Choosing the type of roof, determining the angle of inclination and other parameters of the roof is an important and responsible task that requires knowledge of standards and taking into account climatic features in the region. The article provides a description of a flat roof, its advantages and features. It explains in detail why a flat roof is needed and how it is sloped. The information will be useful to all owners of plots planning to build a residential building, auxiliary or outbuildings.
Flat roof structure
A flat roof is a single sheet, not divided into separate sections, and has a certain slope to organize water flow. There are buildings of complex architecture, consisting of several departments with different levels height. Each part usually has its own roof, but the general rules for each individual area remain the same.
Flat roofs are traditional for the architecture of southern countries, but in the northern regions they are used mainly for non-residential buildings - utility or auxiliary. The reason for this attitude is the abundance of precipitation, which does not occur in such quantities in regions close to the equator.
The traditional design of flat roofs consists of a support system (rafters) forming an inclined plane with selected parameters. A deck of boards is created on top of the rafter system, on which the roofing sheet is attached. This design is simple, erected quickly enough and allows for the removal of moisture from the under-roof space.
The disadvantage is the use of wood, which is prone to warping, rotting and poses a fire hazard. In addition, wooden rafters have limited load-bearing capacity, requiring careful calculation to comply with snow loads. A significant danger is posed by the influence of wind, strong gusts of which can rip off the roof, causing significant damage.
In order to increase the strength and load-bearing capacity of flat roofs, a construction method has been developed in which the construction of the rafter system is abandoned, replacing it with a dense bulk layer - a slope. it is laid at a certain angle to the horizon, forming an inclined plane on which the roofing covering is laid. As a result, the floor becomes the supporting system top floor, and the slope of the flat roof strengthens it and forms the required angle of inclination, optimal for the given conditions and materials.
Advantages of flat roofs
The main advantage of a flat roof is its simplicity and cost-effectiveness of construction. Such a surface is convenient and safe, allowing for maintenance or renovation work V optimal conditions. The surface area of such a roof is significantly smaller than that of pitched structures, which allows significant savings on roofing material.
Additional benefit flat roofs is the convenience and ease of installation of various technical devices and equipment on them - satellite dishes, solar panels, etc. simplifies the repair and maintenance of equipment, which can be carried out at any time of the year.
There are flat roofs, the surface of which is equipped for lawns, swimming pools, recreation areas and other areas. In these cases, the use of the surface is most effective, although it requires significant costs for the design and maintenance of the sites.
Slope for a flat roof: whim or technical necessity
Slope is a necessity caused by the abundance of rainfall. Rain or melt water must be able to be removed from the surface, otherwise the roofing will quickly deteriorate and fail. IN summer time stagnation of rainwater will provoke aggressive effects chemical elements and oxygen dissolved in the mass of sediments. IN winter time the presence of moisture is even more dangerous - when the temperature drops, it will freeze and begin to expand. The smallest cracks in the surface where moisture penetrates will begin to increase.
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To organize efficient water drainage, at least a minimum slope of the flat roof is required, allowing water to be removed from the roof by gravity. The optimal solution to the problem for large roofs is to slope the flat roof using bulk materials, forming a plane with the right angle and at the same time performing the functions of insulation and sound insulation.
Minimum and maximum slope of flat roofs according to SNiP
The angle of inclination of the roof is a value regulated by technical standards. SNiP contains SP 17.13330.2011, or, more simply, in the Code of Roofing Rules. It defines the standard values of the angle of inclination roofing depending on the roof structure, as well as the materials used. SNiP determines the values that the slope of a flat roof has in accordance with the surface properties of various roofing coverings. The degree of roughness of the metal sheet is much less than that of soft or wavy surfaces.
The slope is measured in different units:
In percentages.
Height to length ratio.
In degrees.
This abundance of units of measurement is caused by the specifics of construction work - checking the angle using a protractor on the site is much more difficult than measuring linear dimensions.
