Posted on 4th August, 2025

Spray Foam Loft Insulation

Should I get spray foam insulation installed in my roof?

If you are about to have spray foam installed in your roof space – STOP!

Most importantly, many mortgage lenders will refuse to lend on a property that has spray foam insulation in the roof. Whilst this may not matter to you right now, when it comes time to sell the property, your buyer may not be able to secure a mortgage on your property at that time.  There are also more cost effective and safer ways to insulate your roof space.

There are very few residential properties where spray foam insulation can safely be installed.  These buildings would have been specially designed for spray foam and it would likely have been installed at the time of their construction.

So, if your roof wasn’t originally built with spray foam insulation installed then getting it put in now will likely be a waste of money and could cause costly damage to your roof. In extreme circumstances this could mean that you need to strip off the roof coverings completely and maybe even replace the roof structure.

Cold roofs

Most residential properties in the UK are designed to have “cold roofs”. That means that any insulation is installed on top of the ceiling below to keep the building warm and the roof space cold.

Properties that still have their with original roofs dating from the 1920s or before may have no roof lining at all and simply rely on the slates or tiles to keep water out of the roof structure.

Roofs built or recovered after 1930 will most likely have some kind of roof lining, usually either sarking felt, building paper, close boarding or, more recently, a modern “semi-permeable” membrane. This lining stops any water that gets under the roof tiles or slates from entering the building and directs it down towards the guttering.

It is normal for the roof space to be ventilated to make sure that it is draughty and stays at ambient temperature which both help to keep the roof timbers dry.

The best way to improve the insulation for the habitable accommodation is to increase the depth of the fibreglass loft insulation to that recommended by modern Building Regulations. At the time of writing this article that is 270mm or about 11 inches.  This is a relatively cheap option and provides the best return on your investment.

If you want loft storage, then any boarding can be laid on top of “loft stilts” which provide the extra space for the insulation below them.

What if I’ve already had spray foam insulation installed?

Firstly – don’t panic

Whilst it is likely that the spray foam needs to be removed, unless the roof tiles or slates are in bad condition then it is quite unlikely for it to be causing significant damage to the building right now. However, the longer the foam is in place, the more likely it is for wet-rot decay or other such issues to become serious.

You should note that there are two types of spray foam used for insulation, so called “closed cell” and “open cell”.  Closed cell spray foam does not allow the roof to breathe at all and could pose a significant and more immediate risk.  The open cell variety does allow for some water vapour permeability but it is much less than would typically be required for a standard timber loft structure in the UK and will most likely need to be removed.

Next – beware

It is probably not a good idea to engage the services of any company that knocks on your door or “cold calls” you. Whilst we are sure that there are proper professional companies out there offering to do a good job for a reasonable price, anecdotal evidence indicates that there are a number of very unscrupulous companies offering spray foam removal services. We have heard of several companies based in the South of England either knocking on doors or making unsolicited telephone calls recommending so-called “eco-friendly” solutions for the removal of spray foam.

Often these companies look very professional, with glossy brochures and online advertising that makes them look suitably qualified for the job, but these can be very misleading. On checking, some of these companies have only been in operation for just a few months and sometimes have terrible online reviews. We discovered that some companies get such a bad reputation that they are closed down only to reopen under a different name.

Unfortunately, from what we have seen, the workmanship of some specialist spray foam removal companies has left much to be desired and in one recent case we have dealt with has resulted in the need for a whole new roof to be installed.

Finally – what to do…

Getting spray foam removed is often more time consuming than having it installed. It makes a lot of mess which will need to be properly cleared away.  The waste foam takes up a surprising amount of space and the contractor may well need a waste disposal license.

Typically the spray foam will be stuck to either the back side of the roof slates/ tiles or to the underlining.  If appropriate care is taken then you may find that any lining will be left relatively intact.  However, if the original underlining was in poor condition before the spray foam was applied then you may find that no matter how careful the contractor is then damage will be inevitable.

Getting the job done properly by a careful contractor who knows what they are doing is unlikely to be “cheap”. But, given what we have seen so far, getting the spray foam removal work done to a professional standard now may very well save you money in the long run.  Unfortunately, if the roof lining is severely damaged, the only real solution is to strip the existing roof coverings back to the structure, install a new roof lining and then replace the slates or tiles.

We would recommend that you employ a long-standing, well-known, locally based roofing contractor to carry out any works. Perhaps speak to your friends, family and neighbours first before employing someone.  There are also some online directories, such as Checkatrade; however, there is no cast-iron guarantee of excellence for contractors who list themselves on such websites.

Don’t rely on a single quote; arrange for two or three competitive quotes to see which is the most comprehensive. Be sure that you request detailed quotes from the contractors that fully specify the works to be done.

Once you have decided upon a contractor, we would also recommend that you agree a series of staged payments for the work, for example, a small initial deposit, twenty-five percent when they commence the work, and the balance once you have had the quality of workmanship thoroughly checked.  In some circumstances it may be necessary to ask the contractor to return to complete any missed spray foam.

You may have questions about your own roof and if so then please do not hesitate to contact us.