On the side of my house, a damp patch in the form of a vertical line from the roof to the ground has appeared. It doesn't seem to dry out just got bigger over the past few days as we have had heavy rainfall, although the rest of the wall is dry. I don't know where it's come from as there is no overflow pipe near this damp patch and the guttering above doesn't appear to be leaking? There is a tall tree nearby, would this have anything to do with it? Could leaves have blocked a section of the guttering causing water to spill over? I don't know? Please help?