The roof structure is determined at the design stage of a building or structure. In this case, the roof slope must be selected based on local conditions, taking into account the hydrometeorological situation - the direction and strength of the winds, the level of precipitation and construction costs.
When precipitation occurs, water from the roof must be quickly removed; this is why the slopes are given a certain angle. Its value is determined by the type of roofing material used, installation method, architectural requirements and cost considerations.
From steep roofs, with an angle of 45° or more, water and snow roll off quickly, and for areas with high rainfall this roof design is well suited. But the greater the angle at which the slopes are located, the higher the cost of the roof. If they are made at 45°, then the amount of material will increase by 1.5 times, and if the angle is 60°, then twice as much material is needed as for a flat roof.
But it shouldn’t be flat either. In cases where a flat roof is made, the slope of the roof is specially provided for water drainage, which significantly increases its lifespan. On a flat roof, puddles and places of stagnant water form. To eliminate this, inexpensive fill-in insulation such as expanded clay is used, which creates inclined surfaces and allows for water drainage.
At the same time, wind load must be taken into account. It affects a flat surface to a lesser extent than in any other cases. In areas with strong winds, a minimum roof slope should be used.
How to choose roofing material taking into account slopes?
Below is a chart that allows you to choose the material for the roof depending on the angle of the slopes.
According to their own physical properties and technical and economic characteristics, the materials are combined into groups located above the arc-shaped arrows. The basis of each arrow is an inclined line indicating the angle of the slope to the horizon. Thus, line Y graphically shows the ratio of the height of ridge B to P/2 (half of its depth). The 1:2 ratio at the top shows that the vertical segment B is half the size of the horizontal segment P/2.
On a semicircular scale this line is designated Y and shows the roof slope in degrees, and on a vertical scale it shows the slope as a percentage.
Calculation of roof slope
As an example, we will show the calculation of the roof slope of a building under construction in Moscow. Asbestos-cement corrugated sheets VO will be used as the material in the example.
On the graph you need to find the inclined line where the arrow “Ordinary asbestos-cement sheets” ends. At the intersection of this line and the vertical scale there will be the desired answer. It turns out that for this case the minimum roof slope as a percentage will be 33%.
Since the slope angle Y is equal to the ratio of the height of the ridge to half its depth, it can be determined from the available data. If the height B is two and a half meters and the elevation is 12 m, according to the rules of mathematics it turns out:
U=V: (P:2) = 2.5:6 = 5/12.
To get the result as a percentage, all this is multiplied by 100.
which is greater than the required minimum roof slope percentage. The indicated ratio corresponds to an angle (on the scale of the figure) of 18.2°.
From the example given, it is clear how to calculate the roof slope using ordinary mathematics and the given graph.
All calculations correspond to precipitation for the zone temperate climate. In others climatic zones It is allowed to arrange slopes at angles different from the data on the graph.
In the case of using other materials (such as tiles, slates, shingles, shavings, chips, etc.), the angle values should be determined according to the requirements of the relevant regulatory documents and taking into account construction experience.
How to measure roof slopes?
Slopes can be measured with an inclinometer, shown in the figure below.
The basis is the support rail 11, on which the frame 7 is located. right angle frame between the slats 4, an axis 3 is attached, on which a thread with a pendulum 5 is located. The latter is made of two wire bends 2, a plate 1, a weight 8 with a pointer 9. The pointer with a weight can move between the guides 6. On inside One of the guides contains a 10-point scale. When the support rail is horizontal, the pointer coincides with the beginning of the scale.
For measurements, the support rail is installed on the sheathing perpendicular to the ridge. The pointer on the pendulum will show the slope value in degrees on the scale. The percentage value can be obtained using a graph.
Drainage system for roofs with a slope
The climatic zone and roof design determine how melt and rainwater should be drained. Drainage can be unorganized (external) and organized (internal and external).
To ensure organized external drainage, drainpipes are used, guided by the following requirements:
- suspended or over-wall gutters are placed on slopes made at an angle of more than fifteen degrees;
- the slope along the axis of the gutters must be more than two degrees;
- the sides of the gutters must have a height of 120 mm;
- drainpipes are located at a distance of no more than 24 m from each other;
- cross section drainpipe should be determined based on one square meter of roof area - one and a half square centimeters of pipe cross-section.
