I checked about the exports. They work fine as long as the modifier stack is collapsed before exporting. Anyway, this is the way I do things (probably not the way anybody else does them): The top render is the base model. Everything is neat and clean, CG perfect. It is 272 quad. polygons and took 27 seconds to render (because I used a skylight and Final Gathering.) I could make it as low as 11 polygons, but there is no way then to deform it. The bottom render is after some modifiers were added. It is 1086 quad. polygons and took 40 seconds to render.

Quote - ...the only way to do this in this case is when somebody draws 3 or 4 houses at the same time as a unit and takes care that the ends are straight and square so that an other builder knows where to start...

I think one modeller could send the end bits on to the next modeller and that would enough to give the second modeller a starting point and be able to match up the ends. I Also think it would not be a good idea to model any 'hidden' sides, just wasted polys; unless the buildings where going to be stand-alones that could be used individually.

Friends don't let friends use booleans.