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How to calculate the angle of the roof?

From the investor’s point of view, it may seem that technical knowledge about the angle of the roof is irrelevant. However, the slope of the roof basically affects the body of the entire building and the convenience of its use, and even operating costs.

The roof angle indicates whether we are dealing with a flat, sloping or medium -sloping roof. Therefore, at an early stage of cooperation with the designer, reconstruction of an existing building or buying a ready design, it is worth knowing how much the roof slope is and how it determines, e.g. the selection of roofing, insulation materials or the choice of a roofing crew. We suggest how to calculate the angle of the roof for the investor’s needs and what the meaning it is. The building and the convenience of its use, and even operating costs.

What is the roof angle?

The angle that arises between the roof roof and the level is called the angle of inclination of the roof. Its value is most often expressed in degrees or as a percentage. Typical single-family houses built in Poland have a roof slope of 30-45 degrees. Even in the case of a flat roof, we are dealing with a small slope, which is at least 3 degrees and serves to drain rainwater from the roof (this type of roof is also called a flat roof). Roofs with a larger angle of inclination, i.e. steep roofs having a angle of about 60 degrees, are usually built in mountainous areas, where rain and snow is recorded.

Why does the roof angle matter?

The roof angle is part of the building structure, so when ordering a single -family house design, it is worth discussing it with the designer, taking into account aesthetic, practical and financial issues resulting from a specific type of roof. The finished house design usually contains alternative inclination angles allowed by the author of the project. Increasing or decreasing the angle in relation to these proposals at a later stage of construction has many consequences for the investor, including Increased costs related to the roof structural solutions and even the building, the need to change the type of roofing, as well as re -dealing with formal matters related to obtaining a new building permit.

When considering choosing a roof type, it is worth remembering that:

  • sloping roofs better drain rainwater and minimize the risk of retention of snow binding,
  • The smaller the slope, the more the requirements for the tightness of the roofing, the quality of the materials used and the precision of the roof,
  • The roof angle affects the selection of roofing and individual models (manufacturers describe the minimum angle of inclination), mounting method, as well as the possibility of inserting roof windows,
  • The greater the slope of the roof, the more it is exposed and affects the nature of the entire building,
  • In the case of tiles, a large roof angle (above 4o degrees) requires additional roofing, including fastening to a structure made of patches and counterparts of some tiles or any tile (for a roof about 60 degrees) using special cufflinks,
  • Increasing or decreasing the angle of the roof changes the building of the building and the dimensions of construction wood, and thus requires obtaining appropriate permits.

Roof angle – table

The roof angle is a very important parameter, so it’s good to know its exact value. Depending on the approach, it can be given in degrees or as a percentage.

TABELA:

wzniesienie dachy (w cm)kąt nachylenia stopnie)kąt nachylenia (procenty)
25 cm14°24,9%
30 cm17°30,6%
40 cm22°40,4%
45 cm24°44,5%
49 cm26°48,8%
59 cm28°53,2%
75 cm37°75,4%
84 cm40°83,9%
90 cm42°90,0%
100 cm45°100,0%

What is the roof angle converter?

The roof angle is given in two values: in degrees or as a percentage. Producers of roofing in the description of their products most often determine the minimum roof slope in the degrees, while the roofers use the percentage converter.

In order not to get lost in quite complex calculations, it’s best to use the ready table. The starting point is the calculation of the roof hill in centimeters, on the basis of which you can calculate or check in the table in degrees or as a percentage.

How to measure and calculate the angle of the roof?

Even if the investor does not have technical knowledge, he can independently calculate the angle of the roof. How to do it?Even if the investor does not have technical knowledge, he can independently calculate the angle of the roof. How to do it?

  • We determine on the peak wall a level 1 m long level to determine the roof hill at a length of 1 meter,
  • From one end of the section, we calculate the distance that divides it to the roof slope (vertically); We make the same calculation for the end of the second episode,
  • We subtract a lower value from the value of the longer section – the number is inserted into the table, which determines how much the roof angle in the degrees and percentage is. The table is an abbreviation of the following calculations:
    • inclination in degrees, which is calculated by multiplying the angle tangent by 100, which describes the pattern: slope [%] = 100 * TG α [0]
    • inclination as a percentage for which the formula was used: slope [0] = arctg (slope [%] / 100) * 180 / π.

