There are 3 houses by Bachmann from their Plasticville line (O-scale model train buildings). These are pretty good for 28mm. One is a house under construction, and the other two are pretty much identical houses. They all have removable roofs.
You can see from the model in the last 2 pics that the doors might be a tad big for true 28mms, but it doesn't look bad.
I also finished another log cabin, also from Bachmann Plasticville. You can see from the comparison shot with the Pegasus cabin the difference between the O-scale and 1/72 scale... they look a little silly next to each other on the same board, but each can work with 28mm on their own.