macfrog,

Looking again at your nice house, I see an opportunity to improve your roofs. Currently you are using the standard roof model available in red and blue: a very inefficient model because it's covered in some kind of tiles. They add a lot of detail, but aren't visible. And when you add a texture to your roof, rendering them is a nightmare.

Maybe you'd want to have a look at my latest tutorial on sloping ceilings and roofs. Chapter 3 (page 8) describes an alternative method to make roofs, that may be very well suited for your design. The resulting model is much lighter than your current roof parts, and can be easily customised with different textures on both sides,

Good luck,

Hans