Gable roofs can perhaps be considered the most popular among private developers. Their rafter system is usually not very complex, both in calculations and in practical implementation. But the gable roof itself becomes very reliable, practical, attractive in appearance, and in addition, with proper planning, it allows useful use attic space, right down to equipping a full-fledged living room there.
One of the key parameters when calculating the rafter systems themselves and roofing coverings, including the loads that will fall on them during operation, is the slope angle of the slopes. Its calculation is, in principle, simple, but formulas memorized in school tend to gradually become forgotten. To make your task easier, use the inclination angle calculator gable roof, proposed in this publication. Some necessary clarifications will be given below.
Calculator for calculating the angle of a gable roof
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Choosing a roof slope only based on your aesthetic preferences would be somewhat reckless. Since the reliability and strength of the future structure largely depend on the correctly calculated value of the angle of inclination, taking into account climatic features terrain. That is, the roof slope should be optimal from both a practical and aesthetic point of view.
The fact that ideally “flat” roofs simply cannot be beyond doubt. After all, it should rainwater somehow be diverted from it. Therefore, they make a slope to get at least a minimum slope flat roof.
She makes it possible efficient collection rainwater from the surface roofing and directs it either to the parapet or to the internal funnels.
minimum roof angle
The minimum roof slope depends on many parameters, including the material waterproofing coating, type of roof itself (standard or inverted), quantity waterproofing layers and another.
Basic requirements that determine the slope of a flat roof: SNIP
What will be the minimum roof slope, depending on various factors, is dictated by special building regulations and norms.
The dependence of the roof slope angle on waterproofing is regulated by clause 4.3 of SP 17.13330 for 2011, according to which the slope of a flat roof varies in the range of 1.5–10%. Large angles (up to 24%) are performed extremely rarely, since the choice of material for waterproofing that would not slide to the base of the sloping roof when the temperature rises is very difficult.
On a note
The smallest slope for a flat roof is 1.5% or 1°.
As a rule, a roof with a low slope has a fairly large surface area and achieving its ideal value is very problematic. There will likely be areas where water will stagnate, which can cause wear and tear. roofing material or leaks. You can perform the slope geometry relatively accurately using a screed. It is also possible to use polystyrene concrete or foam concrete filling. To increase strength, a thin layer of durable concrete screed is placed on top of the laid layer.
In turn, there is a specific connection between the steepness of the roof structure and the number of layers of waterproofing. The larger it is, the water naturally leaves faster, which means that fewer waterproofing layers will be required (clause 5.5).
The inclination can be easily checked using a bucket of water. Water is poured onto the selected area; if the water flows almost completely to the funnel, then the slope is flat roof sufficient. A similar check can be carried out on the entire roof surface.
At the design stage, it is determined by calculation how many water intake funnels are required for a given roof, and already during construction, with the help of slopes, it is necessary to ensure unhindered outflow of water into the funnel from any point on the roof.
How to calculate the roof slope: which method is better
As you know, in addition to flat (sloping) structures, there are also pitched and high ones, and there are even more materials for roofing. In order to correctly navigate this diversity, according to SNiP, special tables and diagrams have been developed that reflect the relationship between the steepness of the slope and the type of roof.
The roof slope is determined following parameters:
- the type and amount of material intended for roofing;
- necessary protection from wind and moisture;
- ridge height for repairing an existing roof.
How to calculate the angle of inclination in degrees and percentages
Calculator for calculating roof slope
Using this calculator is extremely simple. In fact, any roof can be divided into ordinary gable roofs, the calculation of which is based on a triangle. It is on this position that the work of the calculator is based. The following parameters are used:
- H – the height of the ridge, that is, the leg of a right triangle;
- W – second leg, equal to half base width;
- L is the length of the rafters, also known as the hypotenuse.
By substituting two known parameters, you can almost immediately determine the slope angle of a roof with similar characteristics. By the way, the third parameter is calculated automatically. Software calculator uses properties isosceles triangle and simple trigonometric formulas.
