how to calculate cost estimate for substructure work $.$

Taking off list

Remove top soil

Retain excavated material on site

Excavate trench foundation

Disposal of exvated material

Concrete the trench

common bricks upto GL

Facing bricks from GL to DPC

Bllock work upto the bottom of the Beam and Block floor

Block wall about Beam and Block floor upto DPC

Forming cavity

Concrete the cavity upto GL

Cavity insulation from GL to DPC

DPC

Backfill to the external side of the trench

Ground Floor Construction

Reduce level dig

Imported filling

Beam and Block floor

DPM

Insulation

Floor board$/$finish

Calculation

Projection width

Assumption

Retain top soil on site

Centreline length of Trench

External perimeter of the wall

Ddt

$\frac{4}{2}\frac{?}{?}\frac{0\mathrm{.}5}{?}$ thk of the wall

Centreline length of brick wall

External perimeter of the wall

Ddt

$4/2/0\mathrm{.}5/$thk of the brick layer

Centreline length of block wall

External perimeter of the wall

Ddt

$4/2/($brick$+$cavity $+0\mathrm{.}5*$ block$)$

Centreline length of external projection

External perimeter of the wall

Add

$4/2/0\mathrm{.}5/$thk projection