21/03/2026
Properties have benefitted from both a primary (tiles/slate/stone slate/roof sheets) and a secondary (felt/breathable membrane/Monarflex-plastic) covering to repel weather for a number of decades now, with felt secondary coverings starting to appear in the 1930/ 40s. It's with this in mind that I decided that I would highlight issues with roof coverings.
This week has included inspections of properties having issues with secondary roof coverings, varying from some which are not vapour permeable at all and are well known for issues with condensation causing damage, whereas others are just not fitted correctly. This got me thinking about why the secondary coverings can be as important as the primary coverings. The primary covering provides the protection in most cases and providing that the covering is intact and in good order this will prevent leaks occurring. When failures or damage occurs then this means that the condition of the secondary covering will mean whether you suffer a leak or not.
Issues affecting secondary coverings can arise because they fail- felt sagging and tearing due to hot roof voids each passing summer, felt is also not air permeable and won't allow air to pass through the material and allow ventilation to occur. Monarflex can sweat when condensation reaches the void which can then raise moisture levels in timbers which lead to fungal decay or insect attack damaging the timbers, plus the material does not allow the passage of air which can reduce moisture levels. Then you have modern breathable membranes some of which are not as effective as people think and suffer from a lack of ventilation and mould growth, usually not helped by extraction fans not being used in bathrooms etc, but also as cheaper membranes are not as effective. Then there is also the issue of the membranes not being fitted correctly by the roofing contractor. A membrane needs to be provided with a drape (slight sag of about 8-10mm and not tautly fitted) between each rafter or truss section so that any rainwater that does manage to bypass the primary covering runs down into the gutters. When a drape is not provided then the rain can track across causing the rain to seep underneath the secondary covering and cause rot to the top of the timber truss or rafter. Whilst this might not cause an immediate issue it can show that a lack of best working practise has been employed when the roof coverings were fitted which could indicate of further issues being present.
This can results in issues arising between the surveyor and estate agent marketing the property as the roof space and roof covering is not always looked at, and when the news reaches the agent and vendor that a repair or new roof covering is then required this can come as a surprise, and not a particularly welcome one at that. It really won't matter if all the internal spaces within the property have been freshly decorated, a new bathroom and kitchen fitted, if the primary and secondary roof covering is found to be defective which will likely lead to leakage which then damages said decorations and fittings. Therefore, if you want to know what the condition of the roof of your prospective property purchase is, what issues are present and what needs to be done about them, an approximate idea on whether the roof is approaching the end of its serviceable life, and also whether this is something you should raise with the agent and vendor and please do get in touch and we will be happy to inspect the roof space and roof coverings on your behalf.
Please do contact
https://howesurveyorsltd.co.uk/
