Installing new tub and tile. I have torn out old tub and tile. The exsisting drywall/concrete is 1 inch thick. I will be installing new concrete board but it is only 1/2 inch thick. What should I do to make this match so I have the 1 inch thickness so all of the walls are flush? Should I install 2 boards so it will be the 1 inch thickness?

Thanks for the advise.

i ran in to this remodeling the bath in my mothers 1932 true brick house.exterior walls contained no stick framing(solid block then airspace and brick and stick interior framing with what appeared one of the first types of sheet rock then skim coated with1/2 inch of concrete. double it up like you were thinking.i used concerte board for both layers and used fiberglass tape covered with thinset on the joints where i was tiling.Do not forget about faucet stem depth if your replacing with new.Just changing out the toilet paper holder was a big job in this bath as it was mortared in to the brick,thought i would reply as i have not received any either.

You could fur the studs out 1/2" to make up the difference. That's probably the cheapest way.