Using a protractor
This device, which is also called an inclinometer, has a simple design: several slats with marked divisions and a pendulum. When making calculations, the main rail is placed perpendicular to the ridge. The pendulum pointer indicates the required angle on the division scale. As you can see, nothing complicated.
Formula for calculating roof slope
And finally, the required steepness of the slope can be calculated by yourself without using slope measuring instruments, mathematically. To do this you will need to know the value
- vertical height (H), measured from the highest point of the slope, usually the ridge, to the lowest point - the cornice;
- laying - the horizontal distance from the bottom to the projection of the top point of the slope.
The angle of inclination of the roof is calculated in degrees or percentages and indicated in the drawing by the letter “i”.
Mathematically, the percentage of roof slope is calculated as follows.
i = H: L, i.e. the roof slope angle is found from the ratio of the roof height to the pitch.
Then, in order to obtain the desired value as a percentage, the value of the resulting ratio is multiplied by 100. A special table of ratios helps to express the value of the slope in degrees.
Let's look at how to calculate the angle of inclination in degrees using a specific example.
Calculation example
Let’s say that the laying length with a roof height of 2.5 m turned out to be equal to 4.5 m.
It turns out that the slope i = 2.5: 4.5 = 0.55. And after multiplying 100 we get, respectively, 55%.
Now you can use the table to convert the resulting value into degrees, we get - 29°.
The lowest slope slope for a particular roofing can be determined from the following graph.
The roof is structural element building, which is responsible for protection from the effects of various external factors. It must effectively withstand precipitation in the form of snow, hail, rain, heavy winds and hurricanes. Correct slope plays a fairly large role in the rapid removal of water and snow cover from the roof. It is capable, in combination with properly installed insulation, of providing excellent protection for the entire building, including its interior.
On roofs with a large roof slope (from 50 degrees), snow will not accumulate, but will fall to the ground under the influence of the Earth’s gravity.
Not only these indicators, but also strength and durability can depend on the correct slope of the structure. How to determine the roof slope angle correctly, what factors should be taken into account, how to make calculations for roofs with different coating? We hope that our material will give you answers to all your questions.
About the factors that influence the degree of roof angle
Types of roofs with different amounts and the shapes of the slopes.
The roofs have different shapes and the number of stingrays. There are one-, two- and four-slope. The degree of roof slope will depend on the number of slopes available on country house or dacha.
The angle of inclination can be calculated using special construction graphs and matrices, or using a triangle.
Construction work on installing the roof may be suspended if it is not decided in advance what material it is planned to make the finishing coating from and what the angle of inclination of the roof will be. It should be remembered that these concepts will be closely intertwined, because the type of roofing material is taken into account when calculating the angle of absolutely any pitched roof.
If the degree of slope of the lean-to structure does not exceed 9-20, you will need to take into account important factors:
- material finishing coating;
- functional purpose of the building;
- climatic conditions.
If the roof has 2 slopes or more, you should take into account not only the above factors, but also the area in which you plan to build the house. It is also worth considering for what purpose you plan to arrange the attic space. If it is intended not for housing, but in order to store temporarily unused things and objects, there is no point in arranging a room for such purposes large sizes(we are talking about ceiling height).
When the owner plans to turn the attic into a living space in the form of an attic, it may be necessary to install a good structure with a large slope.
The degree of angle depends on the terrain
The level of overlap of the tiles depends on the slope angle.
In regions where strong winds often pass, a minimum roof slope is made. Consequently, it will be exposed to the wind. It is worth noting that it is not recommended to make structures without a slope. Similar coatings it makes sense to organize in regions with large quantity m sunny days and a low chance of precipitation.
Wind resistance with a high roof will be significantly greater than with a low one. However, with a very small slope, there is a possibility that the wind will tear off the finishing coating. Therefore, with roofs that are too steep, the same danger exists as with roofs with a low angle. That is why it is recommended to choose the following roof slopes:
- from 35 to 40 degrees with light winds;
- 15-25 degrees with strong winds.
