lapVent: View Message

Author

Date

13:38 28/01/2010

Title

Cornish Roof

I have an old cottage which was re-roofed after the hurricane in 1987. The builder used non permeable plastic underfelt with 2 plastic straight through vents there does not appear to be any soffit type ventilation. Since insulating the loft space with 300mm of insulation I have noticeed a great deal of condensation running down the underfelt and dripping onto the loft floor.The roof, which is about 10m long, is constructed using 50 x 50mm battens spaced at 150mm centres as rafters. There are two large, approx 300x50, intermediate rafters which take the purlins on which the smaller rafters bear. Outside there are asbestos slates, end fixed, which are on 50X25 battens. Is this type of roof suitable for LapVents and if so how many would I need?