated. The lower the angle, the less is the possibility of self-descent of snow masses. At the same time, a large angle of inclination increases wind loads, which are dangerous in that the roof covering can be torn off the supporting surface. The destruction occurring in this case can lead to human casualties and threaten not only this building, but also all objects located nearby.

The choice of the angle is based on the magnitude of the expected loads and is taken in accordance with them. If the roof structure is made of durable materials that can withstand the static load from the weight of the snow, then usually efforts are made to minimize wind effects that are dynamic and unpredictable in direction.

Source architizer.com

How to calculate the slope of a flat roof

The specialized calculation of the angle of inclination is an extremely difficult engineering task. SNiP requirements 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 is 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 obtained value on another resource in order to compare the data and balance the results. It should be borne in mind that online calculations are only advisory and should not be used in the construction of critical structures.

Source blues-dev.ru

Roofing materials for a flat roof, depending on the angle of its slope

The choice of roofing material should primarily be determined by the angle of inclination of the roof. There is a mass options:

Roofs from piece materials and corrugated sheets

Metal roof.

Soft roof.

You can form an angle of inclination by creating a support structure of the desired configuration or by filling the surface with an inclined layer of insulation. There are also specialized types of materials, for example - wedge-shaped insulation from the Technonikol company, the roof slope with which is created by laying slabs of a specific shape.

Source howbuilds.ru

The choice of the most suitable material is made by comparing local climatic conditions, building parameters, capabilities and preferences of the owner. All these factors are equally important, but the priority in decision making is recommended to be given to representatives of the construction company with experience and special knowledge.

Video description

In the video, you can see the device of flat roofs:

Conclusion

In conclusion, the increase in the number of buildings with a flat roof should be noted. The fashion for such architectural solutions, which came from Europe, requires the use of appropriate technologies and materials. It is irrational and impractical to approach construction with the usual standards common in Russia. For buildings with flat roofs, it is required to create a special project that takes into account the peculiarities of the climate, the properties of materials, and hydrogeological conditions.