Household retrofit guidance for private properties Floors

Floor insulation

Insulating the ground floor of your home helps keep it warm. Upper floors usually do not need insulation, as most heat is lost through the ground floor.

Before insulating, it's important to know whether your ground floor is made of solid concrete or suspended timber. 

Solid floors are concrete slabs, while suspended timber floors have floorboards over wooden joists with a space underneath for ventilation.

A person laying green natural wood fiber insulation board on a floor..

Solid concrete floors

Insulating a solid concrete floor involves placing rigid foam insulation on top of the slab, followed by a layer of chipboard for flooring. 

This process raises the floor level, so adjustments to doors, skirting, and sockets may be needed. Insulation under the slab is only recommended if the floor is being fully replaced as part of major renovations.

Suspended floors

Timber floors are insulated by placing rigid boards or breathable materials, like wool, between the joists. 

The insulation must stay within the joist height to maintain ventilation. Wood-fibre insulation is ideal for older buildings, as it allows slow air and moisture movement to reduce condensation.

The Department for Business, Energy and Industrial Strategy  provides a thorough best practice guide to solid floor insulation for your retrofitting project.

The Planning Portal has advice regarding the building regulations for floor insulation.

Risks

For suspended floors, special care needs to be taken to ensure continued ventilation to prevent moisture issues. 

Careful consideration should be taken for the type of insulation to be used. A retrofit designer or coordinator can advise on this type of work.

Other things to consider before insulating suspended timber floors are that the floor structure need to be inspected and any repairs or maintenance completed. 

This also applies to any works required to ensure cross-ventilation under the floor. 

Regulatory considerations

  • Floor insulation generally doesn’t require planning permission for non-listed buildings.
  • Listed buildings need listed building consent.

Major changes to walls, roofs, or floors typically require building regulations approval under the following regulations: 

Cost: £10,000 to more than £10,000

Disruption: Suspended floor: medium, solid floor: high