Calculation By Surface Area Method
Required Data:
- Surface area of the wall.
- Surface area of a standard concrete block.
- Surface area of openings in the wall.
Step 1:
Determine The Length & Height Of The Wall:
Let the Length of the wall = 10 feet.
The height of the wall = 10 feet.
Step 2:
Calculate The Surface Area Of The Wall:
We know, Surface Area = Length x Height
∴ Surface area of the wall = 10 x 10 = 100 sq. feet.
Step 3:
Calculate The Surface Area Of Openings:
If the wall has any openings such as doors, windows, etc, calculate the surface area of openings.
Let the wall has a window of 3′ x 3′
∴ Surface area of the window = 3 x 3 =9 sq. ft
Step 4:
Subtract The Surface Area Of Openings From Surface Area Of Walls:
∴ Final Surface Area of wall = 100 – 9 = 91 sq.ft.
Step 5:
Calculate The Surface Area Of A Concrete Block With Mortar Allowance:
Let the block is 16″ x 8″ x 8″ and mortar allowance is 1″
∴ Surface Area of one block with mortar = (16+1) x (8+1)= 153 inch²
= 153/12×12 = 1.0625 sq.ft
Step 6:
Divide The Total Surface Area Of The Wall By Surface Area Of One Block:
∴ Number of blocks = Surface Area of wall/Surface Area of a block = 91/1.0625 = 86
Consider 5% wastage of concrete blocks.
So the total numbers of blocks required = 86 + (86 x 5/100) = 86 + 4 = 90.
