Slope but not slope of the roof 4. Calculation of the minimum and optimal angle of inclination of the roof in percent and degrees, depending on the type of roof and roofing material. Dependence of the roof material on the degree of slope

Roof of the house

The roof is a structural element of a building that is responsible for protecting it from external factors. It must successfully withstand precipitation in the form of rain, hail, snow, squall winds and destructive hurricanes. The correct roof slope plays a large role in the rapid removal of water and snow from the roof. Combined with high quality waterproofing, it provides excellent protection for the entire structure, including the interior.

Not only these indicators will depend on the competent slope of the roof, but also its long-term work and strength. How to make a calculation correctly, what factors to take into account, how to calculate it for roofs with different coatings - all these questions will be discussed in this article.

On the factors affecting the calculation of the angle of the roof slope

Roofs, as already mentioned on our website, have a different shape and number of slopes. They are one-, two- and four-slope. The angle of inclination of the roof depends on the number of ramps on your home.

Construction work on the installation of the roof may be suspended if you do not decide in advance what material you are going to make the topcoat and what is the angle of inclination of the roof. It must be remembered that these two concepts are closely intertwined, since the type of the proposed roofing material will be taken into account when calculating the angle of inclination of any pitched roof.

Let us dwell on the factors that are taken into account when calculating the angle of inclination of the roof.

For example, when choosing the angle of inclination of a pitched roof within 9-20 degrees, you will need to take into account such factors as

• topcoat material;
• existing climatic conditions;
• the functional purpose of the building.

In the case when the roof will have two or more slopes, then not only the above factors and the area in which the house will be built will be taken into account. It will be necessary to take into account the purpose for which the attic is being arranged. If it is not provided for housing, but should be used to store temporarily unused things and objects, then you should not arrange a large room for these purposes (we are talking about the height of the ceiling). When the owners plan to make a living space out of the attic in the form of an attic, then there is a need for a good roof with a significant slope.

In those regions where strong winds are not uncommon, a minimum roof slope is made. Therefore, it does not have such a strong effect of the wind. It is also not recommended to make roofs without a slope. Such coatings can be arranged in regions with a large number of sunny days and a low probability of precipitation.

Wind resistance with a high roof is significantly greater than with a low roof. However, with very small inclines, there is a possibility that the wind could rip off the topcoat. It turns out that with very steep roofs there is the same danger as with roofs that do not have a slope at all. Therefore, it is recommended to choose the following slopes of the roofs - with light winds, it can have a value from 35 to 40 degrees, with strong winds, the optimal angle of the roof slope is 15-25 degrees.

In areas where there is a lot of precipitation (we are talking about snowfalls, hail and rain), the angle of inclination can be increased to 60 degrees. It is most suitable because it allows you to minimize the load on the roof from snow cover, as well as melt water and a large amount of moisture during rain.

Taking into account all of the above, the angle of inclination of the roof is calculated based on the range from 9 to 60 degrees. Designers usually make appropriate calculations and usually settle for values ​​that range from 20 degrees to 45.

Why is such an angle of inclination of the roof attractive? The fact that you can use any roofing material - metal, corrugated board, slate, etc. Nevertheless, each material for the topcoat has its own requirements, which are taken into account when constructing the roof structure.

1. The use of overlaid materials is most suitable when the roof has a slope of 0-25%. When the slope is 0-10%, then the material must be laid in three layers. If the angle of inclination is in the range of 10-25%, one layer can be dispensed with, but the material must have a dressing.
2. Asbestos-cement corrugated sheets (slate) cover roofs with a roof slope of up to 28%.
3. Shingles are used when the roof has a slope of at least 33%.
4. The steel covering is laid on the roof with an inclination angle of less than 29%.

Material consumption directly depends on the slope of the roof. The larger it is, the greater the consumption of the finishing material. As a consequence, a flat roof in this respect will cost less than a roof with a 45 degree slope.

If you know the slope of the roof, then it is not difficult to calculate the amount of material required. The same can be said for the height of the roof structure.

Let's dwell on each specific type of roofing.

Metal roofing

When compared with other roofing materials, the metal tile has a considerable weight. Therefore, when constructing a roofing structure using such a topcoat, one should take into account all the nuances and try to build it so that it has a minimum roof slope angle.