In areas with severe frosts it is recommended to organize organized internal drains. Such a system consists of a water inlet on the roof, a vertical riser, an outlet and a drain pipe. With the help of such a system, water is collected from the surface and discharged at positive and negative temperatures. It is recommended to drain the collected water in storm drainage. The surface area per funnel is determined from the ratio of 0.75 square meters of surface per square centimeter of the cross-section of the drainage pipe.
The material presented allows us to understand the need the right choice roof design and manufacturing for its reliable and durable operation.
When installing any roof, it is necessary to correctly calculate the maximum and minimum roof slope, since the safety and consumption of materials for construction depend on this. The slope value can be calculated as a percentage, but it is best to do this in degrees, since the Bradis table is very convenient for calculations.
For roofing, the slope is one of the most important parameters included in the calculations. It depends on the material used and climatic conditions.
The slope of the roof depends on the selected material, the shape of the structure, and the expected wind and snow loads. It is recommended to trust the calculations themselves to specialists, although you can do them yourself. You can calculate the slope in percentages or degrees; for this you will need the simplest mathematical formulas and basic knowledge of geometry.
Dependence of slope on roof type and roofing material
To calculate the slope in percentage or degrees, you need to pay attention to the type of structure. All this is closely related to the material used. For, that is, hip, multi-gable, metal tiles, roofing iron, different types soft roof. But for simple roofs use ordinary tiles and slate.
The angle of inclination for such structures can be 30-60 degrees, otherwise the organization of water flow will not be correct. Puddles will begin to accumulate on the roof, and this will lead to damage to the entire structure. In addition to water drainage, it is also necessary to think about the convergence of snow masses and ice accumulations, which also create a certain load on the rafters.
The value of the minimum slope angles for roofs with various types roofing coverings. Here you can see the minimum and maximum angle slope at which one or another type of roofing is used.
For a soft roof, that is, roofing felt, bitumen shingles, a slope of 8 to 18 degrees is allowed; for some types of material the angle may be greater, but it cannot be made smaller, since there will not be the required conditions for water drainage. Only in this case will the roof be reliable.
For complex pitched roofs, sheet material is used. But in order to calculate the slope as a percentage or degrees, it is necessary to take into account many factors, including the type of material, the depth and width of the wave, and the method of installation of the sheathing. Basically, this value ranges from 14 to 16 degrees. Such conditions are good for water drainage and snow melting.
If the slopes are too small, which are easier to calculate as a percentage, you should take into account the need to seal the joints of the slabs or seams so that melting and rainwater did not penetrate the coating. In this case, special ones are used to drain the water. drainage systems, often internal type.
How to measure the slope of a structure?
Table of degree/percentage roof slope ratio. The slope of the roof can be determined by the height of the ridge. To do this, the ratio between the height of the roof ridge and half of the laying is determined, the resulting result is multiplied by 100. From this percentage value the roof slope angle is determined (see table).
Calculation of the roof slope is one of the most important processes, the reliability of the structure and its resistance to a wide variety of loads depend on it. Optimal angle pitched roof- from 11 to 45 degrees. By increasing the angle, you can achieve a reduction in snow loads, but this will only increase wind loads, and this will require strengthening the rafter system, sheathing, and counter-lattice, which will ultimately lead to an increase in the weight of the roof, loads from its own weight, and simply increased construction costs.
It is also important to remember that the slope depends on the type roofing materials, their quality and quantity. The climate region also has a significant influence.
To accurately determine the angle of a flat or pitched roof, it is necessary to correctly take into account all the loads on the structure. These include:
- total weight of the structure being built;
- snow load for a specific region.
Formulas for calculating roof slope. Not only the calculated values, but also the wind/snow load should be taken into account. In areas with strong winds, a minimum roof slope should be used.
The optimal angle is calculated in this way: first you need to determine the mass of one square meter each layer roofing pie, this takes into account rafters, sheathing, insulation, waterproofing, etc. The resulting values are added together, after which the result is multiplied by a special coefficient of 1.1. To do this, we need to use such mathematical data as the length of the rafters, the tangent for the angle of inclination of the roof, half the length of the span of the house, and the height of the ridge.
Except mathematical formulas the Bradis table will be useful, where the required values are indicated. The most common formulas you will need to use are:
- calculating the length of the rafters. This is the height of the ridge multiplied by the angle in degrees between the span line and the slope;
- the height of the roof ridge, that is, the calculation midline a triangle formed by the span and the roof slope.
