Spray foam insulation has become increasingly common in UK homes, particularly where homeowners have been looking for ways to improve energy efficiency and reduce heating costs.
However, when spray foam has been applied to the underside of a roof covering, it can create issues that many homeowners are unaware of until they come to sell or remortgage their property.
For surveyors and mortgage lenders, the concern is not simply that spray foam is present. The difficulty is establishing what is happening to the roof structure behind it.
In some cases, the roof timbers, battens and underside of the roof covering can be partially or completely concealed. This can make it difficult for a surveyor to assess the condition of the roof and determine whether moisture, deterioration or timber decay is developing behind the insulation.
As a Regulated by RICS surveying practice, we regularly encounter properties where spray foam insulation has been installed within the roof space. Here is what homeowners and buyers need to understand.
The image below, was taken during one of our inspections.
What is spray foam insulation?
Spray polyurethane foam, usually referred to simply as spray foam insulation, is applied as a liquid before expanding and hardening to create an insulating layer.
Within roof spaces it is commonly sprayed between or over the rafters, usually immediately beneath the roof underlay, tiles or slates.
There are different types of spray foam, including open-cell and closed-cell products, and the characteristics of the individual product and the way it has been installed are important.
Spray foam itself should therefore not automatically be considered a defect.
The problem is that applying it to an existing roof fundamentally changes the way the roof was originally designed to perform.
RICS advises that most traditional pitched roofs were designed as ventilated “cold roofs”. Applying insulation at rafter level can effectively change the thermal and moisture behaviour of that roof, meaning ventilation, vapour control and condensation risk all need to be properly considered.
Why are surveyors concerned about spray foam?
One of the most important parts of a surveyor’s inspection of a roof space is examining the structural roof timbers.
We are looking for issues including:
- evidence of water penetration;
- dampness and condensation;
- fungal decay or timber rot;
- wood-boring insect attack;
- distortion or movement of the roof structure;
- defective or damaged rafters;
- deterioration of roofing battens; and
- evidence that the roof covering is approaching the end of its useful life.
Where spray foam covers the timbers, these areas may simply not be visible.
A surveyor cannot reasonably confirm the condition of something they cannot inspect.
This uncertainty is one of the main reasons spray foam can become problematic during a property purchase or mortgage valuation.
RICS specifically warns that some spray foam installations can restrict inspection of the roof structure and can potentially hide roof leaks or developing timber decay.
Evidence of deterioration to the roof timbers, surrounded by spray foam insulation. And an image of the roof timbers completely concealed by spray foam.
Damp, condensation and timber decay
Moisture is one of the biggest concerns.
Traditional roof spaces generally rely upon an appropriate combination of insulation, ventilation and vapour control to manage moisture.
If spray foam is incorrectly specified or installed, it may affect that balance.
Warm, moisture-laden air from the accommodation below can enter a roof space. Unless the roof construction has been properly designed to deal with that moisture, condensation can occur.
Problems may be particularly difficult to identify where moisture is trapped behind or adjacent to spray foam.
If roof timbers remain persistently damp, there is a risk of fungal decay developing. In serious cases, structural repairs may eventually be required.
That does not mean every roof containing spray foam will suffer from timber decay. A properly designed and installed system may perform satisfactorily.
The difficulty for a surveyor or mortgage valuer is establishing whether the installation was properly designed in the first place and whether the concealed areas of the roof remain sound.
The image below shows evidence that spray foam was installed and has subsequently been removed as there is still the remains of foam to the underside of the underlining and the timber roof structure.
The below image shows a roof timber with woodworm, surrounded by spray foam insulation.
Spray foam can hide roof leaks
Another concern is water penetration.
With a conventional roof space, evidence of a leaking tile, defective flashing or damaged roof covering may become visible internally through staining, dampness or deterioration of the roof timbers.
Where foam has been applied beneath the roof covering, some defects can be more difficult to detect.
Water may potentially penetrate the covering and affect concealed timbers before obvious evidence becomes visible within the roof space.
This is particularly important with an older roof where the tiles, slates, underlay or battens may already have been approaching the end of their normal serviceable life before the insulation was installed.
Spray foam should never be regarded as a substitute for repairing a defective roof covering.
Can spray foam make a property unmortgageable?
This is probably the question we are asked most often.
The answer is:not necessarily – but it can make obtaining a mortgage more difficult.
Mortgage lenders have their own individual lending criteria.
Some lenders will consider properties containing spray foam insulation, subject to their valuer’s comments and satisfactory supporting information. Others apply considerably more restrictive requirements.
For example, NatWest currently states that properties with spray foam insulation can be considered on their individual merits, subject to the valuer’s comments.
Nationwide’s published criteria take a different approach. Where spray foam is present within the rafters, frame or underfloor, its valuer initially declines the property. Nationwide may reconsider where specified supporting documentation is available or, in certain circumstances, following an invasive inspection by an MRICS or FRICS Chartered Building Surveyor.
This demonstrates why it is misleading to say that a house with spray foam is automatically unmortgageable.
It isn’t.
But its presence can reduce the number of lenders willing to consider the property and can result in additional reports, investigations and costs before a mortgage offer is made.
Lending criteria also change, so homeowners should always check the current requirements of their proposed lender.
Why can spray foam affect the value of a property?
Market value is influenced not only by the physical condition of a property, but also by its saleability and mortgageability.
If potential purchasers have difficulty obtaining mortgage finance, the pool of available buyers may become smaller.
