Green backer board vs. Concrete Backer Board?

https://www.ehow.com/info_8597242_green-board-vs-cement-board.html

follow this link or copy /paste

tells you what you need to know about both backer boards

I'd say based on the info below that you don't need to worry, greenboard use is fine, and less expensive than concrete back board:

"The most practical wall sheathing in a tub or shower area is still ordinary green, water-resistant gypsum board. Since it is impregnated with a waxy substrate, it repels water, but has just about the same strength as common drywall (Sheetrock).

"The difference between concrete backer-board and water-resistant gypsum board lies in the former's strength. So, if you're looking for durability and strength, concrete backer-board will probably be your choice." https://www.silive.com/homegarden/homeimprovement/index.ssf/2008/02/theres_a_big_differrence_betwe.html

I would go after him and his license, but that's me. See if these help.

https://www.doityourself.com/stry/cement-board-vs-greenboard-or-blueboard

https://www.ehow.com/info_8597242_green-board-vs-cement-board.html

https://www.ridgidforum.com/forum/mechanical-trades/construction-discussion-forum/13373-green-board-vs-cement-board

Sheila,

The main difference is if you plan on tiling. Cement board for tile. If you are unable to get the contractor to replace it, use a waterproof membrane like Kerdi over the greenboard.