I have lots of layers. I never make the tile itself not passable, I have a tile for not passable water, one for not passable solid, etc. There is a tile map that is just various states of not passable--or extra fast like movement on a flat road. The tiles themselves are just for show and don't have properties. That layer could just as well be a big image.
Things like flamable, cold, etc are properties on yet another tile sheet layer.
yours
winkr7