Floors
What the domain tests
Floors tests ground and suspended floor construction, concrete slabs, damp-proof membranes, insulation, screeds, finishes, levels and falls.
Core rules
- A ground floor usually has compacted hardcore, blinded sand, a DPM, insulation if specified, a concrete slab and a screed or finish.
- Lap DPM by at least 150 mm, turn it up at edges and do not puncture it.
- Place slab mesh on spacers so it sits within the concrete, not on the ground.
- Suspended timber floors need joists, ventilation, noggins or strutting and a suitable deck.
- Wet areas need falls to drains, commonly between 1:80 and 1:100; habitable rooms should be level.
- Cure concrete and allow adequate drying before laying finishes.
Worked example
A slab is 6 m x 5 m x 0.125 m = 3.75 m³. Add 5% waste: 3.75 x 1.05 = 3.94 m³. Order 4 m³. If ready-mix has a minimum load, confirm before ordering. Reasoning: volume equals length x width x thickness; waste covers spillage and uneven subgrade.
Traps
- Placing the DPM below the hardcore instead of above it.
- Leaving mesh on the ground.
- Omitting falls in bathrooms or showers.
- Insufficient curing before loading the slab.
- Laying timber flooring over a damp slab.