Cavity Wall Insulation Removal in 2026: Damp Problems and Compensation Claims

Between 2008 and 2015 the UK government heavily subsidised cavity wall insulation through ECO and the Green Deal. Around 6 million UK homes had insulation installed during that period. Around 8% of those installations are now estimated to have failed, often years after the fact, leaving owners with damp walls, mouldy interiors and a difficult conversation about whose fault it is.

Why cavity wall insulation fails

Cavities exist for a reason: the gap between inner and outer wall stops water that penetrates the outer wall from reaching the inner wall. Filling the cavity removes this protection. In most homes that is fine because:

• The outer wall is sound and waterproof.
• The home is in a low-exposure location.
• Installation was done properly.

When any one of those is missing, water gets through the outer wall, soaks the insulation, and the insulation acts as a bridge to the inner wall. The result is damp internal walls, mould, and rotting timbers.

Properties most at risk

• Coastal homes with high wind-driven rain.
• Detached and end-terrace homes with exposed gables.
• Properties with worn or cracked external render.
• Older properties (pre-1970s) where cavity workmanship and insulation were inconsistent.
• Properties at altitude (above 250m) where exposure is higher.

Symptoms of failed cavity insulation

• Patchy damp on internal walls, usually concentrated on exterior walls.
• Cold spots that the heating system cannot eliminate.
• Streaking or staining on external walls beneath the damp areas.
• Persistent mould in corners, behind furniture, on exterior wall surfaces.
• Visible insulation slumping or settling, sometimes seen via endoscope inspection.

Diagnosis: the borescope inspection

A specialist will drill small holes (5 to 8mm) in the mortar joints and insert a borescope camera. They check:

• Whether the cavity is fully filled.
• Whether the insulation has slumped or settled.
• Whether moisture is visible on the insulation or on the inner wall.
• Whether debris is present in the cavity.

Inspection cost: £200 to £400.

Removal costs in 2026

Cavity wall insulation is removed by drilling larger holes and vacuuming or blowing out the insulation. Costs:

• Small home (semi-detached or terrace): £4,000 to £6,000.
• Medium home (typical detached): £6,000 to £8,000.
• Large home (4 to 5 bed detached): £7,500 to £10,000.
• Re-pointing and making good after removal: £500 to £1,500.
• Reinstating with a more suitable insulation (typically bonded bead, or external wall insulation): £2,000 to £4,000 for cavity bead, £8,000 to £15,000 for external wall insulation.

CIGA guarantee

The Cavity Insulation Guarantee Agency (CIGA) provides a 25-year guarantee on most installations done by their registered installers. The guarantee covers:

• Repair or replacement of failed installation.
• Removal where reinstallation is not possible.
• Internal damage caused by the failure.

To claim:

1. Find your CIGA guarantee certificate (issued at installation).
2. Submit a claim form to CIGA with evidence (photos, borescope report, surveyor report).
3. CIGA sends an independent assessor.
4. If approved, CIGA arranges remediation through an approved contractor.

Claims are taking 6 to 12 months on average in 2026. CIGA disputes that the failure is “installation related” in some cases; persistence and a chartered surveyor's report typically wins.

Compensation claims against installers

If CIGA refuses or the installer is no longer trading, specialist solicitors handle group action claims against the original installers and ECO scheme administrators on a no-win-no-fee basis. Success rates have improved since 2023 when several test cases established liability.

Typical settlement: cost of removal plus damages for the damp period (often £5,000 to £20,000 in total). Cases proceed in the County Court typically; some have been raised to the High Court for larger values.

Buying a property with cavity wall insulation

Check the TA6 disclosure and the EPC. Ask whether a CIGA certificate was issued. If yes, get a copy. If no, ask the seller to commission a borescope inspection before exchange.

If the property has visible damp signs and cavity insulation, treat it as a known risk. Negotiate seller-funded inspection and remediation before exchange, or a meaningful price discount.

When you should think about removal

• Persistent damp internally despite normal heating and ventilation.
• Borescope inspection confirms slumped or saturated insulation.
• Multiple damp spots on different external walls.
• You are planning major renovation anyway.