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Unread 10-15-2020, 07:49 PM   #211
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Not entirely sure I understand the new plan, Dan. If you have a moisture barrier behind your wallboard and you bond a strip of sheet waterproofing membrane to your tub's tiling flange and the bottom face of your wallboard, what's your plan for the moisture that passes through the rest of your wallboard and collects at the bottom?
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Unread 10-15-2020, 08:22 PM   #212
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Hi CX,

I''ll try and recap where things are at, and what has been discussed.

1. Since the corner is greater than 90 degrees and results in a 1/4" gap between the side walls and tub (image), it was agreed it is ok for the CBU to be flush with the tub's flange (link).

2. It was recommended I use a strip of waterproofing membrane to tie the two together and waterproof that area (link)

3. I seemingly made the wrong choice to nail the tub's flange through the poly (link) and your reaction to it (link).

4. The options I see (link):

4.1. Switch the side wall screws to SS (the back wall is nailed and is fine). Apply a 10" redguard strip over fiba tape.
Or
4.2. Eliminate the side wall screws. Remove the CBU on the side walls. Seal the barrier holes with weathering tape.
Or
4.3. Eliminate the side wall screws. Remove the CBU. Apply new 6 mil poly to the sides overlaping a few inches with the back wall's poly.
Or
4.4. Start all over (including the backwall where the CBU overhangs the flange) with new 6 mil poly everywhere and no screws at the flange for the side walls. The CBU would still be flush or proud of the the flange.

5. From Dan's response here, I understood that I should switch the flange screws to SS and apply a kerdi-band but I wasn't sure if I should apply the band to the back wall if there are no tub flange screw holes through the poly there and the CBU overhangs the flange

Open to suggestions as to the best course of action if at all? At the end of the day, are the screws holding the flange any different than the screws holding the CBU through the poly 1 inch above?

Apologies if wires got crossed
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Unread 10-16-2020, 12:08 AM   #213
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5. I'm thinking Dan was not considering that you still had a full moisture barrier behind your wallboard that lapped over your tub's tiling flange, but we'll need to let Dan address that.

The difference I see between the unavoidable penetrations of the moisture barrier when the wallboard is installed and the penetrations you made when using screws through the membrane to secure the flange is location. Yes, the wallboard fasteners also penetrate the membrane, but experience has shown you can get away with that. It's not ideal, but it's known to work. The holes you poked in the membrane at the tub flange are not at all compressed between wallboard and framing, but just open holes directly where gravity fed moisture is likely to try to make an exit. And instead of exiting into the tub, it can exit behind the flange.

Will that cause your installation to fail next week? No, it won't. Will it cause your installation to fail sooner than it should or would had you not done that? Yes, I think it will. Is that sufficiently worrisome for you to take drastic action to fix the situation? That's entirely up to you. Will adding the strip of waterproofing membrane at the bottom of the wallboard and gluing it to the tiling flange help at this point? I don't think it will help at all and I think it will actually exacerbate the problem. Can I prove that? No, I can't.

Again, the different methods, moisture barrier behind the wallboard and lapped over the tiling flange or the direct bonded waterproofing membrane on the face of the wallboard and attached to the tiling flange are an either/or proposition. You've currently got a damaged either, which cannot be corrected by adding an or.

My opinion; worth price charged.
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Unread 10-16-2020, 05:57 AM   #214
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ok. I'll decide what I want to do.

If I decide to reset the poly, would you recommend to:
1. Reuse the CBU sheets, screw it back through the existing holes that were put in it.
2. Reuse the CBU sheets, screw it back via new locations in the sheet. redguard the previous holes?
3. Use new CBU sheets

Thx
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Unread 10-16-2020, 07:44 AM   #215
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My logic was that if the tile is caulked to the tub deck then the water isn't getting out anyway. You could leave some openings in the caulk but those wouldn't guarantee that water won't accumulate somewhere where along the flanges, and those openings might even allow water to get in, and they might well be a constant area of mold/mildew build up.

Mitigate the potential for water intrusion. Use a porcelain tile and epoxy grout.
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Unread 10-16-2020, 07:54 AM   #216
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same apparent contradiction for the mfrs. recommendation to apply silicone sealant between the CBU and flange (when it overhangs the flange).

What is the SOP for taking CBU off and re-putting on (should i decide to go that route)
?

