This is a question that has been posted to this forum some years ago. At that time there were no real alternatives to wood or engineered wood products for a subfloor. I would like to know if there has been any progress on this front. I am looking for a product that function like a piece of plywood spanning joists to make a reasonably strong fireproof floor. Currently it is possible to build a house that is made from essentially fireproof materials for competitive prices EXCEPT for the subfloor. Now before I am flamed as a wood hater I wish to confess to an undying love of the stuff. I like the way it looks, I like way it feels, I like the way it smells. It does unfortunately burn and while it can be made unfriendly to pests by the addition of cupric cyanide based products there are bugs that love wood even more than I do. I also know that wood buildings frequently last longer in fires buildings with metal beams. I am just curious if something else has been developed. thanks griz

I cannot think of a product similar to wood without having the same problems as wood.  If you happen to live close to a precast, prestressed, hollow-core concrete plank factory, then hollow core planks may be reasonable in price.  A lot of the companies will not only do the engineering and casting the planks but will deliver, erect and grout the planks in place.  As a rule in my area, they do not do the topping slab.  Be aware that a topping slab is highly recommended to increase strength and to make the top of the floor level.  The topping slab can be fairly thin.   Check with the producer about fire resistance.

Of course, floors like Lite-Deck, Insul-Deck, etc. are availabe but I have found they cost more than HC planks.  If the bottom side of EPS forms are used as ceiling, then the foam will need to be protected with drywall, etc.

May not be exactly what you're looking for but one possibility would be to use Warmboard, http://www.warmboard.com. It has an aluminum face on one side. That would be a pretty good fire barrier on one side of the subfloor. Install it upside down if you want the barrier on the bottom side. Price may be its undoing for what you want though. If you want a fire barrier top and bottom install two layers, bottom one upside down and the top one right side up.

You could still use an engineered wood subfloor such as AdvanTech and essentially make it fire proof by sandwiching it between layers of fireproof material. On the top side, install cement board over it with ceramic tile. On the bottom side you could lay down a 1/2" layer of magnesium oxide board on top of your non-combustible floor joists / trusses before the wood subfloor goes down. Instead of magnesium oxide board, you could probably use a layer of 5/8" Type X fiberglass faced gypsum board and get essentially the same results.