And fireproof walls between units. It takes a long time for a fire to penetrate two layers of drywall.
The "Well there's your problem" podcast did an episode on 'five over ones' (five stories of wood over one concrete) and touched on this - IIRC they were most likely to burn down during construction when the fire suppression wasn't installed and active yet.
They also did a more in-depth episode on Grenfell, which touched on a lot of the same issues, except Grenfell was (a) taller and (b) occupied.
I can heartily recommend that episode if you like a podcast to a) be respectful to the victims and b) clown on the people who caused it.