How do I reuse the same apartment layout, including mirrored versions?

Make the flat a Group: select all its elements, Create Group, and name it (e.g. "Unit A"). Then Copy or Mirror the group instances around the building. The payoff comes at revision time — Edit Group changes every instance at once, including the mirrored ones. Just watch what belongs inside the group boundary: keep shared walls between flats out of the group to avoid duplicate-wall fights. Full steps: Mirrored flats groups →