Slate roof slope. Calculation of the minimum and optimal roof slope angle in percentages and degrees depending on the type of roof and roofing material. Rafter system for pitched roofs
The reliability of the building and the comfort of living in it depend on the quality of roof construction. Its design is selected optimal for local operating conditions. Of particular importance is such a parameter as the slope of the roof, which will be discussed further.
The angle of the roof slope depends not only on its design and features of the facade of the house, on the chosen roofing material, but also from other factors. First of all, it is necessary to take into account climatic conditions the area where the building is being erected. Where the number of drops in winter time precipitation is high, a large roof angle is preferable (within 45-60 degrees): this contributes to better snow melting, which means reducing the load on the roof. It also becomes less likely that the surface of the floor will freeze due to compaction of snow covers.
If a building is being erected where weather with strong winds prevails, it is advisable to choose a minimum roof slope angle to reduce the windage of the structure. Otherwise, the structure is in danger of rapid destruction. Most often, the tilt range in this case is 9-20 degrees.
How larger angle the slope of the roof slope - the easier the snow cover comes off it
But basically, the optimal roof slope angle is selected in average values, that is, from 20 to 45 degrees. It is suitable for almost any type of roofing material, for example, corrugated sheeting or metal tiles, which are very popular today.
In areas with a warm climate, where there are much more sunny days than cloudy ones, flat roofs will be more acceptable: their area is smaller than that of other types of structures, which means heating from sun rays will occur to a lesser extent. But such a structure should not be absolutely horizontal: the slope flat roof should be at least within 3-5 degrees. The minimum slope of the flat roof will ensure normal drainage of rain and melt moisture.
Types of roofing structures
Utility and utility buildings are often built with a pitched roof: it is easy to install and does not require large expenses. In fact, such a building has walls of different heights with a ceiling laid on them. The slope of the ceiling is selected within the range of 9-25 degrees, which is well suited for corrugated sheets and metal tiles. This design requires ventilation of the under-roof space.
But the most popular is the gable one: two planes located at an angle are connected along the ridge line. Other (end) planes are vertical and are called pediments. They may have doors to access a balcony or external staircase.
There are many design options roofing
Hip ceilings, the most popular representatives of which are hipped ones, are aesthetically very attractive. In such cases, especially in more complex structures, the slopes can be any: it depends on the chosen design and personal preferences of the developers. Dignity hip roofs– in the absence of restrictions on the use of roofing material.
Option hip design– attic: attic space It is used as a residential building, so the requirements for insulation are very high. The free space under the ceiling is formed due to the high angle of inclination of all slopes, in which the presence of skylights.
Dependence of roof structure on floor material
Before choosing a roofing material, you should study its technical characteristics: this will help you optimally approach the issue and choose the most reliable one. In addition, there is a rule that determines the dependence of the slope angle on the roofing material used.
We list the main ones:
When selecting the slope value, consider strength characteristics roofing structure: the safety margin must be enough not only to withstand its own weight and the weight of the roofing material, but also external loads(gusts of wind, snow). Also, the type of sheathing for laying most materials depends on the slope of the slope: for low values of this parameter, either continuous sheathing, or with a small pitch (350-450 mm). When erecting any roof, especially a flat one, it is necessary to install a system of slopes and drainage. If the area is particularly large, additional drainage will be required.
Calculation of the angle of inclination
The design must meet the following requirements: be strong enough, provide reliable protection from precipitation, have good thermal and sound insulation. It is also important that there is access for repairs and maintenance. How to calculate the angle of the roof so that all these conditions are met? Experts recommend using simple options its devices, which include single-pitch, gable, hip (and half-hip), and attic.
Roofs can have a design of any complexity, with different slope angles
Single-pitch roofs are most convenient for verandas, outbuildings and outbuildings. The principle of creating a single-pitch roof is the same as other types: rafters and sheathing are installed, after which the roofing material is laid. The latter plays a decisive role: for corrugated sheeting an angle of 8-11 degrees is required (it is better to do 20), for metal tiles - at least 25, for slate and seam roofing - 35 degrees.
