Spray foam removal cost: what you are actually paying for

Why no honest firm prices this down the phone

The single biggest variable on a spray foam job is how much of the roof timber has rotted under the foam, and nobody on earth can see that while the covering is still on. Closed cell foam sits hard against the tiles and stops the roof breathing, so moisture sits against the rafters and battens for years with nowhere to go. Some roofs come back clean. Some have battens that crumble in your hand and rafters that need cutting out and splicing. Until the tiles are lifted, that is guesswork dressed up as a price.

So when a firm gives you a figure on a five minute phone call, they have priced a roof they have not seen. One of two things follows. Either the number climbs once they are up there and you are already committed, or they have padded it heavily at the start to protect themselves and you are paying for timber that was never rotten in the first place. We would rather come out, get in the loft, look at what you have actually got and put a fixed written price in front of you.

What you are paying for, line by line

A spray foam removal quote is a roofing quote, not an insulation quote, and it should read like one. Scaffold goes up first, because the work happens from the outside. Then the covering comes off in sections so the house is never left open overnight. The foam is broken out and bagged, and the old underfelt comes with it. Every bag goes off site and is disposed of properly. That disposal is part of the job, not a surprise line that appears at the end of the week.

Then the rebuild. Every rafter, purlin and batten gets checked once it is exposed, and anything gone gets cut out and replaced. New breathable membrane across the whole roof, new treated battens set to the right gauge for your covering, then the tiles or slates back on. Sound tiles get reused. Broken ones get matched as closely as we can get them. New insulation at joist level goes in where the old loft insulation was stripped out or was never there. The written quote sets out the VAT position, so the figure you are given is the figure you pay.

Read that list against any quote you have been given. If it is one line saying remove spray foam with a number next to it, you cannot tell what is included and neither can anybody else. A quote that breaks the work into stages is a quote you can hold someone to. The full scope is set out on our spray foam removal page, and the same sequence is photographed start to finish on the Norfolk bungalow we stripped and re-roofed.

The five things that move the number most

Roof size and shape comes first. A straightforward bungalow hip is a different job from a period house with valleys, dormers and three chimneys, and the difference is days of labour and a much bigger scaffold. Second, the type of foam. Closed cell bonds hard to the underside of the tiles and to the felt, so it takes longer to get off cleanly than open cell does. If you are not sure which one is in your loft, our guide on open cell vs closed cell foam shows you how to tell from the hatch.

Third, whether the tiles survive. Sound tiles come off, get stacked and go back on, which costs you nothing extra. Tiles that are spalling, or that were bonded into the foam and break as they come away, have to be replaced and matched. Fourth, how much timber has gone, which is the one nobody can see up front. Fifth, access and scaffold. A detached bungalow with a drive is cheaper to scaffold than a mid terrace with no side access and a shared alley to carry everything down.

Why the timber line should be separate and provisional

This is the single best test of whether a quote is honest. Timber replacement is the one cost that cannot be known until the roof is open, so it belongs on its own line, priced per rafter or per metre, and it should be marked as provisional. You then pay for what was actually replaced rather than what somebody guessed at, and you get photographs of the timber showing exactly why each piece came out.

The alternative is a firm that buries a fat contingency inside the headline figure. That looks simpler on paper and it costs you more, because if the roof turns out sound you never see that money back and you never find out it was in there. Ask any firm quoting you to split the timber out and to tell you the rate. How they answer that question tells you a great deal about how the rest of the job will go.

How to compare two quotes that look different

Put them side by side and compare scope before you compare price. Does each one include the scaffold, or is scaffold hire a separate invoice landing later? Does each one include taking the waste away, or is there a skip you are paying for on top? Is new breathable membrane going across the whole roof in both, or is one of them re-using the old felt wherever it looks alright? Is there a guarantee behind the workmanship, and for how long?

More often than not, two quotes that look thousands apart are quoting two different jobs. Once you line the scope up, the gap closes and the real comparison becomes obvious. Ask both firms the same three questions: what happens if you find rot, what is the disposal arrangement, and what do I get in writing at the end. If the reason you are doing this at all is a stalled sale, our guide on spray foam and your mortgage covers what the lender is waiting on.

What to do if one quote is far cheaper than the rest

A price well under the others means one of three things, and all three cost you money later. One is a scrape out from inside the loft, which leaves residue bonded to the tiles and the felt, gives nobody a proper look at the timber, and leaves you paying twice when the surveyor comes back. Another excludes scaffold, disposal or timber work, all of which turn up as extras once the job has started. The third is an insulation firm rather than a roofer, taking foam off a roof they are not equipped to put back.

Ask the cheap quote one question: does the roof covering come off. If the answer is no, you are not comparing like with like and the number in front of you is for a different piece of work. Removing foam properly is a roofing job done from the outside with the scaffold up, which is why we do it that way and why it is priced that way. What you should be handed at the end of it is set out in our guide to spray foam removal paperwork.

What a proper written quote has on it

• Scaffold, including how long it is hired for and who pays if the job overruns
• The covering lifted in sections, with the house never left open overnight
• All foam and the old underfelt removed, not just what is reachable between the rafters
• Disposal of every bag of waste, priced in rather than added at the end
• Inspection of every rafter, purlin and batten once exposed, with photographs
• Timber replacement on its own provisional line, with the rate stated
• New breathable membrane and new treated battens across the whole roof
• The workmanship guarantee in writing, with its length stated

Common questions