A very exposed coastal property was inspected by Colin Cockram last week that had a series of mono-pitched roofs. The roof slopes were measured and were found to have a pitch of around 16 degrees. The tiles were also checked and it is estimated that there was a 100mm headlap. The type of tile was seen to be a Marley Eternit single Roman pantile which are designed to go to pitch of no less than 25 degrees with a 100mm headlap. Therefore these roof pitches are far too shallow.
A common way of overcoming this problem was to lay double felt under the tiles to act as a secondary means of defence against rain penetration. Colin’s internal inspection of the roof voids confirmed that the Hessian reinforced bitumous felt had condensated between the layers causing the bottom layer to rot which has now fallen down within the roof space.It is likely that the roofs will need to be stripped and recovered with a different type of material such as single membrane system. This will be very expensive easily justifying the cost of having a full Building Survey undertaken.