The situation is somewhat more complicated when constructing a roof with a large area. It is not always rational to make a slope in such conditions. The solution to the problem is the slope of a flat roof with an internal drain, when the entire roof is divided into relatively small sections with drainage funnels. Water entering them is discharged through a pipeline system to storm sewer. This roof design is more complex and requires the creation of a system of drainage communications, but for large buildings this option is optimal.
In practice, the angles of inclination are much smaller and largely depend on local climatic conditions. Main factors influencing the choice are:
Snow amount V winter period.
The power of the winds prevailing in this region.
The weight of snow is a significant load. It can be determined from the tables in the appendices of SNiP, which indicate the average annual values for different regions of the country. The lower the angle, the less opportunity independent melting of snow masses. At the same time, a large angle of inclination increases wind loads, which are dangerous because the roofing covering can be torn off the supporting surface. The destruction that occurs in this case can lead to casualties and threaten not only this building, but also all objects located nearby.
The choice of angle is based on the magnitude of the expected loads and is adopted in accordance with them. If the roof structure consists of durable materials that can withstand a static load from the weight of snow, then they usually try to minimize wind influences, which are dynamic in nature and unpredictable in direction.
How to calculate the slope of a flat roof
Specialized calculation of the angle of inclination is an extremely complex engineering task. The requirements of SNiP in this matter have a recommendatory value and determine only the permissible limits for each type of roofing. For an unprepared person, performing such a calculation is inaccessible and even dangerous. It is necessary that the design be carried out by competent and experienced specialists.
Alternatively, you can use an online calculator, which are abundantly available on the Internet. It is recommended to duplicate the resulting value on another resource in order to compare the data and balance the results. It must be borne in mind that online calculations have only advisory value and should not be used in the construction of critical structures.
Roofing materials for a flat roof depending on its slope angle
The choice of roofing material should primarily be determined by the angle of the roof. There are a lot options:
Roofs made from piece materials and corrugated sheets
Metal roofing.
Soft roof.
You can create an angle of inclination by creating a supporting structure of the desired configuration or by filling the surface with an inclined layer of insulation. There are also specialized types of materials, for example, wedge-shaped insulation from the Technonikol company, the slope of the roof with which is created by laying slabs of a specific shape.
Choice of the most suitable material is made by comparing local climatic conditions, construction parameters, capabilities and preferences of the owner. All these factors are equally important, but it is recommended to give priority in decision-making to representatives construction company with experience and specialized knowledge.
Video description
In the video you can see the construction of flat roofs:
Conclusion
In conclusion, it should be noted that the number of buildings with flat roofs has increased. Fashion for similar architectural solutions, which came from Europe, requires the use of appropriate technologies and materials. Approaching construction using the usual standards common in Russia is irrational and impractical. For buildings with flat roofs, the creation of a special project is required, taking into account the climate, material properties, and hydrogeological conditions.
In civil low-rise construction, experienced builders call pitched structures the most common, rational and economically feasible type of roof. They can consist of one, two, three or even four slopes, planes that meet at one point, called the ridge. Pitched roofs are distinguished from flat roofs by the angle of inclination, which, according to building regulations must exceed 2.5 degrees. The choice of slope is an important stage in creating a project, on which the strength depends, load bearing capacity and durability of the structure. In this article we will tell you how to choose the right angle of inclination to facilitate snow melting in winter.
The angle of inclination of the roof is a parameter for the engineering calculation of roofing structures, reflecting the ratio of the height of the ridge to the width of the base of the slope. Pitched roofs can have a slope of 2.5-80 degrees, however, the optimal range of slope angles is 20-450. The area of the slopes, wind resistance and snow load depend on this parameter. The following terms are found in the specialized literature:
- Minimum slope. The minimum inclination angle is generally 2.5 degrees, but depending on the hydro used insulating material this parameter may increase. The minimum angle for roll bitumen and membrane coatings is the smallest; it is 2-4 degrees. The minimum permissible value for metal tiles and corrugated sheets is 11-12 0, for ceramic tiles - 22 0.
