In 40 seconds
Removing failed cavity wall insulation in the UK typically costs roughly £900 for a mid-terrace up to £3,500+ for a large detached home, with a common per-square-metre figure of around £21.50/m² and a pre-extraction survey usually adding about £150–£400. Most whole-house extractions take one to three days. Insulation is removed by drilling the mortar joints and using specialist vacuum or compressed-air equipment to clear the cavity, with borescope checks to confirm it is empty. Where retrofit insulation was installed wrongly or in an unsuitable property, it can bridge the cavity and let water cross to the inner wall, which is why damp and mould are the most common reasons people have it removed. If your insulation was fitted under a CIGA 25-year guarantee, that may cover extraction and remedial work — though not every claim is accepted. The honest answer is always a range, because it depends on your property and the insulation used.
Much of the advice online comes from firms that install or remove insulation, so the numbers can be optimistic and the guarantee routes glossed over. The pages below give honest extraction cost ranges, explain how to spot failed insulation and whether it causes damp, set out how the removal process works, and signpost the CIGA guarantee and claims routes factually — before you take a single quote.