--- title: "Deduction rules: brickwork, plastering, painting" subject: "Estimating and Costing" chapter: 2 key: "semester_7/estimating_and_costing:deduction-brick-plaster-painting" source: https://www.bctengineer.com/q/semester_7/estimating_and_costing/deduction-brick-plaster-painting site: BCT Engineering --- # Deduction rules: brickwork, plastering, painting Estimating and Costing · Chapter 2: Method of Estimating - Asked in: 2082 Baisakh, 5 marks - Video: [Fundamentals of Estimating and Costing | Rules for Deduction | Brick work | plaster | Pointing](https://www.youtube.com/watch?v=bOSFczU_r3k) — Tech Civil - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/estimating_and_costing/deduction-brick-plaster-painting - Whole chapter: https://www.bctengineer.com/md/semester_7/estimating_and_costing/chapter-2 ## Question Explain the rules for deduction in quantities for brickwork, plastering and painting works with an example. ## Short answer Brickwork deducts openings over 0.1 m2 in full; plaster deducts none up to 0.5 m2, one face only from 0.5 to 3 m2, both faces above 3 m2. Painting follows plaster rules. For a 6x3x0.23 m wall with 1.44 m2 window and 2.10 m2 door, net brickwork is 3.33 m3 and plaster/painting is 32.46 m2. ## Answer Quantities are measured net, so openings and voids are deducted as per IS 1200 and the Nepal practice. The rules depend on the size of the opening. #### Brickwork (IS 1200 Part 3) - Openings (doors, windows, ventilators) larger than 0.1 m² are deducted in full: opening area x wall thickness. - No deduction is made for openings up to 0.1 m², or for the ends of joists, rafters, purlins and similar members up to 0.1 m² in section. - Reinforced concrete lintels, beams and columns inside the wall (with the bearings of lintels and beams) are deducted from the brickwork. #### Plastering (IS 1200 Part 12) | Opening | Deduction | |---|---| | up to 0.5 m² | none | | 0.5 to 3 m² | one face only, no addition for reveals | | above 3 m² | both faces, and reveals measured and added | #### Painting (IS 1200 Part 15) - Painting on plastered walls follows the plaster rule; openings up to 0.5 m² are not deducted. - For doors and windows, painting is measured on the opening area with the multiplying factors of IS 1200 (for example 1.30 for panelled, 1.80 for louvered). #### Example Brick wall 6 m x 3 m x 0.23 m thick, with a window 1.2 x 1.2 m (1.44 m²) and a door 1.0 x 2.1 m (2.10 m²), plastered on both faces. - Brickwork: 6 x 3 x 0.23 = 4.14 m³; deduct (1.44 + 2.10) x 0.23 = 0.814 m³; net = **3.33 m³**. - Plaster (both faces): gross = 2 x 18 = 36 m². Both openings are between 0.5 and 3 m², so deduct one face only: 36 - 3.54 = **32.46 m²**. - Painting of the plastered surface: same as the plaster quantity, 32.46 m². ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. How are doors and windows deducted from brickwork? A. Only half the volume B. Area only, no thickness C. Not deducted at all D. Full volume: opening area x wall thickness Answer: D. Openings are deducted fully for brickwork volume. (Key point: Brickwork deduction) 2. For a plaster opening between 0.5 and 3 m2, what is the deduction rule? A. Deduct one face only; no addition for reveals B. No deduction C. Deduct both faces and add reveals D. Deduct three times the area Answer: A. Up to 0.5 m2 none; 0.5-3 m2 one face; above 3 m2 both faces with reveals added. (Key point: Plaster 0.5-3 m2) 3. For an opening larger than 3 m2 in plastering, what is done? A. Deduct one face only B. Deduct both faces and measure and add the reveals C. No deduction D. Deduct only the reveals Answer: B. Large openings are deducted on both faces and reveals are added. (Key point: Plaster above 3 m2) 4. In the example (6 m x 3 m wall, window 1.44 m2, door 2.10 m2, plastered both faces), what is the plaster quantity? A. 36 m2 B. 28.92 m2 C. 32.46 m2 D. 34.56 m2 Answer: C. Gross 2 x 18 = 36 m2; both openings are 0.5-3 m2, so one face only: 36 - 3.54 = 32.46 m2. 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