Garage Wall Board

Anyone familiar with a garage board called magnesiacore? The website is

www.magnesiacore.com

HiFive, welcome and Hifive I hope you will enjoy this forum.
Unforturnately I'm not familiar with the product you mentioned.
Are you?

i have never been fussy about a waterproof backing board ,i just use 3/8 plasterboard use the correct adhesive and buy water proof grout not water resistant in powder form the waterproof comes ready mixed,this is the barrier for the water attack,its correctly grouted tiles that are the umbrella,this means the backing board will never get wet meaning you dont need fancy priced backing boards,if you want to ensure there will be no problem then pva the plaster board
hope this makes sense it would be like waking down the street with a brolly yet still feel the need to wear a waterproof hat
regards
martin