The hardscape tool is very comprehensive, but only creates level surfaces - i.e. a zero "slope".
In the real world, hardscapes always have a slope to allow for surface drainage of rain water, etc. If hardscape is modelled without a slope, it can impact on the validity of the model where the hardscape joins other parts of a landscape design - for example:
"A patio / terrace adjoins a house. The patio extends 5 metres out from the house to a retaining wall with steps down to a lower level terrace / lawn. The patio has a fall of 1:75 from the house to the retaining wall edge, which means it's "Z" value drops by 67mm from the house edge to the retaining wall edge.
Not very much, but enough to make construction detail drawings wrong for the retaining wall and steps - unless the lower "Z" value is used for the hardscape - which then makes door thresholds / steps into the house wrong."
I've been using "roof face" as a work-around (suggested by Tamsin Slatter) instead of "hardscape", so that I can give a correct "Z" value and specify the slope I want - but this means I don't have all the hardscape's border / jointing options, and it doesn't give me area sizes, etc. as does a hardscape item.
Another alternative (suggested by Jonathon Pickup) is to create a site-modifier sloping pad at the required finished surface level, and cloak it with a texture bed. This too works for giving a correct 3D view, but doesn't allow the surface material to have a thickness (so construction sections have to be manually edited) and still lacks the hardscape's border / jointing options. It also impacts on doing true site work in my DTM to get the correct pad for the patio foundation, etc.
What I'd like is a "slope" specification in the create hardscape tool, preferably one which operates in much the same way as the sloping pad site modifier - i.e. with a re-positionable gradient arrow which documents the rise or fall, so I can have a diagonal fall if I want, to a corner low-point, or to a central drain gully, etc.
Can I also add that specifying the slope in the pad site modifier (and in my desired hardscape option) should also allow "rise over run" - as with the roof face tool - so I could actually say "1 over 75", rather than having to calculate this as a percentage!