This Architectural Drawing is AutoCAD 2d drawing of Slab details in Stairs section detail drawing in AutoCAD, Dwg files. Calculate the depth of the finished slab, including the concrete and the gravel base. Concrete is typically applied at a minimum of two inches, but I recommend a minimum thickness of 4 inches for a durable stair footing. The waist slab for a staircase is probably more used as a slang not as a professional technical word. This term refers to a slab of the stair that is slanting from the floor slab to the landing slab. This can be imagined like a ramp – not including the steps. For more details and information download the drawing file.