Calculation example
Let's consider the case when the thickness of the laid sheathing is 2.5 cm, and sq. m of roofing weighs 15 kg. In this case, insulation is laid with a layer thickness of 10 cm, the weight of which per square meter. m is 10 kg. When covering the roof, ondulin is used, weight sq. m which is equal to 3 kg.
The load calculation for the slope will be performed as follows:
1.1x(15+10+3)=30.8 kg per sq. m
We also take into account that the load is usually taken to be up to 50 kg per square meter. m, but this figure is somewhat overestimated in order to provide some reserve. That is, the value we obtained is fully consistent with the norm.
The optimal angle of a pitched roof is calculated using a mathematical tool, this is the Bradis table, where the following values are accepted:
- inclination angle in degrees - 5, relative value - 0.8;
- angle - 10, relative value - 0.17;
- angle - 5, magnitude - 0.26 and so on.
Dependence of the attic area on the angle of the roof: if you take the roof angle too high, this will reduce the amount of usable area of the attic. Too small an angle of inclination will lead to difficulties in the operation of the roof itself: cleansing from precipitation, strength.
In this case, the coefficient depends on the slope angle in degrees; if it does not exceed 25 degrees, then the coefficient is taken as one. At an angle from 25 to 16, the coefficient is taken as 1.25 and so on.
For the calculation, the Bradis table can also be used, which then allows you to find out the angle that corresponds to the resulting figure. Ridge height in in this case is defined this way:
- first, calculations are made for the span width;
- the resulting width is divided by two;
- the value is multiplied by the value individual for the angle of inclination.
So how to calculate the roof slope? Everything is very simple: with a building width of 8 m, we get the value of half the span - 4 m. Now we calculate the height of the rafters for a slope of 25 degrees. The table gives us a coefficient value of 0.47. Now we multiply half the width by the resulting number, that is, 4x0.47, and we find that the roof rafters must be raised by 1.88 meters.
To select the slope angle, it is necessary to carry out appropriate calculations. A lot depends on this, including the choice of materials and the height of the ridge. Such calculations are needed to organize proper water flow and resistance to snow and wind loads. In some cases, it is necessary to convert the resulting value into a percentage, but most often the Bradis table is used for calculations. In addition, all values are influenced by the material of the roofing pie, that is, insulation, waterproofing, rafters, coating.
The roof is part of any home. It is very important for her to choose high-quality roofing material. Experts are of the opinion that when choosing it, one should take into account the angle of inclination of the roof, which serves to ensure that water does not linger on it. The slope of the roof is usually called the angle of its inclination to the horizon. It is usually expressed as a percentage or in degrees. Therefore, the higher its value, the steeper the roof will be. We will talk about methods for calculating this indicator further.
Depending on the angle of inclination, the following roof structures are distinguished:
It's worth saying that flat roof is not completely horizontal. Otherwise, the water would not flow from it. Such a roof must have a slope of at least 30 degrees. Depending on the design features There are three main types of roofs:
Arbitrary structures are those for which the load due to the influence of wind and precipitation is not calculated. Such roofs are usually erected only according to the wishes of the owner. They often house storage rooms or even living quarters. The averages represent the most best ratio the angle of the roof slope, taking into account the influence of precipitation and wind. This type of roofing is best built in regions with high humidity. As for the low-slope roof, its design is made in such a way as to minimize the influence of wind force on it. In addition, this coating copes well with precipitation. Such roofs can be installed in almost any region. After all, they have a minimal slope and fit almost every house structure. Low-slope roofing has several serious advantages, namely:
Despite the fact that you may have to spend money on purchasing and installing additional water protection equipment, the undeniable advantages will justify these costs. What does the slope of the roof depend on?