What are the roof inclination angles?

Here are the corners of the roof inclination most often found in Poland:

  • roof angle of 10 degrees,
  • roof angle of 15 degrees,
  • roof angle of 20 degrees,
  • roof angle of 25 degrees,
  • roof angle 30 degrees,
  • roof angle 35 degrees,
  • roof angle 40 degrees,
  • Roof angle 45 degrees.

The roof angle and the type of roofing

The selection of a project with a specific type of roof – sloping or flat – largely determines the choice of roofing. That is why investors most often decide on medium -sloping roofs, which give the largest selection when it comes to the type of covering and specific models in a given style. What roof what cover can be used for?

  1. Ceramic and concrete roof tiles can be laid on roofs with a minimum inclination angle of 10 degrees, with roofs in the range of 10-20 degrees require the preparation of rigid sheathing and insulation with roofing felt or membrane,
  2. Roofing sheet metal is used for roofs with a minimum roof angle of 10-14 degrees (depending on the selected model, e.g. roof tiles from the Blachy Pruszyński sheet have a minimum slope angle of 9 degrees, and panel roof tiles 15 or 20 degrees); Roofs below 15 degrees require tight pre -covering or preparing a sealed pre -covering layer,
  3. Flat sheet and roof panels are perfect for a flat roof and an oblique roof; Flat sheet requires a minimum of 3 degrees of inclination and connection technology to a double seam (for a slope up to 25 degrees), while trapezoidal sheet and panel for seams require a minimum of 5 degrees,
  4. Bituminous shingles are also suitable for flat roofs with a slope of about 11 degrees, with a roofing background for them; A larger slope (about 60 degrees) increases the risk of breaking the cover by strong winds and requires additional gliding the shingle.

Even a slight change in the angle of the slope, especially when we are dealing with border values, can make the model chosen by the investor not be used or you need to modify assembly techniques to increase the overall construction costs.

What angle of inclination is the best for the roof?

It is difficult to answer the question asked in this way, because the location of the building is key – the wind zone and the rainfall zone for its location. The roof should have such a angle of inclination so that it is possible to effectively drain the water and that it does not fall on the snow, which under the influence of frost becomes a considerable load for the roof structure.

In Poland, the most popular are medium-sloping roofs with about 30-45 degrees. They give additional space to use in the attic, thus increase the building size. Their additional advantage is the ability to use both panel metal tiles, roof tiles, concrete and ceramic tiles.

What is the minimum roof angle?

The minimum roof angle is determined for all types of roofing. In the case of roof tiles, it is 10 degrees, a metal roof tile 10-14 degrees (depending on the model), for a bituminous shingle about 10-11 degrees, for trapezoidal sheet 5 degrees and for flat sheet 3 degrees.

Roofers should familiarize themselves with the installation instructions of the roof tile or metal sheet metal chosen by the investor to properly prepare under it a structure consisting of patches and counter data or rigid sheathing (formwork) properly insulated with a special membrane or roofing felt – as is the case with roofs with a small corner slopes (less than 20 degrees).

Angle of inclination of a single -pitched and gable roof – differences

The gable and single -pitched roof are the simplest and fastest to build and the cheapest. The most popular in our climate zone is the gable roof, which copes well with the drainage of rainwater and snow and allows the attic for housing purposes. Due to the fact that there are no breakdowns requiring additional insulation and accessories (as it has on site in multi -hut roofs), the gable roof is a recommended solution in passive construction. Compared to a single -pitched roof, it has a much larger angle of inclination, and thus is more visible. The choice of material for covering and precision of finishing is of great visual importance in this case.

