Insulation
Cavity wall insulation, extraction and refill
Cavity wall insulation, plus extraction and refill of failed or damp-affected fill, to warm walls and reduce condensation and mould.
Why diagnosis matters
Treat the cause, then repair the damage
Cold external walls are a leading cause of condensation and black mould. We install cavity wall insulation and, where existing fill has slumped, bridged or become damp, we extract it and refill correctly. Insulation is considered alongside ventilation, not as a stand-alone fix.
Technical review
Dan, Director / Surveyor
Last reviewed: July 2026. Advice is general until the property, access and visible evidence have been assessed.
Guarantee & aftercare
Written guarantee terms are matched to qualifying work, with inclusions, exclusions and aftercare explained before acceptance.
What we consider
Possible causes and lookalikes
Uninsulated or under-insulated cavities
Slumped, bridged or saturated existing fill
Cold wall surfaces raising surface humidity
Poor combination of insulation and ventilation
Inspection method
A clear work sequence
Step 1
Assess wall construction, exposure and existing fill
Step 2
Extract failed or damp-affected material where needed
Step 3
Install suitable insulation to a correct fill pattern
Step 4
Advise on ventilation so moisture is managed too
Scope boundaries
Honest about what the work does—and does not—cover
We install cavity wall insulation and carry out extraction and refill in-house. Where a wall is unsuitable for cavity fill we say so and recommend an alternative such as internal insulation rather than proceeding regardless.
Common questions
About cavity wall insulation, extraction and refill
Can cavity insulation cause damp?+
Incorrect or damp-affected fill can bridge a cavity and lead to penetrating damp. Where this has happened we extract the old material and reassess whether cavity fill is appropriate before refilling.
Will insulation stop my condensation and mould?+
Warmer wall surfaces reduce the risk of condensation, but ventilation and moisture control still matter. We treat insulation and ventilation together rather than promising insulation alone will cure mould.
Is my wall suitable for cavity fill?+
Not every wall is. Exposure, cavity width, construction and condition all matter. If a wall is unsuitable we will tell you and suggest a better option.
Related services
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Next step
Claim your complimentary survey before choosing a treatment
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