Shower Project

[ss3964spd]

I'd have to guess that their testing suggests there is more risk of those joints cracking where 4 corners meet. If panel seams crack there is a chance the crack will telegraph through to the tile.

[eagle4x]

I have a two-wall separate shower with backer board installed. The pan is prefab cultured marble. I purchased 24" x 48" tile for the job. I test fitted two rows of the tile against the backer using clamps and put a level against it and it wasn't flush against the tile resulting in an approx. 1/8" gap at the bottom. I determined the problem is the 1" flange is at a slight angle sloping towards the pan. I put a 1" wide piece of wood in front of the flange, set a piece of tile on top, and there were no gaps when level put against the tile, so I know the problem is with the flange. Some possible solutions:

1) Even though it would be a pain, remove the bottom backer board and shim bottom out 1/8".

2) install the tile at bottom of backer board so it doesn't protrude over the flange and then install a 1"wide piece of tile to cover the flange, as filling the gap with colored silicone wouldn't look good.

Which of the 2 better options, or other suggestions?

[ss3964spd]

Welcome back, Mike,

I think I can visualize it, but photos always help.

Your pan has a vertical flange that should be snug against the wall framing. You have installed backer board (what brand?) on to the framing. Is the bottom edge of the backer just above the top edge of the flange or does it extend down to cover the flange? If it stops at the top edge of the flange, does the face of the flange stick out past the face of the backer?

IMO, neither 1 or 2 are viable solutions. You really want the wall board to be flat and plumb in all cases, but even more so with those large tiles.

[Tool Guy - Kg]

Hi Mike, I’m not sure I understand. Are you saying that the wall studs do not create a flat plane surface that results in a gap where it intersects your pre-fab pan?

Can you clarify with a picture?

Thanks.


EDIT: Dan has the faster typing fingers this morning.

[John Bridge]

Hi Mike,

Trim the backer board so that it ends just above the top of the flange. Your big tiles will extend ever the flange.

[cx]

Now that we're combined with the original project thread, it appears (post 103) that he has stopped the wallboard above the receptor tiling flange, John, so I'm not sure I understand the problem.

Perhaps another photo as Goldstein recommended would help clarify the situation.

[eagle4x]

@Dan
1) The backer is 1/2" permabase WP.
2) Backer sits on top edge of flange as shown in pics.
3) The top of the flange where it meets the backer is flush, however it's not flush from bottom edge of backer to bottom of the flange (it sticks out past it) because of the slope I mentioned in my previous post (see pic with popsicle stick behind the tile showing the gap).

@Bubba...answer to your question same as #3 above.

[eagle4x]

1st pic: Gap with level against 2 rows of tile, but it's mostly in the center between the 2 tiles.
2nd pic: Level is flat against backer when it's raised above the flange.
3rd pic: Where backer meets top of flange.
4th pic: Shim against backer and slightly below it against flange showing that where backer meets upper edge of flange is flush. From the bottom of the shim to the bottom of the ledge the flange it slopes outward.
5th pic: Popsicle stick placed behind tile showing gap at bottom portion of tile.
6th pic: Tile raised above the flange, which shows the tile is completely flush against the backer.

[cx]

Mike, I think the first thing you need to consider is waterproofing that gap between the wallboard and the receptor flange.

After that, consider that you must have a minimum of 3/32nds" of thinset mortar behind your tiles when set, which would bring your tiles out far enough to fit down over that flange. You won't need mortar behind the portion of your very large tile that overlaps the flange.

I think it's likely to work out OK.

My opinion; worth price charged.

[ss3964spd]

CX got there before me. Agreed; you'll likely be using a 1/2" notched trowel to set those large tiles, resulting in just a bit less than 1/4" of mortar behind them. You'll want to leave 1/8" between the bottom of the tile and the top of the flat, horizontal part of the pan, thus probably avoiding that small inside radius of the pan. If you still need more room you could back-bevel the bottom of each tile.

It appears you've already filled the gap between the backer and the top of the flange. With what?

[eagle4x]

I pulled the top of the 1st row of tile back 1/8" and inserted 2 popsicle sticks and after I put the 2nd row of tile and laid the level against it, there were no gaps from top to bottom. So, this appears to be a "fix", therefore, would it be better to:

1) Shim the outside of the backer.

2) Remove the backer and shim behind it.

My concern with doing #1 is possible issues when thinset applied. And other concern is that the tile is not perfectly flat against the wall without the shims so do know if any other problems could arise using them.

Which method best or other suggestions?

1st pic: the two popsicle sticks inserted.
2nd pic: the side view of the two tiles showing the gap.

[eagle4x]

@Dan
I used Permabase sealant to fill the gap between the backer and the flange.

[ss3964spd]

1) I cannot think of any way to "shim" the outside of the backer. You'd have to add a layer of some kind of filler to build it out. But if you did that at only the bottom you'd have the same issue as #2 below.

2) If you removed ALL the backer then shimming behind it would be a viable solution. If you shim behind only the bottom, the tile still won't sit flat against the backer because now the backer will have a concave bow to it, and it will kick out a bit at the bottom. That kick out might also cause you grief at the vertical axis in corner when you go to set the tile on the adjacent wall.

Place a 1/8" shim flat on top of the pan then rest your tile on it to simulate the 1/8" gap you'll need between the bottom of the tile and top of the pan. Then check again with your level and popsicle sticks. Also check to see if the back edge of the tile is being pushed outwards by that inside radius of the pan. I realize you are doing these mock ups verifying the tile is plumb with your level, but is the wall itself also plumb?

[eagle4x]

@Dan

There are 3 rows of backer board and before I sent the post about this problem, I removed the top 2 rows because I initially thought the problem was with the top not being plumb. I then reinstalled them with 4 screws in each one while doing the testing.

When an 6' level is placed against all 3 backer boards even with the top of the flange it is plumb, so that verifies the studs behind it are plumb, however, when I move the level down another inch to the ledge, it kicks out 1/8" causing a 1/8" gap almost the entire width of the bottom backer.

If I use your suggestion to remove the bottom backer board and put 1/8" shims on each stud, I agree that should work, but it would cause the backer to overlap 1/8" over the top edge of the flange.

[ss3964spd]

Hi Mike, apologies for not being more clear. My suggestion is to remove all of the backer, bottom to top, then shim each stud bottom to top, re-install the backer.

But I'm still not convinced shimming is necessary. See crude drawings below. If your level, or tile is resting on top of the pan they are possibly being forced outward by that inside radius. If that is true you would need to move the level or tile upwards a bit so they clear the radius, then check again.

It still looks to me that once you factor in the thickness of the mortar between the backer and tile you'll be fine. If you find that the tile is still being forced outward by the radius with the 1/8" gap between the bottom of the tile and top of the pan, you could simply back bevel the bottom of the tile to pick up a little more clearance.