Building Materials and Construction
The Building Materials and Construction domain tests whether you can identify, specify and check common materials and describe how they are assembled into walls, floors, roofs and finishes. Expect questions on IS grade limits, brick and cement tests, masonry bonds, damp-proofing and simple material quantities.
Materials and acceptance checks
- Bricks: modular brick 190 × 90 × 90 mm; with 10 mm joints a masonry cubic metre needs about 500 bricks. Check compressive strength, water absorption (generally not more than 20% for common burnt clay bricks), efflorescence and dimensional tolerance.
- Cement: OPC 33, 43 and 53 grades under IS 269, IS 8112 and IS 12269; initial setting time not less than 30 minutes, final not more than 600 minutes. Store off the floor, away from moisture.
- Aggregates: grading per IS 383; sand must be clean and free of silt. Bulking means damp sand occupies more volume, so gauge by weight where possible.
- Steel: HYSD bars are specified by yield strength, e.g. Fe 415 and Fe 500; check rust, bend and weight.
Construction sequence
Set out the building, excavate, lay the foundation, build substructure and superstructure, fix formwork and reinforcement, place concrete, cure, then finish with plaster, flooring, doors/windows and damp-proof course.
Worked example
A 1 m³ brick masonry volume uses a modular brick 0.19 × 0.09 × 0.09 m with 10 mm mortar joints. With joints, each brick module is 0.20 × 0.10 × 0.10 = 0.002 m³. Therefore bricks = 1 / 0.002 = 500. This is a nominal count; add about 5% wastage for ordering.
Traps
Do not confuse cement grade with concrete grade; do not use damp sand without allowing for bulking; do not accept bricks with high water absorption simply because they look hard; and never treat plaster as a substitute for a damp-proof course.