This issue deserves special attention in areas with very strong winds. As you know, the load from the wind has a strong and negative effect on the roof. In this case, the calculation of the roof structure must be done especially carefully. When the angle of inclination of the roof is large, the roof can "swell", which will entail an increase in the load, which will affect the entire structure. In turn, this can lead to premature destruction of the roof.

Roofs, which are covered with metal tiles, must have a minimum angle of inclination within 22 degrees. Empirical evidence suggests that this indicator prevents moisture from accumulating at the joints of the roofing. They are protected from unwanted water seepage in the form of melted snow or rain.

Important! The minimum roof slope, when there is such a need, can be at least 14 degrees. If soft tiles are used as a covering, then the minimum value is reduced to 11 degrees. In this case, it would be correct to arrange an additional solid crate.

Roof from corrugated board

It is known about the corrugated board that it takes the place of one of the most popular roofing materials. Everyone knows its advantages in the form of low weight and ease of installation. It is not difficult to fix profiled sheets on the roof.

Important! It should be noted that when installing such a roof, the requirements for the minimum angle of the roof slope are more than 12 degrees (see the recommendations of the manufacturers).

Roofing using rolled "soft" materials

When the roof is made of soft types of roofing, then we are talking about roofing material, ondulin, polymer (membrane) roofing. When deciding how to calculate the angle of inclination of the roof, take into account the following:

1. The number of covering layers. Depending on them, the angle of inclination of the roof structure can be from 2 to 15 degrees.
2. When covering in 2 layers, it would be good to stop at a 15 degree angle of inclination of the roof. For a three-layer, it is quite enough to have a slope within 2-5 degrees.
3. Membrane coatings, which are optimal for any type of roof, including the most complex in their geometry, are placed on roofs with a slope of 2-5 degrees.

Without a doubt, the angle of inclination of the roof will be chosen by the owner of the building. He must take into account that the roof is designed for temporary and permanent loads. Precipitation and its weight are temporary. These include the wind, which exerts pressure on the roof structure and the finish coat itself. When permanent loads are mentioned, we are talking about the weight of the roof structure itself and the material of the topcoat.

Such a structural element of the roof as the lathing - its type, pitch and design depends on the slope of the roof. For example, the lower the angle of inclination, the shorter the sheathing step in the roofing system should be. The minimum roof slope provides for the lathing step, which is 35-45 centimeters.

One of the main questions is the question of the amount of material for the topcoat that needs to be calculated and purchased. There is such a tendency here - a larger roof slope requires more material consumption.

I would like to offer some practical tips that will be useful when choosing a material for the roof:

• with a slight slope of the roof (less than 10 degrees), the roof can be covered with a material containing stone chips or gravel (5 mm thick for chips and 15 mm for gravel).
• when the angle of the roof slope is more than 10 degrees, then a basic bitumen waterproofing device is required. In the case of using roll materials, additional protection must be applied. This coating is usually a color.
• covering the roof with such roofing material as corrugated board or asbestos-cement sheets provides for the sealing of butt seams. The joints in this case are made double.

We calculate the angle of inclination of the roof

The calculation of the angle of inclination of the roof depends on the height of the ridge. What height the roof in the ridge will be depends on the functional purpose of the attic space.

When a full-fledged attic room is made from the attic, the angle of inclination is calculated as follows:

For example, the end of the roof (gable width) is 6 meters. This figure is halved (6: 2 = 3). The height of the roof in the ridge is always taken as standard 1.8 meters.

Sin A = a / b = 3 / 1.8 = 1.67

Using the Bradis table, an approximate value is found, which has the angle of inclination of the roof with a value of Sin A = 1.67 - this value is in the range of 58-59 degrees. You can stop at the maximum value of 60 degrees, which will become our desired angle of inclination of the roof slope.

In civil low-rise construction, experienced builders call pitched structures the most common, rational and economically feasible type of roof. They can consist of one, two, three, or even four slopes, planes that meet at one point, called a ridge. Pitched roofs are distinguished from flat roofs by the angle of inclination, which, according to building codes, should exceed 2.5 degrees. The choice of the slope is an important stage in the creation of the project, on which the strength, load-bearing capacity and durability of the structure depend. In this article, we will show you how to choose the right angle of inclination to facilitate snow melting in winter.

