Tiling and OSB.

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  #1  
Old 09-02-08, 09:40 PM
D
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Tiling and OSB.

Hi folks,

Remodelling the mudroom/rear entrance to the house. The 70 sq. feet of tiles and grout that were there for 20 years were fine and had not cracked... so when I lifted the old tiles I was surprised to find that the subfloor was 2 layers of 5/8" OSB with about 500 screws in it and that the tile was bonded directly to it.
So a bunch of "no laying tiles over OSB" alarms went off in my head.

My problem is that the existing OSB + tile is level with the hardwood and adding hardibacker or ditra will make the transition too great.

So is laying tile on the OSB really that much of a no-no if the previous floor was fine for 20years?

Thanks,


Thomas
 
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  #2  
Old 09-03-08, 06:36 AM
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daft

I dont know of any thinset manufacturers that say you can set tile directly to osb. For every story you hear like yours, there are many others that did it wrong also and failed. I'm curious, was the tile set with mastic or thinset? When you removed the tile from the osb, did you tear up the osb pretty good or did the tile come off the osb with little to no damage to the osb.

I assume you will be using ceramic tile, and not natural stone tile. You have a couple of options. I think the best would be to add an isolation membrane over the 2 layers of osb. You are talking 1/8" total thickness for ditra (even with the thinset), and even less for Noble CIS. It's not uncommon, to have slight height differences with ceramic tile, due to framing, subfloor and underlayment requirements. There are ways to handle height transitions.

You also have the option of removing the top layer of osb. If the osb is really beat up from the demo, this may be a good idea anyway, provided its just screwed, and not glued as well. From there, you have a whole bunch of options.

There was some discussion in another thread here last year about one of the TEC thinsets that the original poster claimed could be used to set tile directly to osb, but I never did see any documentation that said this could be done. This may be something you want to explore though. The best advice you have to go on here is the manufacturers information. If they say no thinset over osb, then thats what you should do.
 
  #3  
Old 09-03-08, 08:17 AM
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Good advice Johnny.

When thinset manufacturers' tell us not to install ceramic tiles direct to OSB, some assume that it's because thinset will not bond to the OSB. That is not correct. Modified thinsets will bond rather well to OSB. It's the nature of the OSB that is the problem.

OSB is too unstable to be used at 'the' substrate for tile. Sure, it may actually work fine in small dry areas, maybe 60-70% of the time? But, that is not good enough to warrant a recommendation.

I agree that you should use either Noble CIS or Schluter's Ditra. The transition will not be too great. Anything under an inch is easy to cpe with and very common. The alternative is to do the job wrong, and hope for the best.

Jaz
 
  #4  
Old 09-03-08, 11:08 AM
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Daft

Here is what I found at TEC.

http://www.tecspecialty.com/content/newSolutions.aspx

Follow this link down to "single layer floor sytem". Open the pdf document in the bar and read away. Apparantly, TEC has a product that allows you to set tile to a single layer of OSB. I'll be damned. I never used it and don't know much about it, but the info is there for you to read. I'm gonna take some time to read through it when I get a chance.
 
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Old 09-11-08, 02:17 PM
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Thanks to all the replies. Decided to slam 500 screws into the OSB and install Ditra. Did not want to take a chance since it will be 12x24 tiles.
That TEC stuff does look interesting though...
 
  #6  
Old 09-12-08, 07:06 AM
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daft

The ditra is a good choice, much better then the Tec solution in my opinion.

I have no experience with that Tec product, but yeah it is interesting. Before having read that, I've never seen a thinset that you could use to set tile directly to osb, for reasons Jazman stated above. People doing the testing on these new products are much smarter and qualified than me so I'll assume it works. I'm always a skeptic until its been out there and proven for a few years.
 
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