Home efficiency
Floor insulation: suspended timber and solid floors
Insulating the ground floor makes rooms feel warmer and cuts draughts through floorboards. The method depends on whether the floor is suspended timber or solid concrete.
Updated 3 October 2026 · energy.org.uk editorial team
Which floor do you have?
- Suspended timber floor: floorboards on joists with a space underneath. It may sound hollow and bounce slightly. Air bricks low on the outside walls ventilate the space.
- Solid floor: concrete or screed laid on the ground. Most homes built from the mid-20th century onwards have solid ground floors, at least in part.
How each is insulated
- Suspended timber: insulation such as mineral wool or rigid boards fitted between the joists, from underneath if there is a crawl space, or by lifting the floorboards. Energy Saving Trust gives a typical cost of £1,400 to £2,500, depending on the house.
- Solid floors: rigid insulation boards laid on top of the concrete, or below a new floor. This costs considerably more and raises the floor level, so it is usually done when a floor is being replaced.
Even without full insulation, sealing gaps between floorboards and skirting boards reduces draughts; see draught-proofing.
Check
What to check first
- Sub-floor ventilation. Air bricks must stay clear. Blocking them can lead to damp and rot in the timbers.
- Moisture and condensation under the floor, which an assessment should check before work starts.
- Access: whether there is a crawl space, or the boards would need lifting.
- Floor height for a solid floor: doors, thresholds and stairs may need adjusting.
Do
Practical next steps
- Look for air bricks outside and check whether your ground floor sounds hollow.
- If you are replacing flooring or carpets anyway, ask about insulating at the same time.
- Get a quote that explains how ventilation under the floor will be kept.
- Check grants in the support finder.
Take care
Important limitations
- Costs are Energy Saving Trust typical figures, not quotes.
- Savings depend on the floor, the house and how you heat it; we don't give a single payback figure.
- Insulation that blocks ventilation can cause more harm than the heat it saves.