Question answered
Re-roofing a house with spray foam
The short answer
You can re-roof a house that has spray foam under the tiles, but the foam is usually dealt with first or as part of the same job. Stuck-on foam hides the battens, the underlay and the rafters, so the condition of the structure cannot be checked. Clearing it during a re-roof gives access from above, though the Building Regulations thresholds and any thermal upgrade still apply.
A roof with foam stuck to its underside can be re-covered, but the foam changes how the job is planned, what you can inspect and what the new roof must deal with.
Why foam complicates a new covering
A re-roof normally begins with stripping the old tiles or slates, then checking the battens, underlay and rafters, repairing what is found and laying the new covering. Foam sprayed onto the underside gets in the way at each step. The old battens and nail points are set into it, and the underlay may be stuck to it. Pulling a tile off can drag material with it, and the rafters beneath stay out of sight.
That matters because a re-roof is the moment to put right anything wrong with the structure. If you cannot see the timbers, you cannot assess them. A roofer who simply lays new tiles over foamed battens is covering a problem rather than solving it, and a lender or buyer's surveyor may query the work later. For the reasons owners decide to act, read why people remove spray foam.
Removal before the re-roof or during it
On a foamed roof there are two sensible orders, and the hub page on spray foam insulation removal gives the wider context. The first is to clear the foam from inside the house before the roof is touched, which suits cases where the covering is still sound and the owner wants the structure inspected first. The second is to strip the covering and clear the foam from above while the roof is open, which gives direct access to the rafters and often makes cleaning the timbers easier.
Each has trade-offs. Working from inside keeps the roof weathertight throughout but can be slow, since the foam has to be cut and scraped away overhead. Working from above takes the foam off with the battens and gives a clear view of the timbers, but the house is exposed until the new underlay goes down, so the weather and the scaffold matter. The order is settled once we have surveyed, and you hear which we would pick and the reasoning. How long each stage takes is set out in how long removal takes.
Building Regulations and the thermal question
A re-roof can bring Building Regulations into play. The Planning Portal gives two tests for repairs and re-covering: under 25 per cent of the total building envelope affected, and under 50 per cent of the roof. Pass both and you would not normally need an application. Go beyond either and approval applies, and the extra work may include bringing the roof insulation up to standard.
Approved Document L adds that renovating a thermal element can mean upgrading the whole element where more than 50 per cent of its surface is renovated. For a roof that has had foam, this ties into the insulation decision, since the replacement has to be designed with the new covering. If an application is required, we talk you through it and look after the notification. See also open and closed cell foam if you are weighing what to keep.
What should be checked while the roof is open
With the foam gone and the covering stripped, the structure can be examined properly. We examine the rafter ends and wall plates for softness or staining, the battens for nail corrosion, the ridge board, and any areas where water has been tracked. Moisture readings are taken before any of it is covered again. Timbers that are marginal can be dried and treated, and those that are unsound are cut out and replaced with treated timber, spliced in to carry the load properly.
This is also when ventilation and the underlay are chosen to suit the new insulation, and when any damaged battens, wall plates or rafter feet are dealt with while they are in plain view. Because the foam was often applied to hide or stop a problem, the roof frequently reveals why it was installed in the first place. You are given pictures at each stage, so the record is there if a lender or buyer asks, and the same set helps the next surveyor who climbs into the loft. Where condensation is the worry, see does spray foam cause condensation.
Planning the job and the paperwork
Because the order of work affects scaffold, weather cover and waste, it helps to settle the plan early. A short call before the survey, covering when the foam went in and who fitted it, saves time on site. Waste is cleared and taken away at the end, and after the survey we send a written quote that gives one overall price. With any firm, ask whether scaffolding and VAT sit inside the price, because both change the final bill.
Keep the paperwork safe and together: photographs of the opened roof, moisture readings, a note of what insulation went back, and the building control completion certificate if one applies. Put it all in one folder with the guarantee for the new covering. A lender or future buyer may ask for these. Doing the work yourself rather than using a contractor raises its own problems, and removing spray foam yourself sets them out.
Re-roofing over foam: two further questions
Can new tiles go straight over foamed battens?
It is possible in principle, but it hides whatever is behind the foam and ties the new roof to the old problem. A cleaner start costs more on day one and usually less over the life of the roof. We would want the structure inspected and the moisture checked before closing it in.
Will a re-roof by itself satisfy a lender?
Not necessarily. A lender's concern is the foam, so a new covering over it may not change their view. Ask what evidence they want before you decide the scope.
Tell us about your roof
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- Photographs of what we find
- A written quote with one total price
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