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3/4" ply, then hardi? Prep for hextile, subfloor slope

5492 Views 32 Replies 4 Participants Last post by  OurHouse
In the saga project of my bathroom, I have finally finished re-plumbing, set the wiring up for the new lighting locale, and now I have the 3/4" plywood subfloor. We're going to put down small hex tiles that are era-appropriate for the home, however I have some questions.

The floor slopes a little because the floor joists slope a little. I'm not sure what to do. I have 1/4" hardi-backer to put over the plywood, but someone said I am supposed to put mortar UNDER it and then over it? Someone else says I should put PowerGrab all over between the two and then all the screws that it requests. Someone ELSE said lay the hardi straight over the plywood with or without the PowerGrab adhesive, and then pour self-leveler over it, except the lower edge of the room is the doorway to another room, so that's probably going to create a lip of as much as 1/2" on the right side of the doorway, and we just laid carpet in the adjoining room and the door between the rooms is a pocket door that I don't want to have to remove for major adjustments. *sigh* Now I'm confuzzled.
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How bad is the slope?---You may wish to pull out that pocket door before you begin tiling---

If your calculations are off that door may end up trapped,requiring demolition of the new floor to correct the problem.

Self leveling compound can correct a minor slope----major?? It's easier to sister in new joists --


Floor structure for tile--a nut shell---Joists strong enough not to flex and break tiles.
3/4" exterior glued plywood.

1/4" backer board set in thinset and nailed or screwed--(thinset fills voids so backer won't flex when stepped on)

Then Self leveling compound with its primer if needed.

then Tiles set with modified thinset----
 

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Discussion Starter · #3 · (Edited)
I'm going to play with the level tonight and see what the corrections needed at each area are. Eyeballing it last night I was guessing the worst to be 1/2" to possibly like 5/8." I'll update this later, when I get home from work, and an play with it for a real number. The pocket door does scare me. I'm scared I won't be able to get it back in there. I have contemplated using a transition strip under it, and not bringing the tile all the way into the doorway, so that it's an easier ride on that, but I'm still undecided. Would pics help anyone on these issues?

And, as an after thought, if I'm setting the hardie backer in thinset, could I not just leave the thinset thicker in the area that needs to raise up a bit? To be completely honest, I wasn't worried about the slope because it's an old house, and if I wanted all level floors, then I wouldn't have bought an old house, but the plumber who ran the new toilet line said leveling would lessen the stress on the toilet, so if there's a stress issue there that I need to minimize then I guess I have to address the level issue... I always assumed a little slope off the front of the toilet would deter company from sitting on the thinking chair too long LOL
 

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Don't be intimidated by a pocket door----think of it as a slide by closet door that is held in by some trim.

We will walk you through removing it and re hanging the door.

With tile---FLAT is good--level is not as important.

DON"T try to use the thinset under the backer board as a leveler---doesn't work--

You will be nailing that down every 6 to 8 inches---the thinset will squeeze out and the backer will be a wavy mess--- You aren't the first to think of this--

Self leveling compound is scary to use because it doesn't exactly 'self level' you have to help it and it sets fast---However it is not brain surgery and will be successful if you read the instructions and don't waste time.---Mike---
 

· Tileguy
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Would pics help anyone on these issues?
Absolutely YES!

could I not just leave the thinset thicker in the area that needs to raise up a bit?
As Mike has said, it can't be done that way. You should use a 1/4" X 1/4" X 1/4" notched trowel and allow the trowel to gauge the amount of thinset you put on the floor. Don't try to build it up any more than what the trowel gives you.:)

but the plumber who ran the new toilet line said leveling would lessen the stress on the toilet,
Now that's a new one. Never heard that before. I suppose there is nothing worse than a toilet that is stressed out all the time. Can he suggest a place for your toilet to later get therapy if need be?:)
 

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Discussion Starter · #6 · (Edited)


I played around with my level and the doorway, which is right in front of the toilet and gives one just enough space to sit on the toilet, it's about 3/8"-1/2" lower than at the opposite wall (the doorway itself isn't level, it's off by 1/8") The floor is flat, the flange is very tight, and after chatting with the plumber I do think that I had misunderstood his concern (he wanted to make sure the toilet would sit securely). So knowing that the toilet will be tightly secured, is there a reason to level this? The room is only 22 sq feet, so I'd have a whole bunch of extra self-leveler left wasted for... well... for what? Nothing else in the house is level, why should the bathroom be :laughing:?

I hope to get the hardie backer down this weekend, whilst waiting for the tile to arrive, but I suppose the next question is is there an easy way to take out the screw that I stripped that sits too high? I almost forgot it's sitting nearly 1/4" out right now grrrr....
 

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Nothing says a floor must be level. If you are okay with it then that's the end of that issue.

the next question is is there an easy way to take out the screw that I stripped that sits too high? I almost forgot it's sitting nearly 1/4" out right now grrrr....
What screw? Are you taking about the toilet pedestal mounting bolt?:)
 

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Discussion Starter · #16 ·
Well after all the horrors of September, it's October, and the custom ordered hex tiles are here and it is thus time to open up that pocket door, put the hardiebacker down and tile.

Bud? Anyone? I'm nervous. I got the Laticrete multi purpose thinset mortar and was given a 3/16 square notch trowel. Is this the right stuff?

Do I understand correctly that I trowel the thinset down and lay the hardiebacker over it, and screw it down wherever the hardiebacker indicates? I have 1 5/8" course thread drywall screws leftover from another job. Will these work in this application or will I be making another trip to Home Depot, where they really owe me a shrine for the generosities of my wallet?

I assume I screw down the hardiebacker while the thinset is still wet, but do I then need to stay off it for a while, or can I go right into tiling over it? And will the same thinset listed above be suitable for setting the tile? And is there anything else I need to know about setting unglazed ceramic tile? I think after I set it in the thinset, I have to give the thinset 24 hours to cure, then I need to use a spray sealer over the tiles because they are unglazed, then sanded grout, then seal the sanded grout with a precise application of sealer to the grout lines?

Thanks a bunch for words of wisdom.
 

· Tileguy
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Mix the thinset and apply it with a 1/4" X 1/4" square notched trowel. A 3/16" trowel really isn't big enough for the Hardi installation.

After the Hardi is installed and screwed down you can start tiling immediately if you wish. There are special screws recommended for use with Hardi. Drywall screws aren't the ones but you do whatever you want.

I have no idea what "Laticrete Multi-Purpose" is. The Hardi should be installed with unmodified thinset but if you were to use modified thinset it wouldn't be the end of the world.

The tiles you have may be unglazed but that doesn't mean they require sealing. Judging from the tiles you purchased the tiles are more than likely porcelain and they really can't be effectively sealed anyway they are too hard. You should use modified thinset to install the tiles. This may be a good place to use the 3/16" trowel to prevent thinset purging between the tiles.:)

Those spray sealers are useless, take that stuff back and get the money back you paid for it, it's junk.:) If you seal the grout use a "paint-on" type sealer and follow the instructions that come with the sealer. Application-windows of sealers vary.:)
 

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Discussion Starter · #18 ·
Bud, you're awesome. I appreciate having someone who knows. I got the correct Hardie screws with the square driver. When you say "unmodified" I assume that means "just add water" and with modified, I assume that's adding the latex additive to help the tiles set safely.
 

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