Cavity Wall Insulation Problems & Damp
Damp patches, black mould and cold walls that started after your cavity was filled are classic signs of failed cavity wall insulation. Proofterior diagnose cavity wall insulation problems properly — looking inside the wall, not guessing from the outside — and fix both the cause and the damage across Dorset, Hampshire and Wiltshire.
- ISSE accredited
- 25-year insured guarantee
- In-house specialist team
Book your complimentary survey
Tell us what is happening and a specialist will find the real cause and give you a fixed price to fix it. No obligation.
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Genuine reviews from local homeowners
Over 200 verified reviews across Checkatrade, Google and Yell
“Excellent service from start to finish. The survey was thorough and professional, with honest, evidence-based advice rather than trying to sell unnecessary work. I came away with complete peace of mind.”
Alex Richards-Taylor
Google review
“Excellent service throughout. Ashton came out to look at an issue raised on a part-exchange survey and, rather than recommend expensive remediation, told me honestly there was nothing wrong with the wall. Great to have an honest discussion.”
Ian M.
BH16 · Damp Investigation
“Dylan and the Proofterior team were amazing. The report was incredibly comprehensive. Can’t recommend them enough.”
Sam Short
Google review
“Very pleased with the work on our living room and bedroom walls. Punctual, polite and friendly, and completed on time even though it was Easter week. Many thanks to everyone at Proofterior.”
Chris G.
BH20 · Penetrating Damp Treatment
“Dan was very thorough, professional and polite. Quick to respond and I would highly recommend.”
Malik R.
Yell · Quick & Professional
“The workmen were clean, pleasant and efficient and took just one day. The very next day we noticed a big difference with the damp issue. Many thanks.”
Nick Bennett
Google review
“Able to fit my job in for the next day and completed in a day as agreed. Not the lowest quote, but it comes with a 25-year guarantee, which I wanted — long-term peace of mind was vital.”
Alan M.
BH23 · Flat Roof Reseal
“Ashton was so friendly and informative. I’ve gone from worried to empowered — someone you can trust to do the right thing.”
Suzanna Furbank
Google review
“Really amazing service. Dan provided a really thorough damp investigation and a very helpful damp report. Very quick responses too.”
Paul A.
Yell · Damp Investigation
“Happy with the speed — a full flat survey within a week. They explained our options, the price was extremely competitive, and our tenants are pleased with their fresher, safer flat.”
Verified Customer
SP6 · Damp Proofer
“Dan provided a very professional service from start to finish. Very good communication and a first-class job.”
Mark H.
Yell · Professional Service
“Excellent service from start to finish. The survey was thorough and professional, with honest, evidence-based advice rather than trying to sell unnecessary work. I came away with complete peace of mind.”
Alex Richards-Taylor
Google review
“Excellent service throughout. Ashton came out to look at an issue raised on a part-exchange survey and, rather than recommend expensive remediation, told me honestly there was nothing wrong with the wall. Great to have an honest discussion.”
Ian M.
BH16 · Damp Investigation
“Dylan and the Proofterior team were amazing. The report was incredibly comprehensive. Can’t recommend them enough.”
Sam Short
Google review
“Very pleased with the work on our living room and bedroom walls. Punctual, polite and friendly, and completed on time even though it was Easter week. Many thanks to everyone at Proofterior.”
Chris G.
BH20 · Penetrating Damp Treatment
“Dan was very thorough, professional and polite. Quick to respond and I would highly recommend.”
Malik R.
Yell · Quick & Professional
“The workmen were clean, pleasant and efficient and took just one day. The very next day we noticed a big difference with the damp issue. Many thanks.”
Nick Bennett
Google review
“Able to fit my job in for the next day and completed in a day as agreed. Not the lowest quote, but it comes with a 25-year guarantee, which I wanted — long-term peace of mind was vital.”
Alan M.
BH23 · Flat Roof Reseal
“Ashton was so friendly and informative. I’ve gone from worried to empowered — someone you can trust to do the right thing.”
Suzanna Furbank
Google review
“Really amazing service. Dan provided a really thorough damp investigation and a very helpful damp report. Very quick responses too.”
Paul A.
Yell · Damp Investigation
“Happy with the speed — a full flat survey within a week. They explained our options, the price was extremely competitive, and our tenants are pleased with their fresher, safer flat.”
Verified Customer
SP6 · Damp Proofer
“Dan provided a very professional service from start to finish. Very good communication and a first-class job.”
Mark H.
Yell · Professional Service
What is Cavity Wall Insulation Problems & Damp?
