DIY Doctor UK DIY Forums

Hello folks, just wondering if anyone would have any ideas what might be causing these streaks of water in the corner of a bedroom? There has always been an issue with some mould and damp in this corner but never anything like this. The past few weeks, these streaks of water have been appearing. There is no plumbing above it. I thought maybe a leak in the roof but it hasn't actually rained for a few days and it's still happening. Anybody any ideas? Thanks in advance to anyone who has a look.

Hi eagleson12,
If there is a loft above this area it's most likely that there is no loft insulation in the corner above the damp patch. It's probably worth checking that there is loft ventilation in place.
Regards S

Hi, thanks for the reply. I've been up and checked and there is insulation above it. I have since had a roofer out to check it and he has said that it is because of the roofing felt that was used. He said it is the same stuff a brick layer would use and has since been banned for use in rooves. His solution is to put vents in the roof at a cost of £400. Does this sound plausible and if it is the case that the felt is banned, would you have any idea when from? The house was built in 2009, thanks.

Hi eagleson12,
If you have bitumen/hessian type underslaters felt your roof should be ventilated. If it is not, condensation may form on the underside of the felt and it may be running down to the corner where you have damp.
I am not aware that this type of felt is banned but a breathable felt is generally used to reduce the need for cross ventilation.
The least disruptive way of installing cross ventilation is to fit high and low level tile vents.
It is not possible to say whether to do this for £400 without details of what is proposed.
Regards S