I've always wondered - if I lived in a wildfire prone area, could you build a true "shelter" - say (off my head) a fully underground concrete (say 6" walls and roof) room detactched from the house. Say the roof is 12" below grade, and you have steps down, door, corridor, door, room.

I would think with a facility like that (and saw water haze in the corridor), you could stay and defend pretty much till the end, and worst comes to worst, it burns over the top