Okay, here's my situation.

2nd floor living room in Southern California. Place was built in the 80's.

Currently the flooring is a 2' square 1/4" thick plywood tile that appears to be nailed down in the corners.

Subfloor appears to be 3/4" cementitious (gypcrete?) over 3/4 T&G.

What I'm looking to do is lay 3/4" hardwood. So here's my question.

What's the cementitious material doing there? If I demo the current floor and the cementitious material am I going to run into any unexpected issues?

I'm just confused as to why the cementitious is there. Is this common?

What I'm trying to avoid is demoing 50% of the floor and then discovering something odd and being in a mess of trouble.

Advice? Thoughts?

(I know - the first suggestion is just float an engineered floor over the current floor and be done with it. Long story but that's not an option).

Seen ya post this on another forum. If your going to do solid then you need to demo the plywood tiles and gypcrete. Gypcrete is almost always placed to eliminate sound. rip it out, a layer of 3/4 plywood then solid hardwood and you'll be good.