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Unread 02-04-2020, 08:26 AM   #1
pruff
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Thinset under cement board

Is it necessary to apply thinset under cement board before tiling ? I seem to be getting mixed views. Some say as long as you use enough screws, it's not necessary.
Thanks for any advise.
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Unread 02-04-2020, 08:29 AM   #2
smifwal
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Those "some" are incorrect. Yes you need to put thinset under backer board
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Unread 02-04-2020, 08:34 AM   #3
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What does the manufacturer of the cement board say, Kraul?

Unless "Some" are the manufacturers of the product, I would disregard any installation advice that is contradictory in almost all cases.

My opinion; worth price charged.
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Unread 02-09-2020, 01:46 PM   #4
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Yes, it's necessary.
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Unread 02-09-2020, 02:04 PM   #5
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My question to them would be, "How many is enough?"
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Unread 03-07-2020, 11:02 AM   #6
pruff
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tile under or around toilet ?

We are getting ready to tile our new bathroom floor and are wondering it we should tile under the toilet or around it ?

Thanks,
Kraul
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Unread 03-07-2020, 11:15 AM   #7
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Under it, if at all possible.

Is the toilet drain flange installed yet? If so, is it resting flat on the cement board, or is there space under it so that you can slip the tile under the lip of the flange?
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Unread 03-07-2020, 11:16 AM   #8
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A correct installation would require that the floor be tiled, then the toilet drain flange be installed on top of the tile installation, then the toilet would be installed.

Since we don't know anything about the project, it's difficult to guess what you've currently got.

My opinion; worth price charged.
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Unread 03-15-2020, 12:04 PM   #9
JHarbinson
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The UPC and IRC require the toilet flange to be flush with the finished floor. Most flanges are approximately the thickness of tile so I typically run my backer under the flange, screw the flange down tight and then tile tight to the outer edges of the flange. Toilet will sit nice and tight and not rock.
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Unread 03-15-2020, 03:19 PM   #10
cx
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Justin, I believe you'll find that the proper location of the WC flange is on top of the finished flooring, not flush with it.

Like this:

Name:  Toilet Flange Seal Cutaway.jpg
Views: 73
Size:  21.2 KB

I'm thinking that's true even on the Left Coast, but one never knows about that, eh?

And since the OP hasn't returned since he posted that question more than a week ago, I'm hoping he's somehow figured it out.
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Unread 03-15-2020, 03:24 PM   #11
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Flush will get you a leaky toilet, you might get lucky but...
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Unread 03-15-2020, 04:10 PM   #12
Lazarus
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Yeah, "flush" will require a double wax ring...one being a ring with a rubber flange on the floor...and a standard one on the toilet horn. Alternatively, I think they make a BIG rubber seal that can be used. Ask me how I know...
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Unread 03-15-2020, 04:27 PM   #13
jadnashua
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Unfortunately, there are millions of toilet flanges that are installed directly onto the subflooring. It's a matter of cost and timing on building a new house. A lot of times, the rough-in plumbing inspection wants to see the toilet flange installed, and that's usually done prior to closing up the walls and the finished flooring. That doesn't make it right. If using something like a thin sheet goods, there's not a big functional difference. But, with the advent of tile and maybe heated floors that tend to be thicker, that extra height can be a problem.

Related to installing a toilet flange after tiling, you really need to set the toilet in place twice. Once to determine if and where you may need shims to keep the toilet from rocking. Arrange them so the toilet can sit without rocking (often works best to pin the front down, and add shims behind if possible to prevent rocking), pull it, add the wax and set the toilet back. ALso, don't use the bolts to compress the wax ring...push it down, then snug up the bolts...less chance of cracking the toilet, especially if the wax was just brought in from the cold. The typical wax seal can last literally centuries as noted from some wax sealed containers found when excavating things including from ancient Egypt...still works fine. But, it's not a spring, so if the toilet rocks, it will compress when it goes one way, the opens up if it goes the other way.

A stacked set of wax rings can be an issue if you need to plunge the toilet as you can actually blow out the seal. FWIW, the most effective plunging is to pull rather than rapid pushing. That allows what got wedged in there creating the seal to be pulled back, and often then allows it to go down the drain. Vigorous pushing jams it tighter together. It MIGHT push it through, but it often just jams it in tighter.
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