In areas where precipitation falls in sufficiently large quantities, the angle can be increased to 60 degrees. It will be the most suitable because it will minimize the load on the roof from melt water, snow cover and large quantity moisture during rainfall.
The degree of roof slope should be calculated based on a range of up to 9 to 60 degrees. Designers make appropriate calculations and most often settle on values that range from 20 to 45 degrees.
This type is attractive because it is possible to use absolutely any roofing material - corrugated sheets, slate, metal tiles, and so on. Each of the materials for the finishing coating will differ in its requirements, which should be taken into account during the construction process.
Dependence of the angle of inclination on the material
Characteristics of metal tile sheets.
If the choice fell on the use of rolled materials, when laying in 2 layers the angle will need to be made up to 15 degrees, and when laying in three layers - from 2 to 5.
You should know:
- It is most advisable to use weld-on materials when the roof has a slope of 0 to 25%. If the slope is from 0 to 10%, the material will need to be laid in three layers. If the slope is within 10-25%, you can get by with one layer, but the material must have a topping.
- Slate covers structures that have a slope of up to 28%.
- Shingles should be used when the slope of the structure is at least 33%.
- The steel covering is laid on the roof, which has a leakage of less than 29%.
Material consumption will directly depend on the slope of the structure. The larger it is, the greater the consumption of finishing material will be. Flat design in this ratio it will cost less than a roof that has a slope of 45 degrees.
If the owner knows the slope of the roof, it will not be difficult to calculate the amount required material. The same should be said about the height of the roof structure.
Metal roof
The wind load will be strong on the roof negative impact. In such a case, the angle calculation should be done especially carefully. If the angle is large, there is a possibility of swelling, which will lead to an increase in load, which can affect the entire structure. As a result, the structure may fail prematurely.
The roof, which is planned to be covered with metal tiles, must have a minimum angle value - within 22 degrees.
Layers of metal tiles: 1 sheet of steel 0.4-0.5 mm. 2 Zinc coating. 3 Anti-corrosion coating. 4 Primer. 5 Polymer coating. 6 Protective varnish.
Using this indicator, you can avoid the accumulation of moisture at the joints of the roof covering. There will also be protection from unwanted water seepage (rain or melted snow).
If necessary, the minimum slope of the structure can be 14 degrees. If used as a coating soft tiles, the minimum value will decrease to 11 degrees. In this case, it may be necessary to arrange additional continuous sheathing.
For a corrugated roof it will be 12 degrees. It is worth considering the manufacturers' recommendations in this regard. The slope angle will be determined by the owner of the building, but it is worth remembering that the roof is designed for temporary and permanent loads.
Calculation of roof slope angle
The calculation of the angle will depend on the height of the skate. The height of the roof at the ridge will be determined based on functional purpose attic space.
If you plan to make a full-fledged attic space from the attic, the degree of slope should be calculated as indicated below. For example, the width of the pediment (roof end) will be 6 m. This figure is divided in half (6/2=3). The height of the structure at the ridge is always taken as standard as 1.8 m.
SinA=a/b=3/1.8=1.67
Using the Bradis table, you will need to find the approximate value that would be at SinA = 1.67. This value will be in the range of 58-59 degrees. It makes sense to stop at the maximum value of 60 degrees, which will become the desired slope angle of the roof slope.
Good luck to you both in mathematical calculations and in construction work!
The reliability of any building, as well as the comfort of living in it, depend mainly on how well its roof is constructed.
And one of the criteria for the quality of a roof is its slope.
Since the amount of roofing material depends on its size, the choice of the angle of inclination and its preliminary calculations are carried out before the purchase of the selected roofing material begins.
What affects it
Depending on the slope of the roof slopes, the features of its operation depend.
It is customary to distinguish 4 types of roofs:
- high, with an angle of 45-60 degrees;
- pitched, with a slope of 30 to 45 degrees;
- flat, the slope angle is 10-30 degrees;
- flat. Slope of 10 degrees or less.
The choice of the value of this parameter is influenced, first of all, by natural factors that are characteristic of a given area.
