bathroom walls

[dieselfish]

Was wondering how some others do bathrooms walls and shower surounds with tile. I have been doing greenboard , backer board, tiles. I know water gets through everything , Is this enough or too much? any shortcuts?

Also manufacturer says you can tile straight to wood as long as its 3/4" min. which is what i use for countertops but when doing a new floor does anyone still use backerboard over the 3/4" I have always used it to be safe as I know it flexes to allow for settling?

thanks

[jproffer]

The backerboard's purpose isn't necessarily to keep the floor from flexing. It's a decoupling layer, meaning when you install it you should try intentionally NOT to hit the joists with the screws. The plywood should be screwed to the joists, the rock should be screwed to the plywood only. This is to keep the tile from moving (read: cracking) when the house settles or moves. Same idea with the walls, greenboard, backer, then tile sounds good. Also in case you didn't know, the backerboard, whether on walls or floors, needs to be put down on thinset.

EDIT: That isn't meant to sound like the floor CAN flex...that's definately NOT ok :) ...but that's the joists and plywood's job.

[montytx]

I dont put green down before the durock. THats the only extra step I see. And I suppose that is just preference and type of tile edging you are using.

[dieselfish]

I would think that without the green board in a shower surround the water would end up getting into the walls?

[CThomp]

Thats what grout is for. If you figure that the water would have to firt go through the tile and the grout, then through the mastic or thinset, and then through the cement board or durarock. Seems kinda like a waste of money to do green board and then the cement board. another reason people often put the durarock over the 3/4" ply is so the thinset sticks better. It'll attach to durrock or cement board far easier than to plywood. For counter tops the standard I think has already been mentioned. 3/4" ply, durarock or cement board, then tile.

[TnAndy]

I don't use greenboard behind the cement board in a shower or tub surround......it's only "moisture resistant" and if the water gets that far, I doubt the greenboard is gonna slow it up for long.

What I do instead is a layer of 6mil plastic sheeting directly on the studs, then the cement board, then tile.......I sorta doubt any water is ever gonna get back to that layer of plastic, but it's cheap insurance.

The only reason I might use sheetrock behind the cement board was IF my studs were on 24"centers and I need some additional stiffness cause I knew the fat lady that sings to close the opera lived there and liked to wrassle in the shower stall....... :D

[dieselfish]

That sounds good, thanks I think I'll skip the green board. If tiling a complete bathroom ,a wall in the bathroom that is not directly getting wet , is it possible to tile straight to the green board or just easier to durock the entire room?

[CThomp]

Tile on greenboard is how they used to do it anyhow. Before the days of durock. So yeah you can do that. You'll be using mastic on the walls. It's sticky stuff. If it's not a big bathroom I think I'd just durock the whole thing. Its easy enough to work with.

[montytx]

Make sure and tape and mortar those durock seams, that is the 2nd layer defense against water seepage.

[Sweep]

Sorry for the long response but your question reminded me of the BS perpetrated by USG and its rivals for as long as I have been designing buildings.

I'm not sure what "Greenboard" is really for. It was discredited as a tile backerboard at showers and tubs back in the mid 70's when the Tile Council of America removed it from it's standard details (their Sweet’s Catalog brochure had a big black stamp over the wet area detail that said "NOT RECOMMENDED") This sudden action was necessary in order to dodge lawsuits. Greenboard simply didn't work like USG had advertised it.

At that time I was the architect in charge of a 13 story luxury condo in Minneapolis and had insisted on "Wonderboard" (the only cement board at that time) at the tiled showers. The Owner chose to follow his Construction Manager’s advice and use Greenboard (It's the way we do it here). The winning tile subcontractor subsequently included in his price the installation of Wonderboard. When asked by the Owner why he did that he said "I have found that its cheaper than coming back to replace the tile later."

USG didn’t drop it’s recomendation that Greenboard could be used in "wet areas" until it started making a Wonderboard knockoff called DUROCK.

USG now calls Greenboard "moisture resistant" for use where moisture exposure is "incidental" and warns not to use it in tub and shower areas and to not use it for ceramic tile if there is a vapor barrier behind it. (If you wonder why, put a piece of it in a bucket of water overnight) Since this stuff doesn’t offer any advantage over regular GWB with two coats of paint, where would you use it? I'm surprised USG still makes it since for the past 2 years they have been pushing HUMITEK moisture & mold resistant wall board (which also can’t be used at high moisture areas such as tub and shower enclosures). It is, however, pale blue which is cool.

But now USG is pushing a new gypsum wall board called "FIBEROCK Aqua-Tough" which is described as “for wall assemblies in high-traffic areas where abuse, moisture, mold and fire resistance are especially important.” It can be used at tubs and showers but not at gang showers and saunas. It does not have a paper or a fiberglass mat facing. It is made up of 80% Gypsum, 15% Cellulose, 2% Parrafin and 1% Crystalline Silica. Don’t worry, the Respirable Crystalline Silica is only .1% and requires repeated exposure to cause cancer.

For 35 years it has been my opinion that a fiber-reinforced cement backer board should be used at showers and tubs. It really is cheaper than replacing the tile later. A sheet of polyethylene can be placed over the studs to avoid water penetration beyond the backer board (highly unlikely unless you forgot to install the tile) and the rest of the bathroom drywall can be adequately protected by paint.
This design is essentially the same as that used 100 years ago. The tile in my bathrooms was installed in 1903 over cement plaster on wire lath nailed directly to the studs and it is still in perfect shape today. The plaster walls look fine even without an exhaust fan. And the tub, shower valve, toilet, lav. and ceramic tile floor are still good except for the wear on the nickel plated brass fixtures.

The best source for tile construction detailing is The Tile Council of America's 2005 Handbook for Ceramic Tile Installation which can be bought for $9 at:

http://www.tileusa.com/publication_main.htm

That's where all tile manufacturers get their info. so if you set tile you need it!

[Tom R]

Great stuff, Sweep, - - thanks!

[jproffer]

CThomp said:
You'll be using mastic on the walls.

I hope you mean thinset, not mastic. Mastic is pre-mixed, and is junk IMHO. Thinset is powder that you have to mix on the jobsite. Mastic is not good for wet areas, where thinset is. After the thinset is dry...IT'S DRY, that's it, it's not going to "wet" back up.

[CThomp]

Thinset on the walls though? I've never met anyone who uses thinset on the walls. Definitely on the floors though.

[dieselfish]

I use thinset for everything, that premix sucks.

[roger g]

Good article sweep. I've noticed over the years that I'm coming across less and less (nil in fact) soggy drywall around tubs. I don't know whether in the past 20 years the installs are better (which I doubt) or the tiles are better (?) grout is better(?) or the silicone is better(?). I just don't come across soggy drywall in homes though apartment buildings are a different matter for some unknown reason. What I do find is that after 10-15 years people get tired of seeing the same tub and tiles and want it changed. Also most people change houses every few years and want a different look. Sometimes I wonder if a lot of caution is really a "tempest in a teapot". How many house have you been in and taken one look at the bathroom and said "I'd change that in a hurry"
Just some thoughts.


roger