If you're wanting to use UDK then modular is a good idea. Not only because it's "the Unreal way" but because you're going to, er, hit a wall when it comes to collision. Unreal handles collision in a few ways. If you build using BSP then collision is handled automatically. Your model at the moment is so simple that you…
The architecture is basically the single most important thing when deciding how you break it up. If you've got columns in there supporting the roof, they're probably separate meshes. If you only have one column and the rest of the house is simple, the column could be part of the same mesh. But if it's really detailed then…