A single -pitched roof can be a flat roof (above 3 degrees) or an oblique roof, willingly used in outbuildings, outbuildings and modern residential buildings in a modernist style. A single -pitched roof has an uncomplicated structure, allows for effective use of the highest floor (no slants) and is an alternative to flat roofs. In recent years, the flat roof has been eagerly used by architects in more complex projects of modern buildings consisting of several solids. This type of roof can be the only reasonable solution when the building is located on the border of the plot and the outflow of rainwater cannot be directed to the neighbor’s plot. Single roofs are an aesthetic, cheaper solution than flat roofs and are suitable for the installation of photovoltaic panels.

A angle of inclination of a single -pitched roof

A single-pitched roof appears in modern construction projects, as well as reconstruction of single-family houses popular in the 70-80, the so-called “box”. It is assumed that the minimum angle of inclination of a single -pitched roof is 3 degrees and the maximum 45 degrees. A larger slope means that the roof is more efficiently draining rainwater and gets rid of the snow.

A angle of the gable roof

Gable roofs are usually chosen for practical and economic reasons. They can have a medium -sloping or steep roof. The angle created by two tracts is usually 30-45 degrees, and in some areas even 60 degrees. With a large decrease in rainwater and snow, they do not pose a major threat to the tightness of the roof, but the reduction of the slope may require the installation of snow or snow fences.

What to consider when choosing a angle of the house?

Choosing a slope angle at the design or adaptation stage of the project should be well discussed with the architect and thought out with family members – building users. What is worth considering?

  • The size of the plot and location of the building towards the neighboring plot/building
  • Type of roofs and roofing popular in the immediate vicinity
  • How to use the attic
  • building style (modern, classic traditional)
  • Climate conditions in a given location
  • Guidelines contained in the local spatial development plan and/or building conditions for the investor’s plot
  • Potential installation of solar solutions in the future.

Is it possible to change the angle of the roof in the project?

Yes, however, such a change requires fulfillment of specific conditions.

A professionally developed design of a residential or service building contains detailed information about the roof, including its shape with a degree of inclination, type of covering and the technology in which it is to be made. It happens, however, that the investor must correction of the project due to its adaptation to the local spatial development plan and building conditions or due to the need to change the way the attic used. First of all, such a change cannot be made independently and it requires the consent of the designer – author or architectural studio. If the change concerns 5 degrees angle of inclination, usually consent to such a change is recorded in the documentation attached to the project. A greater change requires the assessment and update of the design by an architect who takes into account the technical parameters of the building and aesthetic issues, such as maintaining the proportion of the building’s body. It may turn out that it is necessary to redesign the entire roof structure. Secondly, changing the angle of the slope belongs to the so -called significant changes in the construction design. If the investor has already received a building permit, he must again report to the office a modified project and apply for a new permit.

Is it possible to change the angle of inclination after completing the construction?

There are situations that the owner of the house decides to rebuild the roof, as is the case on the occasion of an older house. A possible change in the angle of the existing roof or raising the roof requires re -calculation of a qualified designer with permissions, because the reconstruction will change the load on the peak walls, foundations and the ceiling. Both the change in the angle of a slope by more than 5 degrees and raising the roof is a serious interference in the block of the building and requires obtaining a building permit.

Changing the building conditions and the roof angle

When joining the construction, the investor must familiarize himself with the local spatial development plan (in short, the Local Plan), and if there is no – with building conditions (in short, WZ). These acts determined by the City Council or Commune define many detailed guidelines for investors, including The slope angle, maximum ridge height, cover color and even the color of the facade. Usually the permissible degree of roof slope is in the range of 15 to 30 degrees. The documents mentioned are available on the city or commune websites in the Public Information Bulletin. You can apply for building conditions without being the owner of the plot and thus filter the house designs that meet him.

If the investor has submitted an application for building conditions and they are unfavorable for him, he may appeal against the decision within 14 days on the basis of the provisions of art. 155 of the Code of Administrative Procedure and submit an application for a change in building conditions. It is worth making sure what documents should be completed, what consent to obtain and what stamp duty to make so that the submitted application has a legal value.

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