### Calculating the volume of excavation for a shed. / Estimation & costing of a shed ( part 1 ).

Let us consider a shed of dimension as shown below.

The plinth size of the shed is 10 ft. × 8 ft.

Let us build this shed with a 6" thick wall using solid concrete blocks.

So, the inner dimension of the shed will be 9 ft. × 7 ft. (after deducting wall thickness) & the centerline of the wall is 9.5 ft. × 7.5 ft. as shown below.

Now, we will excavate a trench of size 2 ft. depth & 1.5 ft. in width with 0.75 ft. on either side of the wall center.

Outer excavation length

= wall center length + (excavation width ÷ 2) × 2 nos.

= 9.5 ft. +( 1.5 ft ÷ 2) × 2

= 11 ft.

Outer excavation width

= wall center width + (excavation width ÷ 2) × 2 nos.

= 7.5 ft. +( 1.5 ft ÷ 2) × 2

= 9 ft.

Now, excavation for the long side of the wall

= (length × width × depth ) × 2 nos.

= (11 ft. × 1.5 ft. × 2 ft. ) × 2 nos.

= 66 cu.ft.

Excavation for the short side of the wall

= (9 ft - ( 1.5 ft × 2 sides) × 1.5 ft. × 2 ft. ) × 2nos.

=( 6 ft. × 1.5 ft. × 2 ft.) × 2 nos.

= 36 cu.ft.

Total volume of the excavation

= 66 cu.ft. + 36 cu.ft.

= 102 cu.ft.

Engineers way of doing estimation:

sl.no.   item           description    length     breadth   depth  nos.    qty.  unit
in ft.        in ft.       in ft.

1.   excavation   long side of wall     11          1.5         2.0       2      66   cu.ft.

2.                       short side of wall    6          1.5         2.0       2       36   cu.ft.

Total quantity =  102 cu.ft.