Construction Technology and Building Elements
Construction Technology and Building Elements tests the build-up of substructure and superstructure and the reasons for each layer. Expect foundations, walls, floors, roofs, openings, damp control and ventilation.
Core rules
- Foundations transfer load to suitable ground: strip, pad and raft are chosen by load and soil.
- Cavity walls use two leaves, wall ties and a cavity; ties are spaced to suit the leaf and exposure.
- DPC stops rising damp in walls; DPM stops ground moisture entering a floor.
- Lintels carry load over openings and need adequate bearings.
- Roofs must be ventilated on the cold side of insulation in a cold roof, and insulation must be continuous.
Worked example
A 6.0 m long by 2.4 m high wall is to receive wall ties at 900 mm horizontally and 450 mm vertically. Wall area = 6.0 × 2.4 = 14.4 m². One tie serves 0.9 × 0.45 = 0.405 m². Number ≈ 14.4/0.405 = 35.6, so allow about 36 ties, plus extra at edges and openings. The reasoning is to work in square metres and round up for a real order.
Traps
- Reversing DPC and DPM.
- Forgetting lintel bearings or the need for a lintel at all.
- Leaving a continuous path for cold bridging at reveals, jambs or floor edges.
- Blocking roof ventilation with insulation.
Name the element, its load path and its damp or thermal control.