- Optimal. Optimal is the most suitable roof slope in given climatic conditions when using a certain waterproofing material. The optimal angle of inclination ensures that snow melts off independently, making roof maintenance easier.
Important! The slope of a roof can be expressed as degrees, as a percentage, or as an aspect ratio. To calculate this parameter of the roof structure, it is necessary to divide half the width of the facade by the height, and then multiply by 100 percent.
Criterias of choice
The choice of slope is based on an engineering calculation that takes into account the climatic conditions of the area where construction is taking place, the characteristics of the roofing and the load-bearing capacity of the rafter frame. To ensure a reliable design, the following criteria must be taken into account:
- Wind load. The steeper the roof, the stronger its sailing ability. Therefore, in regions with strong, gusty winds, flatter roofing structures are preferable. Although, on the other hand, the wind can tear off waterproofing material from low-slope slopes.
- Snow load. The greater the snow load, the more covered the slopes become. A roof inclination angle of 40-45 degrees ensures that snow will melt off the surface of the roofing material on its own.
- Characteristics of the finishing coating. Each roofing covering has an optimal slope that must be taken into account when designing the structure.
- Bearing capacity of the frame. The smaller the cross-section of the frame elements and the greater the distance between them, the higher the slope must be to withstand the snow load.
Optimal indicator for facilitating snow melting
The limiting factor when choosing the angle of inclination of roof slopes is middle lane Russia is characterized by a high snow load, characteristic of this area. Large amounts of snow falling in winter increase the pressure on the rafter system, leading to deformation of the frame and roofing material of the structure. Experienced craftsmen believe that there is a strong correlation between slope and resistance to snow load:
- If it is less than 30 degrees, then snow accumulates on the surface of the slopes. Snow drifts and ice have a significant mass, due to which the load on the rafter frame increases, reaching critical levels. However, some of the snow is blown away from the surface by the wind. If the angle of the roof is in this range, then snow guards are not installed on it, especially if the roofing material has a rough surface.
- At a value of 0 degrees (i.e. for flat roofs), the snow load on the surface reaches its maximum values. Snow on such structures accumulates into large drifts, which lead to the collapse of the frame if the roof is not periodically cleaned.
- If the roof is 45 degrees or higher, then in calculating the load on the rafter frame the weight of the snow can be neglected, since the snow slides off the slopes on its own without stopping on the slope. To ensure safe operation of a roof with a large angle of inclination, snow cutters are installed on it, cutting the layer of snow as it descends into thinner plates that have a lower speed and fall energy.
Please note! According to construction climatology, the territory of Russia is divided into 8 climatic zones, each of which has its own average annual snow load. This reference value is used to calculate the roof slope, the section thickness of the rafter frame elements and the selection of roofing.
Impact on design
It is important that changing the slope to facilitate snow melting greatly affects the roof structure as a whole. An increase in slope has the following consequences:
- Increase in weight of the roofing pie. The weight of 1 square meter of a roofing pie with a slope of 50 degrees is 2-2.5 times higher than that of a roof with a slope of 2 degrees.
- Increasing the area of the slopes. The steeper the roof, the larger the area of its slopes, the greater the consumption, and, consequently, the cost of the roofing material.
- Lightening the rafter frame. In the absence of a snow load, you can lighten the roof frame to save on wood.
- Inability to use roll materials. If the roof slope exceeds 40 degrees, it is not recommended to use bitumen and membrane roll materials, as they are subject to high temperature they can simply “slide” down.
Experienced craftsmen note that right choice helps to increase the service life of roofing structures, facilitate the operation and maintenance of the roof in snowy Russian winters. Errors in the project associated with the wrong choice optimal angle lead to deformation of the rafters, collapse of the sheathing, and the flooding of atmospheric moisture into the joint space during slanting rain or during thaws.
Video instruction
One of the most painstaking tasks during the design of a corrugated roof is choosing its angle. No aesthetic considerations play a role here: the ratio of the height of the roof to its total area in the future will affect how much usable space remains in the attic, whether there will be problems with snow accumulation, and even whether the wind will blow your roof away in a strong storm.
