Hallways
The hardest room in a flat, because it isn't a room — it's a corridor that has to hold coats, shoes, keys and post without stopping you walking down it.
The number that decides everything: leave at least 600mm of clear width to walk past, and 900mm if it's the main route in and out. In a 1,000mm hallway that leaves you 250–400mm of depth, which is exactly why our consoles and benches are that shallow.
Also check the door swing before you commit. A standard 762mm door sweeps a 762mm quarter-circle, and a bench in that arc is a shin injury waiting to happen.