The angle of inclination of the roof is a parameter of the engineering calculation of roof structures, reflecting the ratio of the height of the ridge to the width of the base of the roof. Pitched roofs can have a slope of 2.5-80 degrees, however, the optimal range of slope values ​​is 20-450. The area of ​​the slopes, wind resistance and snow load depends on this parameter. The following terms are found in the specialized literature:

• Minimum slope. The minimum angle of inclination in general for is 2.5 degrees, but depending on the waterproofing material used, this parameter may increase. The smallest minimum angle for rolled bitumen and membrane coatings is 2-4 degrees. The minimum allowable value for metal tiles and corrugated board is 11-12 0, for ceramic tiles - 22 0.
• Optimal. The optimal roof slope is called the most suitable slope in given climatic conditions when using a certain waterproofing material. The optimal angle of inclination ensures that the snow melts on its own, making it easier to maintain the roof.

Important! Roof slope can be expressed in degrees, percentages, or aspect ratios. To calculate this parameter for a roof structure, you must divide half of the facade width by the height and then multiply by 100 percent.

Criterias of choice

The choice of the slope is based on an engineering calculation that takes into account the climatic conditions of the area where the construction is taking place, the characteristics of the roofing and the load-bearing capacity of the rafter frame. In order for the design to be reliable, the following criteria must be taken into account:

1. Wind load. The steeper the roof, the stronger its sailing capacity. Therefore, in regions with strong, gusty winds, flatter roof structures are preferable. Although, on the other hand, waterproofing material can be ripped off low-slope slopes by the wind.
2. Snow load. The greater the snow load, the more covered the slopes are. The angle of inclination of the roof 40-45 degrees provides an independent snow fall from the surface of the roofing material.
3. Topcoat characteristics. Each roof covering has an optimal slope, which must be taken into account when designing the structure.
4. Carrying capacity of the frame. The smaller the cross-section of the frame elements and the greater the distance between them, the higher the slope must be in order to withstand the snow load.

Optimal indicator for facilitating snow melting

The limiting factor when choosing the angle of inclination of roof slopes in central Russia is the high snow load typical for this area. A large amount of snow falling in the winter increases the pressure on the rafter system, leading to deformations of the frame and the roofing material of the structure. Experienced craftsmen believe that there is a strong correlation between slope and resistance to snow load:

1. If it is less than 30 degrees, then snow accumulates on the surface of the slopes. Snow drifts and ice has a significant mass, due to which the load on the rafter frame increases, reaching critical readings. However, some of the snow is blown off the surface by the wind. If the angle of inclination of the roof is in this range, then snow guards are not installed on it, especially if the roofing material has a rough surface.
2. With a value of 0 degrees (i.e. for flat roofs), the snow load on the surface reaches its maximum values. Snow on such structures accumulates in large drifts, which lead to the collapse of the frame if the roof is not periodically cleaned.
3. If the roof is 45 degrees and higher, then in calculating the load on the rafter frame, the weight of the snow can be neglected, since the snow slides off the slopes on its own, without lingering on the slope. To secure the operation of the roof, which has a large angle of inclination, snow cutters are installed on it, cutting the layer of snow when descending onto thinner plates, which have a lower speed and fall energy.

Please note! According to construction climatology, the territory of Russia is divided into 8 climatic zones, each of which has its own average annual snow load. This reference value is used to calculate the slope of the roof, the section thickness of the truss members and the choice of roofing.

Influence on design

It is important that changing the slope to facilitate snow melting greatly affects the roof structure as a whole. An increase in steepness has the following consequences:

• Increasing the weight of the roofing cake. The weight of 1 square meter of a roofing cake with a slope of 50 degrees is 2-2.5 times higher than a roof with a slope of 2 degrees.
• Increase in the area of ​​rays. The steeper the roof, the larger the area of ​​its slopes, the greater the consumption, and, consequently, the cost of the roofing material.
• Relief of the rafter frame. In the absence of snow load, the roof frame can be lightened to save on wood.
• Inability to use roll materials. If the roof slope exceeds 40 degrees, it is not recommended to use bitumen and membrane roll materials, as they can simply "slide" down under the influence of high temperatures.

Experienced craftsmen note that the right choice helps to increase the service life of roofing structures, to facilitate the operation and maintenance of the roof in the conditions of snowy Russian winters. Errors in the design associated with the wrong choice of the optimal angle lead to deformations of the rafters, collapse of the crate, pouring atmospheric moisture into the inter-seam space during slanting rain or thaws.

Video instruction

a - one of most used roof structures, which has two inclined planes separated by an edge - a ridge.

