Oh no, Stacey! You have really had your share of problems with this bathroom haven't you? No advice, just sympathy.

Hi Stacy,
Sorry to hear about this failing. Please describe the tile and the installation process? Large-format glass can develop stress-cracks if installed too tightly (the thermal expansion properties of glass are astounding!) or if no expansion joint was provided for at the corners.
How is this crack manifesting? Is it horizontal, as if along the cement board seam? Does the crack radiate from a corner into the field of the wall? Or does the crack just appear in the center of a tile?
Shaughnn

It'm sure it's not the installation... that was done by a pro:) They're small glass mosaic tiles ( like 3/4" each on 12 x 12 paper-faced sheets). I can't remember the thinset Bill used... something "ultralight"? And he installed them over the walls we provided, which are framed and covered with 1/2" cement board attached with the proper screws. This crack is in a new construction partition wall which is secured both top and bottom (top secured through ceiling to blocking between the joists.) It looks like this crack is along one of the joints in the cement board. It is a horizontal crack which starts in a grout line, jumps up through the center of some tiles (horizontally) then up to continue horizontally along the next grout line.

I've got straight, horozontal cracks in tile in an old bath and assumed they occur where CBU edges are. Does anyone ever sheath shower walls with structrural 3/4" or even 1/2" ply before applying the cement board, to prevent this from happening? I saw similar cracks in tile on a mud wall job that was determined to have been applied too wet in areas, resulting in uneven drying and more shrinkage over the wetter areas.

Bill

Straight-line cracks over CBU are often due to untaped joints or inadequate fasteners (length or quantity). Unless the crack is at the tub edge, it's hard from me to imagine, given only this description, of a "sagging" wall being the culprit.
Yes, sheathing can be used under the CBU but the problem with that is that the entire room then needs and additional layer of sheet rock to compensate for the extra thickness of the added sheathing.
Shaughnn

We did use the exact fasteners (brand, length, size) spec'd by the cement board manufacturer.

It is not happening anyplace else (this tile is throughout the bathroom), just in this one place.

It's just sooo discouraging. I was in the process of gathering materials and energy for the next bathroom renovation, and now I've totally lost my motivation. (I am sorry to whine.... I also had a close family member pass away unexpectedly 2 days ago... so everything just feels horrible!) So discouraging!

I think an isolation membrane would have helped in this case. Like Kerdi.In addition to the waterproofing qualities, it allows the tile to "float" over movement in the substrate.
Casey

Oh, what a bummer. I doubt it's a tile installation issue since you saw movement in the closet first. But do get Bill back because you'll need his professional opinion to go after the builder if it is a joist problem. It wouldn't be normal expansion/shrinkage though, or most every house would experience problems on a semi-annul basis.

Well, we're "the builder".... and my architect dad spec'd the floor joists. They were PT lumber and hugely oversized, so I don't think there's any issue there. We're theorizing that since so much weight was added in that corner, with all the shower cement and CBU, we may see a year's seasonal cycle of changes but hopefully that would be the extent of it.

For now I just need to figure out how to fill the hairline crack in so water doesn't migrate behind there and cause more mold. And hope it doesn't get any bigger.....

hi Stacey,
You used pressure-treated lumber for your joints? I'm not a general contractor, only a specialist, so I may be incorrect here but I believe that this may be part of your problem. Pressure-treated lumber is injected with preservatives and is very very wet. As it dries out, it will warp, twist, bow and shrink. That's possibly the source of your movement?
You could remove the cracked tiles and replace them before grouting? It won't address the compromised underlayment though so you should expect for the cracks to re-appear.
Best of luck,
Shaughnn

PT was spec'd because of the proximity to the earth just below. The ones that were removed were quite rotted. This was spec'd by architect (my dad) and just to double-check I looked it up here in the AFA Details for conventional wood frame construction:

Unexcavated Spaces
Exposed ground in crawl spaces and under porches or
decks is covered with 6-mil polyethylene film. Minimum
clearance between the ground and the bottom edge of beams
or girders is at least twelve inches. Clearance between the
bottom of wood joists or a structural plank floor and the
ground is a minimum of 18 inches, Figure 9. Where it is
not possible to maintain these clearances, approved1 pres-
sure treated or naturally durable wood species are used.

