Topic 4 of 6 · Form 5
Floors, roofs and stairs
Ground-bearing slabs (hardcore, blinding, damp-proof membrane, slab, screed), suspended timber floors, reinforced concrete suspended slabs, and precast beam-and-block floors. Floor finishes: tiles, screeds, timber.
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Floors
Ground-bearing slabs (hardcore, blinding, damp-proof membrane, slab, screed), suspended timber floors, reinforced concrete suspended slabs, and precast beam-and-block floors. Floor finishes: tiles, screeds, timber.
Roofs
- Flat roofs: falls of at least 1 : 80, waterproof membranes, insulation.
- Pitched roofs: couple, close-couple, collar and trussed roofs; gang-nailed timber trusses; steel trusses for wide spans.
- Coverings: IBR and corrugated sheets (minimum pitch), concrete and clay tiles, thatch.
- Wind uplift: hoop iron straps or truss clips anchor roofs to walls.
- Rainwater: gutters, downpipes and rainwater harvesting tanks.
Stairs
Terms: rise, going, tread, riser, nosing, pitch, headroom, handrail, balustrade.
- Comfort rule: 2R + G between 550 and 700 mm (often 600–630 mm).
Worked example: A floor-to-floor height of 2 700 mm is climbed in 15 risers. Find the rise and a suitable going.
Rise = 2 700 ÷ 15 = 180 mm; using 2R + G = 600, G = 600 − 360 = 240 mm
- Minimum headroom about 2 m; maximum pitch limits for safety.
Doors and windows
Frames, linings, ironmongery, glazing, lintels and sills (with drips to shed water).
Check yourself
- What is the purpose of a drip on a window sill?
- State the 2R + G rule.
- Why are trussed rafters popular?
Show answers
- To stop rainwater running back under the sill onto the wall.
- Twice the rise plus the going should be between 550 and 700 mm.
- They are factory-made, quick to erect, economical and span without internal load-bearing walls.
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