But this is not uncommon! Shall we figure it out? So, what is the minimum slope of a corrugated sheet roof? And how to build a roof with a minimum slope - all the pros, cons, recommendations and subtleties of construction are here!
Let's look at the official data. So, according to SNiP, building codes and regulations, any roof can be covered with corrugated sheeting, the slope of which has a slope of at least 8°. This is the only way that precipitation will not be able to penetrate through joints and screws. The sheathing step in this situation should be 40 cm.
But 8° is the minimum angle of inclination for the roofs of utility and industrial buildings, and for residential buildings this threshold is 10°. And if the roof is laid in two or more layers, then minimum threshold will be even higher. That is why modern construction companies give guarantees for their work only on the condition that they cover a roof with a slope of at least 12° with corrugated sheets. But the maximum angle for a roof made of corrugated sheets can be at least 70°, or even more.
Therefore, for profiled steel sheet as a roofing material, SNiP recommends a 20° slope as the most best option. But what if you need to build an almost flat roof? For a garage, outbuilding or gazebo? Then just follow our advice - and no problems will arise!
Degrees, percentages and ratios
The roof slope is 8°, which corresponds to a value of 1:7 - this is the minimum value that can be when installing corrugated sheets. And after completing all the work, it is necessary to carefully check the roof for ventilation. But why do roofers, when determining the angle, talk not only about degrees, but also about percentages and even coefficients? All this is the same thing, the only difference is for design documents and when ordering materials. We have prepared a table for you that will help you figure out what's what:
Now let's understand the construction terms. So:
- Flat roofs are those whose slope angle does not exceed 5°.
- Sloping ones are those that are usually more than 20°. Naturally, pitched roofs are more waterproof, and therefore more popular in private construction.
- Roofs with a slight slope– up to 25°. Here you can already equip attic spaces, but without windows.
- Steep - those that have a slope of more than 40°. Cool ones allow you to arrange a good residential attic, which is never superfluous.
- Large is the roof slope that falls between 45-60°.
- But today the ideal roof slope angle is 38-45°.
So, the minimum angle of inclination of a corrugated roof is 8°. Here detailed video master class on how to build such roofs:
If you need to build a roof with an even smaller slope, then the profiled sheet should already be at the bottom of the roofing cake - like a ceiling. The design principle simply changes.
Pros and cons of a roof with a minimum slope
And now about what you will have to face during the construction of a minimum slope roof and what to expect from it in the future.
Advantages
Let's list the benefits first. The main advantages of building such a roof:
- Less material consumption.
- Easier and safer roofing work.
- No ridge or problems associated with its sealing.
Consider another point: the higher the ridge, i.e. The greater the angle of inclination of the roof, the heavier the roof itself will be. There will be more material available. And this is significant pressure on the house and foundation. IN in this case the load will be insignificant.
Flaws
And so we moved on to annoying disadvantages. The minimum slope of the roof is bad because rainwater will drain much more slowly and will quickly find small cracks and joints to seep into the roofing pie. The threshold in this regard is considered to be an angle of 12°, at which it is still possible to do without additional sealing measures. Therefore, if you are building a flatter roof, the slope angle of which is less than 12°, the overlapping areas of the corrugated sheets will have to be sealed with special roofing sealants.
The chosen angle of inclination will determine what material you can use for the roof. So, for a flat roof and a roof with a slight slope, only durable load-bearing corrugated sheeting with high corrugation is suitable. But on roofs with a steep slope it is allowed to cover them with both a universal and a wall profile - because now the pressure on the sheets will be minimal. In other words, the same snow will easily slide off, and the water will not linger either.
