# Cement Board Shower Niche Questions



## dtbingle (Jul 19, 2017)

Remodeling our 4x8 bathroom + alcove for the bathtub and looking to add a shower niche into the wall. Had a few questions regarding the niche joints and wall tile planning.

1) After framing in the niche, pieces of cement board will be used on the left, right, top, bottom, and back surface inside the niche. For all of the joints in the niche, I planned to use mesh tape + thinset, and then follow up with redgard. *Is this the correct procedure for joints inside and around the shower niche?*

2) *How do you frame the shower niche in prior to tub installation and avoid wall tile slivers around the niche?* My only thought is to do all of the leveling work for the tub and dry fit it. Then mark 1/8" above the top surface of the tub as the point where the bottom of the first wall tile will start. Then calculate up from there using the wall tile dimensions + 1/16" grout line.

Wall tile - 4x16 bright white - link here

Accent back wall of niche - snow illusion accent wall tile - link here


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## carpdad (Oct 11, 2010)

I never used niche before, so guessing, but the best plan would be to make something similar to a story pole on taped sheets of paper as long as the floor to the ceiling. Then dry lay the tiles using grout joint spacers, and around the niche first. Around the square lines and decide if you want the full tiles or cut tiles, cutting real miters and such or cutting the corner tiles. Dry lay the tiles on a flat floor as accurately as possible then transfer those tiles on the wall. Spacers are uniform but tiles may be not, so use the same tiles and start the shower wall with the niche first. Hold the tiles with finish nails. I used 4d finish nails when I used 4x12 marble tiles because you can drive them in. Even with planning, I'd start around the niche and not from the bottom or the top because small spacing changes may mess up the tiles once you get to the niche. 

This is just diy guessing and I've never tiled the niche or such. If cutting the tiles, you may want to finish the butting edge with rounded or bull tiles and such tiles aren't always made. If square cut butt joints, cut joint may have to be filed smooth. DIY videos on tile finishing isn't dependable, I think. Sometimes, even chips or rough edges can be seen. If niche is tiled first, the cut edge can be covered with wall tile but make sure you can leave finish looking edge on tiles that are at the eye level.


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## Nealtw (Jun 22, 2017)

The tub goes in before the cement board so you can build the nitch after the tub is installed and you can figure the tile from there.


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## huesmann (Aug 18, 2011)

dtbingle said:


> 2) *How do you frame the shower niche in prior to tub installation and avoid wall tile slivers around the niche?* My only thought is to do all of the leveling work for the tub and dry fit it. Then mark 1/8" above the top surface of the tub as the point where the bottom of the first wall tile will start. Then calculate up from there using the wall tile dimensions + 1/16" grout line.


Plan out your wall tile layout before cutting for the niche. Account for the thickness of backer on the walls opposing the niche, plus the tile adhesive.

Is your niche gonna be centered on the wall? If so, easy. Just plan the tile layout so that you can have large slices, or even full tiles butting up to the niche.


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## adamz (May 13, 2018)

This link might be helpful
www.youtube.com/watch?v=OKMf4lnUTnM


Also want to mention that some folks might disagree with that video's waterproofing technique (ie not using anything on the seams except the liquid membrane), but the measuring portion is helpful.


Better seams:
www.youtube.com/watch?v=Bx9FjteG82E


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## carpdad (Oct 11, 2010)

I was thinking shower. It would be more accurate if you install the tub first. Then the story pole. Adjust the niche so you don't end with a sliver against the tub and the ceiling. Both sides probably will need cuts. I think the cuts are always needed against the bottom side, tub or the shower pan. I used americast tub and it didn't have a straight or flat edge anywhere. But long time ago.


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## chandler48 (Jun 5, 2017)

Not so much his waterproofing techniques, but using greenboard in a wet area is probably not the best he could have done. I would have opted for durock or hardie backer, and treated the seams with thinset and the proper mesh tape for alkaline resistance.


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## dtbingle (Jul 19, 2017)

So went the route of installing the tub first and then accurately measuring up from the tub deck to the bottom of the niche.

However, after measuring 15 times and getting it framed in, my final measurement revealed that it was 1" too low from allowing a full tile to sit just below the niche. Anyway, I think it would be nicer to be a bit wider as well, so will have to reframe it and correct both issues.

Also will be using durock cement board on all faces. Will cut out the durock and attach it to the back of the drywall for the back niche face using either an adhesive like liquid nails or just use silicone. Then all seams will be mesh tape + thinset.


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## chandler48 (Jun 5, 2017)

No real need to adhere the panel to the sheetrock. Your side and top/bottom pieces will hold it in place. In addition to your seam treatment, I like to Redgard the niches, since there are so many angles and flat surfaces.