Shaughnn's concerns are valid, but Stacey, your point is correct as well. PT is okay with one caveat, it should have been (it may very well have been) kiln dried after treatment. I spec it out as "KDAT".

Typical wet PT 2x10s or 2x12s can shrink big-time as they dry. They can lose as much as 1/2 to 5/8ths of an inch.

Kiln drying after treatment gets the moisture level down to where moisture shrinkage is not an issue.

This foundation has been in since 1990, so there shouldn't bee any soil expansion, compaction, or heaving issues if it went down to frost level and the footings were put over undisturbed soil. Frost is generally 42" to 48" in your location. At least here I think you live. Plus we really don't have expansive clay like other areas.

If the builder poured the footings over backfilled soil, or over old buried construction debris, then all bets are off, even 10 or 15 years down the road. I've even seen the aftermath of footings or slabs poured over buried construction debris, trouble may not show for five years or 20 years depending on depth and moisture within the ground.

While this is a serious disapointment, I hope it isn't "serious" serious.

Thanks Mongo.

I am in Maine.. and actually one of the big problems in our yard is that it is almost totally clay. The previous year, we'd spent an ungodly amount of money having that corner of the yard regraded and a drainage ditch put in, because there were also major drainage issues there. Inches of water would sit on the yard for days after rains. When the floor was torn up, my husband excavated out several more inches of dirt so there was a little more space under the joists... and under the top few inches of sand it was hard, dense, clay (that's why he didn't excavate further... he was doing it by hand in August, shoveling it out a 15" wide hole in the wall we created for that purpose!)

So: maybe the foundation IS moving????

But also, my husband bought the PT, and he said he can't remember if they were KDAT or not. They were 2x12s, and very expensive, he said, and he thinks he asked for floor joist material.... but we can't be sure. There's NO access for a human into that crawl space now that the floor has been sealed up. (The architect/dad spec'd them verbally.... "get pressure treated floor joists" so we have no written specs...)

Soooooooooo..... what now? What should I use to fill in the hairline crack so moisture won't penetrate back there? (It is not noticeable when standing, only when crouching, since you have to be at eye level to see it.) Should I use a thin mix of grout?

I thought you were in MA, not ME.

The good news is that if it's the PT that shrank, it's done.

The bad news is that if the soil is undergoing expansions and contraction cycles...it's unstable.

I don't have a vast amount of experience working in clay, but I had a big bucks job in clay years ago. We actually set up something similar to a drip irrigation system around the perimeter of the foundation.

The purpose was that the drip irrigation would keep the clay continually moist so it wouldn't undergo movement cycles as the clay dried and rewet. It'd essentially stay permanently wet and not move.

Any excess moisture was removed by foundation perimeter and footing drains.

Now, you wrote that the crawl space is sealed up...

1) For clarification, I'm assuming that there is a concrete foundation around the perimeter of this addition? Or is it built on piers?

2) If it's a poured foundation, was a rat slab (thin 2" poured slab) or a full slab poured in the crawl space? Or is the bottom of the subfloor open to soil on the ground?

3) With the clay, did your dad have any engineering analysis done with regards to soil movement or stabilization?

As to "what now"...was this a Kerdi shower? Or did it have a topical membrane (HydroBan, RedGard, etc)? I remember your shower but forget the specifics of how it was built. If Kerdi, the cracks are sort of inconsequential when it comes to water penetrating into the walls. The cracks are more cosmetic unless they really open up.

I'd get in touch with your installer regarding the details of the walls. Depending on how the walls were detailed/waterproofed might give you a warm fuzzy regarding letting things sit as they are while you see if movement has stabilized versus taking action (caulk the crack, etc) if water penetration may be a concern.

I'd mark the ends of the cracks with blue tape and keep an eye to see if the cracks extend or if the movement has stopped or stabilized.

Thanks, Mongo.

