Spray Foam and Timber Surveys: What UK Homeowners Need to Know (2025)

Spray foam insulation has become a major concern for mortgage lenders and surveyors—especially when it comes to structural timber. If your loft has spray foam applied directly to the rafters or joists, a thorough timber survey may be required. But what exactly are surveyors checking for?

In this 2025 guide, we explain how spray foam affects timber assessments, what RICS surveyors prioritise, and how to avoid red flags during property transactions.

1. Why Timber Surveys Are Important with Spray Foam

Spray foam can create a barrier that limits airflow to the timber structure of your roof. Over time, this may cause:

• Trapped moisture
  
  
• Timber decay or rot
  
  
• Hidden condensation issues
  
  

Lenders typically request a timber survey to ensure the structural integrity of the roof isn’t compromised.

2. What Surveyors Look for in a Timber Inspection

Chartered surveyors (particularly RICS-accredited professionals) focus on the following:

• Visible timber condition: signs of warping, rot, or water staining
  
  
• Ventilation: whether foam has blocked airflow
  
  
• Foam adhesion: poor application can trap moisture beneath
  
  
• Roof structure: sagging or weakening due to hidden rot
  
  

Surveyors may also flag properties where spray foam covers every timber element, as this prevents visual assessment.

3. The Impact of Open-Cell vs Closed-Cell Foam on Timber

Not all foam is created equal. Surveyors evaluate risk based on the type of foam used:

• Closed-cell foam: Dense, moisture-resistant but less breathable—may trap moisture and cause timber to decay
  
  
• Open-cell foam: More breathable but still risks airflow restriction if misapplied
  
  

Knowing which type is in your loft can help determine the next steps.

4. Can a Timber Survey Fail Because of Spray Foam?

Yes. A surveyor may be unable to assess the timber condition properly if it’s covered by spray foam. This can lead to:

• An inconclusive or negative survey report
  
  
• A delay or rejection in mortgage approval
  
  
• Recommendations for foam removal before continuing
  
  

To avoid this, some sellers opt to pre-emptively remove spray foam prior to survey.

5. What to Do If Your Timber Survey Flags Issues

If a surveyor identifies problems with spray foam or timber, you should:

• Commission a follow-up report by a timber specialist
  
  
• Request a core sample test (small section of foam removed for inspection)
  
  
• Consider partial or full foam removal
  
  

This process provides lenders and buyers with clearer information.

6. Spray Foam Removal to Assist Timber Surveys

Spray foam removal is sometimes the only way to verify timber condition. Professional removal can expose rafters and joists, allowing for:

• Full structural inspection
  
  
• Moisture testing
  
  
• Timber treatment, if needed
  
  

See more: Spray Foam Removal Process

7. Final Thoughts: Navigating Timber Surveys in 2025

Spray foam insulation isn’t automatically a problem—but it does complicate surveys involving structural timber. In 2025, mortgage lenders and surveyors are more cautious than ever.

If you’re selling or refinancing a property with spray foam, get ahead of the process:

• Understand what surveyors need to see
  
  
• Remove foam if it obstructs visual inspection
  
  
• Get a RICS surveyor’s report to support your transaction
  
  

Need help? Explore our Spray Foam Removal Locations or speak to our team.

Frequently Asked Questions

Can a surveyor see timber if it's covered in spray foam?
No—most spray foam blocks visual inspection, which may result in a failed or incomplete survey.

Will timber always rot under spray foam?
Not always, but it’s a risk if moisture is present and the foam restricts airflow.

Is open-cell foam safer for timber than closed-cell?
Generally yes, but both types pose inspection challenges and risks if not installed properly.

Do all mortgage lenders require timber surveys for spray foam?
Many do—especially if the foam touches the roof structure directly.

Should I remove spray foam before a survey?
If it's preventing access to timber, removal could help avoid delays or refusals.