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.

                                                                                         CONTINUED 👉   PART 2

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