USG does not require a barrier behind Durock?

[dhagin]

2011 TCNA specs for both ceramic & stone using cement or fiber cement backer boards on walls of tub/showers, pages 152 & 252, require either an ANSI A118.10 bonded waterproof membrane or ANSI A108.02-3.8 vapor retarder membrane. The vapor retarder membranes listed are plastic, tar paper, et al...

[gueuzeman]

Nice- but don't Mfgrs. specs trump TCNA?

.

[Crestone Tile]

Bam!

[dhagin]

Yep.

[TileArt1]

Bam what? You do that down there in the Springs Matt?

Thanks CX. It isn't necessarily the body of the board I have issues with, but the edges. The ones along the bottom of the wall can and should be dealt with correctly, of course, but how fast does water wick through thinset at the joints (when they actually are taped)?

And we all know that once that water hits wood it's essentially all for naught.

I am extremely curious about the results of that particular professionally controlled lab experiment you have going on there, though. Dunno if I'll be standing on my seat yelling (about that), but I am curious.

[gueuzeman]

You could always just take the high road and say (like me), " I sell surface membrane installations. You want less, you want someone else."

works for me.

.

[Crestone Tile]

Of course not, Roger.

I install mud walls with bonded waterproofing (aqua d or kerdi). If I used Durock, it would also get aqua d or kerdi.

I agree with your concerns. It's difficult to call out a hack method vs a proper method when when you can't fall back on manufacturer's specs to back up your approach.

[dhagin]

The unfortunate point of the exercise, i think, is that current published installation instructions for hardi or durock, to name just 2, do not require or even recommend a waterproof membrane or vapor membrane. They defer to local codes, and the IRC doesn't require one either... Hardi install instructs do defer to TCNA for steamers, but not tub/showers. Durock install instructs also has this

"Waterproofing
If waterproofing is desired, use
Durock tile membrane. See USG
literature piece CB492 for
Durock tile membrane product
information."

Matthews thread from last year goes into some more detail.

And i agree with Roger, it the edges, seams, penetrations that are the biggest concern. Just like roofing or siding.

[java]

[cx]

I think we'll find the actual problem in the marketing departments of the various manufacturers. If one says you should install a moisture barrier behind his product, two or three others are immediately gonna change their recommendations to say, "You don't need to do that with our product," even if they know that is not the case. You might find that that's actually even happened at least once in this particular argument.

Same sorta thing so many of you complain about in your own businesses when you're out there bidding against folks who care only that their installation lasts long enough to get past any mandatory warranty period. You're bidding your work to be done according to industry standards, they're bidding theirs to meet the minimum legal (mostly) requirements. And you can't always prove what they're doing is wrong.

All we can do is keep trying to educate more folks about more of the problems.

[Tiger Mountain Tile Inc]

For CBU, I use Permabase. This is from their website and it's basically the same as the other manufacturers:

PermaBase is not a vapor barrier and an additional barrier is not required in most conditions. In areas such as indoor pools and saunas, a vapor barrier is recommended.

I still use a moisture barrier on every shower, and personally, I don't see why this is an issue. I've never had a customer not want a moisture barrier. Like Gueuzeman says, if they want to cut corners, they want someone besides me.

[TileArt1]

This is not for a client of mine - it is for information for a reader of my blog. If I get called for a proposal I tell them how I will build the shower - I'm the professional. They will get a topical membrane (or whatever I deem the proper construction method), they will have expansion joints, etc. - or they will have a different tile contractor.

It's not being an ass, I'm the professional and I know what I'm doing. If they want my warranty they'll only get it if I pick the construction method and products. If they are (or want to be / think they are) the professional they certainly don't need me.

[John Bridge]

I'll put this here for the next time this thing is dragged up.


JBF Shower Backer-board Recommendation

The recommendation of the John Bridge Forums is, and has always been, to use tar paper, building wrap (Tyvek), sheet plastic or some other moisture retarder behind the cement board or fiber board IF a surface membrane is not in the works. If a surface membrane is used it's best to omit the moisture barrier behind the board.

When building a steam shower always use a surface membrane.

[jlcollins2012]

Per Tile Elfs comments, the USG (Manufacturers of Durcok) stated to me that I don;t need a vapor barrier behind their product. This is especially weird since they DO acknowledge that Durock is not waterproof, but rather water-resistant. Their main point to me is that if moisture gets behind the Durock, the vapor barrier would keep it from evaporating, trapping it and producing mold. Again, their statements are counter to everything in books and blogs that I've read.

[Hank B.]

Rather than spend the time trying to convince people of the many reasons why you should, let them convince why you shouldn't. As far as I know there are only 3 reasons why you wouldn't, cost, availability or the work involved.

As for cost-if you can't afford the 10-20 bucks for the plastic, flip your couch upside down and raid the ash tray in your car, if you still can't come up with the money, why are you doing this project in the first place.

Availability- even the smallest hardware store has 6mil poly.

The work involved-if stapling some plastic to the studs is to much work for you, quit now, as the rest of the project will surely cause you to drop dead.