Looks like fiber board, but is 2 inches thick? Is it something poured in that hardens? Is it like a frame?

Question

Trying to cut a hole in my floor (no other access to crawl space under additon), but unsure if I should or not. Peeked through a small vent on side and didn't see any floor joists that were more than 2 inches thick. Am afraid if I cut a hole in the stuff I will lose structural integrity.

House was built on fill and one section of room is settling-leaning. No vapor barrier was laid down either.

Answer 1

yep leave it alone, or the floor could fall in , why do you need an access to the crawl space? you didn,t state that?