COMMON DEFECTS IN ROOFSfrom RICS home surveys
It’s very rare to find that complete re-roofing is needed (except flat roofs). However, some relatively straightforward repairs that involve working at height can still be costly to fix if scaffolding is needed. On the other hand, smaller jobs may be accessible with scaffold towers which are comparatively cheap to hire at around £150 for a week.
Things to check
Probably the simplest check involves nothing more than taking a look at the other roofs in the street to see if any have been re-clad. This can provide a useful indicator as to whether the original tiles are nearing the end of their useful life. The need for re-cladding would not normally be expected on most houses built in the last 75 years or so.
Defective flashings and valleys
The most common defects are found at junctions with stacks, parapet walls and dormers windows etc. Look for any gaps or cracks to flashings. Valleys where roof slopes meet are another vulnerable area with a tendency over time to become blocked with moss and debris. Any resulting leaks and damp patches can often be seen in lofts, as well in the rooms below on ceilings, walls and chimney breasts. Lead flashings are normally very durable but sometimes come loose and need re-fixing. Watch out for cheap mortar fillets which are very prone to cracking or botched repairs with short-life DIY tapes.
Slipped or Missing Tiles
The odd slipped tile isn’t usually a problem. But where you can see larger numbers of missing or damaged tiles (typically about 8 or more per slope) the roof is likely to be nearing the end of its life and will need stripping and re-covering. Unlike tiles, the most common cause of slates slipping is rusted fixing nails. The standard method for securing the occasional loose slate is with small metal clips called ‘tingles’. But avoid properties where there are more than about 4 or 5 clips evident per roof slope as the problem is likely to be more widespread.
Sagging Roof Slopes
Slight settlement in roofs is not usually a problem. A certain amount of ‘dipping’ is fairly common particularly where the rafters have settled next to end gables or party walls. More serious sagging may be due to original lightweight Victorian slate roofs having been re-clad with heavier modern concrete tiles without first strengthening the roof timbers. It may also be due to ‘roof spread’ where rafters have pushed the wall outwards and sunk in the middle. In severe cases remedial structural work may be needed (which will require Building Regulations consent) and a structural engineer should be consulted.
Deleterious roof coverings
Asbestos-based roof tiles or artificial slates are not at all common. The former typically take the form of large dark pink coloured tiles laid in a diamond pattern, notably on some inter-war bungalows. The latter were used during the 1970s and ‘80s for new roofs as well as for re-cladding. The cost of removal can be significant so such properties are best avoided. Also, it goes without saying that any roof clad externally in cheap shed roofing felt, or painted over with thick sealant, should be avoided.
N.B. This is by no means an exhaustive list, and much depends on the age and type of property you’re surveying