Spray Foam Insulation

It’s becoming increasingly common for us to come across properties that have had spray foam installed (and sometimes partly removed), and we’ve now written several reports where this was a key issue. So, in this post, I want to explain what the problem is, what we’re seeing on the ground, and what that means for homeowners, buyers and sellers.

What Is Spray Foam Insulation?

Spray foam is exactly what it sounds like - a liquid foam that’s sprayed into place, where it expands, cures and hardens. It’s used to improve insulation performance and is usually applied to the underside of roof coverings, between rafters.

There are two main types:

• Open-cell foam, which is lighter and more flexible;

• Closed-cell foam, which is denser and more rigid.

  
  

Both types reduce breathability of roof systems significantly; this can trap dampness against roof timbers and other components, create hidden dew points and introduce vulnerability into roofing systems.  That’s where the problems begin - especially in older roof structures that rely on good air circulation to work normally.

Why It’s a Problem

Spray foam is often marketed as a quick win for energy efficiency, but when applied directly to the underside of roof coverings, it can:

• Trap moisture against structural timbers;

• Conceal decay or roof leaks;

• Make repairs and inspections more difficult;

• Void warranties or reduce insurability / mortgageability.

  
  

Older roof structures are designed to “breathe.” Covering them with spray foam is like wrapping a wet sponge in cling film - it might look tidier at first, but over time it traps things you don’t want trapped.

What We’re Seeing in Surveys

We’ve recently reported on several properties in the Cotswolds, Gloucestershire and Worcestershire where spray foam had been applied - and in some cases, partly / badly removed.

We observed:

• Residual foam clinging to roof timbers, gables, and sarking membranes - even after ‘professional’ removal;

• Foam fragments littering the top side of ceilings (with unknown fire performance);

• Blocked ventilation to flues and extractors - a serious safety issue;

• Cold water storage tanks contaminated with foam particles;

• Eaves and gables inaccessible for inspection due to thick retained foam.

  
  

Even small residual patches can trap moisture.

What About Damp?

We used our new damp meter to carry out testing on accessible roof timbers.

This new meter allows us to test in timber-prong mode, giving more accurate and targeted data than many standard damp meters.  It’s a valuable tool when assessing risk, especially where spray foam is involved.

What Can Buyers and Sellers Do?

If you’re a seller, and your property has had spray foam installed (even if removed), it’s worth:

• Compiling all records (installer certificates, removal invoices, warranties)

• Having a specialist inspection carried out

• Being upfront with agents and buyers early on

  
  

If you’re a buyer:

• Commission a Level 3 survey if spray foam is present or suspected

• Ask about removal history, guarantees, and post-removal cleaning

• Expect further investigations and possibly budget for remedial works

  
  

In both cases, transparency is key - and so is getting advice from someone who understands both the risks and the context.

Final Thoughts

Spray foam can cause serious long-term issues that buyers and sellers alike must be fully informed on.

We approach every case with a measured, evidence-based mindset.

If you’re dealing with spray foam insulation - past or present - and want a clear, independent view, get in touch. We’re here to help.