The strongest wind high pressure has an effect on high roofs.
Because such roofs, due to the large angle of inclination, have a very large area.
U large area the surface has a very high windage.
Accordingly, the load on the entire structure of the rafter system is very high.
And if you decide to install a high roof with a very large slope, then you should take care of a very solid foundation.
However, in areas where strong winds prevail, it is unsafe to install flat roofs.
With this type of roofing, the lower part of the slope will be exposed to high blood pressure in strong winds.
And if the roof fastening is weakened, the entire structure may fail.
Therefore, in areas where strong winds often occur, it is recommended to arrange pitched roofs with an inclination of 25 - 30 degrees.
If the wind force is small, then the roof slope can be 30-45 degrees.
If in the area where the house is being built there is heavy snowfall during the cold season, then the roof should be built with a large slope angle.
In this case, the high roof is beyond competition.
On roofs with a large slope, snow does not linger.
It is for this reason that in all northern countries the roofs on buildings are very high (Sweden, Finland, Norway, etc.).
How smaller angle roof slope, the longer the fallen snow will remain on the slopes.
The more weight will affect the entire structure.
If the design of the rafter system is made with a large margin of safety, then a certain layer of snow on the roof is not bad.
It provides a little extra insulation.
However, if the design of the rafter system of the structure is not designed for a large load, then there may be big problems.
We choose the slope depending on the roofing material used
Gone are the days when only two types of roofing materials were used for roofing: tiles and slate.
Today there are a huge number of roofing materials!
Each material has its own individual specifications and this must be taken into account when calculating the required inclination angle.
After all, it may happen that the material you like is simply not suitable according to its parameters.
Minimum tilt angle
There is a concept of a minimum value for this parameter.
This parameter is different for each material.
And if the angle of inclination obtained as a result of your calculations turns out to be less than the minimum value for the roofing material you have chosen, then you cannot use it for roofing.
A lot of problems can arise in the future if you break this rule:
- for any piece of inlaid roofing materials, such as tiles or slate, the minimum slope is 22 degrees. It is with this value that moisture does not accumulate at the joints and moisture does not leak into the roof;
- The angle of inclination for rolled materials (roofing felt, bicrost, etc.) depends on the number of layers you plan to lay. If there are three layers, then the slope can be 2-5 degrees. If there are two layers, then it needs to be increased to 15 degrees;
- Manufacturers of corrugated sheets recommend setting a slope angle of 12 degrees when installing a roof from this material. Corrugated sheeting can be used at lower values, but in this case it is necessary to glue the joints of the sheets with a sealant;
- for metal tiles the value of this parameter is 14;
- for ondulin it is a value of 6 degrees;
- the minimum slope for soft tiles is 11 degrees. But at the same time, a mandatory condition is a continuous sheathing;
- for membrane roofing coatings there are no strict requirements for the minimum value of this parameter.
This is about minimum values.
I'll give you some advice - stick to these rules.
So that in the middle of winter you don’t have to re-cover the entire roof.
Now about the optimal values
If rain and snow occur frequently in the region, then the optimal roof would be one whose slope angle would be 45 - 60 degrees. After all, it is necessary to remove the load from water and snow from the roof as soon as possible.
Because the strength of the rafter system is not unlimited.
And thanks large slope roofs, rain and snow will melt as quickly as possible.
If there are constantly strong winds in the region where the house is built, then the roof is dealt with differently.
With a smaller inclination, its windage decreases.
And there are no excessive loads on the roofing material and rafters.
Also, the roof will not be torn off during sudden gusts of wind.
In this case, the optimal roof slope angle is 9 - 20 degrees.
Very often there is snow and wind in the region.
For example, Orenburg region.
In this case, choose the average value of the inclination angle.
As a rule, its value is in the range of 20 - 45 degrees.
If you notice, most pitched roofs have exactly this meaning.
We calculate its value
For a single slope
We draw a perpendicular L d along the wall, originating at the point where the short wall ends and resting on the wall that has the maximum length.
