Preparing a floor before new flooring is usually essential. A subfloor should be clean, sound, level and dry, because bumps, movement or moisture can cause creaking, gaps, lifting boards and mould later. DAC Home Solutions assesses each subfloor in Beckenham and across London before laying, and fits dampproofing or insulation where it is needed.
At a glance
- What it checks
- Level, soundness, cleanliness and moisture
- Common fixes
- Levelling, repairs, dampproofing, insulation
- Older properties
- Check joists and ventilation under suspended floors
- Done by
- DAC Home Solutions, as part of flooring installation
- Quote
- Free and no-obligation
Last reviewed: October 2026. DAC Home Solutions, Beckenham.
What is a subfloor and why does it matter?
A subfloor is the structural surface under your finished floor, such as a concrete slab or timber boards over joists. The finished floor can only be as flat, stable and dry as the surface beneath it.
Problems in the subfloor usually show up in the finished floor within months: boards that lift, squeaks, gaps, or a musty smell where moisture is present.
What does floor preparation involve?
Preparation follows a fixed order so that each step builds on the last.
- Remove the old floor: lift and dispose of existing flooring and fixings.
- Inspect the subfloor: check for rot, loose boards, cracks and damaged joists.
- Test for moisture: confirm the subfloor is dry enough for the new floor.
- Repair and level: fix loose boards, fill low spots and correct high spots.
- Protect from damp: install dampproofing and insulation where required.
- Lay the underlay and floor: only once the base is ready.
How do I know if my floor needs dampproofing?
A floor may need dampproofing if the property is old, the floor is solid and in contact with the ground, or there are signs of damp.
Signs include a musty smell, staining, cold or clammy surfaces, and lifting or cupping boards. A moisture test before fitting confirms whether the floor is dry enough. Where moisture is a risk, a dampproof membrane is installed before the new floor goes down.
What about older houses with suspended timber floors?
Older properties often have timber boards over joists with a ventilated void below, and that ventilation needs to stay clear.
Blocked airbricks, damp joists and old repairs are common findings when old flooring comes up. Checking joists and adding insulation at this stage is far easier than after the new floor is fitted.
Why not just lay the new floor over the old one?
Laying over an uneven, damaged or damp surface usually leads to a short-lived result.
Some products can be fitted over existing floors, but only when the surface is sound, flat and dry. Your fitter should confirm this against the manufacturer's instructions before work begins.