If climatic conditions allow, it is better to make a roof with a slope of 45 degrees: this will allow you to neglect calculations related to the mass of snow. This is an almost ideal pitched roof: the angle of inclination will not complicate its installation and will facilitate maintenance (snow will not accumulate on its surface). But in this case, it will be necessary to strengthen the rafters and sheathing, since the wind pressure on the structure increases 5 times. It should also be taken into account that this will require high costs for materials - approximately 1.5 times.
Roofing material must be selected depending on the roof slope
As can be seen from the graph, each slope corresponds to a certain group of roofing waterproofing materials. There are 11 of them in total, with the inclined lines corresponding to the angle of inclination of the slope. The thick line indicates how the height of the ridge relates to ½ of its depth. It can be seen that the segment h is equal to half of the horizontal segment, designated by the fraction ½. The numbers at the tops of the semicircular scales correspond to the angle of inclination (in degrees), the vertical scale also indicates in percentage. When choosing any roof configuration, you should adhere to these recommendations and purchase roofing materials suitable for your chosen option.
In order to make it clear how the roof slope angle is calculated, we will give an example of calculating the smallest slope angle of a roof with tile waterproofing. On the graph we find a semicircular curve corresponding to a given coverage: this will be the curve indicated by the number 2. Tracing it to the point of intersection with the vertical scale, we find that minimum slope such a roof is equal to 50%.
Taking into account the fact that the slope of the slope is the ratio of the height of the ridge to ½ of its depth, we calculate the slope. That is, with a ridge height h = 4 m and a slope equal to L = 15 m, the slope will be determined as h: (L/2) = 4: (15/2) = 0.53. To display it as a percentage, multiply the result by 100 and get 53%. This value of this parameter guarantees good drainage of rainwater. The minimum slope in the valley is 1%.
Features of calculating a gable roof
The gable roof is the most successful and common design. There are several reasons for this: high reliability, relative simplicity, low cost design. When constructing a roof, not everyone chooses the optimal angle of inclination correctly. two pitched roof.
In areas of strong winds, it is necessary to calculate the gable roof so that its slope does not cause too strong wind loads. The greater the angle of inclination of the structure, the higher its windage.
You cannot reduce it to values less than 25 degrees: precipitation will be less easily removed from the roof, and dampness may appear in the under-roof space. Making it larger than 60 degrees is also not recommended: a strong impulse of faith can destroy the roof. The roof does not have to have symmetrical slopes: if you orient the building with a more gentle slope to the south, the roof will dry better after rain.
Conditions for using roofing materials depending on the slope angle
Useful attic area and drainage system
Effective area attic room depends on the roof structure: the greater the slope angle, the larger the area and vice versa (this is clearly shown in Figure 2). When constructing an attic, you have to make a compromise between the area that can be easily used, the cost of building a roof and the strength of the structure.
The method of removing precipitation can also be different. There are external or internal organized and unorganized - only external. The latter involves installation drainpipes and gutters, while wall and suspended systems are mounted on roofs with a slope greater than 15%. The gutters are attached with a minimum slope of 3 degrees, their sides are made with a height of about 120 mm.
Depends on the angle of the roof effective area attics
The distance between the pipes should be no more than 23 m. The cross-section of the pipe should ensure normal drainage of water and is selected depending on the area of the slope. External drains of an organized type are more suitable for areas with a warm climate. Internal gutters are used for cold climates. Such systems consist of a funnel for receiving water, a riser, an outlet and a discharge pipe. The main condition is that water drainage must be ensured at any air temperature.
Installing a roof is a very important task that requires the participation of highly qualified workers. Installation errors can cost home owners dearly. To avoid troubles, roofing work should be entrusted to specialists with sufficient experience: this will guarantee the reliability of the building and the comfort in it.
