single story house extension

Job ID: 33657393

Budget: £250 – £750 GBP

I am would like a accurate calculation for a single story detached house extension, ( Pad and Ground Beam).
Approximately 16m> , 3 x bricks pillars( 340mm) on each side with window between the pillars, and a sliding door(3800mm) on the end .
Flat roof covered with fiberglass