Cavity wall insulation questions

On our guide ranges a private install runs from about £795 for a mid-terrace house to about £3,795 for a large detached house. The fixed price is confirmed in writing after a free survey, before any work starts; anything that could not be seen at survey is agreed with you before it changes the price.

Installing insulation in a home is zero-rated for VAT until 31 March 2027, then 5%. Supply-only materials, most commercial work, and surveys, removal and repairs (which are not insulation) are standard-rated.

Possibly, through a funded scheme if you are eligible. ECO4 runs to 31 December 2026 in Great Britain; England has Warm Homes: Local Grant, Wales has Warm Homes Nest, Scotland has Home Energy Scotland, Northern Ireland has the Affordable Warmth Scheme. We cannot promise funding, but we will point you to the right route.

Energy Saving Trust estimates at July 2026 prices for a gas-heated home range from about £110 a year for a mid-terrace or mid-floor flat to about £380 for a detached house.

Yes, when it is for an install quote. A standalone report for a buyer, seller or landlord who does not need an install quote is a paid visit, priced before you book.

Homes built from the 1920s onwards usually have them. Brickwork with every brick laid lengthways and a wall over about 260mm thick at a window reveal both suggest a cavity. The survey confirms it.

No. Narrow or dirty cavities, walls in poor repair, homes with undiagnosed damp, very exposed walls and flood-risk properties may not be suitable. We tell you in writing if a wall should not be filled.

No. Timber and steel framed houses with a brick outer skin are not suitable for blown cavity fill.

Usually not. The cavity runs across the whole block, so the work is normally done for the building with the freeholder's agreement.

The extension's walls are often insulated as built. We check where the old and new walls meet, which is a common gap.

For an average house with easy access, the filling takes a few hours. Removal takes longer, usually two to four days for a semi.

There is some dust outside from drilling. Nothing happens inside except a check of the loft and any voids.

They are filled with mortar matched as closely as practical to your pointing. Very weathered or coloured mortar can show slightly.

Your contract is with S&K Property Investments and Improvement Ltd. Installation is carried out by an installer we appoint who is registered with the guarantee and competent person schemes named on your quote, before you book.

In England and Wales, cavity fill is notifiable: a building notice or competent-person self-certification is needed. In Scotland no warrant is needed but the standards apply. In Northern Ireland a building control application is needed. We confirm the route on your quote.

Your quote names the guarantee that will be issued and by whom, for example a CIGA 25-year guarantee where the installer is CIGA-registered. If a job cannot carry an independent guarantee, we tell you before you book.

Correctly specified and installed on a suitable wall, it should not. Problems come from filling unsuitable walls, defects that let rain in, debris in the cavity, or condensation.

Only after a diagnosis shows the fill is the cause. Extraction is not always the right remedy; fixing leaks and defects sometimes solves the problem.

CIGA can confirm cover and issue a duplicate guarantee for a fee, currently £60 including VAT.

Do not sign or pay on the doorstep. Check the company on Companies House, speak to your original installer and guarantee provider, and check any solicitor is SRA-regulated.

England, Wales, Scotland and Northern Ireland, with rules and funding explained for each nation. Remote and island addresses are by arrangement.

No. You contact us.

Yes. We survey in batches, return per-address results and fixed prices, and keep photo records for compliance files.

Yes, after diagnosis. We also check whether a guarantee exists first, because the guarantee route may cover it.