did you take any pictures of the buildout of your shower niche' ??
should not be happening if your shower was prepped properly from point a-z.

heres a few stabs at would/could typically cause this.....

Ill guess you have expansion contraction issue. Perhaps some non spf KD lumber was used and its swelling/moving, perhaps the cement board didnt meet screw placement and count specs, maybe they didnt leave expansion slip joints, maybe they didnt tape the outside corners properly, to tight of tolerances for the tile specific material and its movement etc....

As Avanti says lets hope its waterproofed and no real damage has yet occured.

about 2 dozen possible causes.......guessing here.....pictures help.

When outside corners blow out like that, it's usually a sign of water infiltration getting into the wood substrate (framing). The wet wood swells/expands and pops the joints open.

Is this a corner that sees water? The bottom of the niche, versus the top, for example?

The niche was framed in metal. Dal Seal TS for waterproofing and Laticrete 9235 applied over it. A slight slope to drain out water is also built. Its only the grout thats coming off at the mitered corner - no chipping/breaking of tiles. They used Laticrete ParmaColor sanded grout.

MongoCT, yes it is the lower corner of niche. What is the right fix for it now?

here are some pictures step 1 through 4 of waterproofing & tiling.

So is it at the change of planes? At the change of planes there should be caulking and not grout. Are you pointing out the area where the shelf turns down onto the wall?

looks like the niche was added after waterproofing. How was the waterproofing done after the niche addition?

The horizontal surfaces are pitched down so they shed water?

I personally prefer a butt joint on horizontals where the flat piece comes out flush with the vertical wall surface. The adjacent vertical tile is mitered so that also pitches down and then gout. Have to use bull nose or natural stone which I prefer for shelves.

I don't caulk this type of thing. However I do put a membrane behind the title for pockets like these.

And I lay the shelf title first, right against the back wall making sure the mortar fills that back joint and even a bit high and on to the shelf tile surface. Then the field tile on the wall so water coming down the wall sheds. Kind of like a roof.

Sealing the gout helps too.

I'd pull up the shelf tile, see what's going on and go from there.

Looks like an Ardex 8+9 waterproofing system. Is that right? Looks like this might also be a steam shower build - is that right? Pretty sure Ardex 8+9 is not approved for a steam shower build on it's own right.

No chance you used a Kerdi Board niche there did you? I'm not a fan of those niches.....

Thanks for all comments/questions. Does anyone know the fix from this point? Niche was waterproofed; slope was built; shelf tile was laid before field, and no its not a steam shower. I am really looking for a fix at this point - any diagnostic steps and corrective measures will be very helpful. Thanks.

This is how you fix this.

"....I am really looking for a fix at this point - any diagnostic steps and corrective measures will be very helpful...." - mgandhi

It's very odd what is happening. Could the grout just be coming out from heavy washing? Did you add more water to the grout mix after you first mixed it? This can weaken the grout a lot.

Bathroom · More Info

When setting my mitered corners I like to over cut the 45 angle so it creates like a dovetail lock with the grout. Without room for the grout to slide between the tile it can be weak.

or Perhaps the framing is out of whack? Something settled. on you..

Never seen this before - sorry.

Joseph Corlett, LLC, thank you for sharing this - very helpful! Did you take the old tiles out to build this, or did you build this trim over the old tiles? When you took old tiles out, was there damage to the framing/substrate and you had to fix that? Do you think I can fix this by Schluter's Strip?

John, at another location where we had the same issue, we caulked with latex based caulk, and that also opened up after some time. So, I don't think it heavy washing.

"....John, at another location where we had the same issue, we caulked with latex based caulk, and that also opened up after some time. So, I don't think it heavy washing...." - mgandhi

What products are you using? This sounds like a weird one off. But now you are saying the same thing is happening on another job.

Makes me wonder about the thin-set mix. The amount of water used. Shrinkage and things of this nature.

A proper fix would require taking it apart and solving the underlying issue. Anything less is a topical patch. Just like a bad tooth you must get to the root of the problem.

I found this picture this morning showing more of what I mean about the over cutting of the 45 degree angle. This shot the upper ceiling curb for the steam shower we just finished.

@ JW .....When are you going to unveil the kerdi line steamer??

"Joseph Corlett, LLC, thank you for sharing this - very helpful! Did you take the old tiles out to build this, or did you build this trim over the old tiles?"

