The construction of a new roof or the repair of an old one is quite often associated with the need to perform an independent calculation of the roof. This article will talk about how to calculate the roof of a house, and give an example of self-calculation of a gable roof.
You need to know how to calculate the height of the roof and its other parameters, in order not only to control the correctness of the project, but also to evaluate the ability of the roof to withstand the materials laid on it, in combination with the weight of precipitation and possible overloads.
Important: the question of how to calculate the height of the roof of a house and other parameters is most relevant in the event of a major overhaul on its own, without the use of the labor of hired specialists or organizations.
After an inspection of the old rafter system was carried out and it was stated that roof lathing and beams need to be replaced, many builders choose to build the original structure using the same materials.
At the same time, they face difficulties associated with the fact that logs and semi-logs are no longer used in the construction of roofs, so finding such material is quite difficult.
Its price has increased significantly, and the installation of rafters from logs is a waste, and the bearing load on the foundation and walls increases significantly.
Therefore, it becomes necessary to think about how to calculate the material for the roof again, avoiding unnecessary expenses and increasing loads.
Calculation of materials and roof structures
Currently, for the construction of the truss system, materials such as timber and board are used.
When choosing how to correctly calculate the height of the roof, it should be borne in mind that a high-quality powerful beam with a section of 100x100 mm or 150x100 mm, whose length exceeds 4 meters, is quite rare and quite expensive, but even if you buy it, working with it requires great skill.
It is much cheaper and easier to use boards when building a roof, the cross section of which can vary from 150x50 to 250x50 mm in accordance with the span length.
To calculate the height of the roof and other parameters, it should be taken into account - the longer the span, the greater the width of the board. For example:
- For the construction of the roof of a bath of a small size (3x4 meters), a board with a section of 150x50 mm can be used, small adjustments to the structure can be made using a board with a section of 100x50 mm;
- For the construction of the roof of a house measuring 10x6 m, boards of 250x50 mm are used.
The use of edged lumber in the construction of load-bearing roofing roof structures using recommendations on how to calculate the square of the roof and other characteristics, allows you to build a roof of almost any configuration.
The shape of lumber greatly facilitates the reliable connection of elements due to cutouts in the form of spikes and overhead metal plates.
Self-performing roof calculations
Knowing how to calculate the angle of the roof, its height, load and other parameters, you can assemble the structure of the rafters without assistance. This will require the following necessary tool:
- Saw (manual circular or electric jigsaw);
- Drill and a set of nozzles and drills;
- Hammer.
Useful: in this case, the boards are lifted up, and the assembly of the structure is carried out directly on the roof.
The construction of a simple gable roof is a fairly simple procedure that is not of interest in this article; it would be more useful to talk about how to calculate the size of the roof and attic space, as well as the load on it yourself.
Floor logs (A) are installed on load-bearing walls, fastening them in certain places with the help of spacers made from scraps of the same boards.
This method of fastening increases the rigidity of the structure and prevents the boards from falling to the side, facilitating the following actions:
- The prefabricated log (A) is attached to the Mauerlat with the help of powerful corners. At the same time, vertical racks (B) are installed, based on load-bearing walls. . Racks are inserted into the gaps between the lags, after which all three elements are pulled together.
Important: the racks take on the main distributed load of the roof and snow cover on it, so you should correctly calculate the load on the roof and carefully control the quality of the material.
- Next, the rafters (B) are attached, on which the side roof lathing will be performed. In this case, it is necessary to correctly calculate the angle of the roof so that the rafters do not bear excessive load associated with too much slope of the slopes.
- Next, the installation of roof rafters (G) is carried out, be sure to perform a remote-strengthening insert between the ridge and the screed (C). This will fasten the entire structure and serve as the basis for hemming the ceiling.
- After installing all the legs of the rafters, a cut is made along each of the vertices, into which the prefabricated ridge (15x50x3 pcs.) will be laid. The ridge is fixed with metal mounting plates.
- Now it is possible to carry out a crate made from boards, the thickness of which is 20-30 mm.
Important: fastening elements of the roof structure can be carried out both with the help of studs and self-tapping screws coated with an anti-corrosion protective coating. In addition, powerful nails with special notches can be used for fastening.
Collected rafter leg has a fairly large weight, which makes it almost impossible to install it yourself. Therefore, it is recommended to perform the assembly step by step, first assembling the side rafter legs and then fastening them with two or three crate boards.
These boards will simultaneously serve both as a level and as an element supporting the roof rafters.
Important: the boards of the crate will sag under their own weight during operation, so you should think in advance about how to calculate the load on the roof.
The distance between the rafter legs and their number is calculated based on which material is chosen to cover the roof and which crate is used.
For example, in the case of a continuous sheathing made of OSB material, this distance will be in the range of 0.5-1 m.
An example of calculating a gable roof
There is a common misconception that the amount of material used to cover a roof is directly equal to the area of the roof. In fact, everything is a little different, so let's look at how to calculate the roof using a specific example.
We take the following as initial data:
- Roof type - gable;
- The length of the slopes is 6 linear meters;
- The length of the skates is 9.5 running meters.
Based on this, the roof area will be 6 x 9.5 x 2 = 114 m2. As a material for coating, we take a metal tile with a polyester interprofile.
In this case, the calculation will require the useful length and width of the metal tile sheet, depending on the type of interprofile:
- with a 1-wave interprofile, the useful length and width are 0.35 and 1.1 m, respectively;
- with 3-wave - 1.05 and 1.1 m;
- with 6-wave - 2.1 and 1.1;
- with 10-wave - 3.5 and 1.1 m.
We proceed to the calculation of the cost of this gable roof. The calculation of the required number of sheets for the width of the slopes is made by dividing the length of the ridge, which is 9.5 meters, by the value of the useful sheet width (1.1 m).
As a result, we get 9.5 / 1.1 = 8.63 sheets, we round this value up and get nine sheets.
Next, we calculate the number of sheets required by the lengths of the slopes (using the example of a sheet with one wave). To do this, we divide the length of the slope, which is 6 meters, by the value of the useful length of the sheet, which is 0.35 m.
We get 17.14 sheets as a result. In this case, the value can be rounded down, since the remainder (0.14) is closed by the unspent extreme overlap.
The calculation of the length, expressed in sheets, will eventually look like this: 0.35 x 17 + 0.14 = 6.09.
Due to the fact that the roof is gable, you should multiply the number of sheets by 2, after which the cost of the roof is calculated quite simply:
The cost of a metal tile with an interprofile coated with polyester is 200 r/m2. To cover, eighteen sheets are required, differing in length:
- For the top row - sheets 3.62 m long (the cost of a sheet is 819 r);
- For the middle row - sheets 2.22 m long (the cost of a sheet is 502.2 r);
- For the bottom row - sheets 0.47 m long (the cost of a sheet is 107.3 r).
With the help of simple calculations, we get: the roof covering, the area of \u200b\u200bwhich is 131.9 square meters, requires material for a total of 25712.1 rubles.
That's all I wanted to talk about how to perform roof cost estimate. Do not neglect the calculations during construction, since a correctly performed calculation allows you to avoid errors that can lead to damage or destruction of the roof during operation.
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