Flooring Tile - shower wall treatment

i'm building my own house in nc. i bought 16x16" slate for the floor and much as i would like to run it up the wall, it is too thick....so because i'm working with a squeeky tight budget i can't afford to ceramic tile the shower/tub area...plan b) i found some cement board (not the board we have in fl which looks like concrete over mesh, but this stuff looked like a sheet of concrete)...i was wondering if i could seal it with a marine resin...after sticking and grouting it.....OR.....can i just marine paint the greenboard (or cement board) and be done with it...
and have it be waterproof? i've looked everywhere and talked to dozens of folks and really can't get an answer...

Green board is simply water resistant drywall (not waterproof). Concrete underlayment board (CUB) is waterproof and is recommended for installation in tub shower areas. It can be tiled over or a plastic or fiberglass tub/shower surround installed over it. Shower surrounds tend to be relatively inexpensive and easy to install as a DIY project. Check at your local big box store for prices on inexpensive shower surrounds.

Green board is simply water resistant drywall (not waterproof). Concrete underlayment board (CUB) is waterproof and is recommended for installation in tub shower areas.

Cement board is not waterproof. That is a great misconception that leads many diyers down a road filled with mold remediation and job failure. It is impervious to the affects of water, but by no means will it stop water from getting through. For that matter, sealed grout is not waterproof either. You need to control the water issue by installing 6 mil poly over your studs prior to isntalling the cement board, or apply a topical waterproofer over the cement board, but do not use both. NO marine resins, save them for your boat. They will only serve to prevent the bonding of the thinset. You can use the slate on the walls, no problems there, it just might take some extra time allowing each row to set up before moving up the wall. Not all slate is good for water exposure. let some soak in a bucket and then scrub with a scrubbing pad. If the water starts turning muddy looking, then go with something else on your walls.

AND, What is this slate being installed over, a slab or wood flooring?:)

And, it's not too big for the walls.:)


And, what Tilebri said, cementboard, grout or thinset is NOT Waterproof, just moisture resistent, a membrane must be used to make them waterproof and forget greenboard, it's good for nothing.:)

AND, What is this slate being installed over, a slab or wood flooring?:)

And, it's not too big for the walls.:)

Big duh to me. I just got so wrapped up on the cement board is waterproof comment. You're gonna need an extra strong floor for stone. Thanks Rich.

thanks for the info...i don't want to install a combo unit; wanting something "other"...the slate is natural (charcoal and browns), 16x16, about 1/2" thick (i carried the boxes...1 box, 5 tiles, 50 lbs) so the folks at both homedepot and lowes said no to on the wall...hence the idea to use cement board and sealer; but if that's not a good idea...plan c)?...

plan c, go ahead and use that on the wall. No problems. Use modified thinset from a bag, mixed with water. Go to the big boxes for supplies, just don't let them convince you that premixed thinset is good for your project, and don't ask their advice. :)