Cement board removal under tub edge

Question

I have pulled up 99% of the cement board and tile from my bathroom, and am fighting with the edge that is up against the tub. Some of the board broke off a half inch under the tub, some broke off a half inch out from where the side of the tub meets the floor.

How much do I have to clear out under the tub to slide in new cement board, or am I just wasting time and should run a new straight line with the board and back fill with grout or mortar and some water proofing on top?

Thanks for any advice.

Answer 1

Just make sure the cement board is out from the outer part of the tub. It being uneven underneath is not consequential. You just need your cement board to be able to lay flat and I usually place mine about 1/8" from tub.