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The maximum permissible slope of the roof slope: how to choose the angle of inclination for the roof under the profiled sheet

 The maximum permissible slope of the roof slope: how to choose the angle of inclination for the roof under the profiled sheet


A person for whom construction is an impenetrable jungle is sure that when choosing the angle of inclination of the roof, the architect is guided only by aesthetic considerations. However, this opinion is fundamentally wrong. How much the roof tilts depends on many criteria.

What determines the angle of inclination of the roof

The degree of inclination of the roof truss system prepared for covering with corrugated board is determined by the following main factors:

  • snow load in the region;
  • the volume of annual precipitation;
  • by the force of the wind.

The most common angle of inclination of a roof covered with corrugated board is usually 20-30 degrees

In an area where a thick layer of snow accumulates on the roofs of houses, profiled sheets are laid out at a slope of 20-25°. At this degree of inclination, the roof gets insurance against the formation of a large snow cushion on the slope.

A roof with a slope of 20-25 °, covered with a profiled sheet, is easier to clean from snow

Sometimes fighters with a thick snow cover on the roof take a desperate step - they arrange ramps and put roofing materials at an angle of up to 45 °. In this situation, there is no need to strengthen the rafter legs, because snow and storm streams easily eliminate themselves.

Snow falls off the steep roof slope in no time, eliminating the need to clean the roof for the homeowner

The rainier the weather in the region, the steeper the roof slope becomes. This pattern is easy to explain: water jets cannot escape quickly from a flat roof. This will lead to stagnation of water, the appearance of rust in the attachment points and moisture seeping into the roofing through the joints between the topcoat sheets.

If the corrugated board is laid on a gable roof with a canopy, then the canopy itself is also made at least with a small angle of inclination

But you can design a roof not with straight slopes, but rounded. This solution is both unusual and convenient to use.

Roof with rounded slopes, covered with profiled sheets, does not require snow cleaning and installation of additional gutters for drainage of rainwater

The minimum slope of a roof covered with corrugated board and often watered by rain is 12 °. If you neglect this rule, then the seams between the sheets of material will have to be carefully covered with sealant.

Frequent showers cause the construction of a roof with a sufficiently steep slope.

Strong winds are a reason to make the roof less steep, that is, with a slope of 15 to 25 °. From a slope, inclined significantly, the roofing material can easily fly off if it suddenly falls under the influence of a powerful vortex.

For a large house located in an open area, the option with several sloping roofs covered with corrugated board is perfect.

A completely flat metal roof on a house in a windy area is also not an option. In such conditions, the corrugated board will not be able to stay in place. Therefore, the tilt angle should be close to the minimum value, but not the smallest.

Roofs with a small angle of inclination are also usually erected on detached buildings: a garage, a bathhouse, a balcony on the upper floor and a shed.

Metal roofs with a low angle of inclination are best used on small and detached buildings: this solution helps well in annual roof maintenance

If the intensity of the winds is average, then during the design they stop at an angle of inclination of the roof of 35–45 °. In the area where they only hear about vortices, no frames are placed to select the slope of the roof.

Correctly laid and fixed sheets of corrugated board on any roof will last a long time, but installation technology must be observed

Video: what angle of inclination will allow the roof to remain clean

Roof slope angle made of profiled sheet

Most owners of private buildings prefer to build a roof under profiled sheets with an angle of 12–20 ° and they are absolutely right. According to manufacturers, a slope of less than 12 ° is only acceptable for industrial buildings.

In the case of industrial buildings, it is allowed to use a profiled sheet, even if the roof is tilted by 8 ° True, this material should be special - with additional stiffening ribs.

The minimum slope of the roof from the profiled sheet is close to 5 degrees

The SNiP states that it is permissible to cover the roof with profiled sheets with a minimum slope of 5-7 °. But in this situation, you will have to use a sealant for longitudinal and transverse joints between metal profiles.

With a small slope of the roof covered with corrugated board, only an increase in the overlap between the sheets can save from precipitation and other troubles. The degree of overlapping of material segments on top of each other increases as the angle of inclination decreases.