The addition has a concrete foundation around the perimeter, but there's no rat slab that we know of, unless it's under a whole lot of dirt!! The dirt was filled back in up to maybe 2" from the joists in some places. Yuck. We excavated all we could reach (only about 1/2 the addition was gutted do to the mold problem) and re-installed a good thick plastic vapor barrier. (There's one over the dirt under the rest of the addition as well.) For what it's worth, we've checked the crawl space several times over the last 6 months (we can look in through the vents and underneath the bathtub we can pop up a piece of subfloor) and it's remained totally, completely dry under there...

No formal engineering analysis was done of the clay, though we did have an civil engineer here looking at the drainage issues the year before. Between his comments, my dad's, and the excavators we had come look at it, a plan was devised to create better drainage at that end of the property. So, we've DEFINITELY improved the drainage. It's pretty dry there all the time now, even in spring. Perhaps that is part of the issue: that for years the soil at that end of the house was soggy and now we've dried it out.

Regarding the shower, I believe it was Hydroban. Definitely not Kerdi, though now I wish we'd gone that route, of course :(

I'd walk the exterior and if possible, crawl the interior, of the foundation. Give it a real good look over.

Look for any settlement cracks. The weak points will be around any window bucks or vent frames. Concrete can incur shrinkage/curing cracks. Those will normally be mid-point in a wall and run vertical. The curing process for concrete is exothermic, it gives off heat, and the chemical reaction consumes water in the concrete mix. After curing, shrinkage cracks sometimes occur. They are not structural, but if you have soil issues that could exacerbate the issue.

In the interior crawl space, take a look at the joists, where they meet the rim joist. If the rim and the joists are all PT, then they should have shrunk together. If the rim, or a ledger (I'm not sure how this addition was attached to the original structure) was non-PT, look at the tops of the PT versus non-PT and see if the PT has shrunk below the non-PT.

Take a real good look under the cracked wall area, the closet/bathroom wall. Is that wall anywhere near where the addition meets the original structure?

Sounds like a lot of "look at this..." but that'd be my first inspection. Though you have a good team between your dad and your man-hubby.

Regarding the shower, HydroBan does have some elasticity, it's good for about 1/8" of movement. If the shower corners and panel seams were set with fabric embedded in the hydroban that will give a bit more protection.

Thanks Mongo,
Unfortunately there is no way to get under there and look. There's no human-sized access, other than to peek in the ventilation holes in the foundation or in the little access panel under the tub. We can't see anything from the exterior, and we can't get into the crawl space. So the "why" will have to remain theoretical, and we'll have to deal with the symptoms as best we can.
For what its worth I can't find any other cracks anywhere in the bathroom -yet. I am going to try using some caulk in the crack.
Major, major bummer :(

Stacey,

How did you end up resolving this? Did you determine the cause of the cracking? Has the grout or tile cracked since?

Threeapples- Have you tried sending an e-mail to the OP? This whole thing happened in 2010 and not everyone hangs around here for too long after they are done with a project. The pros do, as they offer some terrific advice, but the people with problems usually go away after awhile.

-Babka

HI guys,
I still get email notifications, so I saw this.
We have not resolved this. Our daughter got ill and I have just not had the wherewithall to try to figure out how to proceed. I was just thinking that I should tackle it this winter. It's sooooooooo sad to have to basically close my eyes every time I use my formerly beautiful shower :(
We have had several tiles pop off the walls in the shower area, as well as those cracks. I think I am going to have to gouge out the grout a bit in those areas and re-grout them. Ugh. I don't know if the grout is going to stick or not. I hope I don't make a bigger mess.

I did contact Bill Vincent, our tile installer, about the proper way to do this but he did not respond. That was quite disappointing to say the least.

So, yeah, my gorgeous bathroom project looks pretty manky now. :(

I'm sorry to hear about your unresolved bathroom issues, especially the lack of response from your tile setter. I hope you figure this out and can enjoy your shower.

Hi Staceyneil, I am sorry to hear of your daughter's illness.

I had read with joy your daughter's bathroom remodel. I put in self leveling compound following your tutorial! Saved it to "My Clippings". And your cute vanity remake is adorable along with the beautiful tiled niche (it was dreamy).

What kind of grout did you use? I know Mongoct has given help on grout removal.