I'm replacing the subfloor in my bathroom with 1/2" plywood and 1/2" cement board. This will be thicker than the original subfloor the last owner put in. As a result, my closet flange for the toilet will be too short.

Is there an adapter I can buy to extend the flange? If so and it's made of PVC, please tell me the best way to attach it to a cast iron flange.

Thanks!