The slope of the roof slopes - what it depends on and how it is measured.
Such an important fact for the roof is its slope. Roof slope- this is the angle of inclination of the roof relative to the horizontal level. According to the angle of inclination of roof slopes there are low slope(sloping), average inclination And roofs with steep(highly inclined) stingrays.
Low slope roof that roof, the installation of which is carried out based on the smallest recommended angle of inclination of the slopes. So, each roofing has its own recommended minimum slope.
What does the slope of the roof depend on?
- The ability of the roof to protect the building from external factors and impacts.
- From the wind- the greater the roof slope, the greater the value of the wind loads. With steep slopes, wind resistance decreases and windage increases. In regions and places with strong winds, it is recommended to use a minimum roof slope to reduce the load on bearing structures roofs.
- From roofing covering (material) - For each roofing material there is its own minimum angle of inclination at which this material can be used.
- From architectural ideas, solutions, local traditions- so in different regions preference is given for one or another roof structure.
- From precipitation: snow loads and rainfall in the region. On the roofs with large slope snow, dirt and leaves will not accumulate in large quantities.
What is the roof pitch angle measured in?
The designation of the roof slope on the drawings can be either in degrees or as a percentage. The roof slope is indicated by the Latin letter i.
In SNiP II-26-76, this value is indicated as a percentage (%). IN this moment does not exist strict rules by designating the size of the roof slope.
The unit of measurement for roof slope is degrees or percentages (%). Their ratios are shown in the table below.
Roof slope degree-percentage ratio
| degrees | % | degrees | % | degrees | % | ||
| 1° | 1,75% | 16° | 28,68% | 31° | 60,09% | ||
| 2° | 3,50% | 17° | 30,58% | 32° | 62,48% | ||
| 3° | 5,24% | 18° | 32,50% | 33° | 64,93% | ||
| 4° | 7,00% | 19° | 34,43% | 34° | 67,45% | ||
| 5° | 8,75% | 20° | 36,39% | 35° | 70,01% | ||
| 6° | 10,51% | 21° | 38,38% | 36° | 72,65% | ||
| 7° | 12,28% | 22° | 40,40% | 37° | 75,35% | ||
| 8° | 14,05% | 23° | 42,45% | 38° | 78,13% | ||
| 9° | 15,84% | 24° | 44,52% | 39° | 80,98% | ||
| 10° | 17,64% | 25° | 46,64% | 40° | 83,90% | ||
| 11° | 19,44% | 26° | 48,78% | 41° | 86,92% | ||
| 12° | 21,25% | 27° | 50,95% | 42° | 90,04% | ||
| 13° | 23,09% | 28° | 53,18% | 43° | 93,25% | ||
| 14° | 24,94% | 29° | 55,42% | 44° | 96,58% | ||
| 15° | 26,80% | 30° | 57,73% | 45° | 100% |
You can convert the slope from percent to degrees and vice versa from degrees to percent using an online converter:
Roof slope measurement
The slope angle is measured using an inclinometer or mathematically.
Inclinometer- this is a rail with a frame, between the slats of which there is an axis, a division scale and to which the pendulum is attached. When the staff is in a horizontal position, the scale shows zero degrees. To measure the slope of the roof slope, the inclinometer rod is held perpendicular to the ridge, that is, at vertical level. On the inclinometer scale, the pendulum indicates the slope of a given roof slope in degrees. This method of measuring slope has become less relevant, since now various geodetic instruments have appeared for measuring slopes, as well as drip and electronic levels with inclinometers.
Mathematical calculation of slope
- Vertical height (H) from the top point of the slope (usually the ridge) to the level of the bottom (eaves)
- Laying ( L ) - horizontal distance from the bottom point of the slope to the top
Using mathematical calculation, the roof slope is found as follows:
The slope angle i is equal to the ratio of the roof height H to the foundation L
i = Н : L
In order to express the value of the slope as a percentage, this ratio is multiplied by 100. Next, to find out the value of the slope in degrees, we translate using the table of ratios located above.