The slopes can be either the same, creating an isosceles triangle in cross-section, or different, having different angles of inclination and area.

In addition, common attic structure a gable roof, when the slopes consist of two planes with different angles of inclination.

This design allows more effective use the attic space for household or residential purposes.

The main advantage of gable roofs is considered simplicity of construction and reliability in operation, absence or small number of valleys or gutters, contributing to the accumulation of water or snow.

The overall structure ensures optimal weight distribution of the rafters and roof onto the walls, contributing to maximum roof life.

You can read more about how to make a gable roof yourself.

During the period of operation, the roof is constantly is under stress different kinds. The problem is not in their presence - this issue is easily solved strengthening... The point is the variety and unevenness of these loads.

Constant and unchanging- the weight of the roofing cake and the roof itself, they create continuous pressure on the elements due to their weight. The additional ones include the wind load and the weight of precipitation.

NOTE!

These factors dangerous because of their unpredictability and a wide range of values.

If the region is dominated by moderate winds of a certain direction, then a one-time gust of hurricane force can cause significant damage or even rip off the roof. In winter, with an abnormally large amount of snowfall, the load on the roof can exceed permissible values, which is fraught with deformations or damage to the integrity of the coating and the formation of leaks.

To deal with such natural manifestations is possible only with preventive measures:

• Creation of a margin of safety in the calculations.
• Taking into account the prevailing winds in the region, their strength and direction.
• Taking into account the average annual precipitation, their composition and quality indicators.
• The correct choice of the angle of inclination of the slopes.

The choice of the correct angle of inclination of the slopes is one of the most effective methods of neutralizing the harmful effects on the rafter system. It allows you to reduce the pressure of snow by eliminating its accumulation, to regulate the wind load by reducing the windage of the roof and to ensure the drain of rainwater, excluding its freezing at night in the autumn.

Wind loads on truss systems

Dependence of the angle of inclination on the choice of roofing material

From the point of view of saving material and reducing the windage of the roof, the angle of inclination of the slopes should be minimal.

At the same time, a roof that is too sloping will hold large masses of snow or impede the effective outflow of water.

But the most the main criterion the choice of the angle of inclination is.

Its characteristics determine the optimum based on the following indicators:

• Rigidity... A value that defines the allowable weight or pressure on a surface without causing deformations.
• Plastic. The ability of a material to change shape under the influence of loads without destruction.
• Waterproof. Water absorption promotes rapid destruction material.
• Surface quality. Snow masses easily come off smooth surfaces, relieving the roof from pressure. At the same time, the descent of large volumes can cause certain harm people or property caught in the snow fall zone.

Based on these parameters, each type of roofing material has its own slope limits... Simplifying a little, we can say that materials with a smoother and more waterproof surface allow the smallest angle of inclination, and more rough and absorbent water require a steeper inclination. Mostly dominated by values ​​from 20 ° to 45 °.

Angle versus angle and roofing material

How to measure the angle of inclination of a gable roof

First of all, you should decide what is the angle of inclination. This is the angle between the plane of the ramp and the horizontal.

It is customary to measure the slope of the slopes. in degrees or percentage... If everything is clear with degrees, then the percentages are obtained from the ratio of the height of the ridge above the ceiling of the upper floor to half the width of the building.

The use of percentages is introduced for simplicity - complex trigonometric calculations fraught with errors, and dividing one value by another is easier and more accurate. However, they often resort to help Bradis tables, to find out the exact value in degrees.

When calculating the angle of inclination of the polygonal slope, the values ​​related to the defined areas are used. This applies both to the width - the part that is covered by the roof section is taken into account, and to the height above the floor.

All subsequent calculations are made for each site separately, display and use some the average is not possible.

This applies to both the determination of the loads and the power of the bearing elements, and the calculation of the required amount of material.

How to measure the angle of a gable roof

The minimum angle of inclination of the gable roof

It is necessary to immediately determine the correct understanding of the term "minimum". This refers to the smallest permissible value of the angle of inclination of the roof, taking into account the wind and snow load.

It is in this moment that many difficulties lie. : the indicated values ​​in different regions are very different from each other, therefore you need to know the average annual rainfall, the volume of snow and its qualitative composition (wet snow is much heavier than dry and can cause destruction incorrectly calculated roof).

In addition, one should have an idea about the prevailing winds, their strength and direction and, which is especially important, about the presence of periodic hurricane force wind gusts in the region.