The result is a right triangle.
If the length of the wall L сд is equal to 10 meters, then to obtain a slope angle of 45 degrees, the length of the wall L bc should be equal to 14.08 meters.
For gable
The calculation principle for a gable roof is similar to the previous principle.
Let's look at an example
Leg C is half the width of the building.
Leg a is the height from the ceiling to the ridge.
The hypotenuse is the length of the slope.
If we know any two parameters, then the angle of inclination can be easily calculated using a calculator.
If the width is 8 and the height is 10 meters, then you should use the formula: 
cos A = c+b
Width c = 8/2 = 4 meters.
As a result, the formula looks like this:
cos A = 4/10 = 0.4
Using the Bradis tables, we find the value of the angle to which a given cosine value corresponds.
It is equal to 66 degrees.
For hipped
And again you can’t do without roulette and Bradis tables.
Knowing several parameters, you can easily calculate others.
Including the angle of inclination of the hipped roof.
It should be remembered that all dimensions must be taken as accurately as possible.
And it will help to measure the slope of an already built roof special tool— inclinometer.
After all, if you make a mistake, then the angles of inclination, length and area may not be correct.
This means that you will make a mistake in the amount of material required or the strength of the roof will be lower than planned.
Watch a video about the slope of the ramps.
Sergey Novozhilov - roofing materials expert with 9 years of experience practical work in area engineering solutions in construction.
Professional builders know that the process of building a roof can sometimes be slowed down due to the fact that it is necessary to choose " the right material» and make an accurate calculation of the roof slope angle. These two issues are closely interrelated, because the choice of material for covering it depends on the angle of inclination of the roof.
We remind you that roofs can be single-, double- and four-sloped; it depends on how many slopes you choose for your roof, and the slope of the slope angle will be determined.
What factors influence the calculation of roof slope
For example, the angle of inclination standard roof with one slope ranges from 9 to 60 degrees - it depends on the following factors:
- The material chosen for the roof;
- Climatic and atmospheric conditions;
- Purpose of the building.
If the roof has two or more slopes, then not only the region in which the building is located matters, but also why the attic is needed. For example, if you use the attic not as a living space, but as storage for old things, then there is no need to build it wide and high. But if you want the attic to become a full-fledged residential attic room, then you need to make a dense roof and know how to calculate the angle of the roof. IN in this case calculation of the roof slope angle depends on the following factors:
- The first is the design of the building and premises itself.
- The second is the choice of materials for the roof.
- The third is the climate conditions of the region.
We choose the material for the roof depending on its slope
In regions with strong winds It is advisable to build a roof with a minimum slope - the material should not be subject to strong wind loads. The same is said about sunny areas, where there are the most hot days of the year - sunny regions have the least precipitation.
In those regions where there is a lot of precipitation (including rain, hail and snowfall), the roof slope should be large, up to 60 degrees, because only such a slope will reduce the load from snow, melt water And various kinds garbage.
So, let's figure out how to calculate the angle of the roof. We need to take into account all the factors that were described above, so the calculation of the roof slope is carried out in the range from 9 to 60 degrees. Interestingly, such a calculation usually leads to one optimal solution- 20 - 35 degrees.
With such a slope, any roofing material is used - profiled flooring, metal tiles, pieces of slate, etc.
All materials have a certain list of requirements that are presented to them during the construction of the structure.
If the roof is covered with metal tiles
It is known that metal tiles have considerable weight compared to other materials. This is why it is important to correctly calculate the slope of a roof with metal tiles, which should be optimally low.
It is important to take this requirement into account in a region with a lot of winds and hurricanes. Therefore, the inclination angle should be as low as possible. Because of of great importance angle of inclination, the roof may swell, which, in turn, will increase the pressure on load-bearing structure roofs. And increased pressure will prematurely destroy the roof.
On average, for roofs that will be covered with this material, the average optimal value the tilt angle is 27 degrees. Consequently, your home will be protected from rainwater and snow infiltration.