The angle of inclination is usually determined depending on the roof structure, the roofing material used, as well as the climate of the region where the house will be built. In order to know how roofing material is selected depending on the angle of inclination of the roof, you need to find out what affects this indicator. These factors include:
UnitsToday, roof slope is mostly measured in degrees or percentages. Correct angle can be selected with both systems. To find out the required value, you can take as a basis the results of measuring the roof itself, as well as a reduced model depicted on paper. The required degree must be laid down when installing the structure. Let's look at how to calculate the roof slope as a percentage. You need to take the height of the ridge, divide the resulting value by half the width of the house, then multiply everything by 100%. As a percentage, 100% corresponds to 45 degrees, and 1 degree equals 1.7%. If in the region where the house is being built, it is possible strong wind, then when calculating the angle of inclination of the roof, it is recommended to make it minimal. To measure and indicate the slope of the roof, there is a special tool called an inclinometer. How to calculate roof slopeUsing a schema
To make it easier, you can use a special diagram that allows you to select the roofing material depending on the level of its slope. The minimum angle corresponding to 0% and the maximum - 100% are indicated here. Percentage values are plotted on a vertical scale. In the center of the diagram there is a semicircular scale, in which there are calculations in degrees. In general, the higher the slope value, the more layers of material will need to be laid on it. By the way, the amount of material needed can be determined by the slope of the roof. Let's look at how calculating the roof slope affects the choice of material. According to the above diagram, if the slope is from 0 to 25%, then rolled materials can be used to cover the roof. With a slope of 0-10%, it is recommended to lay the flooring in three layers. If this value is 10-25%, then you can put one layer, for example, material with bedding. On roofs with a slope of no more than 28%, asbestos-cement corrugated sheets, such as slate, can be laid. If this figure is up to 29%, then it is recommended to use a steel coating. With a slope of 33% and above, tiles are often used as a roofing material. Calculation by formulaWhen the roof slope is determined and required material for covering, it is necessary to calculate the height of the ridge. To do this, you can use a simple mathematical method: you need to take the width of the span of the house and divide it by two. The result of the quotient must be multiplied by the relative value, which is calculated using a special Bradis table. It shows the values for each angle.
Now let's give an example of calculating the roof slope. If the width of the span is 8 meters and the angle of inclination of the roof is 25 degrees, then the height of the ridge is as follows: 8:2 = 4 4 * 0.47 = 1.88 meters. Counting in reverse side Using the same formula, you can determine the angle of inclination of the roof. This is unlikely to be needed during construction, but it may come in handy during renovations. Using an inclinometerThe magnitude of the slope can also be calculated using special tool, which is called an inclinometer. It is a strip with a frame attached to it. Between the slats there is an axis to which the pendulum is attached. There is a graduated scale inside the cutout. When the rod lies horizontally, it corresponds to zero on the scale.
Optimal roof slope for different materials
Important! It is worth understanding that all the values listed here are just recommendations. Therefore, everyone has the right to choose the angle of inclination of the roof to the horizon at their own discretion. Some builders forget about such a very important detail as planning the drain, and it is through it that water flows from the roof. If you do not take care of this in advance, then after the construction of the roof, difficulties may arise with water drainage. |
The roof occupies important place in the design of any type of building, since it is responsible for ensuring elementary conditions does not provide comfort external factors damage the decoration of the house.
Of course, quality shelter requires many factors to be considered during the design process. One of the main positions in this context is the calculation of the roof slope angle.
Why is it so important and what do you need to know so that the calculation is correct and subsequently you won’t have to redo the roof partially, or even completely? We'll talk about this in this article.
Calculation of roof slope it is best to produce using a special online calculator , which is located below.
The angle of the roof slope is the geometric formation of the intersection of two planes. They mean a horizontal plane and a similar slope surface.
So, why measure the roof angle:
- Measuring the construction azimuth, first of all, allows you to “estimate” the feasibility of installing a roof, taking into account the selected roofing material, climatic features, the purpose of the attic and the design of the canopy itself.
- In addition, after making calculations, you can not only rationalize upcoming financial expenses, but also ensure the correctness and reliability of the design, which will not entail losses due to leaks, collapses, cracks in rafters and other incidents.
- The roof slope is taken depending on two parameters - the first concerns weather conditions and precipitation volumes, and the second is characterized by the specifics of the type of roof. Accordingly, when we're talking about about northern and snowy regions, then the future roof will have to deal with significant loads. Residents of mountainous regions are familiar with such difficulties firsthand.
- Some roofs have to withstand snow for 6-8 months a year. In the current conditions, the owners of snow-covered houses have made life much easier by a steeper degree of inclination. In turn, such construction bearings allow the hip to rationally deal with precipitation and its consequences in the form of melt water. Also, with this approach, the size of the usable area increases.
NOTE!
