For jambs, soffits, sills etc, for openings not exceeding 0.5m² each in area, for ends of joists, beams, posts, girders, steps, etc, not exceeding 0.5m² each in area, and for openings exceeding 0.5m² and not exceeding 3 m² in each area, deductions and additions shall be made in the following manner:-

1. No deductions shall be made for ends of joists, beams, posts, etc, and openings not exceeding 0.5m² each and no addition shall be made for reveals, jambs, soffits, sills, etc, of these openings nor for finish to plaster around ends of joists, beams, posts, etc.

2. Deductions for openings exceeding 0.5m² but not exceeding 3m² each shall be made as follows and no addition shall be made for reveals, jambs, soffits, sills, etc. of these openings.

   a) When both faces of wall are plastered with same plaster, deduction shall be made for one face only.

   b) When two faces of wall are plastered with different types of plaster or if one face is plastered and other pointed, deductions shall be made from the plaster or pointing on the side on which width of reveals is less than that on the other side but no deduction shall be made on the other side. Where widths of reveals on both faces of wall are equal deduction of 50% of area of opening on each face shall be made from areas of plaster and/ or pointing as the case may be.

   c) When only one face is plastered and the other face is not full deduction shall be made from plaster if width of reveal on plastered side is less than that on unplastered side but if widths of reveal on both sides are equal or width of reveal on plastered side is more. No deduction shall be made.

   d) When width of door frame is equal to thickness of wall or is projecting beyond thickness of wall, full deduction for opening shall be made from each plastered face of wall.

In case of openings of area above 3m² each, deduction shall be made for opening on each face but jambs, soffits and sills shall be measured.