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.
Complimentary survey
Book Your Complimentary Survey
Over 35 years of independent expertise. Written findings included. No sales pressure. No obligation.
Book your complimentary surveyTechnical 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.
Complimentary specialist survey
Your Complimentary Specialist Survey
Backed by over 35 years of independent damp and timber expertise.
We believe in diagnosis before treatment. That's why we offer every homeowner and property manager in Dorset, Hampshire and Wiltshire a complimentary specialist survey — carried out by an experienced specialist, not a salesperson.
Over 400 combined reviews across Google and Checkatrade. Over 35 years protecting Dorset homes.
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.
Is the specialist survey really free?+
Yes — completely. We offer every homeowner and property manager across Dorset, Hampshire and Wiltshire a complimentary specialist survey at no charge. This includes an on-site inspection, written findings, a clear scope of any recommended work, and an honest referral if the problem falls outside what we do. You pay nothing for the survey. You only pay if you commission the remedial work, and you are under no obligation to do so. The reason we do this is straightforward: we believe in diagnosing the problem before recommending a treatment. A proper inspection takes time, and we'd rather invest that time up front than quote a solution before we've understood the cause.
Not sure if this is your problem?
That's exactly what the survey is for. Book your complimentary specialist survey and one of our experienced team will identify the cause on-site, consider the alternatives, and give you written findings — at no charge and with no obligation.
Related services
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Recent work
Photographed on our own projects
A selection of real jobs from this service, photographed on site across Dorset, Hampshire and Wiltshire.
Reviewed by local homeowners
Trusted across Dorset, Hampshire and Wiltshire
Independent feedback from customers on Google and Checkatrade — alongside over 35 years of damp proofing and plastering experience.
Next step
Claim your complimentary survey before choosing a treatment
Tell us what you can see, when it changes and where the property is. Photographs can help us triage the next step.