Floor insulation

While roof and wall insulation are the highest priorities, floor insulation can make a significant difference to the comfort of your home, especially by removing cold spots and draughts at ground level.

Suspended vs Solid floors

How you insulate your floor depends on what is underneath your floorboards.

1. Suspended Timber Floors

Common in older homes, these have a gap (a crawl space) underneath the floorboards. You can usually identify them if you have air bricks on the outside of your house below the floor level.

  • How to insulate: Lift the floorboards and lay mineral wool insulation between the joists. The insulation should be supported by netting or plastic strips to prevent it from sagging.
  • Alternative: If you have a deep crawl space, a professional may be able to spray insulation from underneath without lifting the boards.

2. Solid Concrete Floors

Common in modern homes. These are harder to insulate as they require adding a layer of rigid insulation on top of the existing concrete.

  • How to insulate: Lay a damp-proof membrane, followed by rigid foam insulation boards (like PIR), and then a new floor finish (like chipboard or screed) on top.
  • Note: This will raise the floor level by about 50-100mm, which means doors may need to be trimmed and skirting boards moved.

Benefits

  • No more cold feet: Improves the surface temperature of your floors.
  • Draught-free: Seals the gaps between old floorboards where cold air whistles in.
  • Energy savings: Can save an average home between £50 and £100 per year on bills.

Ventilation Warning: If you have a suspended floor, you must not block the air bricks on the outside of your house. These are essential for allowing air to circulate in the crawl space and preventing the timber joists from rotting.

Quick fixes

If lifting floorboards or raising floor levels isn’t an option, you can still improve comfort by:

  • Using a silicone sealant or specialized “StopGap” strips to fill the gaps between floorboards.
  • Adding a high-quality, thick underlay beneath carpets.
  • Using rugs in areas where you sit or stand frequently.