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Unread 01-18-2022, 12:51 PM   #16
PhilWA
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Quote:
Originally Posted by Jadnashua
The instructions for HardieBacker specifically say that the board MUST be terminated ABOVE the top of the mudbed, and NOT embedded IN it.
Is this embedded board alone cause to demo the shower? This testing seems to indicate embedding the board won't immediately cause a complete failure of a shower? https://www.johnbridge.com/articles/...d-cbu-showers/

Quote:
Originally Posted by Jadnashua
It does make the HardieBacker stiffer, but also, will swell if it gets saturated. Inside of a mudbed of a conventional shower pan, it WILL get damp.
Does hardibacker really swell? I was under impression swelling wasn't a major concern with hardibacker, although I've seen this posted before? This link discusses people claiming that it dissolves, but seems to indicate it's stable (plus, I didn't see mention of it swelling) even when soaked for long periods. https://www.johnbridge.com/vbulletin/archive/index.php/t-103730.html

Quote:
Originally Posted by Jadnashua
Since cellulose is also organic, it is subject to support mold growth.
I suspect soap and human body grease are far and away primary contributors of food for mold in any shower.
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Unread 01-18-2022, 03:14 PM   #17
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When installed properly, (i.e., not embedded in the shower pan in this case), the panel will get essentially dry and stay no more than slightly damp on the surface. Cellulose does expand when it gets soaked. On a wall where it might only get damp, it has a chance to dry out in between, but in a typical conventional shower pan, that never happens on a shower used regularly.

There's a reason why the manufacturer calls for building your shower this way, with the board terminated above the top of the pan. That's also a reason why the TCNA procedure calls it out in a separate entry, different from when a 'conventional' cement board is used.

How long it may take could vary, but it would be worse if the pan liner wasn't sloped, as the pan would become saturated versus just being damp.


The manufacturer does the testing so that the customer doesn't have to. Why second guess them? If they felt it wasn't a potential source of failure, they'd follow the rest of the cbu panels out there.
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Unread 01-18-2022, 03:20 PM   #18
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Phil, from the little bit of testing of various CBUs for wicking and water penetration I've done, I'd be inclined to agree with you. The industry does restrict the bedding of the Fiber/Cement boards in the top mud bed in a traditionally built shower receptor, though. Would I tear out an otherwise properly completed shower based solely upon that? I don't think so, but it does stray from the Standard requirement.

In none of my testing have I ever seen Hardiebacker swell when wet, even after a year or more, but that doesn't prove it can't happen, I suppose.

My opinion; worth price charged.
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Unread 01-18-2022, 03:31 PM   #19
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Quote:
Originally Posted by Phil
Does hardibacker really swell?
Yup. I was using a piece of BH to enlarge the sliding table of my wet saw to cut some mesh mounted glass tile, on and off over the course of 6 or so weeks (shower accent and vanity back splashes). It did swell. Not a lot, but noticeable.

No idea if swelling HB is what caused the OP's wall to floor joint grout to crack. Using "crack" to describe that wall to floor joint doesn't seem accurate, as it appears the floor tile pulled away from the grout, making the joint wider than it originally was.
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Unread 01-18-2022, 04:01 PM   #20
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Quote:
Originally Posted by khipshire
Our builder has agreed to fix the crack in the grout with silicone in whatever manner we would like. So I am back to the original question of the correct manner to go about that. Many thanks for any advice on the correct steps for him to take.
There was another post within a few weeks ago that was similar such that the builder asked the homeowner for instructions on how to make repairs; I can't find the post. Anyhow, the wiser people here pointed out that the builder was using a dodge to pressure the homeowner into coming up with methods/repair instructions. The clever part of the dodge is that it makes the homeowner responsible if the repair doesn't work or if results of repair were still unsatisfactory or cause additional damage (lazy repair technique could cause damage to adjacent tiles or puncture the liner). It's the builders responsibility to know/find out how to properly fix mistakes.
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Unread 01-18-2022, 04:28 PM   #21
PhilWA
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Quote:
Originally Posted by jadnashua
The manufacturer does the testing so that the customer doesn't have to. Why second guess them? If they felt it wasn't a potential source of failure, they'd follow the rest of the cbu panels out there.
Good point. There are maybe 3 or more construction errors in this shower, and if the cumulative errors result in shower that only lasts ~10 years (instead of 30+ for a properly built shower), it seems like it would be hard to press the builder into a rebuild? Tough situation after the house is already built and you're 4months past moving in.

Those open questions about the potentially missing shower curb & flat liner could represent faster failure modes for the shower failing much sooner...
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