Hardibacker or plywood for tile?

15 years ago

I am going to be installing sheldon slate 1/4 inch floor tiles very shortly. I am also replacing the hardwood floor so I hope to get the tile at the 3/4 height that the floor boards are.

I am not sure if I will be doing it or hiring someone.

I have gotten two estimates so far. I will be laying the base layer myself. 3/8 plywood was suggested and I was told not to use hardibacker?

Why is this, and should I ignore the advice and use hardibacker set in morter anyway? I was reading 1/4 inch hardibacker will bring the 1/4 inch tile to the hardwood level.

Also, I think one guy uses adhesive, is this the proper thing to use or is that the same thing as morter?

Featured Answer

bill_vincent

15 years ago

Am I correct in assuming that I would need much more than 1/4 inch backer board to install slate tile?

You sure would. First of all, you're just about right at L/360 for deflection along the joists. The longest those 2x10's could be without support would be about 10 feet. In order to do the slate, you'd have to sister each one of the joists with at the very least, 2x6's just to stiffen up the framing. Once that's done, you'd need a layer of 5/8" plywood before cement board, Ditra, or whatever.

As for this statement:

I believe you can also use Schluter's "Ditra" system over top of the hardiboard (or plywood but why not use cementboard). This system "decouples" the tile or slate from the joists and minimizes the chances of grout cracking.

You wouldn't even need the hardi board, if you were going to use the Ditra. You could lay it right over the plywood. However, the floor MUST meet deflection standards, both along the joists (sistering them up) AND BETWEEN them (second layer of plywood), before installing it.

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Comments (9)

bill_vincent
15 years ago
Use the Hardibacker. But first check your joisting and make sure the floor's strong enough for it. That floor has to literally be twice as stiff as it does for any other floor, including ceramic tile. Find the width, heigh, and length of the joists, as well as the unsupported length, and take those values and plug them into the appropriate spots at the following link, and it'll tell you if you're ready for natural stone or not.

As for the adhesive, if he brings over something already mixed in a pail, and just has to take the top off and spread, throw him out. Literally. He has no idea of what he's doing. He MUST use thinset, both for under the Hardibacker and for under the slate.

Here is a link that might be useful: John Bridge's World Famous Deflectolator!
ccoombs1
15 years ago
Someone at a tile store once told me that as long as I had 1 1/4" of plywood (3/4" OSB with 1/2" plywood on top) that I didn't need hardibacker. So I believed them. And for as long as I lived in that house, I had problems with cracking grout. I'll never do that again! Hardibacker is way more trouble to put down than plywood, but SO worth it.
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bobkatt
Original Author
15 years ago
I just measured the subfloor and it's 1/2 inch plywood over 16 on center 2 x 10's with a 13 foot run of the joists
Am I correct in assuming that I would need much more than 1/4 inch backer board to install slate tile?
I am wondering if I am better off scrapping this idea and just installing the hardwood floor, I am too far along to add plywood to existing floor to raise it up.
tootsall
15 years ago
I believe you can also use Schluter's "Ditra" system over top of the hardiboard (or plywood but why not use cementboard). This system "decouples" the tile or slate from the joists and minimizes the chances of grout cracking. It may be a bit more expensive but compared to the cost of having to redo possibly costly tile, what's a bit more in the first place?
bobkatt
Original Author
15 years ago
Thanks Bill, You're information has been great and just what I needed to find out.

I managed to get the order canceled and I will just go with the hardwood for that area. There is a doubled up 2 x 10 in that area and one that is 6 inches center to center. I hadn't measured the sub floor till this morning, assuming ( never assume I know lol ) it would be 3/4. Without the hardwood boards on it, I can feel a little flex if I hop on it. Not worth the trouble later on and I don't want to raise that area up that much, people will be tripping over the step as it's a 6 1/2 foot arch from the foyer into the living room.
Thanks again for your help.
It would have looked good, but
bill_vincent
15 years ago
Better to find out now. :-)
mikeyarch
15 years ago
Bobcatt

The John Bridge forum is a great resource for tiling - old school and newer methods. TONS of great info...

http://www.johnbridge.com/vbulletin/index.php

MIKE
bill_vincent
15 years ago
Absolutely. I can advise you here, OR there. :-)