#1, because I feel sure there’ll be more 🙂
It’s been raining a fair bit recently and when I went into the observatory the other day I discovered a puddle of water on the floor halfway along one of the side walls. There’s no way water can get in there, so tracking it back I discovered that rain is pooling in the gap between the roof rail and the side of the warm room roof and running or being blown down the side of the rail until it reaches sufficient volume that it runs down the wall.
For the moment I’ve blocked that gap with a bit of membrane and that’s helped, but I need a better solution. I know someone else has fixed the same issue by making a small “wall” of off-cuts of EPDM to fill that gap. That may be the simplest way forward for me too, but I think I shall also remove the rails that are alongside the warm room roof and bridge the gap underneath with some silicone sealant, to stop water running down the inside of the rail. I might also remove each of the screws holding the rails down and put some more sealant into the holes. Hopefully that will be sufficient to stop water running in from anywhere.