Set your CBU on the lip of the tub for a flat fit and one that won't tend to wick up moisture from the tub ledge. Your tile will jump the gap with no problem.


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## dtbingle (Jul 19, 2017)

chandler48 said:


> No real need to adhere the panel to the sheetrock. Your side and top/bottom pieces will hold it in place. In addition to your seam treatment, I like to Redgard the niches, since there are so many angles and flat surfaces.
> 
> Set your CBU on the lip of the tub for a flat fit and one that won't tend to wick up moisture from the tub ledge. Your tile will jump the gap with no problem.


Sounds good! I planned to install the cement board as you showed just above the tub flange, followed by tape/thinset at every seam, then painted with redguard - including the niche.

I'm not convinced on the 6 mil poly sheet for vapor barrier though behind the cement board if the entire surface is being redguarded and the bathroom having adequate ventilation.

As far as the gap between the bottom of the cement board and the top of the tub, your diagram shows it to be filled with silicone. I've also seen this gap be filled by using mesh tape between the cement board and tub flange, then fill the gap with tile thinset to be flush with the cement board. Then the entire face (cement board + thinset extension at bottom) is painted with redguard. Is one way better than the other?


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## chandler48 (Jun 5, 2017)

That is super messy. Leaving the gap between the bottom of the cbu and the tub surface is tiled over. It also prevents wicking of water, since there is nothing there to allow it. Your tile will jump the gap just fine.


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## huesmann (Aug 18, 2011)

As long as you're not using some kind of short height tile as a border or something like that!


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## dtbingle (Jul 19, 2017)

Caulking it is!

Any comments on silicone vs. a polyurethane caulk?

Came across some resources online talking how thinset and silicone don't properly bond to each other and using a polyurethane caulk would be a better option. Thinking this would only be an issue at the wall corners where the seam makes it down to the tub flange, but never-the-less, this could be a water entry point for anything that makes it behind the tile/grout/final caulking.

If polyurethane caulk is recommended, what would be an example of brand/type? The only option that comes up on Home Depot's site for "Polyurethane Caulk" is this - link here.


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## huesmann (Aug 18, 2011)

For this kind of use I prefer silicone over polyurethane. The latter hardens and then cracks over time and movement; the former stays pretty flexible.


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## Calson (Jan 23, 2019)

Put in blocking for adding grab or shower bars later and make a sheet detailing the locations for them. 

For the niche you can cut the tiles on the sides to allow for adding two horizontal pieces back to back for the shelf. It makes for a cleaner look and is faster to do.


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## chandler48 (Jun 5, 2017)

Definitely as @Calson mentioned. I put 2x10's all around where practical at 34" centered AFF. It gives leeway to meet most customer's requests.


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## dtbingle (Jul 19, 2017)

Calson said:


> Put in blocking for adding grab or shower bars later and make a sheet detailing the locations for them.
> 
> For the niche you can cut the tiles on the sides to allow for adding two horizontal pieces back to back for the shelf. It makes for a cleaner look and is faster to do.


Thanks for the tip. I added the blocking for the shower curtain rod, but nothing extra for grab bars.

Not sure I follow what you're saying about cutting the tile though to have two horizontal pieces back to back.


For the bottom of the niche, going to cut down a 1/2" 6x36 marble threshold to size.

Then install the Snow Illusion accent tile in the back.









Then use bullnose tile inside the niche for the perimeter - like the picture below - and fill out the remaining depth on the wall and top niche surfaces with a narrow subway tile cut.









Does this seem OK?


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## dtbingle (Jul 19, 2017)

Another question. After planning out the wall tile, realized the tub deck is 1/8" out of level across the 5' tub. Using full tiles would mean a gap between the tub deck and bottom of first tile row of a 1/16" at one end, and 3/16" at the other. I feel that this might look bad with the gap height changing 1/8" over the back wall of the tub.

This seems like a common issue and is dealt with by cutting this first row of tile. However, the things I've read mentioned it will look weird if you start at the lowest point with a full tile and then just take slivers off of the tiles while working to the high side. The better approach would be to cut the tile at the lowest point to around 3/4 height and that this hides the level issue much better.

In my situation, 3/4 of the 4x16 subway tile leaves a 3 in height. This means:
3" tile height
- 1/8" gap between CBU
- 1 1/4" tub flange
+ 1/8" gap between tub deck and tile

= 1 3/4" of tile ON the CBU
1 1/4" of tile OFF the CBU

Is this 1 3/4" of tile height adhered the CBU enough to actually hold it over time? The only other option I can see is to shim out the studs and drop the CBU over the tub flange. Suggestions?


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