Can Spray Foam Rot Your Roof?

Spray foam insulation has been marketed as a modern solution to heat loss and rising energy bills — especially in older UK homes. But many homeowners are now discovering the hidden problems that come with it. One of the most serious? Timber rot.

At Countrywide Roofing and Insulation, we regularly inspect properties where spray foam has done more harm than good. If you're wondering whether spray foam can cause your roof to rot, the answer is yes — and here's what you need to know.

How Spray Foam Traps Moisture

Roof timbers need ventilation to stay dry and healthy. Even in well-built homes, small amounts of moisture naturally enter loft spaces. Normally, airflow takes care of that. But once spray foam insulation is added — especially closed cell spray foam — the moisture can't escape.

Closed cell foam forms a hard, airtight seal. If any water gets into the roof space, it becomes trapped. Over time, this can soak into the timber and lead to rot. The danger is made worse by the fact that this damage is often hidden behind the foam.

Even open cell spray foam, which is more breathable, can absorb moisture and mask signs of early decay.

📊 Stat: Around 1 in 4 homes with spray foam insulation develop moisture or timber-related issues within five years of installation.

Why You Might Not Notice Until It's Too Late

One of the biggest dangers with spray foam is how well it hides problems. Because it's sprayed directly onto the rafters and felt, any signs of rot, mould, or water damage are covered up.

Lenders and Surveyors Are Flagging It

Spray foam isn't illegal in the UK, but it is now a major red flag for mortgage lenders and surveyors. Most won't approve a mortgage — or will heavily condition it — if the loft has spray foam insulation. The reason? They can't assess the condition of the timber underneath.

If you're planning to sell your home, refinance, or apply for equity release, spray foam can delay or even block the process until it's removed and the roof structure has been inspected.

📊 Stat: More than 70% of UK lenders now restrict lending on homes with spray foam insulation in the loft.

Open Cell vs Closed Cell: What's the Difference?

Understanding the type of spray foam in your loft is key to knowing the risks:

Open Cell Spray Foam

Light, soft, and slightly breathable

Absorbs moisture like a sponge

Easier to remove

Still problematic for surveys and valuations

Closed Cell Spray Foam
Hard, dense, and rigid

Creates a full vapour barrier — traps moisture

Strong bond to roof timbers and felt

More likely to cause rot and structural damage

More difficult to remove

We offer safe, professional open cell spray foam removal and closed cell spray foam removal throughout the UK. Our team carefully removes the foam and restores the breathability of your loft, helping protect your home from long-term damage.

Like Wrapping Timber in Cling Film

Think of your roof beams like skin — they need to breathe. Now imagine wrapping that skin in cling film. You might stay warm, but eventually, you'll start to sweat. That trapped moisture leads to discomfort and damage. It's the same with spray foam. It seals everything in — and that's where the trouble starts.

What to Do If You Suspect Roof Rot

If you've already had spray foam installed and are worried about the effects, don't ignore it. Here's what you should do:

1. Book a Professional Survey
We'll inspect the type of foam and assess your loft for any signs of damage — even those not visible to the eye.

2. Request a Spray Foam Removal Quote
We'll provide a free, no-obligation quote tailored to your home and the specific type of insulation.

3. Restore Breathability and Protection
After safe removal, we can help improve loft ventilation and insulation, making your home healthier, mortgage-ready, and rot-free.

 FAQs: Spray Foam

1. What are the top signs that I need closed-cell spray foam removal?

If you notice cracks, damp smells, mortgage refusals, or structural shifts, it could be time to remove the insulation. Discover the 5 most common red flags:
👉 Top 5 Signs You Need Closed-Cell Spray Foam Removal

In many cases, equity release is blocked or heavily restricted due to spray foam's effect on surveys and valuations. Here's how it impacts your financial options:
👉 Understanding Equity Release If You Have Spray Foam

While manufacturers claim lifespans of 20–80 years, real-world issues like poor installation, moisture, or roof damage can cut that down drastically. Find out what to realistically expect:
👉 What Is the Lifespan of Spray Foam?

Removal becomes necessary when spray foam affects mortgages, causes damp issues, or fails a home survey. Learn how to identify the right time to act:
👉 When and Why You Need Spray Foam Removal

Homeowners across the UK are removing it due to survey failures, property devaluation, trapped moisture, and restricted home improvement plans. Learn more:
👉 Why Are People Removing Spray Foam Insulation?

Closed-cell foam bonds tightly to surfaces, making it labor-intensive and risky to roof timbers if done improperly. Learn what makes it so tricky:
👉 Why Closed-Cell Spray Foam Can Be Difficult to Remove

Spray foam can trap moisture, block ventilation, and release chemical off-gassing if applied incorrectly — leading to health, structural, and financial risks. Learn the dangers:
👉 Why Is Spray Foam Hazardous?

Spraying foam directly onto roof tiles or felt can lead to decay, trapped moisture, and mortgage refusals. Here's why professionals advise against it:
👉 Why Shouldn't You Spray Foam Your Roof?

Final Thoughts