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Gambrel roof calculator

See also: Roof pitch calculator, Gable roof calculator

Drawing scale:

Fill in dimensions in mm:

Height difference Y, mm
Roof width /2 X, mm
Overhang length C, mm
Roof length B, mm
Height Y2, mm

Roof construction materials:
(fill in 0 if no need)

Rafter width S1, mm
Rafter thickness S2, mm
Rafters spacing S3, mm
Roof verge distance S4, mm
Roof boarding width O1, mm
Roof boarding thickness O2, mm
Roof boarding spacing R, mm
Roofing sheet(or tile) height L1, mm
Roofing sheet(or tile) width L2, mm
Sheet overlap % L3


This online application provides the accurate and reliable estimation of the gambrel roof including the square of the roof, amount and square of the under-laying materials and roofing ones, quantity of rafters and roof boarding. Your choice of the roofing materials to cover the roof would depend on your preferences and financial possibilities. There are such options as the slate, tile, metal sheets or rolled roofing material (shingles, bituminous slate and others).The strengthened design of the roof should prevent the roof sagging caused by the metal tile sheets, profiled sheets, slate or tile, as all mentioned materials are of heavy weight. Any soft cover of the roof, shingle, roofing felt, and others are comparably light roofing materials, which will not create additional pressure on the roof structure. Therefore, this free online gambrel roof (roofing) calculator estimates:

  • total area of the roof surface including the length of each eave;
  • total square area of the mansard excluding the space under the side slopes;
  • amount of the materials required for the rafter system;
  • quantity of rafters needed for the whole structure at specified pace;
  • required amount and square of the roofing material (tile, metal, slate, etc);
  • total amount of the roof boarding rows in line with the specified parameters of the roof;
  • quantity of the boards needed for the roof boarding of the whole structure;
  • total area of the under-laying materials taking into account the overlap;
  • truss design.

It is convenient to use the software as gambrel roof truss calculator. The gambrel truss is a kind of a supportive structure used in the roof design. The main purpose of the truss is to provide the support to the roof transferring the weight of the roof onto the walls of the structure. The slopes of the truss are strong against complicated weather conditions. There are different types of the trusses design and some of them can give larger floor area and more head space, which is an actual concern when you build a mansard-type house.

This information will help you when you are trying to design the gambrel roof by yourself. Regardless you plan to construct it yourself or pay for the skilled personnel services; it will definitely help you to assume the future costs and expenditures for your roof. The figures you get are preliminary and they greatly depend on the measurements you have taken and the way you can use drawings. You can easily do all measurement by simple measurement tape used in construction. The result should be converted into mm, and then entered into the corresponding boxes of the estimator

Beside the application helps you to calculate approximate price and costs by knowing an amount of gambrel (mansard) roofing materials needed, it can be also used to calculate other parameters of the future roof. As an output of the program work, you will get the volume and amount of the construction materials for a half of the roof and the same data but for the whole roof given nearby in brackets.

There is an important notice: if you are going to estimate the quantity of the materials supplied in sheets (metal tile sheets, slate and so on), this online application provides the calculation based on the data of the surface area. Therefore, it is recommended to purchase the gambrel roof construction materials with some extra stock, as in any case you will have unusable waste.

3 Responses
  1. Maryann says:

    Genuinely when someone doesn’t be aware of afterward
    its up to other users that they will help,
    so here it occurs.

  2. Robert Gail says:

    Please, check the overlap calculation. Not 100% sure.

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