How To Estimate The Roofing Sheet Requirement For a Building
Let us Calculate the Number Of Roofing Sheets required for the belowgiven building.
Given data:
Length of the building = 20 ft.
Width of the building = 15 ft.
Overhang on all four sides = 1ft
Angle θ = 50°
Calculation:
First, we have to calculate the roofing length & width over the building.
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Roofing length
= [building length + overhang on 2 sides]
= [ 20 ft. + (2nos.× 1 ft.)]
= 22 ft.
As you can observe in the above drawing, the sheet is sloped on the width side of the building.
Let us redraw the roofing triangle for a clear understanding.
Sloping length of the roofing
= [AC + (2nos. × overhang)]
Now, let us calculate the length of AC as follows.
By trigonometry,
sinθ = opposite / hypotenuse
In the above triangle,
Side AC = hypotenuse
Side BC = opposite.
So,
Sin50° = [ 15 ft. ÷ hypotenuse]
0.766 = [ 15 ft. ÷ hypotenuse]
By Cross Multiplying,
Hypotenuse = [15 ft. ÷ 0.766 ]
AC = 19.58 ft.
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The length of the roofing sheet
= [AC + (2nos. × overhang)]
= [19.58 ft. + (2nos. × 1 ft.)]
= 21.58 ft.
Sheet Calculation:
We will consider buying Tata dershane roofing sheets for this building.
Now, the effective width of this sheet after overlapping is shown below.
Given data:
Effective cover width We = 1015mm.
Total width Wt = 1072mm.
Roofing length Wr = 22 ft. ( calculated)
a. Sheet calculation on length side of the building
The number of roofing sheets required for a single row
= [length side of the building for roofing ÷ effective width]
= [Wr ÷ We]
By converting the effective width unit into ft.
(1mm = 0.00328084ft.)
We = [1015mm × 0.00328084]
= 3.33 ft.
Number of roofing sheets for a single row
= [22 ft ÷ 3.33 ft.]
= 6.6036 sheets
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By rounding off the sheets, we need 7 numbers roofing sheets for a single row.
b. Sheet calculation on width side of the building
Total required sloping length as calculated =21.58 ft.
Let us provide an overlapping of 250mm. ( 10″) between the two sheets.
So, the total length of sheets required
= [slopping length + overlapping ]
= [21.58 ft. + 0.833 ft.]
( as 10″ = 0.833 ft.)
= 22.413 ft.
We will go for the 12 ft. length sheets for this building.
Total sloping length after overlapping
= [ (2nos. × sheet length) – overlapping]
= [ ( 2nos. × 12 ft.) – 0.833 ft.]
= 23.167 ft. > 22.413 ft ✔ OK
So, we have to buy 14 nos. of 12 ft. length sheet for the roofing work of the building.
Note:
Thank you for going through this article.
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