Building Construction Practices: Masonry, Concreting, Plastering and Finishing
This domain tests the correct sequence of operations and the workmanship limits for masonry, concrete, plaster and finishes.
Sequence
Excavation → levelling and anti-termite treatment → PCC → footing and column starter → plinth beam → backfill → masonry → lintel → slab → finishing.
Masonry
Soak bricks before use; mortar 1:6 for 230 mm walls, richer for load-bearing; joints about 10 mm; English bond for strength, Flemish for appearance; raise walls evenly, roughly not more than 1 m per day; leave toothing at junctions; cure the masonry.
Concreting
Weigh batching preferred; place in layers; vibrate with a needle, never use it to push concrete along; construction joints at approved locations; cure for at least 7 days with OPC and about 10 days with blended cement; strike formwork per IS 456 Table 11 - props under a slab spanning up to 4.5 m come down after 7 days, beam soffits after 14 days.
Plastering and finishing
12 mm single coat or 20 mm two-coat; mortar 1:4 to 1:6; hack and wet the surface; fix chicken mesh at concrete-masonry junctions; cure 7 days; check with a 2 m straight edge, plumb and square; then putty, primer and paint or tiling.
Worked example
A slab 3 m × 4 m × 125 mm in M25. Volume = 3 × 4 × 0.125 = 1.5 m³; add 5% wastage = 1.575 m³. Reasoning: the pour is planned in one continuous operation with vibration and 7-day curing, and props stay for 7 days because the span is under 4.5 m.
Traps
Curing for only two days; striking slab props after three days; using a 1:3 plaster mix that shrinks and cracks; laying dry bricks; vibrating reinforcement instead of concrete.