Deduction for Openings and Bearings in Masonry Works Measurements No deduction is made for following: (i) Opening each up to 1000 square cm 0.1 square meter (ii) Ends of beams, post, rafters, etc. up to 500 square cm or 0.05 square m in section. (iii)Bed plate, wall plate, bearing of balcony (chajja) and the like up to 10 cm depth. bearing of floor and roof slabs are not deducted from masonry.