1. Reuse the CBU sheets, screw it back through the existing holes that were put in it.
2. Reuse the CBU sheets, screw it back via new locations in the sheet. redguard the previous holes?
3. Use new CBU sheets
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Unread 10-16-2020, 09:01 AM   #217
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I'd go with #1, Dan.
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Unread 10-16-2020, 09:49 AM   #218
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The only time I've actually heard a manufacturer's rep address that question in a technical committee meeting he recommended not using the old fastener holes, but rather to fasten through new locations. That was USG for Durock.

And if you're gonna remove your wallboards, I'd recommend you remove the moisture barrier entirely and use a direct bonded waterproofing membrane over the entire interior of your walls and kill all the birds with that stone.

My opinion; worth price charged.
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Unread 10-16-2020, 10:34 AM   #219
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Quote:
Originally Posted by cx
And if you're gonna remove your wallboards, I'd recommend you remove the moisture barrier entirely and use a direct bonded waterproofing membrane over the entire interior of your walls and kill all the birds with that stone.
Yeah, I was thinking about how much I hate alcove tubs, and how poly doesn't seem ideal in a situation where there is space between the tub and the studs, the CBU doesn't overhang the flange, and you try and secure the tub to the studs.
In a previous remodel I trusted my ability to hang a sheet of nylon but didn't trust my ability to correctly apply the membrane. Since then I have applied it on a floor and a niche without issues.

1. If the poly is out, and redguard is in, the kerdi-band is in as well right (for the CBU that is flush with the flange)?

2. If the kerdi-band is back in, then back to the original question, do I need to apply it to a redguard'd back wall where the CBU does overhang the flange?
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Unread 10-17-2020, 08:42 PM   #220
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Today's progress.

Hi poly...
...bye poly
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Unread 10-17-2020, 08:44 PM   #221
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And the CBU is back up again
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Unread 10-17-2020, 08:49 PM   #222
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Quote:
Originally Posted by ss3964spd
Where the backer abuts the apron of the tub - the leg, I'd be tempted to seal that joint with Kerdi Fix, but the little void you have (see pic below) will be a challenge. I'd probably cut a new piece of backer so most of that void is filled
Done (pic attached).

Up next, taping the sheets and niche.

I do have these questions:

1. If the poly is out, and redguard is in, the kerdi-band is in as well (for the CBU that is flush with the flange), right?

2. If the kerdi-band is back in, then back to the original question, do I need to apply it to the redguard'ed back wall where the CBU does overhang the flange?

3. Does the band go before or after redguard is applied?

4. Do you patch with thinset the CBU screws before applying redguard (like you would patch drywall screws sort of a thing)?
Either way, I will fill with thinset the prior CBU screw holes.

5. Previously when using poly, I only applied redguard to the niche's seams. Without poly, should redguard be applied to the inside of the ready made niche as well?

Thanks for the help
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Unread 10-17-2020, 09:09 PM   #223
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1. Dan, consider what your goal is here. When you switched to a direct bonded waterproofing membrane you created a need for the entire inside surface of your walls to be waterproofed. On the walls that stop above the tub's tiling flange, you must have a way to cover that gap and still have a continuous membrane on the wall. That's where the sheet membrane shows its colors. It can do that. I even recommend you give the membrane a bit of a wedgie into the gap to provide for extra movement accommodation.

On the back wall where the wallboard covers that gap, you have no need for anything other than the same direct bonded watrproofing membrane you plan to use on the rest of the wallboard. The movement accommodation is provided by the wallboard not being attached to the tub and the liquid-applied membrane, if that's what you elect to use, will be adequate.

If it somehow makes you feel better to have the Kerdi Band go all the way around the bottom of the wallboard, do that. It will also serve the waterproofing purpose there if that's what you wanna do.

My opinion; worth price charged.
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Unread 10-17-2020, 10:36 PM   #224
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awesome, thx.

What do you think about these:

3. Does the band go before or after redguard is applied?

4. Do you patch with thinset the CBU screws before applying redguard (like you would patch drywall screws sort of a thing)?
Either way, I will fill with thinset the prior CBU screw holes.

5. Previously when using poly, I only applied redguard to the niche's seams. Without poly, should redguard be applied to the inside of the ready made niche as well?
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Unread 10-18-2020, 07:20 AM   #225
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IMO, Dan, if you use Kerdi band only on the end walls you present an opportunity for water from the back wall to get in behind the band - unless you are able to completely seal the ends of the band.
  • I would install the band first, then RG over the edge of it.
  • I would fill the holes with mortar before RG'g them.
  • If that niche is made of a water proof material I see no benefit of applying RG to the inside of it.
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