To make it clearer, let's look at an example:
Let it be:
Laying length 4.5 m, roof height 2.0 m.
The slope is: i = 2.0: 4.5 = 0.44 now multiply by × 100 = 44%. We translate given value according to the table in degrees and we get - 24°.
Minimum slope for roofing materials (coatings)
| Roof type | Minimum roof slope | ||
|---|---|---|---|
| in degrees | V % | in the ratio of the height of the slope to the foundation | |
| Roofs made of rolled bitumen materials: 3 and 4 layers (fused roofing) | 0-3° | up to 5% | until 1:20 |
| Roofs made of rolled bitumen materials: 2-layer (fused roofing) | from | 15 | |
| Seam roofing | from 4° | ||
| Ondulin | 5° | 1:11 | |
| Corrugated asbestos cement sheets (slate) | 9° | 16 | 1:6 |
| Ceramic tiles | 11° | 1:6 | |
| Bituminous shingles | 11° | 1:5 | |
| Metal tiles | 14° | ||
| Cement-sand tiles | 34° | 67% | |
| Wooden roof | 39° | 80% | 1:1.125 |
In everything globe there are thousands and thousands of architectural traditions in terms of the appearance of roofs. But modern architects have completely changed the idea of culture suburban construction, introducing pitched roof forms as ideally combined with landscape design and diverse in execution. Of course, this new fashionable tone was set by the residents of Australia, where the absence of snow at all is like natural phenomenon allows them to create whatever their imagination dictates with the architecture of residential buildings.
But in the snowy regions of Russia such a roof can be built, but with the 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 how to calculate.
Step 1. Calculate permanent and dynamic loads
First of all, calculate the loads on a pitched roof. They are usually divided into permanent and dynamic. The first is the weight of the roofing covering, which is always located on the roof, installations such as antennas and dishes, a chimney, etc. Those. everything that will be on the roof both day and night.
And dynamic loads, or, as they are also called, variable loads, are those that happen from time to time: snow, hail, people, repair materials and tools. And also the wind, which really likes to tear off pitched roofs due to their windage.
Snow loads
So, if you make a pitched roof slope of 30°, in winter the snow will press on it with a force of 50 kg per square meter. Just imagine having one person per meter sitting on your roof! This is the load.
And if you raise the roof to above 45°, the snow will most likely not be able to stay at all (this also depends on the roughness of the roofing). But for middle zone In Russia, where snowfalls are moderate, it is enough to make a pitched roof within 35-30°:
The minimum angle that must be so that snow can slide off a pitched roof on its own is 10°. And the maximum is 60°, because there is no point in making the roof steeper. The same applies to snow, which clings even more to such a roof.
That's why owners of lean-to outbuildings In winter they often take up a shovel. The only thing that saves is the coverage area: 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. For comparison: a pitched roof slope of 11° experiences exactly 5 times more wind force than a slope of 45°. In view of this, please note that a pitched roof is always made with the low part towards the leeward side.
Combined loads
And be sure to calculate for a pitched roof such a value as the combination of the most unfavorable permanent and temporary loads. Those. that critical point that the rafter system must be able to withstand. By the way, this is often forgotten! They think the roof can withstand the snow and the wind too...
What if you and a friend have to climb out onto the roof during a heavy storm and snowfall? Is the design designed to withstand snow, wind, and the legs of at least two people at the same time? This is how trouble happens.
Step 2. Select the roof slope
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 planning 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 make it flatter. And also from many other factors, including aesthetic ones.
Steep pitched roofs
The greater the angle of such a roof, the faster 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 chosen roof is more visible. flexible tiles or metal profiles, which often plays a big role for the owners.
