A good tool would be something similar to the paint tool, that could apply a finish with a thickness, we are asked to produce a model of our works only (Building Envelope Contractor). If we are creating something like a hot melt polymeric bitumen roof it is very difficult to model as we are not responsible for the underlying concrete deck. We can model the flat portion of the roof with the roof tool as we can create a composite roof type for the main roof area, however, when it comes to the upstands etc, modelling the hotmelt up and over these becomes a pain. I know we could just paint the faces but this doesn't then allow for the thickness of the system (10mm), that can affect other items such as cappings, clearances to BMU tracks. I suppose it is the difference between BIM of Architect and BIM for detailed construction & contractor design.