Hmmm think you should get some advice from a few contractors see what they say. So you can compare responses. Just want to be careful when you seal stuff up. A lot of times it's just masking the problem on the surface. I once had a leaky pipe concealed running from my attic that I didn't know about - it was a problem for A FEW YEARS no kidding. Until I got a guy to really do a thorough check only I managed to spot and fix it. Same thing - the earlier contractor just sealed the leaking area but didn't trace where the real problem was