SW-04Sand the walls - method depends on the wall typeOn solid brick or block walls with a skimmed plaster finish, sand lightly with 180-240 grit on a pole sander or hand block; solid plaster can take gentle pressure. On plasterboard walls the sanding itself is identical whether the studs behind are timber or metal - you're only touching the painted or skimmed surface, not the frame - but check joints don't feel bouncy as you go. Dot-and-dab plasterboard needs the lightest touch of all: don't lean into the sander near joints or over the dabs, or you risk cracking or loosening the board. Lath and plaster is older and more fragile, so sand by hand with light pressure, avoid power sanders, and stop if you feel flex - a crumbling patch needs re-skimming, not more sanding.