If damp appeared after cavity wall insulation, record when and where it occurs, check obvious external and plumbing defects, find your guarantee paperwork and request a documented inspection. Extraction should only be considered if evidence connects the insulation or cavity condition to the moisture problem.
When this guide fits
Clues worth recording
- New damp patches after rainfall
- Symptoms concentrated on exposed elevations
- Cold bands or patchy surface temperatures
- No previous history of the same damp location
Deal with active leaks first
Overflowing gutters, damaged downpipes, roof leaks and plumbing defects can require immediate repair. If electrical fittings are wet or masonry looks unsafe, isolate the area and seek suitable professional help.
Build a useful timeline
Note the installation date, when symptoms began, the rooms involved and whether rain, wind direction, heating or occupancy changes them. Keep dated photographs and avoid redecorating before the inspection where practical.
Ask for an evidence-led inspection
A useful investigation combines external condition, moisture distribution, ventilation and targeted cavity inspection. Moisture-meter readings alone do not identify a cause. Ask the inspector to explain alternative causes they considered.
A thermal image can show temperature differences; by itself, it cannot prove that insulation is wet or defective.
Use the complaint and guarantee route
For insulation funded by the Energy Company Obligation (ECO), Ofgem’s published steps are: find your paperwork and contact the installer; then the oversight or certification body (TrustMark may be able to help if the work was TrustMark-registered and handed over after 1 January 2020); then the guarantee provider; then the energy supplier that funded it. Ofgem can confirm the installer for ECO work from April 2015, but it does not regulate the insulation industry, and local authority or devolved-government schemes have their own routes.
For a CIGA guarantee you do not need the certificate: CIGA says it can search its records by property address and postcode, and that it handles the complaint itself if the installer is no longer trading.
Questions homeowners ask
What people usually want to know
Can damp appear years after installation?
Yes, but timing does not establish the cause. Later changes to pointing, gutters, exposure, heating or ventilation may be relevant.
Will a damp meter prove the insulation is wet?
No. It provides a reading at the tested surface or material. Diagnosis needs context and, where appropriate, direct cavity investigation.
Can I make a guarantee claim without the certificate?
It depends on the provider. CIGA states that it can search its database using the property address and postcode.
Sources & review
Evidence behind this guide
Reviewed 2 October 2026. We use primary guidance where available and label trade-body advice clearly.