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Discussion Starter · #1 ·
Hi group, I'm an electrician, hiring a tile contractor, have a question on using a membrane vs red gard vs ardex 8-9.

1. Tub surround has waterproof paper on the studs, and wonderboard. I was going to redgard, then a membrane sheet, but a little worried about my buddy who did the wonderboard because the corner seams are a bit rough not too straight. Should I have the tile guy fix that after the membrane or before.
2. Cracks on the cement in the vanity, would you use a membrane sheet or ardex 8-9 or is redgard sufficient.
3. Kitchen was leveled with no cracks on the surface, not sure if I should add a membrane, ardex 8-9, or redgard. Thanks in advance for your time and help. Dave
 

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Hi group, I'm an electrician, hiring a tile contractor, have a question on using a membrane vs red gard vs ardex 8-9.

1. Tub surround has waterproof paper on the studs, and wonderboard. I was going to redgard, then a membrane sheet, but a little worried about my buddy who did the wonderboard because the corner seams are a bit rough not too straight. Should I have the tile guy fix that after the membrane or before.
2. Cracks on the cement in the vanity, would you use a membrane sheet or ardex 8-9 or is redgard sufficient.
3. Kitchen was leveled with no cracks on the surface, not sure if I should add a membrane, ardex 8-9, or redgard. Thanks in advance for your time and help. Dave
What's waterproof paper?

If he put plastic on the face of the studs then wonderboard I wouldn't put another layer of waterproofing.

Need more details to answer the other questions...
 

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Fix the walls now, Call the tile guy over let him take a look, He may be the guy to fix the walls. Then ask him about water proofing. Red guard and hydroban are membranes.
 

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What's waterproof paper?

If he put plastic on the face of the studs then wonderboard I wouldn't put another layer of waterproofing.

Need more details to answer the other questions...
Completely wrong advice. The fact that there is waterproofing under the cement backer board means nothing. The substrate needs to be waterproofed. For the couple hours it would take, I would re do the poor wall board installation. If it's not right from the get go, you'll have a mess on your hands all the way through.
 

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This won't win me too many friends with the backer board crowd, but oh well.
Do this:
1. Remove and trash blunder board.
2. Have a qualified tile guy run Aquabar (or equivalent) water barrier paper straight to studs, overlapping a good 4-6".
3. Metal lath. Again, overlap, 2" minimum
4. Scratch coat.
5. Float surface perfectly flat, level, plumb, and square.
5. Roll on RedGuard for extra protection against cracking and water issues. (Optional, but a good idea)
6. Tile and grout as usual, and walk away knowing you've had it done right.
 

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Completely wrong advice. The fact that there is waterproofing under the cement backer board means nothing. The substrate needs to be waterproofed. For the couple hours it would take, I would re do the poor wall board installation. If it's not right from the get go, you'll have a mess on your hands all the way through.
So what's the problem with properly installed 6mil poly behind cement board? If I already had that installed I wouldn't bother ripping it down.
 

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So what's the problem with properly installed 6mil poly behind cement board? If I already had that installed I wouldn't bother ripping it down.
Cement board is not waterproof. Your quote "I wouldn't add another layer of waterproofing" is absolutely incorrect. You can discuss all you want, but my advice would be to keep your advice about tile work to yourself.
 

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Discussion Starter · #9 ·
Hi everyone, I have a massive head cold wasn't clear on my original post, apologies.
I meant we put 15lb felt on the studs, then wonderboard, when I said should I put redgard then a membrane, meant all the contractors were telling me to put redgard on before they came. I was sort of shocked they said this to me, but I guess they think I am in the biz... and I should do some of the work. (Not sure why) anyway, I am also thinking my friend did a crap job, but I wasn't really looking at his work as I had my hands full repairing all the electrical mess I had until today.

The wonderboard is straight but not the corners, they look bad, but the three guys didn't think it was bad they simply want to make sure water doesn't go up at the tub edge, and they want to make sure the all the grout lines won't leak.

