This is not an exhaustive or a complete subject.  It is likely to change over time, with edits, additions and deletions, and is simply a collection of my thoughts based on many years of experience.   You should follow your instincts, and you must always seek your own professional advice.


I have previously written about the concern within the heritage sector of the consequences of using spray foam products.    These products have been used in the UK for about thirty years, maybe more, but have been hugely marketed using social media over the most recent few years.  There are fundamentally two types  – which can be categorised as being either closed cell or open cell.   Closed cell foams tend to be older whereas the ones sold more recently are open cell.   The differences are important to be aware of.

RICS has recently published a very useful Consumer Guide which is well worth reading.

In my opinion, these foams should be NEVER be used on any Listed Building.    They are wholly unacceptable.

Closed Cell Foams

These foams are firm to the touch and very easy to identify.   When prodded, they do not compress.  They may have a slightly darker, nicotine-like, colour although this is not always the case.   They seem to be sensitive to UV light exposure and will darken with age.    We understand that they were primarily sold initially for stabilisation of an already failing roof.   They tend to be found sprayed directly to the underside of a roof tile/slate and tend to be quite ‘thin’.

These foams are highly controversial and they are very high risk to causing, or being a contributor to causing, severe wet rot.

If found in-situ, there is a very high likelihood that a full replacement of the roof covering is likely to be required.   The work is likely to require a 100% replacement of the roof covering and may additionally require timber repairs or replacements when found.

Listed Building Consent would be required.

Surveyors who identify this product in a roof should advise their client of the high costs involved and that at the current times the property may not be eligible for a mortgage loan until the foam has been removed.


Open Cell Foams


These foams are soft to the touch, look a little like the meringue on a pie, and are very easy to identify.   When prodded, they compress easily and you can poke a finger in without any resistance.   They tend to be white in colour.   They are often found to have been sprayed to the full depth of the rafter, or thicker, and have most recently been sold on the basis of providing thermal insulation qualities.

These foams are supposed to be sprayed on to a separating/dividing sleeve to provide an air gap.   They are often sold with the promise of having a BBA or KIWA certificate.    These certificates are not a warranty or provide any form of guarantee whatsoever and consumers should not be misled into believing otherwise.

In the last year or so, there has been an increase in alternative uses of these foams and we are now seeing them sold for application by robot devices to insulate the underside of suspended timber floors.    This is very concerning within the heritage sector, they will be highly likely to cause severe timber-decay in the floor joists (especially risky are the ends of the joists) and they should not be used under any circumstances.   Consumers should not be fooled by persuasive marketing literature or thermal images which show alleged benefits.



Until further notice, the situation remains worrying and uncertain.

It seems to be the case that, at the time of writing, there are no lifetime/equity mortgage lenders who are willing to offer a loan on property that has foam insulation in place.   These lenders are requiring the foam to be removed before being willing to offer a loan.

For the mainstream mortgage loan, there seems to be a ‘silent policy’ of initially refusing to offer a loan pending an independent inspection by a specialist.   There is no consensus yet as to who the specialist should be, what the scope of an inspection might be and whether the inspection would be protected by Professional Indemnity Insurance.   The experience of some people who have been through this process seems to indicate that there is still a presumption to not loan on the property until the foam is removed.

Consumers are advised to be extremely cautious and to be fully aware that the consequential risks are severe and the potential costs of foam removal are likely to be very high.


Buildings Insurance

We are starting to hear cases of homeowners being refused Buildings Insurance where spray foam has been installed.   All buildings have an element of fire risk and contain combustible materials.   Spray foam adds to those materials and can be especially risky when it has been sprayed over electrical cables.


Update – September 2023

This video by another building surveyor is well worth a look.   It covers all the same points made above..

spray foam video


Update – March 2024

New guidance has been published by the HSE..:

HSE guidance on spray foams on pitched roofs



Disclaimer:   Anything posted in this Blog is for general information only and it is not in any way intended to provide any advice, legal or otherwise, on any general or specific matter that you can rely on.  You should always seek your own legal and surveying advice.