--- title: "Detailed specification of cement plaster 1:4" subject: "Construction Management" chapter: 12 key: "semester_8/construction_management:detailed-spec-plaster-1-4" source: https://www.bctengineer.com/q/semester_8/construction_management/detailed-spec-plaster-1-4 site: BCT Engineering --- # Detailed specification of cement plaster 1:4 Construction Management · Chapter 12: Specification - Asked in: 2077 Chaitra, 4 marks - Video: [How to Check Plastering Work on Construction Site | Plaster Ratio, Thickness, Explained](https://www.youtube.com/watch?v=LkoEJISl4ms) — The Institute of Construction Managment - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/construction_management/detailed-spec-plaster-1-4 - Whole chapter: https://www.bctengineer.com/md/semester_8/construction_management/chapter-12 ## Question Write a detailed specification of cement plaster of 1:4 in brick wall. ## Short answer Cement plaster1:4,12 mm average thickness on brick wall. Mortar used within30 min; surface prepared by raking jointes12–15 mm and wetting. Applied between screeds, finished with wooden float. Curing7 days. Measured in m², with opening deductions per rule. ## Answer #### Detailed specification: 12 mm cement plaster 1:4 on brick wall **Scope:** Providing and applying cement sand plaster 1:4 (1 cement : 4 sand) of 12 mm average thickness on brick walls (internal/external), complete with curing, as per drawings. **Materials** - **Cement:** OPC 43 grade/PPC, fresh. - **Sand:** clean river sand, free from silt, clay, organic matter and salts; passing a 2.36 mm sieve, FM about 1.5–2.0. - **Water:** clean, potable. **Mortar:** 1 : 4 by volume, mixed to a uniform consistency and used within 30 minutes; no re-tempering. **Surface preparation** - Brick joints are raked to a depth of 12–15 mm, and the surface is cleaned of dust, efflorescence and loose mortar. - The wall is wetted thoroughly (but not saturated) a few hours before plastering. - The masonry should have settled, and pipes and electrical conduits are fixed first. **Application** - Level guide strips (screeds) of mortar, 15 cm wide, are fixed at about 2 m intervals, truly plumb and in the same plane. - Mortar is thrown on firmly and pressed into the joints, filled between the screeds, and levelled with a straight-edge (a flat wooden rule). - The surface is finished with a wooden float to a uniform, even surface; for a smooth finish, a thin coat of neat cement slurry (punning) may be applied with a steel trowel. - Plaster is applied from the top downward, and at the end of each day the work is cut clean and straight. Edges and corners are finished plumb and square. - External plaster in one panel is done without joints; where a joint is unavoidable, it is placed at a corner or a groove. **Curing:** Kept moist for at least 7 days and protected from sun, wind and rain. **Tolerance:** thickness not less than 10 mm at any point; the surface should not deviate more than 3 mm under a 2 m straight-edge. **Measurement and payment:** measured in **square metres** of finished surface. For a wall plastered on both faces: openings up to 0.5 m² are not deducted (and jambs are not added); openings of 0.5–3 m² are deducted from one face only (jambs not added); openings over 3 m² are deducted from both faces, and jambs, soffits and sills are measured. The rate includes materials, scaffolding, curing and labour. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. How is the brick wall prepared before plastering? A. Joints raked 12-15 mm, surface cleaned and thoroughly wetted (not saturated) B. Left smooth and dry C. Coated with oil D. Covered with paint Answer: A. Raking provides key for plaster; wetting prevents the wall absorbing water from mortar. (Key point: Surface preparation) 2. What is the purpose of the guide strips (screeds)? A. To decorate the wall B. To hold scaffolding C. To make the plaster surface truly plumb and in one plane, with thickness control D. To cure the plaster Answer: C. Screeds 15 cm wide at 2 m spacing guide the straightedge to get a plumb, even surface. (Key point: Screeds) 3. What tolerance is given for plaster? A. Thickness not below 10 mm; surface within 3 mm under a 2 m straightedge B. Thickness any; 50 mm deviation C. Thickness 25 mm minimum D. No tolerance Answer: A. Minimum thickness is 10 mm at any point and the surface should be within 3 mm of a 2 m straightedge. (Key point: Tolerance) 4. How is plaster measured? A. In m3 B. In kg C. In m2 of finished surface, openings up to 0.5 m2 not deducted D. In running metres only Answer: C. Plaster is measured in square metres; small openings up to 0.5 m2 are not deducted. 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