Group D · Floors, basements and underfloor heating
Suspended timber floor insulation
Mineral wool or rigid board between the joists with an airtight membrane.
Price by property type
Suspended floor insulation
- Mid-terrace£1,200–£3,000
- Semi / end-terrace£1,500–£4,500
- Detached£2,500–£6,500
- Bungalow£2,500–£6,000
- Flat / block£1,200–£3,000ground floor
Before grants · updated 11 October 2026 · a survey confirms the final figure.
- Best for
- Victorian, Edwardian, 1930s homes
- Guarantee or standard
- Void ventilation maintained
- Time on site
- A suspended floor is typically done room by room over a few days; working from the void below can be quicker where access allows.
- Typical price
- From £1,200
What it is
What is suspended timber floor insulation?
Mineral wool or rigid board between the joists with an airtight membrane.
Best for: Victorian, Edwardian, 1930s homes.
Build-up
Suspended timber floor
Room
Ventilated void
- 1Floorboards
- 2Airtight membrane
- 3Insulation between the joists
- 4Netting or battens
- 5Ventilated void — air bricks kept clear
Who it suits
Which homes is suspended timber floor insulation suitable for?
Is my home suitable?
Pick your property type for a straight answer on suspended timber floor insulation.
Guidance only — every home is different, and a survey confirms what suits yours.
Houses
- Detached house
- Semi-detached house
- End-of-terrace
- Mid-terrace
- Townhouse
- Mews house and cottage
- Detached bungalow
- Semi and terraced bungalow
- Chalet and dormer bungalow
- Period home
- 1930s home
- Post-war and ex-council house
- Non-traditional / system-built
- Listed building or conservation area
- Farmhouse, barn conversion or rural home
- New build or self-build
- Park and mobile home
Flats and blocks of flats
Commercial and public buildings
Usually suitable Depends — a survey confirms
Materials and brands
What we use
Mineral wool or rigid board between joists, held with netting or battens, with an airtight membrane.
Insulation brands we work with
- Knauf Insulation (Earthwool, Supafil blown)
- Rockwool
- Superglass
- Isover
- Kingspan
- Celotex
- Recticel
- Xtratherm
- Steico wood-fibre
- YBS and Actis multifoil
The exact system and brand for your home are confirmed in your written quote.
Heat, bills and EPC
What it does for your heat loss, bills and EPC
Suspended timber floors lose heat through the boards and let cold air in through the gaps; solid floors conduct heat into the ground. Insulating the floor and sealing the gaps lowers the floor's U-value and cuts draughts, so rooms feel warmer at the same thermostat setting, and the EPC usually improves.
See the EPC points and savings for your home in the EPC plannerU-value before and after, typical heat and bill saving, and EPC points — worked out for your property.Price
How much does suspended timber floor insulation cost?
Prices change with your property type. Pick your column — the quote builder then refines it for your home.
| Measure | Mid-terrace | Semi / end-terrace | Detached | Bungalow | Flat / block |
|---|---|---|---|---|---|
| Suspended floor insulation | £1,200–£3,000 | £1,500–£4,500 | £2,500–£6,500 | £2,500–£6,000 | £1,200–£3,000ground floor |
Indicative ranges for London and the South East, supplied and installed, including VAT, before grants. Updated 11 October 2026. A survey confirms your final price.
0% VAT on energy-saving materials
Insulation, solar panels, batteries and heat pumps installed in homes in Great Britain are zero-rated for VAT until 31 March 2027. Windows and doors are not included.What to expect
Time on site, disruption and approvals
Time on site
A suspended floor is typically done room by room over a few days; working from the void below can be quicker where access allows.
Disruption
Lifting floorboards means clearing the room and taking up carpets or flooring. Working from the void below avoids this.
Planning and building control
No planning permission is needed. Underfloor ventilation must be kept clear, and new or renovated floors must meet Building Regulations Part L.
Guarantee and standard
Void ventilation maintained. The guarantee and certification for your job are confirmed in writing in your quote.
60-second grant check
Could a grant help pay for it?
Grant eligibility checker
About 60 seconds · plain results: likely, possibly or not eligible
Before we start
What type of property is it?
Questions
Suspended timber floor insulation: your questions answered
How much does suspended timber floor insulation cost?
Typical installed prices in London and the South East, including VAT and before any grant: £1,200–£3,000 for a mid-terrace; £1,500–£4,500 for a semi-detached or end-of-terrace house; £2,500–£6,500 for a detached house; £2,500–£6,000 for a bungalow; £1,200–£3,000 for a flat (ground floor). Prices updated 11 October 2026. A survey confirms your final figure.
How do I know if I have a suspended timber floor?
Floorboards that sound hollow, air bricks low down on the outside walls, and a house built before the 1950s are the usual signs.
How is a suspended timber floor insulated?
Floorboards are lifted, mineral wool or rigid board is fitted between the joists on netting or battens, an airtight membrane goes over it, then the boards go back down. Where there's a deep enough void, we can work from below instead.
Will floor insulation stop draughts through the floorboards?
Yes — the airtight membrane and sealing at the skirtings make a big difference to draughts in most older homes.
Does the void under the floor still need ventilating?
Yes. The air bricks stay clear so the void stays dry and the joists don't rot.
Group D
More in floors, basements and underfloor heating
Underfloor insulation from the void
Insulation fitted from below through a crawl space, without lifting floorboards.
Solid floor insulation
PIR or XPS boards over the slab with a new screed or floating floor.
Insulated floor screed
Insulation plus screed, ready for underfloor heating.
Underfloor heating insulation
Insulation boards under wet or electric UFH so heat goes up, not into the ground.
Floors over garages and open space
Insulating floors over unheated garages, passages, undercrofts and overhangs.
Basement and cellar insulation
Insulating basement walls and floors with tanking or cavity drain membranes.
Begin your project
Price suspended timber floor insulation in two minutes
See a price range for your property type, with grants and 0% VAT applied where they fit. A survey always confirms the final figure.