The angle of inclination of the roof made of corrugated board affects the amount of overlap between the sheets

Experts advise making a choice in favor of a larger angle of inclination of the roof than a smaller one. A sloping roof tends to collect a lot of dirt, besides, it is quite difficult to mount corrugated board on it.

According to the maximum value, the angle of inclination of the roof from the corrugated board is not limited by the rules.

If desired, under the profiled sheets, you can build a roof even with a slope of 70 °. There is only one obstacle to the implementation of this project - bad weather conditions in the region.

Video: an example of creating a roof from a profiled sheet with a slope of 5about

Calculating the slope of the roof slope

The angle of inclination of the roof is calculated as follows:

  1. Measure the width of the building wall.
  2. The resulting value is divided in half - determine the length of one side of a right-angled triangle (adjacent leg).
  3. Find the length of the opposite leg, that is, measure the height of the roof (the distance from the base of the roof to the ridge beam).

    The angle of inclination of the roof is found through the table of tangents, dividing the height of the roof by half the width of the house

  4. Determine the tangent of the angle of a right-angled triangle (Tg A) - the length of the opposite leg is divided by the length of the adjacent leg.
  5. A value close to the resulting number is found in the table. The degree indicator located nearby is taken as the angle of inclination of the roof.

Table: tangents of angles from 1 to 75 degrees

AngletgAngletgAngletgAngletgAngletg
1about0.017416about0.286731about0.600946about1.035561about1.804
2about0.034917about0.305732about0.624947about1.072462about1.8807
3about0.052418about0.324933about0.649448about1.110663about1.9626
4about0.069919about0.344334about0.674549about1.150464about2.0503
5about0.087420about0.36435about0.700250about1.191865about2.1445
6about0.105121about0.383936about0.726551about1.234966about2.2460
7about0.122722about0.40437about0.753552about1.279967about2.3559
8about0.140523about0.424538about0.781353about1.32768about2.475
9about0.158324about0.445239about0.809854about1.376469about2.605
10about0.176325about0.466340about0.839055about1.428170about2.7475
11about0.194326about0.487741about0.869356about1.482671about2.9042
12about0.212527about0.509542about0.900457about1.539972about3.0777
13about0.230828about0.531743about0.932558about1.600373about3.2709
14about0.249329about0.554344about0.965759about1.664374about3.4874
15about0.267930about0.577445about160about1.732175about3.732

Imagine that half the width of the house is 3 m and the ridge is 2 m high. In this case, Tg A is 0.6666. It turns out that the angle of inclination of the roof is approximately 34 °.

Determination of the optimal angle of inclination of the roof

Is the selected angle of inclination suitable for the roof under the corrugated board, check step by step:

  1. On the map with the classification of the country's regions according to the snow load on the horizontal plane, the required value is found. The indicator is multiplied by a correction factor (based on the degree of roof slope). When choosing an angle of inclination of the slope up to 25 °, it is equal to one, with a slope of more than 60 ° - zero. If the slope of the roof is from 25 ° to 60 °, then the formula is used to calculate the coefficient µ = (60 ° - α) / (60 ° - 25 °), where α is the slope of the roof that we would like to use.

    Depending on the snow load, Russia is divided into 8 regions

  2. Using the map with the designation of wind loads for all regions of Russia, it is determined with what force the wind acts on objects in a particular area. Using the formula W = Wn x Kh x C, where Wn is the maximum load for a certain region, Kh is the coefficient determined by the height of the house, C is the aerodynamic coefficient (0.8), find the wind load characteristic of the roof.

    By wind load values, Russia is also divided into 8 regions

  3. Both loads (snow and wind pressure) add up. The resulting value is compared with the bearing capacity of the selected brand of corrugated board, which is learned from the manufacturer of the material. For example, if this parameter is 253 kg / m², and the total roof load is 255 kg / m², then you should choose a different slope angle that would help reduce the pressure on the roof. Or choose a more suitable brand of professional sheet.

