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ceramic tile on bouncy subfloor

12272 Views 16 Replies 10 Participants Last post by  10fingers
Any help from tile experts will be appreciated:

Planning for ceramic tile in the kitchen. Pulled up vinyl and lauan to find another layer of vinyl, then 5/8" ply, then 3/4" osb. OSB is too flexible between joists for my comfort.

Planning on 1/2" cement backer board. Will that be enough to handle the flex? Was it a mistake to pull the 5/8" ply?

Also, I have found Durrock to be tougher than Hardibacker because of the mesh. Do you think it's the better product, especially since I"m concerned about flex?

Thanks.
1 - 17 of 17 Posts
The backer doesn't contribute
anything to strength.
Make sure the OSB is oriented
on the strength axis, then re-lay
5/8", also perpendicular to the joist.
If the subfloor is springy, run a row
of screws between the joist.
Any help from tile experts will be appreciated:

Planning for ceramic tile in the kitchen. Pulled up vinyl and lauan to find another layer of vinyl, then 5/8" ply, then 3/4" osb. OSB is too flexible between joists for my comfort.

Planning on 1/2" cement backer board. Will that be enough to handle the flex? Was it a mistake to pull the 5/8" ply?

Also, I have found Durrock to be tougher than Hardibacker because of the mesh. Do you think it's the better product, especially since I"m concerned about flex?

Thanks.
There are ALOT of layers to this floor. Maybe spongy area is a repair or moisture infiltration.:whistling

I would remove everything down to the 5/8" ply then figure out where problem areas are first. then lay backerboard, etc. Good luck.
Good guess on the moisture. 24 year old house and only got a vapor barrier 5 years ago. Even with that, the crawl is more moist than I'd like. Welcome to NC. And in my experience osb reacts worse to moisture than ply.
There are ALOT of layers to this floor. Maybe spongy area is a repair or moisture infiltration.:whistling

I would remove everything down to the 5/8" ply then figure out where problem areas are first. then lay backerboard, etc. Good luck.
Why not run another 5/8" ply then a layer of Ditra? Should take care of any deflection.
What are the joist specs? 12 or 16 OC, etc

OSB is a big NO NO for tile. If the floor is bouncy, then adding Ditra may not be good enough. You need a solid subfloor. Consider removing the whole subfloor and put down a minimum of 3/4 inch plywood or better.

Just my two cents. I don't like Durock or Wonderboard. I don't have faith in anything you can literally break with a good kick. Hardibacker is much stronger. Although as it was already mentioned, cement board doesn't add strength.
Never use OSB for flooring. Soon as it gets wet, it's over...:no:
Good guess on the moisture. 24 year old house and only got a vapor barrier 5 years ago. Even with that, the crawl is more moist than I'd like. Welcome to NC. And in my experience osb reacts worse to moisture than ply.
Guess I gotta go back and repair half of the houses I have worked on in 25 years.

Cmon, this is merely your opinion. While my opinion is that plywood is definitely stronger and holds up better to water, I realize that price can also come into play. If price is no problem, then by all means use plywood. But for the rest of us, osb can and has been used a lot.
Never use OSB for flooring. Soon as it gets wet, it's over...:no:
Yes, merely my opinion. I've used both materials on everything also. OSB is as strong as plywood but costs roughly 30% or less. For walls, sheathing, etc., a great alternative. However, if water gets on an OSB floor for extended periods, ie., water infiltration, it starts to chip up and fall apart. Just my experience.

revised opinion;): I would not recommend OSB for flooring in wet locations. Rooms like kitchens and baths where the possibility exists for water infiltration. Any other dry locations using OSB for flooring is perfectly fine. (I thought it over, Warren. you're right!..:))
Guess I gotta go back and repair half of the houses I have worked on in 25 years.

Cmon, this is merely your opinion. While my opinion is that plywood is definitely stronger and holds up better to water, I realize that price can also come into play. If price is no problem, then by all means use plywood. But for the rest of us, osb can and has been used a lot.
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Which is why I suggested running 5/8 ply over the OSB then installing Ditra. Brings the height back up, eliminates almost all of the bounce, and won't be adversely impacted if the OSB were to get wet. Wouldn't hurt to glue and screw the ply. Just MY opinion. ;)
Darwin - then you have been using the wrong OSB product
guess so
Darwin - then you have been using the wrong OSB product
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
revised opinion;): I would not recommend OSB for flooring in wet locations. Rooms like kitchens and baths where the possibility exists for water infiltration. Any other dry locations using OSB for flooring is perfectly fine. (I thought it over..:))
JHM,
What is the floor joist length and depth? If it can't carry the load, your effort is futile. If you have access from below, you can shore up the joists with a beam.

olzo
Finally, some common sense. :thumbsup:
JHM,
What is the floor joist length and depth? If it can't carry the load, your effort is futile. If you have access from below, you can shore up the joists with a beam.

olzo
Absolutely true. This is one of the biggest misconceptions in the tile industry....and its damned hard to get these "been doin it this way for 30 years" guys to understand that.

OSB is perfectly fine for use with Ditra, which is what I'd use, once the deflection is brought up to spec.
The backer doesn't contribute
anything to strength.

Make sure the OSB is oriented
on the strength axis, then re-lay
5/8", also perpendicular to the joist.
If the subfloor is springy, run a row
of screws between the joist.
Any help from tile experts will be appreciated:

Planning for ceramic tile in the kitchen. Pulled up vinyl and lauan to find another layer of vinyl, then 5/8" ply, then 3/4" osb. OSB is too flexible between joists for my comfort.

Planning on 1/2" cement backer board. Will that be enough to handle the flex? Was it a mistake to pull the 5/8" ply?


Fir plywood TG with PL400, and lots of it. Screws at every 4 inches on the perimeter and 6 inches in the field. I find this process creates a beam out of the floor and relies less on the joists for support. If this does not take out significant deflection then I would go the Shlutter route. Ditra will decouple the tile from the subfloor.
1 - 17 of 17 Posts
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