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Shower walls prep for tile

Posted by sriirvine (My Page) on
Fri, Sep 7, 12 at 18:26

Hello, we are doing a home addition with a new master and master bath. The master bath has a shower with a bench in it. Our GC has hotmopped the shower (we are in CA) and it looks good. Now I started doing research and it looks like Bill V and others recommend some sort of cement backerboard with Hydroban onto which the tile is floated?

I talked to my GC about it and he says that what he does is to put down a lath, tar paper and mud that (I hope I'm getting his terms right). His words were "I'm old-school and that has worked well for a long time".

I did a bit of looking around and it sounds like the there are some who do the hot-mop + lath-tar-mud combo, but that's the old way. The problem is that I don't know enough about this to even question him on it. Does that seem like a suitable way to prep a shower wall? Anything in particular to be careful of with this method?

We'll be using 6"x3" shower tile if that matters.

Thanks!


Follow-Up Postings:

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RE: Shower walls prep for tile

The "old way" is the better way.

When your house falls apart in 100 years, the shower will tumble to the ground, perfectly intact.


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RE: Shower walls prep for tile

Wow, thanks for the super quick response! I'll ask for more details from my GC, but can someone describe how this method works? Water would penetrate grout/tile and also the mud, but the tar paper would just funnel the water to the drain?

If this way is better why do so many people do things like the kerdi method?

Thanks.


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RE: Shower walls prep for tile

Your "old school" guy needs to go back to school. He forgot the pan membrane. Ask him what he'll use for the pan membrane. Also, if he's doing it old school, he should be using either tar paper or plastic sheeting behind the cement board.


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RE: Shower walls prep for tile

Hi, Bill, he is using tar paper in the shower.

I thought the pan membrane was for the shower floor? The floor and bench seat are hot mopped, or is there some sort of additional membrane that's placed on top of the hot mop?


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RE: Shower walls prep for tile

Okay-- my bad. I missed that part. Carry on!


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RE: Shower walls prep for tile

Could I ask a followup? I just spoke with my contractor about the shower walls he will be installing, along with a Kohler cast iron shower base. He said he doesn't need to use a membrane in addition to the durock, as long as the durock extends over the lip of the shower receptor, and all the corners/seams of the durock are sealed up. Does that sound right, oh wise ones?


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RE: Shower walls prep for tile

I'm not one of the experts like bill or mongo, but can answer your question. NO. Absolutely not okay. Durock is NOT waterproof. Water will get through it and into your walls. You need a membrane/water barrier either behind the durock or on top of it. Perhaps you should look for a contractor that knows how to install a tile shower.


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RE: Shower walls prep for tile

Well yikes! He's got 30 years experience, and seems very confident that the pre-fab shower base removes the problem of water getting up behind the durock.


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RE: Shower walls prep for tile

Grout is not waterproof. Water will seep through it to the durock, then through the durock and into your wall. It will take time, but it is a matter of WHEN, not IF the water will get through.

It always amazes me the number of "experienced professionals" that don't know enough about their chosen profession to be truly competent.


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RE: Shower walls prep for tile

I really like this guy, and hate to contradict him, but here's a case where I'll have to put on my "I'm neurotic and obsessive" hat and have him include a waterproof layer. Now that I've done some more research, I see that even the Durock website says to use a different product if waterproofing is essential.


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RE: Shower walls prep for tile

grout and tile will SHED 90% of the water. But some does get thru, and for that reason, either a paint on waterproof surface membrane, or a tar paper or plastic vapor barrier behind the cement board is REQUIRED.


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RE: Shower walls prep for tile

He's assuming water runs downhill (to the shower pan) which is does, but the durock will become ever so slightly damp, maybe more so if there's a pinhole or whatever. That dampness goes through to the studs behind, rotting them and promoting mould.

To a large extent, OLD SCHOOL isn't necessarily better - I would argue in almost all cases, building technology and techniques have improved (Ok, craftsmanship has probably gone downhill) - who would want a place built now, done like 100 years ago? Draughty, with dodgy electrics and lead plumbing? (ok, knob and tube can theoretically last forever)


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RE: Shower walls prep for tile

Speaking of old school, I was surprised to read that tar paper is okay as a waterproof layer; I would have immediately thought plastic sheeting.

But I've gotta say (as I sit here listening to them demo my upstairs), seeing how stout the lathe and plaster walls are makes me understand how this house has stood for over 100 years without a problem. I didn't get that same sense from our previous house, built in 1957.


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RE: Shower walls prep for tile

One more clarification that is bugging me. It sounds like our tile guy is considering doing the mud set with lath, tar paper and mud but without backboard. Does the 'old school' method require a backboard or drywall or does the combo just hold together without requiring the support of a drywall or backboard?

Thanks!


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RE: Shower walls prep for tile

In my town greenboard is required for shower walls (although these days it seems to be purple). Here are a couple of in-progress pictures.


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RE: Shower walls prep for tile

A floated mud wall does not need cement backer board.

Floated mud walls are usually built with tar paper, lathe, mud, and a strong shoulder.


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RE: Shower walls prep for tile

Cement based products (like grout and backer board) are waterproof only in the sense that water does not damage them.

Water passes through them by wicking just fine.

It will then wick into the studs supporting the backer board, and slowly cause them to rot.

A vapor barrier is NOT adequate.

You need a waterproof layer between the backer and the studs, or under the tile (like Kerdi) to stop the water from the grout lines completely.

If you use the shower once a day for a single person with short showers it might survive a long time, especially if the stud cavity is not well sealed.

The air leakage will allow the water to evaporate and disperse.

Use the shower a couple times a day for longer times and problems show up remarkably fast.


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RE: Shower walls prep for tile

mongoct, appreciate the help!


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RE: Shower walls prep for tile

"A floated mud wall does not need cement backer board.

Floated mud walls are usually built with tar paper, lathe, mud, and a strong shoulder. "

Sorry for bring up an old thread, but I would like to know that since water will penetrate cement board or mud wall, then what is the advantage of doing a mud wall?

My contractor is doing the tar paper, lathe, mud combo with no backer board and it costs $300 more than using cement board.

Should I put a roll on water barrier on top of the mud wall?

Thanks


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