When the slope is set at 45 degrees and above, the calculation of the snow load is no longer taken into account, since such a roof is “self-cleaning”.
Of course, not everything is so good with a sharp point, because as the slope increases, the need for additional volumes of both roofing materials and structural elements increases proportionally. Also becomes topical issue increasing the durability of load-bearing parts.
No less important when calculating the slope is the specificity of the material that will complete the structure of the canopy with outside. It's no secret that each type of roof top element differs in performance properties and cost.
At the same time, nuances can be provided that are characteristic exclusively of this type of top layer of the roof. For example, it may be necessary to lay additional layers, or higher costs will be required for thermal and waterproofing.
The slope angle depends on the wind rose
Perhaps the third most important factor on which the calculated slope depends is establishing exploited or non-exploited status. The non-exploitable surface provides for the exclusion of space at the junction of the ceiling and the external protective structure.
Visually, the interpretation of the concept looks much simpler, since when you see flat hips or there is a slight slope (in the range of 2-7%), it immediately becomes clear why it received such a name. An usable attic indicates the presence of attic space.
Calculation of roof slope angle: calculator
Field designations in the calculator
Specify roofing material:
Select a material from the list -- Slate (corrugated asbestos cement sheets): Medium profile (11 kg/m2) Slate (corrugated asbestos cement sheets): Reinforced profile (13 kg/m2) Corrugated cellulose-bitumen sheets (6 kg/m2) Bitumen (soft , flexible) tiles (15 kg/m2) Galvanized sheet metal (6.5 kg/m2) Sheet steel (8 kg/m2) Ceramic tiles (50 kg/m2) Cement-sand tiles(70 kg/m2) Metal tiles, corrugated sheets (5 kg/m2) Keramoplast (5.5 kg/m2) Seam roofing (6 kg/m2) Polymer-sand tiles (25 kg/m2) Ondulin (Euro slate) (4 kg/m2) m2) Composite tiles(7 kg/m2) Natural slate (40 kg/m2) Specify the weight of 1 square meter of coating (? kg/m2)
kg/m2
Enter the roof parameters (photo above):
Base width A (cm)
Base length D (cm)
Lifting height B (cm)
Length of side overhangs C (cm)
Front and rear overhang length E (cm)
Rafters:
Rafter pitch (cm)
Type of wood for rafters (cm)
Working area of the side rafter (optional) (cm)
Lathing calculation:
Sheathing board width (cm)
Sheathing board thickness (cm)
Distance between sheathing boards
F (cm)
Calculation of snow load (pictured below):
Select your region
1 (80/56 kg/m2) 2 (120/84 kg/m2) 3 (180/126 kg/m2) 4 (240/168 kg/m2) 5 (320/224 kg/m2) 6 (400/280 kg/m2) 7 (480/336 kg/m2) 8 (560/392 kg/m2)
Wind load calculation:
Ia I II III IV V VI VII
Height to the ridge of the building
5 m from 5 m to 10 m from 10 m
Terrain type
Open area Closed area Urban areas
Calculation results
Roof angle: 0 degrees.
The angle of inclination is suitable for this material.
It is advisable to increase the angle of inclination for this material!
It is advisable to reduce the angle of inclination for this material!
Roof surface area: 0 m2.
Approximate weight of roofing material: 0 kg.
Number of rolls insulating material with 10% overlap (1x15 m): 0 rolls.
Rafters:
Load on the rafter system: 0 kg/m2.
Rafter length: 0 cm
Number of rafters: 0 pcs.
Lathing:
Number of rows of sheathing (for the entire roof): 0 rows.
Uniform distance between sheathing boards: 0 cm
Number of sheathing boards with a standard length of 6 meters: 0 pcs.
Volume of sheathing boards: 0 m3.
Approximate weight of sheathing boards: 0 kg.
Snow load region
Decoding calculator fields
Roof slope in percentage and degrees
How to determine the angle of a roof in degrees? Oblique angle, like 
any similar figure, according to geometric canons, is measured in degrees.
But in many documents, including SNiPs, this value is displayed as a percentage, so there are no strict requirements and justifications to be guided by only one unit of measurement.
The main thing in this situation is to know the proportions for the relationship if you suddenly need to convert degrees to percentages and vice versa, for example, for convenience during computational operations.
In general, the degree to percentage conversion factor ranges from 1.7 (for 1 degree) to 2 (for 45 degrees). In cases where indicators expressed not as a whole percentage are fundamentally important, ppm - hundredths of a percent - are used in digital display.
