Backerboard or Mold Resistant Drywall

April 8, 2009 6:34 PM

Bathroom DIY Filter: Do we need to use cement board (backer board) for the walls around the bathtub/shower that we're going to retile?

Right now the tile is attached directly to the dry wall. We were planning on replacing most of that drywall with the mold resistant dry wall (I think that's called green board), but Home Depot and Lowes keep pushing the cement board for the part that we're going to tile (around the tub/shower).

Is it ok to use that drywall instead of the cement board (backer board)? If we use it, should we put RedGard on it (it's supposed to make it waterproof)?

posted by chndrcks to home & garden (18 comments total)

We just had our bathroom redone professionally. They used cement board to go under the tiles and put RedGard on it. We had to have the bathroom redone because the person who redid it before didn't seal the tile properly and all of the drywall washed away.

It was awful and it was expensive to repair.

I would use the cement board if I were you.
posted by sugarfish at 6:40 PM on April 8, 2009

When I redid my bathroom, I used cement board in the shower, and behind the sink. I used greenboard for the rest of the walls. I then tiled over all of it. The idea is that the cement board will remain stable, even if it gets wet. The greenboard, on the other hand, is only meant for damp environments, and would probably crumble if it got wet.
posted by Midnight Skulker at 6:43 PM on April 8, 2009

Don't send plaster to do fibrous cement's job.
posted by flabdablet at 6:45 PM on April 8, 2009 [4 favorites]

Use cement board unless you are prepared to redo the whole thing in a couple of years, and possibly clean up after additional damage.
posted by aramaic at 6:49 PM on April 8, 2009 [1 favorite]

Cement board. Just do it. I like the Hardie brand stuff, because I find it easier to work with.

For tiling advice, go to the John Bridge Forums.
posted by jon1270 at 6:55 PM on April 8, 2009

a couple of extra bucks now will put off or eliminate a screaming nightmare of suicide inducing proportions in the near future, but, hey! it's your call...!
posted by Redhush at 6:56 PM on April 8, 2009

Greenboard is moisture resistant but if water ever penetrates the water resistant paper the drywall becomes very compromised. If I was going to remodel my own bathroom, I would use regular drywall and make sure the tile job was done correctly with a good coat of semi-gloss paint on the rest of the walls to help lock out moisture.
If the tile is laid right, you shouldn't get any water on your sheetrock wall. Durock seems like over kill to me but I would use it before I used greenboard. Also I hang this stuff for a living for what it's worth, so thanks for asking a question I know something about cause I'll never be able to help anyone on askme with thier printer.
posted by nola at 7:03 PM on April 8, 2009 [2 favorites]

Cement board. Tear the drywall out all the way back to the studs. If you have the tile professionally installed, the installer will take care of putting up the cement board (it's often called "wonder board" and it's HEAVY).

If you lean against the walls of your shower, or engage in any rigorous activities in there, the greenboard can flex, which can crack your tiles/grout, or cause the thinset to loosen. Another reason to go with cement board.

If you are tiling up all the way to the ceiling, you could probably get away with doing cement board up to the shower head and then greenboad above.

You will STILL want to seal your groutlines to further make the shower moisture-proof.

We just re-did our bathroom after dealing with rotted studs and rotted subfloor due to the previous owner's negligence when it came to the shower. It was NOT a fun experience, and I recommend installing things right the first time.

Every single place that we talked to recommended the cement boards. I am very happy with the result.

You could do greenboard behind those big cultured marble panels, if you chose.
posted by Ostara at 7:21 PM on April 8, 2009 [1 favorite]

The person who owned my house before I did put particle board in the bathroom under the ceramic tiles. Of course I had to redo it all and I hate this guy now, even in absentia.

Cement board it is!
posted by Danf at 8:15 PM on April 8, 2009

Cement board, 3/4 inch. Not the thinner stuff.
posted by inkyr2 at 8:20 PM on April 8, 2009

Yes! My bathroom shower was done with greenboard before we bought the house and it lasted a few years. When it fell apart, it was a disgusting hole.
posted by zinfandel at 8:22 PM on April 8, 2009

We just had our bathroom retiled and the tile guy used cement board up to 6" and green board to the ceiling. The previous owners installed a plastic shower surround with drywall remnants and particle board behind it. Moisture inevitably got back behind the surround and caused a mold problem. We had to pay someone to tear the whole wall out and redo it the right way. I vote for doing it right the first time.
posted by pluckysparrow at 8:51 PM on April 8, 2009

The person who owned my house before I did put particle board in the bathroom under the ceramic tiles. Of course I had to redo it all and I hate this guy now, even in absentia.

Pretty much: me too. The cost difference between doing it the right way, and doing it the crappy way is really minimal, but five years from now (not to mention fifteen or twenty years down the road), the difference in the results is extraordinary.

There are easier ways to save a few tens of dollars.
posted by Forktine at 9:23 PM on April 8, 2009

There are several options, but really cement board is the best bet. The really really best bet. If that tile is going to take any kind of load at all, and/or if your wall is not insulated, you need to put some very rigid backer board in there as well, something like AdvanTech (probably overkill) or some nice thick OSB, and then your cement board.

Tile breaks when it flexes.

Also, while you're remodeling your bathroom, eliminate most of the issues associated with mold/condensation/vapor infiltration by installing a humidistatically controlled bathroom vent fan that vents directly to the outside, and minimize turns/bends in the pipe. Yea, it'll run at night sometimes, but it will make everything else work better.
posted by TomMelee at 9:26 PM on April 8, 2009

I am pretty sure code requires at least greenboard if not cement board. Go with the cement board. Do it right.
posted by caddis at 4:04 AM on April 9, 2009

Yes, the code now requires cement board. (each community gets to write its own code but most will just adopt the IBC.)
posted by caddis at 6:07 AM on April 9, 2009

Just to echo everyone else, please don't install tile over drywall or plywood.

Cement board is good and waterproof membranes (like Schluter-KERDI) have been making inroads lately. I don't know if Home Depot carries that sort of thing, though.
posted by ODiV at 8:28 AM on April 9, 2009

Also: Instructions say that you should frame all four edges of your cement board. Place a horizontal line of framing between your studs at that 3- or 5-foot level above the floor.
posted by Midnight Skulker at 10:01 AM on April 9, 2009