The one negative with a single story is the need to be quiet when young children are sleeping. We have to wait at least an hour after my 5 and 6 year old are a sleep before watching a DVD with speaker/surround sound. Also another negative is difficulty having small parties with young children sleeping such as hosting a poker night with the guys from work. In in our old place we had a two story and noise wasn’t much of an issue. On the other hand, a one story is easier to maintain and clean. You mentioned that you have a 15 year old, so the evening noise issue may not apply. The one thing I would consider with a single story is the placement of the master to the secondary bedrooms – ours is just too close and, well, as you might imagine, late night noise issues must be considered. (if you know what I mean…)
