Shower walls/Durock

[Vader,Darth]

I'm prepping the shower stall, and haven't put in the mud floor yet.
Should the durock hit the bottom of the lead pan, or should I leave it an inch higher than the floor and mud up to it?

[tileguytodd]

Heya Darth, Is this an old Lead Pan??If you decide to use the lead(wouldnt be my first choice) Yes, keep the CBU up 1" and mud up to it.No nails below the 6" mark,the Mud will hold the bottom in.
Check out our liberry on building shower pans and shower curbs.The link is at the top of the page

[swkiser]

Well...I am at the same stage as Darth but I have a PVC pan that I have pre-sloped in. My question is the is the same. Do I take the durock down below the final mud layer? Michal Byrne's article idicates that I should leave a 1/8 to 1/4 gap at the base to provide for a control joint. Does this apply to the tiles being set only and that the durock is still beneath the mortar floor pan? Or am I to leave the Durock gapped between the pan base as well. What is this backer rod and sealant control joint Mr. Byrne is talking about?
All the help you can provide at this stage of the game would be helpful.

Thank you, thank you, thank you...

Kiser

[bbcamp]

The idea is to bury the bottom edge in the mortar bed to hold it in place, since you can't nail the bottom edge without punching holes in the pan. Some of the backerboard companies don't recommend this practice on the fear that the board will wick up moisture, but they don't offer a solution to the support issue. Others compromise and smear silicone caulk along the bottom edge of the backer board to control the wicking, then bury the edge in the mortar bed. Usually, we're of the first school of thought: bury the backer, and wipe the shower down after each use to limit water penetration.

As far as a control joint is concerned, the joint between the bottom row of wall tiles and the floor tiles is caulked, as are the corner joints where two walls meet. This accounts for movement between those flat planes. Of course, if we're talking about a steam shower, the rules are a little different.

[John Bridge]

Hi Darth, Hi Kiser, Welcome aboard.

I could only repeat what Bob has already said. Mr. Byrne and Mr. Bridge don't agree on a whole bunch of things.

I would not worry about wicking. I WOULD wipe down the shower completely each time it's used.

In my opinion, it doesn't matter whether the wall tile goes down into the floor or whether is is installed above the floor tile. The movement that does occur at the juncture is not going to be severe.

[Vader,Darth]

Thanks.
It'll be buried then. I'm not worried about moisture pick up, after all, this stuff is made mostly of fiberglass particles and won't rot.

I've seen a piece of this a tile co. has had in a jar of water for the last 8 years. The rock is just as strong as it was then.

[davem]

I don't think the fear is that the board will deteriorate, but having constanly moist wall boards will cause mold/mildew problems for the studs and/or tile.

I believe that a shower built with a proper pre-slope will go a long way toward eliminating the problem. Because of the pre-slope, the liner at the walls is higher than the liner at the drain, so the floor will dry fastest near the walls.

[flatfloor]

Backer rod is a round flexible styrofoam like material that is used to fill the bulk of the joint space. You fill the joint with the rod and then caulk. Comes in rolls, different thicknesses 1/4"-1/2" etc.

[swkiser]

It looks like John says it doesn't matter if the wall tile extends below the mortar floor pan. Do you mean the Cement Board or do you really mean the wall tile? It seems to me that if you ever should have problems (no, not me...uh-uh), the bottom coarse of tile would be a problem if you ever needed to remove and replace one. I like the idea of tiling the wall and then covering a portion during the final pan mudding. Brainless and painless. Something tells me I should follow Darth's lead, though, and bury the CBU but not the wall tile. Tips on that please?

None of my showers have caulk betwwen the floor/wall joint...only grout. Was this a possible cause of my shower wall failure? Nothing looked bad along the floor/wall joint?? Actually I think it was a propensity to bleach the mildew away without a follow up seal.

One more thing. Should I grout and caulk at the base or just caulk?

Thanks for so much info guys! I should have written much, much sooner. I have been pondering these questions as I have made excuses for the last month as to why the shower hasn't gotten finished (chuckle). I have worked my way through preslope and PVC liner install, Niche building right up to where I am now. I owe it all to you guys!

Steve (Kiser)

[bbcamp]

Hi Steve! No, bury just the cement board. You should caulk the intersections of any two planes. Some advise to grout there and hope for the best, knowing that you can scrape it out later and caulk. But, you don't caulk over grout.

You wanna tell us a little bit about your project?

[swkiser]

Sure, but give me a day. Gotta go to work on it now!

SWK

My cement backer board was buried in the mud floor and when they ripped open my shower it had toxic mold on the board that was buried in the floor. The shower was less than nine months old. Just my own personal experience.

[davem]

Good info Courtney. Why was it torn out at 9 months? Was there a pre-slope under the liner?

Our floor tile was discoloring in the shower. It turns out that walls were installed first, then the concrete for the floors was put in. The board that went down in the floor about an inch and water got trapped between the concrete and the board and mold grew.

[John Bridge]

Hi Courtney,

From what you say, the problem was not with the board being buried but with the pan itself or lack thereof. As Dave explained, if the pan is pre-sloped and the drain weep holes are not clogged, you won't have a problem. It would not be possible for water to get trapped, as you say, if the pan had been installed correctly.

Steve,

Being able to bury a bit of the bottom course means you don't have to figure the exact height of the tile field when you start the walls. And it does not matter that a little of the tile is buried. It's up to you, though.