If you trust the theory, then the inclinations can reach 60 and even 70 degrees, but in practice this will not look entirely appropriate. Yes and by appearance the impression is “so-so”, unless your house is located somewhere in the Alps and you need to build a roof that is constantly exposed to snow loads.
Converting degrees to percentages
Specifics of flat and pitched roofs
Flat floors are not represented strictly horizontal surface, no matter how misleading its name is. The construction azimuth in this situation also has a slope, although not significant - its the minimum value should be 3 degrees.
NOTE!
There is one nuance that must be taken into account when designing a flat surface. Required condition- installation of drainage funnels, the walls of which will tilt by 1.5 degrees.
As for the optimal values for flat coatings, then slope flat roof fluctuates around 5-7 degrees. This is due to the fact that roofs with an angle greater than 10º can hardly be called flat. In turn, 12-15 degrees in most situations is already interpreted as the minimum threshold for sloped surfaces. The optimal values are wide enough.
Optimal roof angle for snow melting is 40-50 degrees.
Flat roof slope
For example, for lean-to sheds a range of 20 to 30 degrees is assumed, and in the case of gables this figure rises to 45º.
It’s just that this volumetric interval largely indicates the individual characteristics of the roof type and climatic features.
CAREFULLY! If the azimuth is small, the joints must be treated with frost- and water-resistant sealant.
If the indicator is 15 degrees or higher, then the corrugated sheeting should be laid with an overlap of 200 mm, and if the roof slope is less than 15º, the overlap increases by two “waves”.
Minimum roof slope
- Roofing material, which is one of the main elements of the structure of the upper plane, also provides certain slope recommendations depending on its type. In the case of corrugated sheets, set the angle at 12 degrees , for metal tiles this indicator should
- increase to 15º. Ondulin or soft tiles in common language you can lay on a slope of 11 degrees . But in this case there is also one nuance, which is
- in a continuous frame. When hiding ceramic tiles incline. It is also worth considering that the rafter system is subject to heavy loads if the slope is slightly inclined. To avoid overloads, this factor should be taken into account during design.
- The most common type of surface covering is slate. When laying asbestos-cement corrugated sheets, the roof slope indicator should not exceed 28%. The same requirements apply to steel planes.
- Minimum roof slope from sandwich panels according to the standards is 5 degrees, if windows are planned in panels, then the slope increases to 7 degrees.
Dependence of slope on the choice of roofing covering
How to determine the roof pitch yourself
To measure the slope angle, you can use a miracle device that can relieve you of all the computational burden. The name of the device speaks for itself - inclinometer (protractor).
In general, you can turn to a mechanical inclinometer for help - a budget option, but additional hassle is not excluded, especially if you are using such a device for the first time.
However, we will tell you the specifics of this device - perhaps, thanks to it, our reader will very soon be familiar with this element.
- A standard inclinometer without electronic bells and whistles is presented in the form of a rod with an attached frame. At the junction of the slats there is an axis on which the pendulum is fixed. Its unique set includes 2 rings, a weight, a plate and a pointer. The device is complemented by a scale with divisions, which is located in the inner part of the cutout. If the staff is placed horizontally, the pointer will coincide with the zero division of the scale.
- Now let's move on to the main process for which the device is intended. Align the protractor rod perpendicular to the ridge. After this, the required value in degrees will be displayed on the pendulum pointer.
- Option based on carrying out your own calculation task to measure the slope by mathematical calculations , unattractive. In any case, we will try to clearly explain how you can do this yourself. First of all, you need to find out the length of the hypotenuse and legs. When it comes to measuring the slope of the roof, the straight line of the slope is the display of the hypotenuse.
- Then we calculate the length of the opposite and adjacent legs. The first of them is presented in the form of the distance separating the ceiling and the ridge, and the size of the second should be taken as the distance between the middle of the ceiling and the eaves overhang of a certain slope.
- Now, having already received two values, finding the third by applying trigonometry is not difficult. As a result, knowing the sine, cosine or tangent (depending on the size of the components), we use an engineering calculator to calculate the digital value of the slope as a percentage.
- Still have questions? Watch the video lesson below or use our online calculator.