Table: the value of the altitude factor for determining the wind load

Object height, mOpen area (banks of reservoirs, steppe, forest-steppe, desert, tundra)Small towns, woodlands and other areas with regular obstacles above 10 metersMedium and large cities with building heights from 25 meters
up to 50,750,50,4
from 5 to 1010,650,4
from 10 to 201,250,850,53

Possible consequences of non-compliance with standards

It is very difficult not to comply with the SNiP standards for choosing the angle of inclination of the roof under the corrugated board, since, according to the rules, this angle can be almost any. Therefore, the main condition for building a roof is to accurately calculate the load on the roofing material, select a profiled sheet of the required bearing capacity and follow all the rules for its installation. Otherwise, the following problems may appear later:

  • roof leakage during rains;
  • deformation of the roof slope under the snow masses;
  • heat leakage through the roofing material;
  • curvature of the coating under the influence of vortices.

Video: a strong wind blew off the roof

It is important to correctly calculate the slope angle for the roof. Experts advise making the slope under the corrugated board steep to reasonable limits, rather than completely flat. Otherwise, you will have to lay the sheets with a large overlap, because of which you will need to increase the amount of purchased material.


The influence of the angle: the dependence of the profiled sheet on the slope of the roof

The angle of inclination of the slopes in relation to the horizontal plane is an important indicator for the roof. It affects design and performance and is therefore selected after analyzing the final roofing. For example, a profiled sheet makes special demands on the roof slope.


↑ Roof covering: how to choose

At the stage of planning the construction of a house, each developer thinks about the choice of a roof. Whatever roofing material is chosen, it must comply with such modern parameters:

  • price - it must be acceptable for the developer
  • design - for a modern roof, the design must match the style of the house and site
  • durability and reliability
  • ease of installation.

When choosing a material, climatic features are also taken into account.

Important! It is more correct to choose a roof at the design stage of a house in order to take into account all the loads on the rafter structure and calculate the required materials and roof assemblies.

To cover the roof of a house, different types of roofs are used: hard and soft, roll and piece, profile and flat. Some materials are best used for country cottages and summer cottages, while others are better for city buildings or for outbuildings. To dwell on a specific material, you need to have an idea of ​​the characteristics of roofing materials.

Today the building materials market has a very wide assortment and is represented by a large number of roofing materials.

The most popular roofing materials are:

  • metal tile,
  • ondulin or euro slate
  • flexible shingles: ruflex roofing, technonikol roofing
  • corrugated board
  • folded roof.

The popularity of these materials is due to:

  • quality characteristics of building materials,
  • availability.


Types of metal profiles for the roof

The metal profile is considered one of the most practical roofing materials made on the basis of galvanized steel. Unlike sheet material, it has a pronounced profile, which increases the rigidity of the material and its load-bearing capacity. The thickness of the coating sheets can vary from 0.5 to 1.2 mm, and the dimensions depend on the customer's preferences.

The metal profile can be of two types:

  • Decking.
  • Metal tiles.

The first roof covering is produced from galvanized sheet steel, at one of the production stages a rectangular or trapezoidal profile is formed. The height of the profile can be different, from 1 to 10 cm, which significantly affects the bearing capacity of the sheet and its strength, the roof of the metal profile also looks different. The installation of profiled sheets is carried out on a crate of boards or bars, while the roof slopes must have a slope of more than 12 degrees. According to experts, it is possible to cover the roof with a metal profile with a slope of 8-9 degrees, but on condition that thorough waterproofing is carried out at the joints.

As for the cost, it is lower for a metal profile than for a metal tile, but decorative properties are also characterized by less potential.

The metal tile is also made on the basis of galvanized steel, but unlike the first option, it has a protective polymer coating. The profile of this material is shaped like a wave, which allows you to create a semblance of a classic tile. The thickness of the sheet and the height of the profile are significantly less than that of the profiled coating, but the visual appeal is higher. Convenient sheet sizes and special locks greatly simplify installation work.