CAREFULLY!

Ignore such extreme weather events for reasons of "maybe it will blow" under no circumstances because one single case is capable of destroy the entire roof.

Given these circumstances, the minimum angle can be determined as the smallest value stated in SNIPs, adjusted for climatic conditions. Experts unambiguously consider for pitched roofs at least 20 °, which only applies to non-residential or unused attics.

Finding the minimum angle

Optimal angle of inclination of the gable roof

The angle of a regular gable roof lies within 20 ° -45 °, which corresponds to the scatter in the values ​​of material properties and averaged climatic parameters.

The angle of inclination of the gable roof - important indicator, affecting the durability and integrity of the entire building, and it is impossible to treat it as a secondary factor.

Taking into account all possible loads, both permanent and one-time extreme, will help to ensure safety and comfort of your home.

More accurate values ​​are selected based on factors such as:

• Appointment of the attic.
• Roofing used.
• Climatic conditions.

Optimal angle of inclination of the gable roof

It has a number of its advantages, such as: less materials will be spent on its installation, ease and simplicity of installation and additional useful territory.

For many, the phrase flat roof is in no way associated with a slope. Although this is far from the case. Even the flattest 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 safely drain into the installed funnels, which are part of the internal catchment, or into the gutter of the external system.

In addition, it is easy and simple to install additional necessary equipment on such a roof. Today, there are several types of flat roofs:

• Operated roof;
• Unexploited roof;
• Traditional roofs;
• Inversion roofs.

The slope that should be on this type of roof is approximately 1-5 degrees, if we neglect this, then water, both rain and melt, will accumulate, which in turn will damage the roof.

In summer, you may not face such a problem, since rainwater dries up under the rays of the sun. In winter and autumn, such water can freeze at night and melt during the day.

Puddles form, which ultimately leads to the fact that 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 be covered with dust, which in due time settles on the bottom. The 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 the 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 procedure for unfolding the roof... Such a complex manipulation is carried out at the time of the construction itself.

The process itself is quite complex, and includes many activities that are different in structure. The purpose of this procedure is for the roof itself to acquire the necessary slope..

But before you start spreading the roof, you need to find out what a flat roof consists of.

Flat roof

In fact, it is a pie of several layers:

• Immediate base, which is reinforced concrete slabs that have a certain wave height;
• which can be made from different materials such as bitumen or roll materials;
• The next layer is which can be made of rock wool or other durable material.

The ingredients of such a pie can be changed if the builder wants to make the entire roof with new building materials. It should be understood that a procedure such as bias, carried out directly at the time of laying the insulation.

It is important that in addition to such basic layers of the roof, there must be water intake funnels or gutters.

The angle of the roof slope is very important, and it depends on many parameters. The first thing to look out for is wind impact... 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 the sheets of the roof... 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 step.

Obviously, the steeper the slope of the roof itself, the faster the outflow of water is.

Percentage slope

Minimum angle and roof slope calculation

The minimum slope angle can be determined based on the materials of the roof itself:

• If the roof is made of, then its 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 cracks in the material, and other joints, must be treated with a special sealant - frost-resistant / waterproof. If the angle of inclination is 15 degrees, then the sheets of material should overlap about 200mm if the angle is less, then the overlap should increase;
• The minimum slope angle can be in cases where if the roof of your house is made of artificial materials... These, in turn, include membrane coatings, materials based on bitumen. It is logical that by the value of the slope angle, the number of layers of the roof itself also affects... If, for example, the roof is made in two layers. then an angle of inclination of 15 degrees is quite enough;
• Having covered the roof, you should understand that 11 degrees of inclination is quite enough, but at the same time you need to make a solid type crate.

Such a process as the sloping of a flat roof, made of such materials:

• Extruded polystyrene (TechnoNIKOL);
• Cotton wool, both mineral and glass / basalt based;
• Polyurethane foam;
• Foam concrete;
• Foam glass;
• Various kinds of filling materials.

Each of the materials has its own pros and cons. And before starting work, it is worth correctly calculating the angle of inclination itself... In fact, it is quite easy to carry out this calculation, for this you need to use a goniometer, or else with fairly simple mathematical formulas.

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

The instructions for the use of bituminous and polymer coatings for slope indicate that the optimal slope angle should be 1.5 degrees. It is permissible to perform a slope of 1-2 degrees.

