Plastering Deductions as per IS Code 1200 → For small opening up to 0.5 m‌2 area, no deduction in plastering is made → For opening of size 0.5m‌2 to 3m‌2 area, deduction is made on one face of the wall. → For openings of size above 3m‌2 , deduction is made on both faces of the wall, but the area of sill, jamb and soffits of the opening is added. There are many other clauses in IS Code such as: 1. If both sides of wall are plastered with a different mix 2. If only one side of the wall is plastered and other side is not plastered.