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Unread 04-01-2019, 11:57 AM   #1
worldknown
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Laying new tile on second story - Old tile was cracking along with grout

Hi,
I am having a gentleman retile my upstairs master bedroom. The townhome was built in 1978. Since i bought the home 5 years ago the existing tile has cracked along with the grout cracking. I want to make sure that my installer does this installation correctly to ensure that i don't have this issue again in the future and especially since i will be laying down marble.

The plywood underlayment i have upstairs is very old. Other than replacing the plywood is there a best practice? I was thinking i could screw in the existing plywood with wood screws every 6-12inches to reinforce the subfloor. On top of this plywood i would install hardibacker. Or instead of doing hardibacker should i install another layer of plywood?

The reason the old tile was cracking i believe is because the tile installers did not screw down the hardibacker and did not apply appropriate amounts of thinset to the tile before adhering it to the hardibacker.
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Unread 04-01-2019, 12:19 PM   #2
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Hi Mike -

It's a bit more complicated than simply making sure Hardibacker is adequately screwed down, and enough thinset is used to set the tile (although those are critical items).

For marble, your floor framing has to be twice as stiff as for ceramic tile. Click on the "Deflecto" in the blue bar above, then enter your joist information. At a minimum, you'll want L /480, and L/720 is ideal.

In addition to that, stone requires 2 layers of plywood, each of proper thickness, grading, orientation, and offset, plus each being installed with the correct fastener length and pattern. That's before any tile underlayment, which typically is only for bonding the tile, not for adding substrate strength.

You'll want to make sure these initial criteria are satisfied before moving ahead.
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Unread 04-01-2019, 12:26 PM   #3
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Are you saying that i am better off installing ceramic porcelain tile? Does this hold true for travertine as well or just marble? And also are you saying that i will need two layers of plywood in addition to a layer of hardibacker?
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Unread 04-01-2019, 12:54 PM   #4
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Ceramic (porcelain) tile *only* requires L/360 deflection, so it doesn't require as stiff a framing structure as stone. Nor does it require 2 layers of plywood. So if it would take a good amount of labor and expense to adequately prep for a stone install, then yes - you may be better off aiming for porcelain tile.

Stone includes travertine.

For stone installs, yes - you need 2 layers of the appropriate plywood, correctly installed. Then you install the tile underlayment. Whether that's Hardibacker, Durock, Ditra, etc, etc.
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Unread 04-01-2019, 02:18 PM   #5
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Okay so i am probably going to return the stone because i am more concerned about durability than i am about looks, although not by much. Provided i go with ceramic/porcelain style is there a way to reinforce the floor to prevent cracking again in the future? Should i do a more flexible thinset?
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Unread 04-01-2019, 05:29 PM   #6
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Mike, I would first verify that the joists are adequate to support a tile installation. If they are, then I would secure the floor to the joists with deck screws every 6". Then I would install a layer of 3/8" or 1/2" plywood over the existing subfloor, since you said the floor is old.

After that, properly installing a tile substrate and the tile would give you the best chance for a successful tile floor.
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Unread 04-01-2019, 07:19 PM   #7
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Mike, until you verify and evaluate your subfloor structure, we can't help as much as we'd like. The joist spacing will also have a great deal of influence on what you need for your subflooring.

My opinion; worth price charged.
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Unread 04-01-2019, 09:31 PM   #8
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If there is a heat register in the floor, you might be able to get an idea of the joist spacing and existing subflooring material if you remove the grate. Otherwise, it can be tough to evaluate the structure until you've removed the tile and cbu down to the ply. Then, you can probably view the fasteners to check the joist spacing. If you drill a small hole and take a metal wire, you can check the depth of the joists.

It is a rare wood-framed condo that would be stiff enough for stone tile.

Cracks implies movement beyond the strength of the materials. That could also be improper installation techniques, but is more often the result of inadequate structure. You may find that the structure isn't viable for even ceramic tile, but then, it should not have passed the building inspection. Sometimes, that happens, though.
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Unread 04-06-2019, 10:29 AM   #9
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So what do you recommend? I returned the marble today and am now searching for ceramic. What’s the best way to make sure the new installation doesn’t move? Should I cut out a piece of the subfloor? Should I just install plywood over the existing plywood then Hardibacker?
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Unread 04-06-2019, 11:02 AM   #10
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If you add a second layer of plywood, just screw it to the bottom layer, not to the joists. But, what thickness is the plywood you now have?

If you use any type of cement board or Hardi, remember to use thinset under it as well as screws. This may be part of why the first install failed. I would use Ditra instead of cement board.

Read Cx's post 7 again.
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Unread 05-31-2019, 10:59 PM   #11
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Best Modified Thinset under Ditra / thinset above

Hi guys,
I know it says to use modified thinset below ditra when dealing with a plywood subfloor. In this case which modified thinset are there? I'm overwhelmed by the choices available.

The tile i am laying down above the ditra is a 12x24 tile.

The instructions also say unmodified above, but on this forum i have read people using modified above. Which is the best unmodified thinset to use above?
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Unread 06-01-2019, 12:56 AM   #12
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Mike, is this the same project as this one?

I ask because in that thread you said someone else is installing the tile. My answer would be different if that's the case.
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Unread 06-01-2019, 09:09 AM   #13
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Yup You are correct. It’s part of the same project
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Unread 06-01-2019, 09:32 AM   #14
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Ok, let's keep all questions related to this project on this thread so that questions and answers aren't duplicated, and the history is in one place.

If you've hired someone to install the tile, I would defer to him on which mortar to use. The reason is because if there's an issue down the road, you don't want to be on the hook for that.

If your installer has chosen the proper mortar, and something goes wrong, then it's on him to fix it. If you've chosen the mortar, he has an avenue to assign blame to you.

Hope that makes sense.
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Unread 06-01-2019, 09:50 AM   #15
worldknown
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Kman, i dont know where you live but installers in Phoenix Arizona only warranty their work for 1 or 2 years max. I want to provide the right mortar so it's done right.

Like i said before when i bought the house it was all fine and dandy on the second floor until 3 years had passed and now tiles were cracking and coming up.

So i have 2 Questions


First
The subfloor upstairs is a 3/4" Plywood that is nailed into the joists. I am thinking of two different options:
1) Removing the existing Plywood (its only 100 SF), then installing new 3/4" plywood or 1 1/8" plywood screwing and nailing it down.

or

2) Adding another layer of plywood above the existing plywood - only issue is i have a floor transition into this room, and adding a substantial amount of height to the flooring in the bathroom could make for a somewhat awkward entrance.

Second
What is the best modified thinset for underneath the ditra and the best unmodified for above it? I am shopping at floorndecor and they pretty much carry the whole Mapei line. I could also go to Lowes or Home Depot as well.

Thank you for your help!
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