Roof

 From:  SteveMacc (STEVEH)
4807.5 
If you use a polygon modeller for this, like Modo, you could use replicators, which are place holders until actual rendering. This make the model very light. I have created renders with several million polygons using this method (1 billion was the most I managed).

If you do this in nurbs, like Michael says, you really need distinct objects.