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05-02-2002, 06:49 PM
I am gutting my bathroom back to the studs and will install a new shower to be separate from the bathtub area.

I am planning on Wonderboard or Durock for the shower walls and ceiling, with a mortar bed floor. I think I'm clear on that. I am planning greenboard for the non-wet walls in the rest of the room, with regular drywall on the ceiling.

But ... I will be tiling the non-wet walls up to wainscote height, and tiling up 16" around the tub. The tub will be just a tub, since there will be a separate shower. Is greenboard OK there or should I use the CBU up as high as the tile goes ? And will the greenboard be OK behind the tile on the non-wet walls or should I have cbu from floor up to wainscote height ?

And why can't I tile with thin-set right on the CBU ? I keep seeing mention of painting a waterproofer on TOP or the CBU, when I was really only planning on some poly BEHIND the CBU.

The tile for all these walls will likely be 8x10, 12x16 or something. Fairly large, anyway. I haven't decided on the tile yet.

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Rob Z
05-02-2002, 06:53 PM
Hi Dreamer

You can set the tile right over cbu with thinset...the use of a waterproofing procuct is optional.

You can use the drywall out in the rest of the bathroom as a substrate for the wainscot tile, but.....since it is only a small amount of work to add cement board in those areas, why not keep everything the same?

05-02-2002, 07:19 PM
Thanks for the quick reply, Rob.

I'm planning on the CBU going right on the studs in the shower -- nothing but poly underneath. To keep a flush surface, I can do the wainscot CBU the same way and an inspector is not going to be bothered ?

05-02-2002, 08:34 PM
No problem with doing the wainscot the same way as the shower. It is a bit of overkill but there are no adverse effects.

As for the inspector, the "inspectors" in the Austin, TX area are more concerned with the actual plumbing, framing, and electrical than the use of CBU vs Greenboard as a tile substrate. Heck, I don't think they are informed of the differences. I've never seen a home in my neck of the woods be flagged by an inspector due to tile substrate, preparation, or even shower pan fabrication.


Bud Cline
05-02-2002, 08:40 PM
Are you also planning to shim the studs above the pan liner in the shower???

I thought so.

05-02-2002, 09:04 PM

Yes, I had thought of that. I plan on ripping pressure treated 2x4 to make a narrower curb than usual. I'll rip a few extra and use those pressure treated 1/4" thick pieces as furring for the entire wall that runs into the shower -- except for the lower ten inches of the shower area which will be left un-furred to allow for liner. The pressure treated is overkill, but I'll have them as scraps so may as well use 'em. I expect to have to fur the wall anyway to achieve square, flat and plumb.

I've been reading and paying attention, honest :D

While I've got your attention, is there some sort of cable or coping saw that will cut good holes (starting from a drilled hole, of course) in the center of wonderboard for electrical outlets and such ? Or am I just supposed to live with the ragged holes that punching through it with a chisel will leave ?

Bud Cline
05-03-2002, 05:42 AM
You could use a carorundum coated blade in a jig saw, that's about the cheapest way out.

I don't know about these other guys but I wouldn't use "treated" material for the curb, especially if you plan to rip it.

Treated lumber has a high moisture content from the "treatment". In time this lumber will dry-out and tends to twist and curl and bend and just plain and simple could go nuts.

I would stay with a "kiln dried" material that already has a low moisture content.

If you want to see what I'm talking about go to your local Big Box and cruise through their treated lumber department.

Rob Z
05-03-2002, 05:22 PM
Hi Kirk

Depending on what your tool budget will allow, the base model Rotozip will cut the Wonderboard and the wall tile for you. I think I saw the cheapo model of Rotozip at H*** D**** for $69.

It also cuts holes in drywall, plaster and plywood.

05-03-2002, 05:58 PM
Well, dang it, Bud. I can't remember now where I picked up the idea that pressure treated lumber was best for a curb. It isn't in John's article or MB's articll that's linked in the liberry here. Maybe it was in MB's 1987 book.

Here I thought I was going to overkill and use pressure treated lumber for all the framing around the shower.

I picked up the lumber the other night at HD, and I did notice it being very heavy with moisture. I didn't think about it warping as it dried -- or even that it would dry out, as I wasn't sure what the base was for that arsenic pesticide they are treated with.

I think I'll return it and get plain KD like everywhere else. I wasn't really looking forward to ripping it, since there are warnings about the sawdust.

Rob, I hadn't thought about a RotoZip. They really go through tile ?? I don't mind spending money on tools that actually work.

[Edited by dreamer on 05-03-2002 at 08:26 PM]

Bud Cline
05-03-2002, 06:38 PM
They really go thru WALL TILE only.

05-03-2002, 08:16 PM
Rotozip no good on Porcelain ; so-so on floor tile; pretty good on wall tile.

A jigsaw with a masonry blade works pretty well. For most cutouts, a scoring tool and a hammer is the best solution. Coping saws are available at the Big Boxes but there application is limited by the small size of the saw. Hard to get to the interior of a large sht of CBU