No. The molding and sill were siliconed over the tile.

"When you took old tiles out, was there damage to the framing/substrate and you had to fix that? Do you think I can fix this by Schluter's Strip?"

I think your problem is building movement which has not been accommodated. You can tear out the tile and replace, but if the building moves again, you're back where you started. That's the beauty of my repair; it accommodates some building movement.

I think the Schluter Strip is a superior detail to a mitered tile edge, but that's my opinion. Since it's bedded in the thinset, I doubt it's going to accommodate much building movement. Can you fix this with it? Sure, but that's a lot more work than custom molding and it it moves again you're back to square one.

Can you call it a Kerdi Line steamer when I removed all the Kerdi from the drain and all the kerdi from the floor, curb and walls? lol

Glass just went in last week. I need to do some silicone loving in the corners.

Butech Tile Edging Profiles · More Info

That is the Frameless Kerdi Line tile grate. The thing is a beast and has so much metal. Would hate to drop that on my toe. Looks all right with the Butech Profiles I think.

"Joseph Corlett, LLCI think your problem is building movement which has not been accommodated. You can tear out the tile and replace, but if the building moves again, you're back where you started. That's the beauty of my repair; it accommodates some building movement."

I have many other mitered corners in the shower - both vertical and horizontal, but the only one opening up in both bathrooms is the lower shelf corner of the niche. The opening starts at the lower shelf corner like in my picture and is also expanding to the side vertical corners of the niche. If it was building movement, other corners in the shower should also pop open, not just the niche? btw, thank you for staying engaged on this discussion.

1 other option you may take is to open the wall behind the niche ( if thats possible) and investigate the framing and possible water damage swelling the lumber.

I know it stinks and you want a magic fix here but you likely will HAVE to tear it apart to truly FIX the issue long term.

Remind me again why the Tiler that built this shower is not taking care of this for you?

On a positive note, the install looks nice and great mortar coverage/setting....

"John Whipple - By Any Design ltd. No chance you used a Kerdi Board niche there did you? I'm not a fan of those niches….."

No, its not a Kerdi Niche.

I will ask the tiler to cut back on 45 degrees next time - i like that idea.

What else should I consider when diagnosing? Should I take out the waterproofing to see if there's damage to frame and/or screw spacing is not enough or slip joints etc?

"Tundra Finish Works LLC 1 other option you may take is to open the wall behind the niche ( if thats possible) and investigate the framing and possible water damage swelling the lumber."

Not possible on this niche. But possible in other bathroom niche. Even if I diagnose from the back side, fix will have to be from the tile side.

"Remind me again why the Tiler that built this shower is not taking care of this for you?"

If you have any clients in NYC and they want to know who NOT to hire, let me know.

"....No, its not a Kerdi Niche...."

Thats good.

"....I will ask the tiler to cut back on 45 degrees next time - i like that idea....."

I cut back more than 45 - not 45 exact. This makes a wedge shaped space

"....What else should I consider when diagnosing?...."

I hate to say it. But perhaps your waterproofing (I'm thinking 8+9) was defective or perhaps too old. It is a cemintious product and should be used within 6 months to 1 year of production. Do you have the product box still at your home? Some of my US clients have found it hard getting fresh product. You can look up my blog page to understand how to read their date codes.

Perhaps the SK mesh was not used as well. I think you need to remove a couple tiles sadly to find the root cause.

Link URL: http://no-curb.blogspot.ca/2013/06/how-to-read-date-code-on-ardex-setting.html

Very sorry to hear that.

If this was my problem and the other niche did the same thing Id take and cut a hole in drywall behind that niche as my first and least damaging option( drywall paint EZ fix) I would get to the bottom of niche and inspect for water while running shower head in that vicinity for a quick spell.

If you find signs of water that will tell us the lumber is or is not getting wet and drying causing expansion issues.

based on what I find there I would start carefully taking niche mitered jamb pieces out. If we know we will have to rebuild the niches It will require the perimiter tiles around the whole niche come out. ( do you have more or access to more if this exact tile?

Then all these pros here on GW can help guide you to rebuild your niches properly and tie it back into the waterproofing you have. Solving the problem long term and permanantly.

We still dont know what that is yet. so start with the least evasive troubleshooting is my best advice.

It's tough to give you a diagnosis. At least for me. All I can do is speculate.

