** The 3 most common mistakes done while calculating the number of roofing sheets required for the building are as follows.**

**1. Slope calculation:**

If the length of the building is 10ft. and suppose if the slope given is 2ft then the length of the sheet to cover the building will be the hypotenuse of the triangle, i.e. 10.20 ft. as shown in the drawing.

Instead of calculating the slope length, some contractors simply take the outer dimension of the plinth i.e. 10ft. which gives a shortage of 0.2 ft. in the sheet length.

** 2. Overlapping calculation :**

Let us consider the length of the roofing sheet as ' L ' and the length of the overlapping as ' d ' as shown in the drawing.

Then the length covered by the 3 sheets is equal to** ( 3L - 2d ). **

If you deduct the overlapping ' d ' for the no. of sheets taken i.e. **( 3L -3d )**, then it is a calculation mistake.

**Note: **

**This calculation should be done in both the axis, i.e. length as well as width side of the roofing sheet.**

**3. Dimensional unit calculation :**

Normally when we purchase the sheets from the market, the dimensions referred to by the trader is say 10 ft., then the actual size of the sheet maybe 3.0 meters. When we convert the 3mtr. in to feet, it comes to (3.0m ×3.281) = 9.84 ft. instead of 10 ft.

This difference of 0.16 ft. cumulatively for all the sheets gives a big calculation mistake.