Sagging felt in garage roof

[yottie]

The garage is a continuation of the bungalows low pitched concrete tiled roof.
We are having damp patches appearing in the plaster after a good downpour. This is only in one section of the plaster-board and seems to be in line with the loft opening in the main building. Thought it might be sagging felt due to the wider space between the joists along that line ? As there is no loft space in the garage roof I thought I might cut a hatch(s) in the plasterboard above the leak with a view to sliding in an additional support for the felt (and also to find out if this is the problem) ???

Many thanks for any advice

 

[Burnerman]

Sagging felt often means destruction of the timber beneath the felt due to leaks over a period of time, unfortunately - especially if chipboard has been used.
Certainly it would be a good move to remove the ceiling beneath, to expose any potential nasties!
John

 

[yottie]

Thanks, I should have mentioned that the whole roof, including the garage has been re-felted and the tiles replaced about 3 years ago and the wood was OK then. There are 3 properties with similar roofs, the original problem seems to have been an insufficient tile over-lap, needed for the very low pitch on this side of the roofs. We get some strong winds which seem to blow the rain upwards at times !
I have been in the loft and all seems OK there.

 

[Burnerman]

You couldn't post a pic for us, could you?
John