Sorry for the delay in replying.
I have attached a picture of the mark caused by the leak.
I know it is quite faint but I want to prevent it getting any worse.
Thanks for everyone's help.
The NHBC Report does mention a glass reinforced plastic valley gutter. This is damp and mildewy.
How much condensation would there need to be to create enough liquid to stain the ceiling, please? And why would the stain suddenly appear rather than gradually build up, please? And at a...
At the beginning of November I noticed a mark on the ceiling. Suspecting a leak, I got a roofer in to trace the source. He confirmed that the valley was defective and would need replacing. As the house was under 10 years old, I lodged a claim with the NHBC. The inspector from the NHBC said the...