You wrote: "The niche was framed in metal." Are you saying that the niche itself is metal? Is the niche manufactured, or was the niche built on site? Is the framing in the wall metal studs? Or are there wood studs in that wall?

So, a few comments:

1) Photo #1: I see very few fasteners heads in the backer board. Doesn't
mean the backer board wasn't fastened to the framing according to
schedule, it just means I can't see them.

2) Photo #2: Alice commented on this earlier; usually the niche is installed, then the entire assembly is waterproofed. Since they 9235'd the wall and installed the niche afterwards, there is a chance that something didn't properly bond to something else. Or that reinforcing fabric wasn't used in the corners where is should have been, and movement caused a perforation/tear in the 9235, allowing moisture to get past the membrane.

But again, it's all guesses. The movement could be due to water infiltration and substrate expansion. But with metal studs, a preformed/manufactured niche, and Hardi backer board, nothing in that recipe invites expansion when exposed to moisture.

The movement could be due to insufficient framing behind the backer board, or insufficient fasteners used to secure the backer board to the framing, or the niche improperly secured to the framing, and the niche/backerboard junction simply "floating", and separating on its own.

But I'm tossing out ideas. Nothing firm. Speculation.

"John Whipple - By Any Design ltd. I hate to say it. But perhaps your waterproofing (I'm thinking 8+9) was defective or perhaps too old……"

I don't know what is 8+9. We have used poly, backer board, then nobelsealant TS (or DalSeal TS) installed over it, and then mesh with laticere 9235 poured over it.

" MongoCT …….Is the niche manufactured, or was the niche built on site? Is the framing in the wall metal studs? Or are there wood studs in that wall?"

The niche is perforated, and then waterproofed to blend with the rest of waterproofing. All metal studs, wood studs not allowed in NYC.

Attaching some more pics to give an idea of original framing as well as waterproofing layers….

I would not even consider the fix suggested by Mr. Corlett. It does not address the source of the problem and it leaves you with a dam at the front of your niche, trapping water with no way to drain it - just begging for more problems in the future. It is likely you need to tear out some tile and the niche to ensure proper installation. What a mess that will be, but better than living with a problem that will only degenerate further.

"I would not even consider the fix suggested by Mr. Corlett. It does not address the source of the problem and it leaves you with a dam at the front of your niche, trapping water with no way to drain it - just begging for more problems in the future."

aliceinwonderland_id:

My linked fix does no such thing. The solid surface sill extends past the wall tile and has a drip slot on the bottom preventing the water evacuating the sloped sill from running down the wall, unlike the original tile installation.

This is a failure to accommodate building movement, whatever the cause. My solution is quick, inexpensive, reversable, and accommodates building movement.

Game changer there with steel studs....( horsecrap for building showers IMO, but code in your situation).

As Mongot said; were all Guessing

seems a lack of screw count in this pic and backer butted to tight in corner.

"...I don't know what is 8+9. ...."

I see you used a liquid waterproofing from Laticrete now. Was the reinforcing mesh used? Was the concrete board all first taped with mesh and thin-set and allowed to dry prior to waterproofing? Was the waterproofing given seven days to cure prior to flood test? Did you flood test?

"....Attaching some more pics to give an idea of original framing as well as waterproofing layers…....."

I don't like any of the framing you show in that first picture. The walls appeared to be framed with "Hat Track" which we use for boarding ceilings here in Vancouver. You would expect to see 2"x4" wall studs metal with 2"x4" Metal Track top and bottom. Seeing these I fear your wall assembly was not rigid enough and the failed grout the result of the wall flexing when pushed on.

At the very top you see the Metal Track. There is one up and one down. Both pinned to the concrete floor and ceiling with wedge pins. I raised the ceiling to make room for the rain head and am adding a boarder inside the shower to continue the old ceiling height.

Even these studs are pretty light weight. I believe the proper stud by the book is the heavier gauge stud. The kind not stocked in Home Depots but rather the drywall metal speciality stores. Local inspectors let this fly but crack down hard on wood framing and no firestopping. The spray foam I used in stead of throwing away. I find it adds one more level of strength to a new dropped in stud. Once dry it gets screwed off from the back side.

Why does it appear you used two layers of 1/4" backer board. Looks like first 1/4" Wonderboard then 1/4" Hardie? The poly behind the backer board would be I think designed to lap over a rubber liner or something like Noble Company's Chloral.

Link URL: http://noblecompany.com/products/chloraloy/