Hi there.
My house was finished in December 2017. The roof has breathable felt and originally no ventilation as it's not obligatory with the breathable felt (according to NHBC). The roof was very, very wet for about 5 months, like sodden, until the warmer weather came and it has now dried out. Ventilation has been added to prevent it reoccuring this winter.
Although it is now dry, dry mould and mildew remains in the roof on the wood, some nail heads are rusty and the loft steps have mildew on them, which go into my daughter's room when we pull down the ladder.
The builder says that as it's now dry I don't need to worry about the dry mould remaining. I would like it treated (as he originally said he would do). It looks older than it's 9 months! Do I need to worry about this or should I just forget it and be happy now it's dry. What would you do? Thank you for reading and helping x