The architectural standard would be to show solid walls as double lines with grey or hatching between. Railings would be a double line with no shading. Windows would be like railings but with a thin line down the center to mark the glass or transparent aluminum or whatever. The steps of stairs would be marked by thinner lines. A lot of the details would be marked down in the text, like, "is that a half wall or wrought-iron grillework?" I'd probably mark a pipework-style railing as a thin solid line with dots along it.

Architects say a whole lot with line widths...