As part of our home's remodel we are putting solid wood maple flooring in several rooms. The first two rooms went well. But in the living/dining area, there was a problem. Upon pulling-up the carpet we noticed that about halfway out from the exterior wall, the subfloor starts to slope down. It drops about one-half inch over a distance of about eight feet before meeting the interior wall. (I'm attributing this to foundation settling. After moving into the house last year we did hire some work to address settling.) When installed, the 2 1/4 inch maple planks will go at a right angle to the floor joists for support, which will have them running parallel with the floor's change in angle. My concern is that as the floor undergoes natural expansion and contraction, the planks will develop a ridge or peak where the two different planes of floor meet.. Assuming that is a legitimate concern, what are my options? I would prefer to not pull-up the subfloor and plane or in some other way level the joists. That's a bit more than I want to tackle. But is there any way to build-up part of the subfloor to create a flatter surface? A contractor suggested I use some uncoupling membrane, such as is used for ceramic tile, to bring the floor into a flatter plane. But I'm a bit skeptical of that approach. Suggestions?