Everything is very simple here. You need to know the height of the roof and its width... Further, simple trigonometric formulas will help you calculate the right angle (sine, cosine, tangent). And according to the existing table, which was calculated earlier, you can find out the value as a percentage.

There is another way of calculating - the value of the height of the roof, must be divided by half the width, and the result already obtained is multiplied by one hundred, after that, in the table, you can find out the percentage of the future angle of inclination. This option is faster, but both are correct in terms of accuracy.

Minimum slope

Expansion of a flat roof with bulk materials

If you decide that the deflection 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:

1. First of all, on the concrete base itself, it is necessary to lay a layer of glass insulation... This material has not only a long service life (30-35 years), but also has a high level of waterproofing;
2. Farther, it is necessary to pour the main material on it - expanded clay... But at the same time, everyone needs to create the right bias;
3. Necessarily you need to cover a layer of expanded clay, with a special plastic wrap... It is important to note that it must be overlapped;
4. Further, it is necessary to apply the prepared sand-cement screed, doing it smoothly, slowly. Its essence is to level the layer of poured expanded clay;
5. After these events, you can start carry out the formation of 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 preserved.

ATTENTION!

If you are worried that the expanded clay will shift when you start laying a sand-cement screed on top of it, you can fill it with cement milk... But it should be understood that because of him, the structure becomes heavier.

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

Bulk material

Heat insulating materials

Another good material for roof deflection is thermal insulation materials. Experts say that this is the most affordable option.

Its advantage is that it is light enough and quite cheap, which plays a very important role in the construction site. Mineral wool, the best material. The process diagram is quite simple.

It is necessary to attach the material to the base itself, using self-tapping screws or dowels. Some people prefer sheets, such cotton wool to be glued on a previously cleaned base, with a special glue. This process can be performed both during and during the installation of the roof.

Heat insulating material

Foam concrete

A good material that can be used for flat roofing is foam concrete. It should be noted right away that such a procedure must be carried out using special equipment.

On the base itself, a layer of foam concrete is poured, but at the same time the angle of inclination itself is noted, and after make a special screed from foam fiber concrete... Next, it is important to apply a waterproofing material.

A huge plus of this type of deflection is high rate of thermal insulation, as well as other mechanical characteristics... For example, strength and durability.

Speaking of the minuses, they are there too, or rather one. This is the price. It is quite high. And again, it will not work to carry out such a procedure on your own. Therefore, in this case, it is worth contacting professionals.

• If the roof has a minimum slope, then it is important to note that in this case, it is necessary to install the correct drainage systems... The bias itself is done exclusively to the side (funnel, gutter);
• If your roof is bituminous, it is worth making the slope angle less than 6 degrees, while the bottom layer of waterproofing must be made of membrane materials;
• It is very important to know that at low slope angle indicators, it is necessary to perform ventilation of the under-roof space itself, with all the stingrays. The thickness of the gap also depends on the value of the angle (the larger the angle, the smaller the thickness, and vice versa).
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There are thousands upon thousands of architectural traditions all over the world in terms of the appearance of roofs. But modern architects have completely changed the idea of ​​the culture of suburban construction, introducing lean-to roofs as ideally combined with landscape design and diverse in execution. Of course, the inhabitants of Australia set this new fashionable tone, where the absence of snow in general as a natural phenomenon allows them to create with the architecture of residential buildings whatever their fantasy dictates.

But in the snowy regions of Russia, such a roof can be built, but with an appropriate slope and in the right direction. In a word, the main parameter of functionality is the angle of inclination of a pitched roof, which we will now teach you to calculate.

Step 1. Calculate permanent and dynamic loads

The first step is to calculate the load on the pitched roof. They are usually divided into permanent and dynamic. The first is the weight of the roofing, which is always on the roof, such installations as antennas and dishes, a chimney, and so on. Those. everything that will be on the roof both day and night.

And dynamic loads, or, as they are also called, variable, are those that happen from time to time: snow, hail, people, repair materials and tools. And also the wind, which, well, loves to tear off lean-to roofs due to their windage.

Snow loads

So, if you make a slope of a pitched roof at 30 °, in winter the snow will press on it with a force of 50 kg per square meter. Just imagine that on your roof there will be one person for every meter! This is the load.

