I recently bought a house with a 15 year old inground pool in need of a new liner. We believe the bottom of the pool is sand but we are not sure. The contractor has suggested putting a 2" layer of a vermiculite-cement mix on top of the sand bottom to improve durability and insulation for an additional cost of $1,600. I am not convinved this is necessary or worth the additional cost. The pool is still in excellent condition, we never detected any foot prints or other problems on the bottom of the pool. It seems the liner simply wore out after a good long life. Any thoughts on the utility of putting vermiculite over sand or the benefits of such added insulation would be GREATLY appreciated.