The minimum angle of inclination of the roof is only 14 degrees. If soft tiles are used, then the angle of inclination can be 11 degrees, but the roof must be additionally slatted.
Corrugated roof
Corrugated sheeting is the most popular material for roofing - it is light in weight, durable, fastened and mounted quite easily.
Roof slope with corrugated sheets and loads.
If the roof is covered with various soft materials
Such materials include roofing felt, ondulin, polymer (membrane) roofing.
For such a roofing structure, you need to make the angle of inclination from 6 to 15 degrees - the value varies depending on the number of layers of soft material.
For example, if the coating is two-layer, then the angle of inclination is taken to be equal to 15 degrees, but if it is three-layer, then the value can be reduced to 3-5 degrees.
But the membrane coating can be used on any roof, of any condition, in any conditions, here the angle of inclination can be reduced to 2-5 degrees.
From all of the above, we conclude that how to calculate the slope of the roof is decided by the owner of the building himself. However, we take into account a certain dependence: the roof must withstand not only temporary, but also permanent loads. “Temporary” includes rain, wind and the weight they exert on the roof covering; permanent load is the weight of the roof covering and material.
Slope for roofing made of soft materials
The amount of roof slope determines the type of sheathing and pitch. For a roof with a low slope, the sheathing pitch should be as short as possible. For a roof with a minimum value, the sheathing pitch is 35-45 cm.
Also, everyone is interested in one question - how much roofing material should be purchased.
The greater the angle of inclination of the roof you make, the more material will need to be used up.
The greater the angle of inclination of the roof you make, the more material you will need to use.
If you adhere to all these requirements, you can make a roof that will last for decades! All the above requirements and factors help you understand how to calculate the roof slope. However, we remind you that the calculation is made individually for each house.
Finally, we'll give you a few useful tips that will help you choose roofing material:
So, if your roof slope is small, up to 10 degrees, then you can even cover the roof with stone chips or gravel (we calculate 5 mm for the roof and 15 mm for gravel).
If the angle of inclination of your roof is 10 degrees or more, then we use the basic bitumen waterproofing. Applying roll material, do not forget about the additional protective coating, which can be regular painting.
If you are planning to cover the roof with corrugated sheeting, you need to seal the butt seams. The joints must be double.
How to calculate the angle of a roof?
As a rule, to know how to calculate the slope of a roof, you need to know how high you will raise the ridge (and the height of the roof with the ridge depends directly on what the attic is intended for). So, if from the attic you make residential attic, then we consider the following calculations valid.
We determine the width of the pediment - the roof end, for example, let it be 6 m. We divide the width in half: 6:2 = 3 m, and according to the standard, the height of the roof at the ridge is 1.8 meters.
tg A=a:b=3:1.8=1.67
We take the Bradis table and find an approximate value - if tg A = 1.67, then the angle of inclination will be approximately 58-59 degrees. We can take the maximum angle value as 60 degrees. This will be our desired roof slope angle.
The slope of any roof is given in accordance with climatic conditions and the structure of the building. The abundance of precipitation makes the roof slope steeper and vice versa. In general, you need to remember that before calculating the angle of the roof, keep in mind that the slope of the roof can range from 10 to 60°. The steeper the roof, the more material you will spend.
The slope of the rafters or the height of the ridge is determined mathematically or by measurements.
It is known that roofs with a slope of 35-45 degrees are not made, since such a range will create all the conditions for snow accumulation in winter time, and such roofs do not withstand winds well. Monolithic roof it is impossible to do, so the material is laid with joints. The joint is a place with an increased risk of corrosion, so they are given special attention Special attention during calculations. Also, during a hurricane, leaves and branches can get stuck in the cracks, which then swell and the roof deteriorates. Openings are created for rain and snow to penetrate, and the roof collapses.
When calculating the slope of the roof, remember not only about savings (cost of rafters, material, work), but also about performance. If the roof is installed according to all the rules, it will cost more, but your home will be warm and dry, which ultimately helps save significant amounts of money on repairs. This is where the correctly selected roof angle plays a role!