A purchaser may also factor into their offer the cost and uncertainty associated with investigating or removing the insulation and potentially repairing the roof afterwards.
This does not mean that spray foam automatically reduces a property’s value by a particular percentage.
Each property needs to be considered individually.
RICS guidance confirms that the presence of spray foam can be a factor affecting a surveyor’s professional opinion of value and that further specialist investigation may be required.
What paperwork should be available?
Documentation is extremely important.
Where spray foam has been professionally installed, homeowners should retain as much information as possible, including:
- the original installation contract;
- details of the exact product used;
- the manufacturer’s installation requirements;
- a pre-installation roof survey;
- evidence that the roof was suitable for the system;
- condensation risk calculations;
- details of ventilation and vapour-control measures;
- BBA, Kiwa or other relevant certification;
- installation photographs;
- guarantees or warranties; and
- confirmation of whether any guarantee is transferable to a future owner.
RICS recommends retaining relevant design, installation and certification documentation because it can assist with enquiries from surveyors, lenders and solicitors when the property is eventually sold.
A certificate simply confirming that spray foam was installed is not necessarily sufficient.
The important question is whether theparticular product was suitable for the particular roof and was installed correctly.
I’m buying a house with spray foam insulation – what should I do?
Don’t automatically walk away from the property, but don’t ignore it either.
If spray foam is identified during a RICS Home Survey or Building Survey, further investigation may be recommended.
Before committing to the purchase, you should establish exactly what has been installed and obtain all available supporting documentation from the seller.
You should also speak to your mortgage lender or broker as early as possible. There is little benefit in proceeding towards exchange of contracts only to discover later that your proposed lender will not accept the property without further investigation.
Depending upon the circumstances, an independent inspection of the roof may also be appropriate.
Most importantly, the person advising on the condition of the roof should be independent of anyone financially benefiting from selling either spray foam installation or removal services.
I already have spray foam – should I have it removed?
Not automatically.
Discovering spray foam in your roof doesnot mean that it must immediately be removed.
RICS recommends obtaining independent professional advice and understanding the particular installation rather than assuming that removal is always necessary.
Removal itself is not necessarily straightforward.
Foam can adhere strongly to roof timbers, membranes, battens and other components. Poorly executed removal can damage the roof structure or underlay.
It is also important to be cautious about companies offering removal following an unsolicited telephone call or claiming that removing the foam will automatically restore the property’s mortgageability.
Removal may form part of the solution, but the condition of the underlying roof still needs to be established.
If decay or damage has occurred, simply removing the insulation will not repair it.
The below image showing the formally installed spray foam has been removed, revealing that there is also no breathable or bitumen waterproof membrane to the back of the roof tiles.
What happens after spray foam has been removed?
This is another area where homeowners can encounter difficulties.
Following removal, a surveyor may be asked to inspect the exposed roof structure.
The purpose of this inspection is normally to establish, as far as reasonably possible, whether the accessible timbers show evidence of excessive moisture, decay, damage or other significant defects.
However, even following removal, areas of foam may remain attached to timbers and other components. Damage caused during removal may also need to be distinguished from defects that existed beforehand.
For this reason, homeowners considering removal should obtain advicebefore the work starts wherever possible.
Photographic records should also be retained throughout the removal process.
What if you are thinking about having spray foam installed?
Our advice would be to obtain independent professional advice first.
Do not rely solely upon the company selling the insulation to determine whether it is appropriate for your property.
The entire roof construction needs to be considered, including its age, condition, roof covering, underlay, existing insulation, ventilation and moisture characteristics.
For a conventional loft that is not being used as habitable accommodation, improving insulation at ceiling level may often be a simpler option. RICS notes that increasing conventional mineral wool insulation at ceiling level can be considerably cheaper and leaves the roof structure easier to inspect and maintain.
You should also speak to your mortgage lender and buildings insurer before proceeding.
Spray foam and listed buildings
Particular care is required with listed buildings and other protected properties.
RICS states that spray foam insulation should not be installed in a listed or protected building without obtaining the necessary consent beforehand. Because spray foam can be difficult to reverse without damaging the underlying historic fabric, its use can be particularly problematic in traditional buildings.
Specialist conservation advice should therefore be obtained before carrying out this type of work.
The important point
Spray foam insulation is not automatically a disaster, nor does its presence automatically mean that a house cannot be sold or mortgaged.
But it is a significant alteration to a roof, and it should not be treated in the same way as simply adding another layer of conventional loft insulation.
The main concerns are straightforward:
Can the roof structure still be properly inspected?
Was the system correctly designed and installed?
Has moisture been adequately controlled?
Are the roof timbers dry and structurally sound?
Will a mortgage lender accept the property?
Until those questions can be answered, there can be uncertainty for buyers, homeowners, surveyors and lenders.
Buying or selling a property with spray foam insulation?
If you are purchasing a property where spray foam has been identified within the roof, or you own a property and are concerned about how an existing installation could affect its sale or mortgageability, obtaining independent advice at an early stage can help establish the appropriate next steps.
As aRegulated by RICS surveying practice, our surveyors provide independent property advice and can identify where spray foam or other roof alterations require further investigation.
A RICS Level 2 or Level 3 Survey can help you understand the condition of the property before you commit to a purchase and highlight matters that should be investigated further before exchange of contracts.
Below is an image of spray foam to the inside of the roof structure.
