What is the correct way work with level based features (not really sure the proper terminology for such features!!) - ie roofs and walls which are added to a level.
For example I wanted to put a roof on this wall:

by mistake, I clicked on level 2 which happened to be the floor but in reality I wanted the roof on top of the walls.
Is the correct way to add an elevation to the top of the walls? Or, it is possible to use define a workplane and then add the roof to the workplane?
The reason for asking is that if you take a building say with floors on different levels, and ceilings, maybe dormers or a balcony you could see that there are potentially going to be elevations galore just to define the base of walls / roof levels / floor levels for each particular level... Are elevations the correct way to do this? Can you place walls and features on a workplane?