We recently bought and moved in to a house. It's 16 years old. One of our walls has developed a patch of wetness. This wall is part of what was once the garage, and has since been converted into a dining room.
The wet patch is shaped like a sand timer, and is at eye level (so not near the ceiling or at ground level). I don't think there are pipes behind it.
What could this be? And how do I go about fixing it if there's a problem?