Low-slope pitched roofs
The speed of flowing rain and melt water on low-slope slopes is much lower, and therefore there is a risk of water stagnation, dirt collecting and ice getting stuck. On such roofs, moss quickly develops and leaves stick to it. Especially if the roof covering is rough.
As for rainwater, the main requirement for the roof is that the water on it, when the snow melts or after rain, does not remain on the surface of the roofing material, but rolls off easily. If it has too low a slope (for a certain area), then the liquid will sit for a long time in all the irregularities and seams. And the longer, the more chances it has to penetrate inside and create many problems in the form of dampness, deteriorated insulation and corrosion of the metal elements of the roof:
But, if such a building rises big roof at home, then it’s okay:
But there is still a plus here: the smaller the angle of inclination of the pitched roof, the closer the geometry of the interior is to a traditional cube. This means it is more easily perceived 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 thawed and rainwater could not penetrate the rafter system. That’s why these are already needed here roofing coverings like membranes roll insulation or whole sheets.
With a standard slope angle, a pitched roof is built as follows:
Minimum pitched roof angle
A pitched roof, the angle of which is only 3-5%, is often made inverse. Those. subject it to certain additional loads: they walk on it, grow a garden on it, or even use it as open terrace. Like here:
In addition, at a certain angle, a pitched roof directs the air flow in the desired direction, capturing precipitation and dispersing it. Remember this!
Step 3. Determine the slope requirements
IN functionally Shed roofs are divided into three main types: ventilated, unventilated and combined. Let's consider each option in more detail.
Ventilated design
These are installed in buildings closed type. Ventilation is provided by vents and special voids between the insulating layers, through which air passes, capturing droplets of moisture from the insulation and carrying them outside.
If such ventilation is not provided, then moisture will remain inside the insulation (and it still gets into it, albeit little by little), and the insulation will begin to become damp and deteriorate. And as a result, the entire roofing pie will gradually collapse.
But the ventilated pitched roof has its limitations. So, its inclination angle can only be in the range from 5% to 20%, otherwise the air will not be able to pass through the vents effectively.
Non-ventilated design
This type of pitched roof is advantageously built on terraces and outbuildings. Typically, the angle of such a roof is in the range of only 3-6%, although there are no restrictions on it.
Ventilation in such roofs is not needed because the air in a room without walls or with frequently open wide doors(as in the case of a garage) and itself ventilates well, carrying any water vapor outside. Which, by the way, are not particularly formed in such buildings:
Combined design
Such roofs combine the design of both previous types. Here, the required roof slope is achieved through thermal insulation. It turns out to be economical, but in winter you will have to constantly clear off the snow.
But the structure 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: there is corrugated board underneath, two layers of insulation on it and good waterproofing.
The angle of a pitched 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 angle of the slope
The angle of a pitched roof is usually called the angle at which the rafters and roof slope are inclined towards horizontal plane ceiling. Moreover, 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 degrees are 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 cornice to the horizontal of the slope, multiplied by 100.
There is another interesting point: many architects specifically calculate the angle of a pitched roof so that it is equal to angle the elevation of the sun in a given area in mid-spring. Then you can calculate down to the millimeter when and what kind of shadow there will be, which is important for planning terraces in front of the house and other recreation areas.
Step 5. Limiting the choice of roofing covering
Modern roofing materials also have their own requirements for the minimum and maximum angle of inclination of a pitched roof:
- Profiled sheeting: min 8° - max 20°.
- Seam roofing: 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 felt, corrugated sheets and the like.
You will be surprised, but today, especially for low-slope roofs, the same types of roofing coverings are being developed that are usually used with a slope of at least 30°. For what? This is the fashion in Germany, which has reached us: the pitched roof is almost flat, and the roof is stylish. But how? It’s just that manufacturers are improving the quality of locks, making the overlap area larger and thinking more carefully about protection from dirt. That's all the tricks.
Step 6. Deciding on the rafter system
And based on the selected 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 types in total: hanging rafters, layered and sliding.