I guess I should have them rip the wonderboard out but so far no one is sending an estimate, I always get the estimate out that night or next day by 12pm... Very odd group of guys... I hate asking favors of people I know, but might have to.
 

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So what's the problem with properly installed 6mil poly behind cement board? If I already had that installed I wouldn't bother ripping it down.
imho, if you're using plastic it should only be put behind the walls of a shower. In a shower, any water that gets through or condenses on the plastic would drain into the mudbed. In a tub situation, where would that water go?

Regarding the moisture sandwich theory, I think it would only apply to a Northern climate. But we are taking about water vapor if the waterproofing is done correctly.
 

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This won't win me too many friends with the backer board crowd, but oh well.
Do this:
1. Remove and trash blunder board.
2. Have a qualified tile guy run Aquabar (or equivalent) water barrier paper straight to studs, overlapping a good 4-6".
3. Metal lath. Again, overlap, 2" minimum
4. Scratch coat.
5. Float surface perfectly flat, level, plumb, and square.
5. Roll on RedGuard for extra protection against cracking and water issues. (Optional, but a good idea)
6. Tile and grout as usual, and walk away knowing you've had it done right.

It's a regional thing, isn't it? California, Texas, Pennsylvania and maybe a few others.

What you imply is that ALL mud jobs are good. Perhaps only mud jobs done right last. Just like the cement board jobs. The installer is the difference.
 

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Cement board is not waterproof. Your quote "I wouldn't add another layer of waterproofing" is absolutely incorrect. You can discuss all you want, but my advice would be to keep your advice about tile work to yourself.
You should read up a little on the TCNA website where it clearly shows two approved methods. One using 6 mil poly behind concrete backer, the other with surface applier waterproofing. Certainly the surface applied is better but the former method is by no means unacceptable.

I encourage you to purchase the TCNA section B415-2013 if you are interested in learning how to properly construct a shower.

imho, if you're using plastic it should only be put behind the walls of a shower. In a shower, any water that gets through or condenses on the plastic would drain into the mudbed. In a tub situation, where would that water go?

Regarding the moisture sandwich theory, I think it would only apply to a Northern climate. But we are taking about water vapor if the waterproofing is done correctly.
The plastic goes over the tile flange and excess moisture would drain into the tub. But as you said there is little water penetrating the wall assembly.
 

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I have a TCNA manual. You were assuming that the plastic under the cement board was done correctly, and your advice was that no other waterproofing was needed. If you still stand behind your advice then that's up to you.
 

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I have a TCNA manual. You were assuming that the plastic under the cement board was done correctly, and your advice was that no other waterproofing was needed. If you still stand behind your advice then that's up to you.
Correct if I assumed everything was built incorrectly I'd say buy a can of gas burn it down and start over.
 

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[QUOTE="Inner10;
The plastic goes over the tile flange and excess moisture would drain into the tub. But as you said there is little water penetrating the wall assembly.[/QUOTE]

How would it drain into the tub? That spot is usually caulked.

In a shower, it would drain into the mudbed.
 

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Poly has to be mechanically attached to the studs. To me, this leaves too many areas of weakness. Also you have to prierce the plastic with the backer fasteners. I can't imagine how anyone could consider that a waterproof installation. While the TCNA May say its an acceptable practice, it isn't always the best practice.

But if you insist it staying, it would HAVE to be tied into the shower pan, overlapped properly and all of the fasteners waterproof. You would then still need to waterproof all fasteners used to install your substrate.
 

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This all sounds so backwards . I don't understand the theory behind waterproofing behind the backerboard . This would allow for mold to grow in an ideal place .The fact that moisture is getting behind the backerboard to me means an installation failure . I think experience and common sense should prevail over any TCNA manuals . If there is gaps in the corners and joints use thinset and backerboard mesh tape to fill it in and then hydroban or redgard to waterproof it . Done !!
 

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It's a regional thing, isn't it? California, Texas, Pennsylvania and maybe a few others.

What you imply is that ALL mud jobs are good. Perhaps only mud jobs done right last. Just like the cement board jobs. The installer is the difference.
It's not a California thing that I know of.
 
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