I definately agree with carpdad! I would be seriously looking at experience, and most importantly one who will correct the problem the right way. Get at least three estimates, and details of the work, such as type of wood they plan on using, flashing, ect. Let us know what you find out. From ones I have done in the past, it always seems improper flashing is the culprit! I would be interested in knowing if this problem of yours exists by a deck? Ive posted some pictures of a recent one.