Detailed specification of cement plaster 1:4

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.