Installing Cement Board for Floor Tile

[George Bokros]

Going to be starting a bathroom remodel soon. It will include porcelain tile on the floor which will installed over cement backer board (Hardie Backer). Hardie says to set the Hardie Backer into thin-set then screw down, Doing this will make it impossible to remove the floor in the future as the sub-floor will be destroyed removing the backer board. My house was build in the late 90's so the sub floor is likely installed with nails and construction adhesive.

I will not likely remove the floor in my lifetime so I should not be worried but I like to think about the next person. I am thinking that if I screw the backer board into the floor joists we should have a solid base for the tile.

Your thoughts, opinions, experience.

Thanks

[Jason Roehl]

Do what Hardie says. It's not like you'd be able to easily unscrew the cement board whether it was bedded in thinset or not--would you want to dig the thinset out of each screw head?

Bedding the cement board in thinset helps stiffen the floor to reduce flexing and cracking. Don't forget to mesh tape and thinset any seams in the cement board after you screw it down.

[Phil Thien]

You can remove it, actually. You just pound on the backer board with five-pound hammers and it breaks the thin-set bond. You can then remove the concrete backer and use an ice scraper to remove the thin-set from the subfloor (a little more pounding may be required to break it up). This works better, BTW, on plywood than OSB-type underlayments.

The overall longevity of your tile job will depend on the rigidity of your flooring system. So depending on what you have for a subfloor, you may actually consider adding another layer (if there is room) of plywood before the concrete board.

[Rich Engelhardt]

George,
Mosey on over to John Bridge and ask there.

I'm pretty sure you need the thinset in addition to a bazillion screws.

FWIW - I'd use Ditra- Heat myself - if I was forced to use real tile.
I've become a big fan of and believer in groutable vinyl tile.
It's so much nicer and warmer on the old feet.

[Bob Winkler]

Use the thinset as per instructions. Also, I read that the screws should avoid the joists because there is more movement in the joists than in the subfloor. And don't forget to use the correct epoxy coated screws for the longest lasting installation. It's worth going the extra mile in a bathroom given its such a small space where the extra cost is minimal.

BTW, avoid HardiBacker dust when cutting because it contains silica. I use a nibbler that cuts it like butter without dust.

Good luck,
Bob

[Ole Anderson]

I will attest that it is a pain to get up, especially if you are pulling up a layer of stapled Luan at the same time as the cement board and tile. But after 20 years on my kitchen floor, there was not one crack or squeak.

[Jim Matthews]

Do what Hardie says. It's not like you'd be able to easily unscrew the cement board whether it was bedded in thinset or not--would you want to dig the thinset out of each screw head?

Bedding the cement board in thinset helps stiffen the floor to reduce flexing and cracking. Don't forget to mesh tape and thinset any seams in the cement board after you screw it down.

+1 The recommended backer is made to prevent the tiles from popping free.
One tile, that is slightly raised above all others, will be a trip hazard.

[Jim Matthews]

I went with 6mm thick solid cork "tiles" that can be cut with a sharp knife.
(Not laminated to any backing - just cork.)

No grout, no tile saw, no thinset.
The joints are tight and it feels warm underfoot.

It's in 'my' bathroom, so I'm cautious about spills.
I wouldn't put it in a child's bath.

http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1

[Tom M King]

thinset is easy to use, and pretty cheap. I wouldn't skip it.

[Mike Cutler]

George

As others have stated, you should follow Hardie's installation instructions.
The thinset you will be applying between the subfloor and the Hardie board will be a modified thinset which has an elastic polymer property to it, and will also act as your "shear plane". The thinset for the tile will be spec's by the tile maker.
Basically the tiles represent one plane, the subfloor another plane and the backer board yet a seperate plane. During the floor's life, the subfloor and the tiled surface will expand and contract at different rates. The Hardie board is the transition shear plane that will allow both surfaces to move independently at their own rate and not result in cracks or seams in your tiled floor.
The backer board does not screw through to the joists, just the subfloor.

No worries about adding the extra thinset and screws. Tearing up a tiled floor is a messy job, no matter what. BTDT.

The recommend for the John Bridges Tile Forum is a must. He also sells a book via the forum which is a very valuable resource, and worth the $$$.

[Tom M King]

use a very large notched trowel to spread thinset on the subfloor with. hold the trowel straight up on edge, and the big notchs will leave the thinset in raised rows with somewhere for it to spread out to inbetween the ridges. drop a big glop. like at least a gallon at the spot, on the floor, and spread it around. it will go pretty quickly if you aren't reluctant.

[Dave Kirby]

I'm no professional tile guy but I don't think I have ever seen anyone (even the professionals) actually install Hardie Backer into thinset. Seems like such overkill and I would think could even cause some definite problems in certain installations! I have done many tile installs in my own home as well as others and Have always just used the screws, rated for the cement board; screwed it down to the wood subfloor and called it a day. I have never had any problems. It's more important to apply your thinset properly for setting the tile, on TOP of the Hardie Backer board, obviously. Good luck with it!

[Kevin Bourque]

Use Thin-Set.

It fills in gaps and voids in the subfloor and it holds down the backer board.

[Mike Lassiter]

Use Thin-Set.

It fills in gaps and voids in the subfloor and it holds down the backer board.

That is what I understand as well. I am planning to do this in the master bathroom of a single wide mobile home when I get that far along with everything. I have been researching this too. The thin set is used under backer board or Ditra to give full contact so there is no place that has give in it to cause movement and cracking of the tiles or grout lines. Moving is shear with either doesn't create cracks, but flexing from weight pushing down does is how I understand it.

Consider it is much easier to do it as recommended the first time, than have to repair or tear out and replace later down the road. I am going to use the Ditra material as it states it will work fine with 5/8" floor sheathing on 16" centers which is what the mobile home floor showed to be. New floor sheathing replaced in much of the bathroom (and most of the outside wall area too) and there are places the original has swelled slightly and is proud of the new sheathing. Much faster and easier to fill the low areas with thin set than try to sand down the high areas to match the low ones.

[Rich Riddle]

I have far too much experience installing the system you discussed. Do it the way the instructions indicate. If you go to the John Bridge website you can enter your information into the calculator and calculate the floor deflection. Laying the tile the way they indicate stiffens the floor and is needed to properly install tile/stone.