And if you raise the roof to above 45 °, the snow will most likely not be able to linger at all (it also depends on the roughness of the roofing). But for central Russia, where the snowfalls are moderate, it is enough to make a pitched roof within 35-30 °:

The minimum angle that must be in order for the snow to be able to come off the pitched roof itself is 10 °. And the maximum is 60 °, because there is no point in making the roof steeper. The same goes for snow, which clings even more to such a roof.

That is why the owners of lean-to outbuildings in winter often take up a shovel. Only the coverage area saves: the smaller it is, the less likely it is that the snow will be able to bend the material.

Wind loads

But in windy regions, it is impossible to build roofs with steep slopes at all. By comparison, an 11 ° slope of a pitched roof experiences exactly 5 times more wind force than a 45 ° slope. In view of this, keep in mind that a pitched roof is always made low to the leeward side.

Combined loads

And also be sure to calculate for a gable roof such a value as a combination of the most unfavorable permanent and temporary loads. Those. that critical point that the rafter system must be able to withstand. This, by the way, is often forgotten! They think that the roof will withstand the snow, the wind too ...

What if you and your friend have to climb onto the roof in a strong storm and snow? Is the structure designed for snow, wind, and the legs of at least two people at the same time? This is how troubles happen.

Step 2. We select the slope of the roof

The slope of a pitched roof is in a fairly wide range: from 6 ° to 60 °. It all depends on the area in which you are going to build: if you need to successfully dump tons of snow every winter, then make the slope steeper, if you plan to protect yourself from the wind, then flatter. And also from many other factors, including aesthetic ones.

Steep pitched roofs

The greater the angle of such a roof, the faster the water flows down it into the gutters. Neither leaves nor dirt will linger here, and therefore the roofing itself will last much longer. In addition, on such a roof, the visual aesthetics of the selected flexible tile or metal profile is more visible, which often plays an important role for the owners.

Low slope pitched roofs

The speed of rain and melt water flowing down on low-slope slopes is much lower, and therefore there is a risk of water stagnation, collecting dirt and ice stuck. On such roofs, moss develops quickly and foliage sticks. Especially if the roofing is rough.

As for rainwater, the main requirement for the roof is that the water on it, when snow melts or after rain, does not remain on the surface of the roofing material, but easily rolls off. If it has too low a slope (for a certain area), then the liquid will stand for a long time in all irregularities and seams. And the longer, the more chances it has to get inside and create many problems in the form of dampness, deteriorated insulation and corrosion of metal roof elements:



But, if a large roof of a house rises above such a building, then it's okay:



But here it still has its own plus: the smaller the angle of inclination of the pitched roof, the closer the geometry of the interior spaces to the traditional cube. This means that it is perceived more easily and used with greater benefit.

Therefore, the lower the angle of inclination of such a roof, the more you need to take care of its waterproofing so that melt and rainwater cannot penetrate into the rafter system. Therefore, such roofing coverings as membranes, roll insulation or solid sheets are already needed here.

With a standard angle of inclination, a pitched roof is built as follows:



The minimum angle of a pitched roof

A pitched roof, the angle of which is only 3-5%, is often made inversion. Those. they subject it to certain additional loads: they walk on it, grow a garden on it, or even use it as an open terrace. Like here:



In addition, at a certain angle, the pitched roof directs the air flow in the desired direction, capturing precipitation and diverting it. Remember this!




Step 3. Determine the requirements for the slope

In functional terms, pitched roofs are divided into three main types: ventilated, non-ventilated and combined. Let's consider each option in more detail.

Ventilated design

These are equipped in closed-type buildings. Air vents and special voids between the insulating layers serve as ventilation, through which the air, passing, captures droplets of moisture from the insulation and carries them out.

If such ventilation is not provided, then moisture will remain inside the insulation (and it still gets into it, albeit a little), and the insulation will begin to dampen and deteriorate. And as a result, the entire roofing pie will gradually collapse.

But a ventilated pitched roof has its limitations. So, the angle of inclination can only be in the range from 5% to 20%, otherwise the air will not be able to efficiently pass through the vents.



Non-ventilated design

This type of pitched roof is advantageously built on terraces and outbuildings. Usually the angle of such a roof is in the range of only 3-6%, although there are no restrictions to it.

Ventilation in such roofs is not needed because the air in a room without walls or with wide doors often open (as in the case of a garage) and itself ventilates well, taking any water vapor to the street. Which, by the way, by themselves, are not particularly formed in such buildings:



Combined design

Such roofs combine the device of both previous types. Here, the desired roof slope is provided by thermal insulation. It turns out economically, but in winter you will have to constantly clean off the snow.