Hanging rafters
Hanging rafters are the only option when the connection must be rigid, but there is no way to support the rafters between the side supports.
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 responsibly. The whole problem is large spans and in the pressure that is exerted on the walls:
Or like in this project:
Layered rafters
Here the entire roof is already pressing on at least three supports: two external walls and one internal. And the rafters themselves are dense, with a section of at least 5x5 cm bars and 5x15 cm rafter legs.
Sliding rafters
In this rafter system, a log in the ridge serves as one of the supports. And to connect the rafters to it, the following are used special elements, like “slippers.” This metal elements, which help the rafters move forward a little when the walls shrink to avoid cracks. Very little! And thanks to this device, the roof easily tolerates even quite noticeable shrinkage of the log house, without any damage.
The point is simple: the more nodes there are in the rafter system, the more flexible and durable it is. The more a pitched roof can withstand the pressure of the weight of the roofing and snow without breaking. 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 desired height of a future roof.
Method number 1. Geometric
A pitched roof has the shape of a right triangle. The length of the rafter leg in this triangle is the hypotenuse. And, as you remember from your school geometry course, the length of the hypotenuse is equal to the root of the sum of the squares of the legs.
Method No. 2. Trigometric
Another option for calculating the length of the rafter legs is this:
- Let us denote by A the length of the rafter beams.
- Let us denote by B the length of the rafters from the wall to the ridge, or the length of part of the wall in this area (if the walls of your building are of different heights).
- 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 required values, and you will receive all the parameters of the future roof.
Method number 3. Online calculators
Have you figured it out? Now let's move on to the construction of the roof itself:
We hope you figured it out easily!
The content of the articleThe roofs of private houses, as a rule, always have slopes - this roof structure is the easiest to operate and maintain. Water and snow drain better and faster from such roofs, which guarantees excellent waterproofing. Yes and appearance a private home becomes more attractive.
Moreover, it appears additional room in the attic, which can be used for living and installing an attic or for numerous household needs.
Factors influencing the shape of the roof
To make the roof reliable and comfortable, it is necessary to correctly calculate the angle of the roof slope, which depends on many reasons. First of all, these are the climatic conditions of living and the characteristics of the roofing material. Natural conditions affecting the size of the roof slope:
- As the roof slope increases, the wind load on the roof structure increases. For example, if the angle of inclination is increased from 10 degrees to 45 degrees, then the load on the structure due to wind will increase five times. If the angle is made small, less than 10 degrees, then there is a high probability of the covering sheets being torn off due to strong wind that gets under the joints;
- Precipitation in the form of rain and snow also affects the slope of the roof. As the slope increases, precipitation flows off the roof slopes better. Greatest snow load in winter it happens on slopes with a roof angle of about 30 degrees. At an angle of 45 degrees the snow will disappear completely.
With a low slope of the roof slopes, as a result of strong gusts of wind, water can get under the joints of the covering.
In the question of what angle of the roof slope should be made, the type of roofing matters:
- When using metal tiles as a roofing material, you need to take into account the considerable weight of this coating. Therefore, the angle of inclination of the roof should not be very large. This is especially important in areas where constant and strong winds prevail, as the mechanical load on the roof structure increases. For this coating, the minimum slope angle is approximately 22 degrees. In this case, moisture will not accumulate, but will be effectively removed from the roof. In addition, the joints of the coating will be reliably protected.
- Corrugated sheeting is currently the most popular roofing covering for private homes. It is lightweight, easy to install and maintain the roof. The minimum roof slope using this material is 12 degrees.
- When using roll materials, they are also called soft roof, the angle of inclination of the slopes depends on the number of layers of coating. For a coating that consists of two layers, the minimum tilt angle is up to 15 degrees. For three layers this value should be from two to five degrees. If the roof needs to be covered with a membrane covering, the angle of inclination should also be from two to five degrees.
