Even though I play Command Combat: Civil War in 15 mm, I've often been using 10 mm buildings by the company Buildings in Turmoil. The reason is two-fold. First, 15 mm buildings are sometimes too large. Even though they're supposed to be appropriately scaled to 15 mm figures, the fact is that each figure isn't supposed to be representing 1 person; it represents dozens or even hundreds, so it's actually more appropriate to go one scale down for the buildings.
I met John from Buildings in Turmoil at Historicon, and he let me sell my rules at his table. I was putting on Gettysburg that day, and was short an important house, the Bryan house, which was essentially the goal of Pickett's charge. His buildings are all based on real buildings from the battle fields, (he lives at Gettysburg,) so I asked him to paint one up, and his son Jeff had it to me the next morning. They're a great group of sculptors and painters, and I highly recommend them.