But the device of such a pitched roof is already different, because dynamic and dynamic loads are now added to the variable and static loads. And usually everything looks like this: the bottom is corrugated board, on it there are two layers of insulation and good waterproofing.

The angle of the shed roof also depends on parameters such as the type of connection of the rafters to the Mauerlat or walls. Let's take a closer look.

Step 4. Calculate the exact slope angle

The angle at which the rafters and the roof slope are inclined to the horizontal plane of the ceiling is called the angle of a pitched roof. And take this scheme seriously if you want to provide your roof with the correct mechanical strength:



The angle of inclination of the slopes is measured in percentages and degrees. But, if with degrees it is even more or less clear (thanks to the school geometry course), then what are percentages? Percentage is the ratio of the difference in the height of the ridge and eaves to the horizontal of the ramp, multiplied by 100.

There is another interesting point: many architects specially calculate the angle of the pitched roof so that it is equal to the angle of the sun in a given area in mid-spring. Then you can calculate down to a millimeter when and what kind of shadow will be, which is important for planning terraces in front of the house and other recreation areas.

Step 5. Limiting the range of choice of roofing

Modern roofing materials also have their own requirements for the minimum and maximum angle of inclination of a pitched roof:

• Decking: min 8 ° - max 20 °.
• Seam roof: min 18 ° - max 30 °.
• Slate: min 20 ° - max 50 °.
• Soft roof: min 5 ° - max 20 °.
• Metal tiles: min 30 ° - max 35 °.

Of course, the smaller the angle, the cheaper materials you can use: roofing material, corrugated board and the like.

You will be surprised, but especially for low-slope roofs today, the same types of roofing are being developed that are usually used with a slope of at least 30 °. What for? This is the fashion in Germany, which has come down to us: the lean-to roof is almost flat, and the roof is stylish. But how? It's just that manufacturers improve the quality of the locks, make the overlap area larger and think more carefully about the protection from dirt. That's all the tricks.

Step 6. We decide on the rafter system

And from the chosen angle of inclination of the roof and the loads planned for it, we determine the type of fastening of the rafters to the walls. So, there are three such types in total: hanging rafters, layered and sliding.

Hanging rafters

Hanging rafters are the only option where the connection must be rigid, but for the rafters between the side supports there is no way to support.

Simply put, you only have external load-bearing walls, and no partitions inside. Let's say this is a rather complex rafter system, and its construction must be approached with responsibility. The whole problem is in large spans and in the pressure that is applied to the walls:



Or like in this project:




Sliding rafters

Here, the entire roof presses on at least three supports: two outer walls and one inner one. And the rafters themselves are used here dense, with a section of at least 5x5 cm of bars and 5x15 cm of rafter legs.

Sliding rafters

In this rafter system, a log in the ridge serves as one of the supports. And to connect the rafters with it, such special elements as "sliding" are used. These are metal elements that help the rafter to move forward slightly when the walls are shrinking to avoid cracks. Very little! And thanks to this device, the roof easily tolerates even a rather noticeable shrinkage of the log house, without any damage.

The bottom line is simple: the more knots in the rafter system, the more flexible and durable it is. The more a pitched roof is able to withstand the pressure of the weight of the roofing and snow, and at the same time not break. But there are rafter systems where the connection is generally static:



Step 7. Calculate the height of the pitched roof

Here are the three most popular ways to accurately calculate the correct height for your future roof.

Method number 1. Geometric

A pitched roof looks like a right-angled triangle. The length of the rafter leg in this triangle is the hypotenuse. And, as you remember from the school geometry course, the length of the hypotenuse is equal to the root of the sum of the squares of the legs.

Method number 2. Trigometric

Another option for calculating the length of the rafter legs is as follows:

1. Let us denote by A the length of the rafter beams.
2. Let's denote by B the length of the rafters from the wall to the ridge, or the length of the part of the wall in this area (if the walls of your building are of different heights).
3. Let X denote the length of the rafters from the ridge to the edge of the opposite wall.

In this case, B = A * tgY, where Y is the angle of inclination of the roof, and the length of the slope is calculated as follows:

X = A / sin Y

In fact, all this is not difficult - just substitute the required values, and you will get all the parameters of the future roof.

Method number 3. Online calculators

Calculated? Now let's move on to the construction of the roof itself:



We hope you figure it out easily!