From the above we can conclude that making a decision on the optimal roof slope angle depends on natural conditions, type of roofing material and capabilities of the home owner.
With a large slope, the consumption of materials during roof construction increases.
In addition, the type and pitch of the sheathing depends on the slope of the roof slopes. The smaller the roof slope, the smaller the sheathing pitch should be.. For minimum angles it is approximately 35 to 45 centimeters.
- with a roof slope of up to ten degrees, the roof covering can be made using stone and gravel chips;
- if the roof slope is more than ten degrees, then waterproofing using bituminous materials should be used. For rolled materials, it is necessary to use an additional protective coating;
- When using corrugated sheeting and slate, it is recommended to seal joints and seams; the joints should be double.
- If the amount of precipitation in the area where the residential building is located is high, then it is better to make the tilt angle 45 degrees. With minimal precipitation, the roof slope can be made at 30 degrees. With strong and frequent winds, the angle of inclination should be from 15 to 20 degrees. If the wind loads are small, then it is better to make a roof with an inclination angle of 35 to 40 degrees.
When calculating the angle of inclination of the roof, it is necessary to take into account that the higher the average annual temperature and the less precipitation, the more flat the roof can be built.
It is necessary to take into account that the type and design of the drainage system of the entire house depends on the slope of the roof.
Choosing the angle of the roof, depending on various factors
When determining the roof slope there is no perfect solution, which is suitable for all climatic requirements. It is important to find here best option, on which the consumption of materials and costs of funds depends.
How larger area roof, the more expensive it costs.
The recommended roof slope angle is from 20 to 45 degrees. When increasing it, it is necessary to take into account the creation of additional structures to strengthen the entire structure. And reducing the angle will lead to additional costs of materials to ensure normal waterproofing of the roof of the house.
Any house is crowned with a roof - one of the main structures of the building that protects it interior spaces from rain and snow. One of the main criteria for any roof is the steepness of the slopes. Because flat roof is distributed mainly only in multi-storey residential and industrial construction, this issue is especially relevant for owners of private houses and cottages.
The amount of roofing material depends on the slope of the roof, so the choice of the slope angle and its preliminary calculations should be made before purchasing roofing material.
Let's consider how to determine the angle of inclination of a pitched roof and its connection with the design of the entire roofing structure.
In this article
What determines the steepness of a roof?
The angle of the roof directly affects its performance characteristics. In construction, there are 4 types of roofing structures:
- Steep with a slope of 45-60°;
- Sloping – 30-45°;
- Flat – 10-30°;
- Flat with a slope of less than 10°.
Determining this value depends on a number of factors:
- Exposure to wind. The wind exerts the greatest pressure on steep roofs, since they have the greatest windage due to their large area surfaces. When settling in similar design It is important to pay special attention to the strength of the rafter system.
In areas with high wind loads, it is also dangerous to install flat and flat roofs: if the structure is weakly fastened, it may collapse. Thus, in areas with strong winds, the recommended roof pitch is in the range of 25-30°.
In areas where a significant amount of snow falls during the cold season, a steep roof, on the contrary, has advantages. Snow does not accumulate on it. At a lower angle, the snow will lie on the roof longer, creating additional load on the rafter system.It is not necessary to equip a steep roof: a certain amount of snow lingering on the roof for a long time winter period, It has useful property keep warm. However, it is important to calculate the load exerted by the snow cap on the structure in order to prevent it from collapsing.
- Roofing material. Each type of roof has its own limitations on the angle of inclination of the slopes. If you plan to use a specific roofing material, then it is important at the design stage to correlate the desired slope of the roof with its technical characteristics.
- Attic size. The angle of the roof directly affects the size of the room below it. The steeper the roof and the higher the ridge, the more spacious the attic and vice versa. When planning a room under the roof, we must not forget about the risks inevitably associated with a steep structure and its high cost compared to the construction of flatter roofs. A broken type can come to the rescue in this situation, which allows you to save the maximum volume for arranging the room, saving on the height of the ridge.
