THI Foam Removal
Open-cell and closed-cell spray foam
Two kinds of foam, and two different jobs. Here’s how they differ, why it matters for removal, and why it’s fine not to know which one you have.
The difference
Side by side
| Open-cell | Closed-cell | |
|---|---|---|
| What it’s like | Open-cell: Softer and spongier | Closed-cell: Denser and rigid |
| Moisture | Open-cell: More vapour-permeable | Closed-cell: Less vapour-permeable |
| Often used to | Open-cell: Insulate the underside of a roof | Closed-cell: Insulate and stabilise a roof, or improve airtightness |
| What it means for removal | Open-cell: Softer foam, but it still needs care and containment. How it comes away depends on what it was sprayed onto | Closed-cell: Harder to remove, especially if bonded. Where it’s applied directly to tiles, removal may also involve roof work |
What it’s stuck to
Where it was applied matters as much
On felt or a membrane
There’s a layer between the foam and the tiles. What matters is the condition of that layer once the foam is off.
Directly on tiles or slates
With no layer in between, the foam may be bonded to the roof covering. Removing it can disturb the covering, so roof work may be part of the job.
On boards or sarking
Boarded roofs behave differently again. We’d record what’s there, and what can and can’t be seen.
A specialist surveyor records this too, along with whether the timbers are covered, the moisture readings, and how the roof is ventilated. Foam isn’t a problem in every roof.
Which do I have?
You don’t need to know
Most people don’t. Please don’t cut into it, scrape it or lift it to find out. If you have the installer’s paperwork, it may say. If not, choose “not sure” on the form and we’ll identify it at the survey.
Photos are welcome but optional. We won’t diagnose your roof from a photo.
What we’ll take on
Tell us what you can see, or send photos, and we’ll say whether it’s work we take on before anyone visits.
If a job is outside what we can do well, we’ll say so rather than quote for it.
FAQs
Foam type questions
Is one type worse than the other?
Not in itself. What matters is how it was applied, the roof it’s on and whether anyone can inspect the timbers. A specialist surveyor can tell you about your roof.
Does closed-cell always mean a re-roof?
No, but it can involve roof work, particularly where it’s bonded directly to tiles. That’s something to establish at the survey and state in the quotation.
Why does the type change the price?
The two come away differently and take different amounts of time, and bonded foam can bring roof work with it. See the cost factors.
Keep reading
Related pages
How removal works
The stages, from survey to records.
Cost factors
What affects the price of removal.
Do you need removal at all?
Start with the official guidance.
Request a Loft Assessment
Not sure what type you have? That’s fine. Start with your name, postcode and how you’d like us to get in touch.
We reply as soon as we can.