Preface: This article is based on a genuine Chartered Building Surveyor’s report carried out in September 2025. The identity of the homeowner has been changed to protect their privacy.
Spray foam insulation has become one of the most controversial home upgrades in the UK. Once marketed as a quick efficiency fix, poor installations are now being linked to roof damage, trapped moisture, and reduced property value.
A recent independent report by a Chartered Building Surveyor (MRICS) in West Sussex illustrates the risks. The findings read like a checklist of what can go wrong when spray foam is applied without ventilation design, condensation risk assessment, or adherence to British Standards. If you’ve received a similar report, professional spray foam removal is usually the first step to putting things right.
A Real Case: Homeowner A in West Sussex
The property was a typical detached family home with a loft conversion. During inspection, the surveyor found open-cell spray foam applied across multiple roof spaces, in some areas up to 300 mm thick, and in others missing altogether.
Crucially, sections of foam had been sprayed directly onto non-breathable bituminous underfelt and onto close-boarded timbers. Eaves ventilation paths were effectively sealed. Even on a warm, dry inspection day, the survey recorded elevated moisture readings in the boarding—an early sign of humidity being trapped against timber.
The Surveyor’s Findings (in Plain English)
- No condensation risk assessment before installation.
- Foam applied to high-resistance underfelt (non-breathable) and to close boarding.
- Blocked eaves ventilation—a “cold roof” turned into a sealed box.
- No vapour control layer at ceiling level; recessed spots allowing moist air up.
- Uneven thickness (100–300 mm) and missing coverage in one roof section.
- Elevated moisture readings despite dry weather.
The report referenced BS 5250:2021 (Management of Moisture in Buildings) and echoed the Health & Safety Executive’s 2024 guidance that such constructions present a high risk of timber decay over time.
For homeowners, blocked airflow often manifests as damp smells, staining, or dripping in colder months. If that sounds familiar, read our primer on loft condensation in the UK.
Why This Happens (and Why We Don’t Recommend Spray Foam)
Unfortunately, cases like this aren’t rare—and they often stem from how spray foam has been sold to homeowners. Many companies promoting spray foam aren’t genuine insulation experts like us—they’re sales-driven installers following generic manufacturer scripts, not moisture-management science.
At Carbon Zero Solutions, we don’t install or recommend spray foam insulation under any circumstances. We’ve seen first-hand how it traps moisture, damages roof timbers, and leaves homeowners facing lender refusals and costly repairs. Our expertise lies in removing spray foam safely, restoring airflow and insulation properly, and helping homeowners reclaim a roof that breathes, performs, and lasts.
The Hidden Threat Most People Miss: Foam Residue
Removing the bulk of the foam isn’t enough. Tiny residues cling to rafters, noggins, and close boarding. Those residues continue to trap surface moisture against timber, encouraging mould growth and long-term decay—even when the roof “looks” clean.
This is where we specialise. Carbon Zero Solutions carries out professional spray foam removal that goes beyond the obvious: controlled mechanical scraping, vacuum-assisted extraction, and meticulous surface checks to ensure residues are gone and timbers can dry properly.
Repair & Restoration: Doing It Safely
The surveyor rightly warned that foam bonded to bituminous felt can tear the underlay during removal. If that happens, sections may need stripping and re-felting. This is why you need experienced specialists who can minimise risk and document every stage for your surveyor or lender.
After safe removal and residue cleaning, we reinstate a healthy roof build-up: restoring airflow with products such as Felt Lap Vents and installing modern, breathable loft insulation in line with BS 5250 principles. Where appropriate, we’ll also discuss high-performance alternatives like Actis Hybris insulation to achieve efficiency without repeating past mistakes.
The Homeowner Impact
For Homeowner A, the findings were more than a technical report—they were a shock. Like many families, they’d invested in spray foam believing it would make their home warmer and more efficient. Instead, they were faced with the realisation that their roof could decay from the inside out, and their home might be unmortgageable until the foam was removed. It’s a story we hear time and again across the UK.
According to the Health & Safety Executive, poorly installed open-cell foam on non-breathable felt can increase the risk of timber decay by over 25%. Always ensure your insulation strategy follows BS 5250:2021 principles and maintains effective ventilation.
Working with Surveyors, Satisfying Lenders
We regularly attend properties following Chartered Surveyor inspections and provide photographic evidence of removal, residue cleaning, and ventilation reinstatement. This transparency helps satisfy lender requirements and supports a smooth remortgage or sale.
Spray Foam Removal: Frequently Asked Questions
Will spray foam insulation affect my mortgage or remortgage?
In many cases, yes. Lenders frequently flag properties with spray foam due to moisture/ventilation risks and lack of compliance evidence. They usually require full removal and proof that the roof has been restored to a breathable, standards-led build-up before proceeding.
Do you install spray foam?
No. We don’t install or recommend spray foam under any circumstances. Our role is to safely remove it, clean residues, and reinstate healthy ventilation and modern loft insulation that aligns with BS 5250 principles.
Can you remove spray foam without damaging the felt?
Often, yes — but it depends on the existing underlay. Foam bonded to bituminous felt can tear during removal. We use controlled techniques to minimise risk and, if needed, coordinate strip-and-refelt works. Everything is documented for your surveyor/lender.
Why is residue removal so important?
Residue left on rafters and close boarding can continue to trap surface moisture, inviting mould and decay. Our service includes mechanical scraping, vacuum extraction and surface checks to ensure residues are gone, restoring the roof’s ability to breathe.
How do you restore ventilation after removal?
We reinstate airflow pathways as designed for the roof type. That can include eaves ventilation and targeted products such as Felt Lap Vents, followed by compliant insulation to current standards.
What are the warning signs of a problem?
Musty smells, damp staining to ceilings, dripping in cold snaps, or a surveyor highlighting blocked ventilation/non-breathable underfelt. If any of these sound familiar, read our guide to loft condensation in the UK or speak to us.
What insulation do you recommend instead?
We specify breathable, standards-led systems suited to the property. Options include modern quilt/board combinations and high-performance solutions like Actis Hybris, installed alongside correct ventilation strategy.
Conclusion: Fixable—With the Right Team
Homeowner A’s case is not unique. Across the UK, surveyors are flagging similar installations, and lenders are insisting on removal before lending or remortgaging. The good news is that the problem is fixable with careful, standards-led work.
If you’ve received a report like this—or you’re unsure how your foam was installed—talk to us about our spray foam removal service. We specialise in safe removal, thorough residue cleaning, and full loft restoration so your roof can breathe, perform, and pass scrutiny.
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Related reading:
Loft Condensation & Health Risks •
Home Insulation 2025
