Building Construction
What the domain tests
Building Construction tests construction sequence, detailing and workmanship from excavation to handover, with emphasis on defects that appear on Pakistani sites: dampness, honeycombing, poor brickwork and premature cracking.
Core rules
- Substructure: set out, excavate, apply anti-termite treatment, place PCC, footings and plinth beam, then DPC at plinth level. Shallow foundations include strip, isolated and raft; deep foundations include piles. Soil bearing capacity drives the choice.
- Superstructure: RCC frame with masonry infill. A standard brick is about 225 x 112.5 x 75 mm; a 9-inch wall is full-brick and a 4.5-inch wall is half-brick. English and Flemish bonds distribute load; mortar is commonly 1:4 or 1:6.
- Concrete: nominal mixes such as 1:2:4 are not a substitute for designed mixes. Keep water-cement ratio about 0.45-0.55, compact fully, and cure OPC concrete for at least 7 days. Typical cover is 25 mm for slabs, 40 mm for beams and 50 mm for columns and footings.
- Waterproofing: DPC at plinth, plinth protection, roof slope about 1:100, expansion joints and proper sumps.
Worked example
A slab is 10 m x 8 m x 0.125 m = 10 cu m. Add 10% wastage = 11 cu m. For a 1:2:4 mix, dry volume = 1.54 x 11 = 16.94 cu m. Cement volume = 1/7 x 16.94 = 2.42 cu m. At 0.035 cu m per 50 kg bag, cement = 2.42/0.035 = about 69 bags. The reasoning matters: wastage and bulking are added before proportioning.
Traps that cost marks
Using a nominal mix where a designed mix is required. Forgetting wastage. Placing DPC at the wrong level. Short curing. Insufficient cover. Striking formwork before strength is reached.