Spray Foam Insulation – an introduction

Our experienced surveyors at Harrison Clarke are often asked for information on spray foam roof insulation and how it might affect the structural integrity of properties. In this article we look at what spray foam insulation is, why it could pose problems for your building, and the importance of seeking advice from qualified Building Surveyors.

What is spray foam insulation?

Spray foam insulation is a polyurethane foam insulation applied by a spray gun, most commonly to the underside of roof coverings, or between and under the timber rafters. Intended to improve thermal efficiency and reducing energy costs, it is installed relatively quickly and can be an easier way to insulate large or more complex roofing. Insulations can be of a low density ‘open cell type’ or a more rigid ‘closed cell type’, however installing spray foam insulation can have serious consequences for your property in the future.

Is spray foam insulation a problem?

When building owners look to sell a property or raise finance against one, through a mortgage or equity release scheme, it is common practice a surveyor will inspect the roof space and notify the lender or potential purchaser about the present of spray foam insulation.

The presence of spray foam could have a negative impact on the surveyor’s opinion of the properties ‘value’, and they will have to conform to the instructions and policy of their lender clients. This could result in the lender refusing finance or further specialist investigations needing to be commissioned at additional cost which can ultimately affect future saleability.

Why do lenders and surveyors see spray foam insulation as a problem?

Lenders and surveyors may see spray foam insulation as a problem for several reasons.

Spray foam usually conceals most of the structural timbers which form the roof frame, therefore potentially concealing pre-existing structural problems or decay. The timbers cannot be fully assessed to determine their condition or their ability to adequately support the roof covering.

A leaking roof may go unnoticed for a long time due to moisture that may be trapped by the foam which causes unseen decay. In the worst cases, spray foam insulation has been applied directly to the underside of slates and roof tiles which were already in poor condition and significant deterioration has occurred. The cost of replacing the damaged timbers and roof coverings, as well as removing the foam, is significant.

In the event of a fire, combustible polyurethane foams increase the likelihood, as well as the extent, of damage to a property and any adjoining buildings. These foams should not be installed near sources of potential ignition.

Modifying the insulation and ventilation of the roof space is a significant change from the way it was originally designed to perform and can result in unanticipated consequences, particularly from condensation. Our surveyors have found many installations have been inappropriately installed, or they have not been undertaken in accordance with the manufacturers’ recommendations or approved British Board of Agrément certification. This causes or creates significant risk of condensation moisture becoming trapped between the insulation and roofing felt against the timbers and can cause unseen decay. In most cases where insulation has been incorrectly or

inappropriately installed, we find higher moisture content within the roof timbers where they are concealed by foam, increasing the risk of rot damage.

Significant costs can be incurred by removing the foam and if the roofing felt is old and brittle, this could become damaged in the process of removal, leading to more significant roof repairs.

Roofing felts or underlays should drape between the rafters to allow any rainwater which bypasses the tiles to run down behind the tile battens towards the eaves. The foam may push the roofing felt upward against the tile battens allowing moisture to become trapped against the tile battens and may also result in their deterioration.

We will be explaining the risks of condensation in more detail and how the installation of spray foam may not always improve energy efficiency in upcoming blogs, with further blogs looking at how we inspect roofs where insulation has been installed.

I have spray foam insulation installed, what next?

If you are concerned about spray foam insulation installed in your property and the risk of damage or potential future problems, we recommend you speak to a qualified Building Surveyor who will be able to provide you with advice and if necessary, make further inspections.

Please do not hesitate to contact us here at Harrison Clarke on 023 8155 0051, where one of our qualified team of Building Surveyors will be more than happy to assist you. We look forward to hearing from you.

We would welcome the opportunity to help with any queries or needs you may have.

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Paul Badham, associate director and building surveyor at Harrison Clarke chartered surveyors.

About the author

Paul Badham,

BSc (Hons) PGDipSurv MRICS

– Associate Director

Paul joined the team at Harrison Clarke in 2021, having previously worked with Daniells Harrison Chartered Surveyors, Vivid Housing and First Wessex Property Services. Paul first started surveying in 2008, becoming a Chartered Building Surveyor in 2015. 

Paul brings experience from his previous career in shipping, and has a degree in Shipping Operations, as well as a Post Graduate Diploma in Surveying. Paul is an RICS Registered Expert Witness and is experienced in technical due diligence, dilapidations, party wall, and contract administration.

When not beavering away at work, Paul can normally be found renovating his house, running the occasional 10k or spending time away with his family at their caravan.