I've seen some discussion of Building Spawning, but I do have one question that doesn't seem to have been addressed yet (apologies if it has and I missed it).
When opening a door, you reveal all zombies in the building by pointing to a room and drawing a card, spawning per that card. What happens if a Manhole or Zombie activate card is drawn? Is that card resolved as normal (possibly spawning or activating Zombies that are outside of that building) or is it just ignored or ignored and redrawn?
The latter two aren't supported in the rules at all. The first one seems the most likely per the rules as written but doesn't feel right thematically as you're supposed to be determining what Zombies are in that building.