Ratio of ridge height to span
In general, the algorithm for conducting settlement operations can be divided into four steps. First we take into account external natural factors influence on the future surface layer, we check our construction plans with price tags for the necessary resources in online stores, we decide on the type of material for the roofing and do not stop getting information from specialized sites and, if possible, consult with professionals.
Regarding loads - it’s better not to bother minimal slopes, as this could end badly for a “fresh” roof.
But if the roof is flat and there is nowhere to go, then do not neglect fortifying redoubts.
When calculating the cost, also do not ignore such concepts as the weight of the house structure and, again, the load from precipitation - this will help you find not only the right, but also an economically pleasant solution for your wallet.
Roof calculation If the inclination is up to 10 degrees, then suitable option
there will be surfaces made of gravel, up to 20º - corrugated sheets and slate. Steel and copper sheets are advisable even in very “steep” cases, when the upper point reaches 50-60 degrees.
Actually, that’s all the information you need to independently calculate the roof slope angle.
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An important stage in the design of house construction is the calculation of the roof and the choice of covering material. The main parameter that affects the functionality of the roof and the integrity of the entire structure is the angle of inclination of the slope. Moreover, there is a relationship between the characteristics of the roofing material and this value.
What is a roof and roofing? The construction of a building is unthinkable without the construction of a roof. It consists of rafters and roofing. Rafter system
performs a load-bearing function, and the roof plays the role of a fence and makes the building attractive. Roofing is the upper element of the roof, which absorbs the influence of external factors.
Requirements for the roofThe roof is very important for a proper structure Roof - important detail
- , therefore the design must have the following characteristics: Level of strength, resistance to loads that arise due to exposure and under the influence of other factors.
- Resistance to constant vibrations temperature regime and the influence of ultraviolet radiation.
- Water-repellent properties. To reduce the influence of atmospheric moisture, they are used technical methods protection from water: a drainage system is constructed and the roof structure is sloped. The porosity of roofing materials matters. Materials with high porosity have better waterproofing properties. As porosity decreases, they decrease performance characteristics roofing material, which in case of freezing will cause destruction.
- Durability of the structure. Minimum service life, in case correct installation and normal operation, is up to 30 years.
- Attractive view. Harmonious combination all elements of the house, compliance with the architectural style.
- Safety of materials in environmental terms.
- Ability to save original appearance and color when exposed to sunlight.
Classification of roof structures
Roof structures are varied, which affects the calculation of the angle of inclination of the structure. House layout and accepted architectural solution determine the shape of the roof.
Single-pitch. The simplest option designs. The rafters and truss rest on load-bearing walls, located in different levels. It is used in the construction of house extensions and utility buildings, it is reliable and economical.
Gable. A structure like this is a classic solution for roof construction. Support on the walls bearing loads. At the end, the roof forms a triangle, so the second name is gable.
Tent. Represents four slopes representing equal triangles with vertices converging at one point. Such a roof covers buildings with a square shape or a polygon.
Domed. Such a roof looks like a ball that has been cut in half. This hemisphere has a cylindrical support. Four arched vaults make up the dome.
Hip. Two trapezoidal and two triangular slope at the ends they make up the roof structure.
Half-hip. Two triangles with the vertices cut off above the ends.
Folded. Trapezoidal elements with folded joint.
Vaulted. Arc-shaped, representing a cylinder cut in half. This design option is an alternative to a flat roof.
Multi-pincer. Complex constructive solution roof, which is characterized by a combination of several types of structures.
Types of roofs Factors affecting roof pitch
When calculating the angle of inclination of the roof, the covering material and operating conditions of the building are important.
The construction of a roof is impossible without determining the covering material and calculating the angle of inclination. These two parameters are related to each other. The angle is determined using construction matrices and graphs.
It is possible to calculate this parameter using a school square.
When determining the angle of inclination during the construction of a roof with one slope, the influence of:
- properties of the roofing material;
- climate;
- operational features of the structure.
When installing a roof with several slopes, the above factors and the area are taken into account construction site. The functional purpose of the attic is also taken into account. If it is not planned as a living space, then the ceiling height does not need to be increased. In the case of arranging an attic, this circumstance must be taken into account when designing the roof, ensuring desired angle tilt
In areas where winds prevail, a roof with a minimum slope is constructed. This measure will reduce the load on the upper element of the building. At the same time, it is not advisable to completely abandon the slope. This design is allowed if the region is dominated by sunny days with minimal precipitation.
