Underfloor Insulation Cost in the UK: Prices, Savings, and Options

The financial case is strongest for suspended timber floors insulated DIY from below, and weakest for solid floors, which cost considerably more to insulate. Solid floor insulation makes most sense when you are already replacing the floor covering for other reasons.

Use our insulation savings calculator for your specific property type.

Suspended timber floor: Common in homes built between the 1850s and the 1950s, including most Victorian and Edwardian houses. The floor sits on timber joists with an air gap underneath. You can usually identify it by the slight bounce when you walk, visible air bricks in the external wall near ground level, and floorboards visible at the edges of rooms. If you have a cellar or crawl space, you can see the underside of the floor.

Solid concrete floor: Usual in newer homes. The floor is a concrete slab sitting directly on the ground. It feels rigid with no give. There are no air bricks at ground level on the relevant walls. A home built to recent building regulations will usually have floor insulation already.

If you are unsure, check your EPC certificate, which states the floor type and insulation status. Use our EPC improvement planner to see how floor insulation would affect your rating.

From below (best approach if accessible)

If you have a cellar or a crawl space deep enough to work in safely beneath the floor, insulating from below is the least disruptive method. Rigid insulation boards (PIR or EPS) are cut to fit between the joists and held in place with friction, battens, or netting. The void below must stay ventilated.

Doing it yourself costs only the materials. Check the joists first: the Energy Saving Trust says only go ahead if they are sound and free of damp, wet rot or dry rot, and get professional advice if they are not. Keep the space under the floor ventilated, and consider a vapour-permeable membrane, which manages moisture without trapping it against the timber. Avoid boxing the insulation in with plasterboard unless the joists are dry and the airflow is good, as it can trap moisture.

From above (when no access below)

If there is no access from below, the floorboards must be lifted, insulation fitted between the joists, and the boards relaid. This is more disruptive, and the Energy Saving Trust puts a typical professional suspended floor job at £1,400 to £2,500. It is disruptive because it involves moving furniture, potentially relaying floor coverings, and careful handling of old floorboards that may crack during removal.

This approach is best combined with other floor work such as replacing damaged boards, sanding the floor, or fitting new carpets. Doing the insulation at the same time adds relatively little to the total disruption and cost.

Solid floor insulation involves laying rigid insulation boards on top of the existing concrete, then a new floor surface on top. This raises the floor level, which affects door clearances, skirting boards, stair transitions, and kitchen units. If you replace 50% or more of a floor, building regulations require you to insulate it; the Energy Saving Trust gives the typical requirement as at least 70mm of high-performance rigid foam or around 150mm of mineral wool, depending on the floor.

The Energy Saving Trust says solid floor insulation can cost considerably more than a suspended floor, and this complexity is why. The work is disruptive: the room must be completely emptied, the old floor covering removed, insulation laid with a damp-proof membrane underneath, and a new floor surface (screed, floating boards, or tiles) installed on top.

Solid floor insulation rarely makes financial sense as a standalone project. It is best done when you are already renovating the ground floor, replacing the floor covering, or converting a ground floor room, when the extra cost of the insulation is a small part of work that is happening anyway.

Suspended timber floors rely on air circulation underneath to prevent moisture buildup and timber rot. Air bricks in the external wall allow air to flow through the void beneath the floor. Never block these air bricks when insulating. The insulation should sit between the joists, not across the bottom of the void.

If air bricks are blocked by soil, debris, or overgrown plants, clear them. Blocked air bricks can lead to damp and rot in the floor timbers. Replace any air brick covers that are damaged.

The ECO4 scheme funds underfloor insulation for eligible households as part of a whole-house retrofit. If you qualify for ECO4, the assessor may include floor insulation in your package if your property needs it. ECO4 closes on 31 December 2026, and the work has to be finished by then. Use our grant eligibility checker.

If you pay yourself, installing floor insulation in a home is zero rated for VAT until 31 March 2027, and 5% after that (HMRC VAT Notice 708/6).

Floor insulation saves less per pound spent than loft insulation (about £600 to £750) or cavity wall insulation (about £2,200, with a measured saving of about £105 a year for a 3 bed semi on gas). The recommended upgrade sequence is loft first, then walls, then draught-proofing, then floors. Floor insulation is the finishing touch, not the starting point.

However, if your suspended timber floor is the main source of draughts and cold feet, addressing it earlier delivers an outsized comfort improvement even if the pure financial return is lower.

See our full guide to improving your EPC rating for the complete priority list.

Costs, savings, damp advice and building regulations guidance from the Energy Saving Trust (floor insulation, updated 19 May 2026). Loft and cavity wall comparisons from our guides, which use NEED Impact of Measures 2026. VAT from HMRC.