Spray polyurethane foam (SPF) is often applied to a sloping roof in poor condition, as a quick fix, or as a quick alternative method of improving insulation. It appears to be becoming increasingly popular, and unfortunately it may become more prevalent with the Government’s Green Homes Grant, supplying up to £5,000 of vouchers towards insulation improvements. Whilst contractors may push the benefits of spray foam, lenders will often insist that surveyors take a different view. Surveyors and valuers will often have to discount the value a property or request a specialist report, because it has SPF insulation. It may even make a property unmortgageable in the eyes of a lender.
SPF is more expensive than traditional types of insulation. It is applied as a liquid foam that is lightweight and hardens in situ. It is normally sprayed on to the underside of the roof approximately 100mm in thickness and the installation may emit lingering toxic fumes. SPF is unsightly and cannot be decorated over. It does have the advantage that, as spray foam insulation it is a better insulator than mineral wool (100mm of spray foam insulation is equivalent to around 170mm of traditional loft insulation). A thinner layer of SPF is required to get the same insulating effect. As it is applied to the roof slope, it also facilitates the installation of floorboarding in the loft.
SPF comes in two forms: closed cell and open cell. Closed cell dries rigid and is firm when pressed. It does not allow moisture to pass through it. Open cell is spongey when pressed and is not as good an insulator. It is a good sound absorber and does allow water vapour to pass through.
SPF might be mis-sold as a long-term energy saving investment, lasting for more than 80 years, which will stop tiles and slates from slipping and will strengthen the roof by holding them in place. An installer may also advise that it not only increases the insulation and may lower energy bills by up to 20%, but will also protect water tanks and pipes from freezing and create a dry, clean and useful loft space. Such claims are all very debatable.
The main problem with SPF is that it can lead to severe condensation in the roof space by blocking ventilation. Whilst this is reduced with the open cell “breathable” type, condensation can still occur where the foam and roof covering material meet. The resultant moisture can then lead to rot in roof timbers. Both types can also conceal defects in the roof covering that can result in water penetration – again leading to rot in roof timbers.
If dampness is found in a roof, professional advice should be sought from a chartered surveyor as to whether it is penetrating or a condensation issue.
Spray foam should never be used on an older building. These commonly have stone flag, slate or hand-made clay tile roofs. A percentage of the flags, slates and tiles can often be reused when these older roofs are re-covered but not if spray foam has been applied as a quick fix. There is no substitute for having a roofing contractor properly repair or re-cover an aged period roof.
As ever, lender guidance for surveyors on sprayed roof coverings varies from reflecting the potential cost of renewal of the roof covering in the valuation, through to requesting a report from a structural engineer or reputable roofing contractor, to declining the property. Valuers should consult the latest guidance notes for the specific lender if they come across a sprayed roof when carrying out a mortgage valuation.
Similar considerations apply if a roof has been sealed externally e.g. by applying a fibreglass coating or by “turnerising” (covering with a mesh and coating the roof with bitumen).
Some mainstream lenders, even now, have yet to state a policy and remain silent on the issue, leaving it up to the valuer to decide what to do. This may mean withholding a valuation and calling for specialist reports and quotations if there appear to be problems with the roof or simply reflecting the future need for re-covering of the roof in the valuation. This is best achieved by including a minus adjustment representing the cost in the comparable matrix.
In any event, it is always wise to take a photograph of the sprayed foam, whilst in the roof space, for the site note records.