The angle of roofs is important for the effects of precipitation A high roof can resist wind flow more than a low one. On the other hand, a small angle of inclination often causes the roof covering to be torn off by the wind. Thus, the risk of damage to the roof remains both at a large angle of inclination of the roof and at its insignificant value.
- in case of moderate wind load – 35-40 degrees;
- in the presence of strong gusts of wind – 15-25 degrees.
If precipitation prevails in the area where the building is used, then it is allowed to increase the angle of inclination to 60 degrees. This solution will ensure unimpeded drainage of snow and water from the roof.
The angle of inclination will be shown by devices Taking into account the described circumstances, the range of the roof inclination angle is within 9-60 degrees. When carrying out calculations when designing a building, it narrows to 20-45 degrees. This is due to the fact that with this value of the angle of inclination it is possible to use any roofing material.
In case of use roll materials, the angle changes as follows:
- laying in two layers requires creating a slope not exceeding 15 degrees;
- with three-layer laying - 2-5 degrees.
Slate is used with a slope of up to 28%.
The use of tiles is possible with a slope of at least 33%.
Steel covering is used when constructing a roof with a slope of no more than 29%.
The slope of the slope affects the need for roofing material. As it increases, consumption increases.
Thus, a flat roof is cheaper than constructing a 45-degree slope.
Metal roofing
The greater weight of metal tiles compared to other roofing materials makes it necessary to provide for the minimum possible angle of inclination of the roof when designing.
When carrying out construction in windy areas, take into account negative impact increasing the wind load on the roof structure as a whole. Exceeding the angle of inclination of the structure can cause the phenomenon of “swelling” of the roof, which leads to an increase in the magnitude of the operating loads. If it is permanent, it leads to deformation and destruction structural elements roofs.
From the data obtained empirically, it is clear that the minimum permissible value– 22 degrees. This value is optimal for maintaining the operational properties of the structure and does not allow the accumulation of precipitation.
If there is a need to create a flat roof, then the minimum slope value should not be less than 14 degrees. When using tiles from soft materials, which is mounted on the sheathing, the angle is reduced to 11 degrees.
Corrugated roofing
Corrugated sheeting is one of the popular roofing materials. It is lightweight, easy to install and quick to install.
The construction of a roof from this material takes into account that the minimum permissible angle of inclination is about 12 degrees. The manufacturer provides precise recommendations in the accompanying documentation.
Roofing made of rolled “soft” materials
Soft coverings on construction market represented by roofing felt, ondulin, polymer materials.
Depending on the number of layers of coating, the slope of the roof structure can be 2-15 degrees. As the coating thickness increases, the angle decreases. Polymer coatings allow you to create a roof of complex configuration with a small slope of 2-5 degrees.
When determining the angle of inclination of the roof, keep in mind that it must have strength that ensures the integrity of the structure under constant and short-term loads: it must withstand the weight of the entire roof and the weight of atmospheric precipitation.
How to calculate the roof slope angle?
To determine the angle of the roof slope, they use trigonometric functions or resort to using an inclinometer - a device that determines the desired value. The angle value is expressed in degrees or percentage.
The mathematical method is to calculate the sides right triangle. The hypotenuse is the length of the slope line. The opposite leg is the length of the segment from the overlap to the top.
The adjacent leg is equal to the distance from the middle part of the ceiling to the eaves overhang.
How to calculate the angle of a roof? If you calculate the two sides of a right triangle, you can get the roof slope value. According to one of trigonometric functions the required angle value is easily determined.
When using another method, the ratio of the height of the ceiling to half of its width is determined. The value is expressed as a percentage, so the result of dividing the indicated values is multiplied by 100. After this, the value is determined from a special table.
When installing such structures, pay due attention to the drainage. In case of organization internal system For water collection, it is planned to create a roof slope towards the receiving funnels. If an external catchment is used, the slope is directed towards the gutters.
A roof whose slope does not exceed 10 degrees, according to the recommendations of experts, should be covered with a membrane covering. This will make it possible to create reliable protection from water penetration.
Be sure to provide ventilation in the under-roof space. This requirement applies to all stingrays. Moreover, as the angle of inclination decreases, the gap for ventilation increases.
When choosing bitumen shingles and the slope is less than 6 degrees, the waterproofing is constructed from polymer materials.