A cavity wall has an outer and inner leaf with a gap between them that was designed to stop rain reaching the inside. Cavity wall insulation fills that gap, and in the right wall it works well. Problems happen when it is installed where it should not be, or when conditions change. Wind-driven rain soaks the outer brick and wet fibre carries it across to the inner wall. Fill that has slumped or was never fully injected leaves voids, which become cold spots where warm, moist air condenses and mould grows. Mortar droppings and debris in the cavity, failed pointing, cracked render and leaking gutters all let more water in. Over time, damp insulation can corrode steel wall ties and rot the ends of timber floor joists built into the wall. These cavity wall insulation problems look a lot like condensation, rising damp or penetrating damp — so getting the diagnosis right is what saves you money.
The warning signs to look for
Catching the problem early keeps repairs simpler and less costly. If you notice any of these signs, it is worth booking a specialist survey before the damage spreads.
Book a complimentary survey- Damp patches on external walls, often at random heights
- Black mould in corners, around windows and behind wardrobes
- Damp that is worse after storms and driving rain
- Cold, clammy walls and condensation on inside surfaces
- Tide marks, salts, blown plaster or peeling wallpaper
- A musty smell in rooms on weather-facing sides of the house
- Horizontal cracks in mortar joints from rusting wall ties
- Soft skirting boards or floor joists near outside walls
Our treatment process
Every job follows the same careful, diagnosis-first method — so you know exactly what is happening and why at each stage.
Listen and look: we talk through when the damp started, when the insulation went in and how the rooms are used.
Inside the cavity: borescope inspection at several points to see the type, condition and dampness of the fill.
Measure: moisture readings, thermal imaging and humidity checks to rule condensation, leaks and rising damp in or out.
Outside: we check pointing, render, gutters, downpipes, sills, weep holes and how exposed each wall is.
Report: a clear written diagnosis with photos, explaining exactly why the insulation is failing and what it needs.
Put it right: removal, repairs, re-insulation, mould treatment and re-plastering by our vetted, Proofterior-trained team.
Wind-driven rain and exposed walls
Britain is mapped into exposure zones for wind-driven rain, and much of coastal Dorset and Hampshire falls into the more severe bands. Rain driven hard against brickwork soaks the outer leaf far more than in sheltered areas.
In an empty cavity that water simply runs down and drains away. In a filled cavity, some types of insulation give it a path straight to the inner wall — which is why weather-facing walls are where failed cavity wall insulation usually shows first.
Cavity Wall Insulation Problems & Damp — from our recent projects
Real photos from Proofterior jobs across Dorset, Hampshire and Wiltshire — carried out by our own in-house team.
Included as standard
Built to impress, built to last
Diagnosis first
We identify the real cause before recommending any treatment. No guesswork, and never unnecessary work.
In-house specialist team
Vetted, Proofterior-trained specialists, managed by us from survey to completion. No compromises.
25-year guarantee
Every treatment is backed by our 25-year insured guarantee, giving you lasting protection and peace of mind.
Cavity Wall Insulation Problems & Damp across Bournemouth, Poole & the South Coast
The South Coast is one of the toughest places in the country for cavity wall insulation. Much of coastal Dorset and Hampshire sits in a high exposure zone for wind-driven rain, so filled walls in Bournemouth, Poole, Christchurch, Lymington, Southsea and Hayling Island see far more failures than sheltered inland homes. We also see cavity wall insulation problems in post-war estates around Southampton, Portsmouth, Andover and Salisbury, where insulation was installed in bulk. Our team works across Bournemouth, Poole, Christchurch, Southampton, Portsmouth, Winchester, Salisbury and the towns and villages in between.
Covering Dorset, Hampshire & Wiltshire
Local knowledge, specialist expertise and lasting protection for the home you care about.
Everything you might be wondering
Wet insulation carrying rain across the cavity in exposed walls, slumped or patchy fill leaving cold spots, debris bridging the cavity, and insulation installed in walls that were never suitable — such as narrow cavities, non-traditional construction or walls already suffering damp.
Yes. Gaps and slumped areas in the fill leave parts of the inner wall colder than the rest. Warm, moist air condenses on those cold spots and black mould grows. Wet insulation also keeps the inner wall damp, which mould loves.
Some show within a winter or two; others take years as fibre settles, pointing ages or gutters fail. Damp that starts at any point after the cavity was filled is worth investigating.
It could. Condensation, penetrating damp and failed cavity wall insulation often look alike. A borescope survey, moisture readings and humidity checks tell them apart, so you do not pay for the wrong fix.
It can. Some lenders and surveyors flag cavity wall insulation problems, especially where there is visible damp. A specialist report and, where needed, removal and a guarantee help reassure buyers and lenders.
Over time, yes. Constant moisture can corrode steel wall ties and rot timber joist ends and lintels that sit in the wall. Our survey looks for early signs of both.
Get clear, honest answers about your home
A qualified specialist will visit your property, carry out a thorough inspection and give you clear recommendations in plain English — everything explained in one visit, with no obligation.