Second point: material consumption will also increase, because The overlap of the sheets on each other will have to be made a little larger. So, if you are going to build a roof with an angle of 12° to 14°, you will need to increase the overlap of the sheets, but you can still do without sealant; if less, you will need both. This is why a slope of 15-30° is considered optimal for a corrugated roof. Here is a more detailed table of this data:
Although to install steep roofs from corrugated sheets you will have to build quite long rafters, and more bars will be needed, but you will save a lot on roofing material. It will be possible to use corrugated sheeting that is cheaper, with a lower wave height, because now its load-bearing capacity will play a smaller role than with flat roofs
In addition, if the angle of inclination is insufficient, it is impossible to equip a residential attic, which reduces the heat loss of the house through the roof by up to 9%.
And finally, roofs with a slight angle of inclination require the construction of a much more complex rafter system that could withstand a lot of weight. The smaller the angle of inclination, the more additional support elements there are.
And now we will disappoint you a little: even after weighing all the advantages and disadvantages of a roof with a minimum angle, and giving our preference to the value of 8° as more suitable, it may not be possible to build just such an option. Or rather, it will not even be safe! Why? Read on!
Wind and snow loads
Determining the angle of inclination of a corrugated roof is actually influenced by many initial data. First of all, these are the climatic features of the area where your house is located. Therefore, find out in advance what the usual depth of snow cover is on the winter days, how often it rains, how strong the wind is and what its predominant direction is:
After all, the slope of a roof made of a material such as corrugated sheets is calculated not for aesthetic reasons, but based on weather factors. Thus, the slope of the roofs of those houses that are located in areas with strong wind loads tends to a minimum value. In these areas, the so-called “roof windage” is dangerous. Have you heard or seen how powerful polycarbonate greenhouses, torn down by the wind, sometimes “walk” through the fields? But they were also not placed on the ground without fastening. And now imagine possible consequences, if part of your roof is already literally ripped off. Do you remember what the main disadvantage of corrugated sheeting is? "Sail"!
Here are the SNiP requirements in this regard. With an average wind load, the slope angle should be 35-45°, and with strong winds - 15-25°. In places where strong winds are the norm, make the roof angle made of corrugated sheets close to the minimum in order to minimize wind resistance. But almost flat roofs made of this material run the risk of being easily torn off, and therefore the complete absence of steepness in this case is also no better. Here is a rather impressive recording from a DVR, where the wind tears off a flat roof made of corrugated sheets:
Therefore, do not think that wind load is more harmless than snow load. In the Novgorod region, for example, the average value is 23 kg/m, where snow cover is about 75 kg/m.
Then shouldn't all roofs be flat? Not at all. In Russia, as everyone knows, there is snow up to the neck in winter. But snowflakes that seem so fragile at first glance actually weigh a lot. For example, in one unremarkable winter, so much snow can accumulate on a flat roof as if a whole company were standing closely on it. No rafters can withstand this, and therefore in areas with significant snow loads the roof slope has to be made up to 45° - so that the snow does not linger. Then there is no need to strengthen the rafters - precipitation on such a foundation will no longer be retained at all. After all, snow slides easily only from steep roofs.
Here's a map to help you find the parameters for your area:
Let's scare: in Yakutsk the snow load on the roof sometimes reaches 550 kg per person square meter. And this is already half a ton! This is why the roofs of houses in this region are always so high and steep. But in southern countries They can even be covered with straw in a horizontal position.
Even a small layer of snow is much heavier in weight than you can even imagine. And, unlike rain, snow lingers on the roof, and in some regions of Russia its height on roofs sometimes exceeds more than a meter. And the worst thing in this regard is precisely the minimum slope.
Therefore, you need to make a decision about whether to make the roof angle of corrugated sheets so small.
How to calculate the angle of inclination yourself?
First of all, pay attention to what kind of roofs your neighbors have. We mean the place where you are going to build. Usually they have almost the same slope, the value of which has been hard-won over centuries and tested by hurricanes. And you can calculate the exact angle of inclination of the finished roof either using special graphs and matrices, or armed with a regular square.