Advantages of pitched roofs

We have already mentioned some of the advantages of pitched roofs. It is simple and easy to install. Now let's consider the other advantages of such a roof:

  • The construction of such a roof can significantly save the developer's money on wood. This is especially true for regions where wood is a scarce material. Indeed, for the installation of a pitched roof, it is necessary to use a minimum amount of wood.
  • The minimum slope angle of the pitched roof reduces windage. Thanks to this, the space under the roof is used rationally. Such a building lacks a functional and uncomfortable attic.
  • This type of roof is used for the construction of non-residential utility rooms. In this case, the walls should be of different heights.
  • If there is a carriageway near the house, then everything can be built in such a way that snow and rainwater are not dumped onto the carriageway.

Experts recommend installing a special curb on the roof where the drain is located, securely fixed with galvanized iron. This avoids the possibility of damage to the structure by strong wind.


Roof and roof construction

As for the roof, I thought over many options, but in the end I decided to make it out of roofing material. And this is my next miscalculation, but more on that later.

Along the rafters, I made a continuous crate from a board of 150x25 mm.

He also opened it with an antiseptic, but only from the outside.

For the roofing I bought two rolls of RPP-350 roofing material. I cut it into pieces of 4 meters and laid it along the roof slope with an overlap of 20 cm. The joints were fixed with a 40x20 mm rail.

I hoped that this roof would serve me for several seasons, but I was mistaken, after two weeks the roofing material just broke in several places. The roof had to be redone.

The reason for this was the roofing material of poor quality. From now on, I do not recommend making a roofing material on a paper basis. It is better to use euroruberoid 3-4 mm thick, which will last more than one year.

This time I made an even simpler option - a greenhouse film roofing with ultraviolet protection. And so, on a solid crate, I laid a substrate made of reinforced polyethylene (I bought it when I was planning to make a roof from ondulin).

On top, in a continuous piece, I put a greenhouse film with a density of 150 microns. It was fastened, like roofing material, with a 40x20 mm rail. For six months, there were no problems with this roof, I'll see how it goes next.


Limiting evenly distributed loads on corrugated board - bearing capacity

Bearing capacity - the maximum permissible load on building structures, at which the latter do not lose their properties, while maintaining deformation stability.

Depending on the scope of application, a distinction is made between profiled decks for roofing, for slabs and for the manufacture of wall railing.

By profiling high-strength steel, the required rigidity and deformation resistance is given to ensure a high level of load-bearing capacity: the higher the corrugation and the thicker the steel, the higher the maximum load capacity.

When choosing a corrugated board for roofing and wall fences, this indicator is of decisive importance. It is worth remembering that there are several types of design loads on the profiled sheet:

  • Wind
  • Snowy
  • Dead weight (for roofing)

Characteristics of the bearing corrugated board

Bearing corrugated board is a type of profiled sheet material, characterized by high strength and deformation resistance. It has a high corrugation, additional stiffening ribs. It is used in roofing and general construction works for the manufacture of permanent formwork, sheet reinforcement, etc. The carrier sheet can have a zinc and decorative protective polymer coating.

Calculation of the bearing capacity of corrugated board

The bearing capacity of the profiled sheet is determined by the permissible loads that the material can withstand without the manifestation of irreversible consequences: deformation, rupture, etc. The table below provides reference values ​​for popular wall, universal and load-bearing grades.

Important! The maximum permissible load limit depends not only on the inherent properties of the corrugated board, but also on the laying pattern and the pitch of the supports (span).

The most popular styling schemes:

  • Single-span
  • Two-span
  • Three-span
  • Four-span

The spacing of the supports can be from 1 to 6 meters with the width of the extreme support - at least 40 mm and medium - at least 80 mm

Limiting evenly distributed loads on corrugated board

The table shows reference values ​​in kg / m2 for steel with the minimum permissible thickness. To calculate the load in the case of profiling steel of other thicknesses, the tabular value is multiplied by the ratio of the steel thickness in the table and the thickness of the profiled sheet steel for which the calculation is carried out.


Watch the video: 5 Tips and Tricks for Roofs in Revit Tutorial