Backstory: we bought a ~130 year old wood-framed house a year ago in MA. The previous owners maybe 10 years ago added a two car garage to the back of the house and a large deck on the roof of the garage.
The issue: in heavy rains we have been having water seeping into the house from the point where the deck attaches to the house. There is a drain under the deck, and the first and second time it was partially blocked, but we made sure it was cleared and it just happened again. Aside from the obvious repairs we now need to make to the room below it (that opens into the garage), we need to figure out the long-term solution to the issue. I think that might involve flashing, more drainage, and definitely will require some demo and reconstruction of the deck where the issue is.
My question is mostly: what type of contractor should we call for something like this? We don't know who did the original install. We also don't have an established relationship with a GC or anyone similar.