im not entirely sure about the wall behind/under the deck because it looks like the siding may have been cut out when the joict plate was installed for the deck. Why they went so high is beyond me. Another weird thing is the piece of "L channel" that's installed on the top of the deck. This I think confirms my thinking that they cut the siding away when built the deck. I've attached a few more pics for you to see these areas I'm talking about. First pic is from my initial inspection report so nevermind the red arrow I'm just trying to show how high the deck sits above the siding. Second and third pics show the L channel along the top side of deck and last pic shows in bottom right the foundation concrete to help get an idea of where things are at. And lastly, to answer your other question about the basement, the basement is fully finished ceiling and walls. I pulled the carpet up down there and there's no sign of water seepage, yet.