Professional builders, for example, calculate the slope of a roof using a device such as an inclinometer, or using some geometric formulas. The result is written in degrees or ratio:
Or even simpler. As you probably remember from school course geometry, the first thing you need to know is the length of the hypotenuse and leg. The hypotenuse is the straight line of the roof slope, and the distance from the ridge to the ceiling is the opposite leg. The distance from the middle of the ceiling to the eaves slope is the adjacent leg. Now let’s use the trigonometric function or arm ourselves with an engineering calculator:
The second one is no less common and is like this the right way: we determine the ratio between the height from the ridge to the ceiling and half the width of the ceiling. Divide the height by half the width of the building, and multiply by 100. Simple!
So decide what the slope of your roof will be based on four main factors:
- Planned budget.
- Estimated snow loads.
- Average wind value.
- The need for useful under-roof space.
And, if you finally come to the decision that you need a roof with a minimum angle, we will tell you how to avoid mistakes in construction and what you need to do.
Other important aspects of construction
Typically, minimum roof slopes with reinforced rafters are made in the roofs of those houses that are located in areas with frequent sunny days and little rainfall. To reduce heat interior spaces, in the roofing pie provide thermal insulation materials and a ventilated gap. Otherwise, all that remains to be taken care of is that no water gets into the house.
Leak protection
On flat roofs, when installing corrugated sheets, be sure to use sealing tapes and mastics for overlaps and joints of sheets. And such a roof is protected from leaks and damage by special membranes. waterproofing materials. Here is a standard pie of this design: corrugated board => rafters => insulation => waterproofing => sheathing.
There is still such a moment. If you are making a roof with a slope of less than 10°, use a modern three-layer membrane as waterproofing. Only this material can protect roofing pie from dampness inside.
And finally, no matter how minimal the roof slope is, drainage system you still have to build one for it. Moisture, like snow, lingers on such surfaces longer than many expect. Therefore, plan the slope so that it goes towards the water intake funnels, if the collection system is internal, or towards the gutters, if external.
Rafter system and sheathing
As in conventional projects, with a minimum slope, the corrugated sheeting is also laid on the sheathing and secured with self-tapping screws with rubber gaskets. But clamp the overlap, from 10 cm to 20 cm, with steel rivets. We recommend making an overlap of two waves.
There is such a dependence: the smaller the angle of inclination of the roof, the wider it is necessary to overlap the sheets. And the smaller the effective area of the material:
- Within 15-30° of inclination, make an overlap of 15-20 cm.
- But when building a steeper roof, with an angle of 30°, the overlap should be from 10 to 15 cm.
- If the angle of inclination of the roof is already less than 14°, then the sheets must be laid horizontally with an overlap of 20 cm.
- At minimum angle 8° slope of the metal profile roof, the joints between the sheets must be made double, carefully sealing them with sealant so that water does not get inside.
The usual rafter system is installed in increments of 60 cm to 1 meter, but with a minimum roof slope it is better to reduce this increment to 40 cm. The base will be stronger and will more easily withstand the accumulation of snow on the roof.
In addition, with minimum slopes between the rafter system and the corrugated sheeting, a ventilated gap is required - this is also a measure to reduce heat loss. More specifically: the smaller the angle of inclination, the wider you will have to make the gap for ventilation - and this is at least 50 mm.
Installation subtleties
Here detailed master class How to install corrugated sheeting on such a roof:
Follow the technology, follow our advice - and everything will work out!
The roof occupies important place in the design of any type of building, since it is responsible for providing basic conditions of comfort and preventing external factors from harming 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 do this 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, 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 volumes of precipitation, 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. The issue of increasing the durability of load-bearing parts also becomes relevant.
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 if there are 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 covering (? 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 of 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 by a purely horizontal surface, no matter how misleading its name may be. 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 coverings, That The slope of a 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 be 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 sheathing.
- When covering ceramic tiles, tilt must be at least 22º. 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 using 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 influencing the future surface layer, we compare 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 is better not to bother with minimal slopes, as this can 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 slope is up to 10 degrees, then gravel surfaces would be a suitable option, and up to 20 degrees - 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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