Minimum tilt angle
Such a concept as the minimum angle of roof inclination is related to the roofing material used. All roofs are provided with technical specifications, which, among other things, clearly indicate the slope limits for use. These rules cannot be violated, since in this case the roofing material will not retain its original functions and advantages.
Let's consider the main roofing coverings and the minimum angles for them:
- Piece roofing materials (slate, tiles) are laid on roofs with a slope of 22°. This indicator is due to the fact that in this case at the junctions roofing elements water does not accumulate and, accordingly, cannot seep under them;
- In work with roll materials It is important to determine the type of roofing material in advance with the number of layers. If you plan to lay 2 layers, then the roof angle should be at least 15°; when laying 3 layers, this value can be reduced to 2-5°;
- The corrugated sheet is installed at a slope of 12°. A lower value will require treating all joints with sealant;
- Metal tiles spread at a value of 14°;
- Ondulin – from 6°;
- Soft tiles can be laid on a roof with a slope of 11° if there is a continuous sheathing;
- Membrane roofing materials are the only ones for which there is no minimum threshold. They can be successfully used on flat roofs.
Following the above rules is extremely important, since even a slight violation of them will result in the destruction of the roof and, possibly, damage to the rafter system.
Calculation of the angle of inclination
Except minimum angle, there is such a thing as the optimal angle of inclination. With it, the roof is subjected to the minimum possible loads from wind, snow, etc. Let us give examples of such optimal values:
- In areas with frequent precipitation in the form of rain and snow, it is optimal to build a roof with a slope of 45-60°, as it gets rid of precipitation faster, which minimizes the load on the rafter system;
- If the roof is being erected in a windy region, then it would be good to place its angle of inclination in the range of 9-20°. It will not play the role of a sail, catching the passing wind, but it will not capsize due to its sharp gusts;
- In areas where both wind and snow occur regularly, average values of 20-45° are used. This range can be called universal for pitched structures.
Independently calculating the angle of the slopes comes down to a simple geometric process, which is based on a triangle. Its legs are the height of the ridge and half the width of the house, the hypotenuse is one of the slopes. And the angle between the hypotenuse and the leg is the desired value of steepness.
The angle of the roof is directly related to the height of the ridge. There are two options for calculating these values:
- Known roof height. If you want to arrange a spacious area under the roof living room with an acceptable ceiling height, the ridge height can be determined in advance. Having known two legs, it is easy to find out the value of the desired angle.
Let us accept the following notation:
- H – ridge height;
- L – width of half of the house;
- α is the desired angle.
Find the tangent of the desired angle using the formula:
tg α =H/L
We find out the magnitude of the angle from the obtained value from a specialized table of tangents.
- Pre-determined tilt angle. If you want to use a specific roofing material or due to weather conditions in the region, the roof slope can be determined in advance. Based on its value, you can determine the height of the ridge of the house and check whether it is possible to create a living room under this roof. To arrange the premises, the height of the ridge must be at least 2.5 m.
We leave symbols from the previous example and substitute the known quantities into the following equation:
H = L * tan α
Thus, the process of calculating the angle of inclination is much simpler and faster than analyzing all the aggregates to determine its optimal value for a particular region and building.
Due to the fact that the pitched roof rests on walls that have different heights, then the calculation of the given angle of inclination is carried out by simply raising one of the walls of the house.
We draw a perpendicular L d along the wall (the length of the house wall), originating at the point where the short wall ends and resting on the wall that has the maximum length.
If the length of the wall of the house L сд is equal to 10 meters, then in order to obtain an angle of inclination of 45 degrees, the length of the wall L bc should be equal to 14.08 meters.
Conclusion
In roof design, finding optimal angle tilt is important. This parameter depends on a correct assessment of weather conditions, the choice of roofing material, and the desire to create a living space. Its correct definition is the key to long and successful roof service in all weather conditions.
