Laying Tile

Here's a remodeling question for experienced tile layers. I was told by some experienced people that laying tile on a floor made of waferboard is bad. I have waferboard. The method they showed was as follows:
1. 1/4" thinset on floorboard (plywood, not waferboard).
2. 1/4" wonderboard screwed to the floor.
3. 1/4" thinset over wonderboard.
4. tile.
The concern they have is that water from the thinset will dissolve glue in the waferboard and compromise it's strength.
Also, I've heard a different approach is to skip the thinset layer between the floor and wonderboard but simply screw it down with nothing in between.
I'm seeking other opinions before replacing the boards in my bathroom.
Any thoughts?
Kevin
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Kevin:
I remodel/repair for a living, and cannot see why you would thinset anything to waferboard/OSB etc. I wouldn't be as concerned about the waferboard dissolving as I would that the moisture would suck out of your thinset too fast and you would just have a sandy mix underneath your cement board.
If you want to use the cement board, try glueing your board down and screwing it to hold. There are many good glues available for this, just check with your tile supplier.
I would suppose that this floor is either a second story floor, or a floor in a pier and beam house. You should know that the cement board will work itself loose after a few years of foot traffic on a floor that flexes, as I mentioned above. The screws hold fine, but the head wallows around and "works" inside the hole until it is loose. Then your problems start as it will soon start to crumble underneath. There may be some out there, but I haven't seen any cement board that is intended for weight bearing/foot traffic underlayment.
Here's what I do:
I put down two layers of 1/4" tempered masonite (the brown stuff, no pattern - think peg board without the holes) making sure the joints are perpendicular to each other. The first layer will act as a slip sheet, and allow the floor to flex without harming your tile.
We nail this down with 6d sinkers (flatter heads than screws, and they don't make a mushroom in the masonite) and do NOT use any glue or adhesive. Tack the first layer down, then nail the snot out of the second layer. When the second layer is installed and finished, we spray a latex bonding agent on the floor similar to the stuff the wallpaper guys used to seal a wall.
The tile is then installed with latex mastic, and grouted as usual.
My old tile guy showed me this 25 years ago, and I have never had a complaint since I have done it that way.
Robert
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On Fri, 24 Mar 2006 22:32:21 -0800, nailshooter4 wrote:

I'll give this some thought although it goes against what I've learned elsewhere, i.e., stay away from masonite and mastic. Sounds like it's worked well for you, though.
Thanks,
Kevin
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I think you better slow down and tell everyone what kind of tile you are talking about. One poster assumed VCT. I suspect ceramic. If you are talking about ceramic, the big issue is floor deflection, you should be up toward L/600. Only you can tell about the floor stiffness and thickness. On most existing floors a 7/16 wafer board cap followed by a 1/2 or 5/8 Durock type cement board cap, followed by a ceramic install will give you one heck of a speed bump coming in the bathroom. If I have guessed wrong about your circumstances it can only be due to an inadequate description on your part and wild guesses on mine. ______________________________ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net

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I would suggest you go here for technical ceramic advice: http://www.tileusa.com/faq_main.htm ______________________________ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net

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On Sat, 25 Mar 2006 14:39:52 -0600, DanG wrote:

Thanks for the link. I have a better idea of what the floor rigidity numbers refer to now, although they don't provide much instruction on laying tile. If I had more time I'd think about buying their book which looks fairly exhaustive.
Kevin
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On Sat, 25 Mar 2006 14:26:06 -0600, DanG wrote:

Right you are. I'm laying down ceramic tile (1/4" thick) . . . should have said so. Sorry, but I don't understand what L/600 refers to, but I share your concern over the "speed bump" problem. I've also heard of any underlayment material called hardibacker. Is this an option?
Kevin
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Hardie backer is certainly an option, it saved a quarter inch. I am sorry, I gave you the wrong site to study about ceramic tile. This is the really good one: <http://www.johnbridge.com/serv02.htm#shower%20pans You can literally spend an hour or two getting some of the best advice possible. ______________________________ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net

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On Sun, 26 Mar 2006 10:58:47 -0600, DanG wrote:

It looks like a great resource. I'm leaning toward screwing down hardie backer and laying the tile on that with a total elevation of about 3/4" off the floor but won't do anything until I've spent time at their site.
Thanks again.
Kevin
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pakdog wrote:

I would tend to doubt your floor is waferboard. Most likely it is OSB (oriented strand board), which looks like particle board but has larger slices of wood and is made with superior adhesives. It is a pretty standard subfloor material. It can take getting rained on a bit while the house is under construction, but can swell up if exposed to standing water.
I am a strong believer in thinsetting any type of cement board to the subfloor. It makes the whole assmebly act as one unit and eliminates any potential flexure between mechanical fasteners. Flexure is what causes cracking in brittle tile and failures in grout lines.
So the questions are really how much water is actually released by the thinset and absorbed by the OSB, how will the OSB be affected, and how can the moisture be prevented from being absorbed if it is a problem.
If the thinset is mixed correctly there is not a lot of excess moisture. Almost all of the water should be taken up by the chemical curing of the thinset. The water can also be replaced entirely by latex additive which would release even less moisture and has the additional benefit of adding flexibility to the thinset and increasing adhesion.
A latex bonding primer can be brushed or rolled on to the OSB to act as a barrier coat. You can buy quarts of it at Home Depot in the tile section next to the self-leveling floor patch bags.
As an alternative to using thinset, construction adhesive can be used. The bead of adhesive should be spaced closely to fully bond the board to the subfloor. Figure laying down the beads approximately two or three inches apart.
R
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Hmmm....
Dan G wrote:
<<I think you better slow down and tell everyone what kind of tile you are talking about. One poster assumed VCT. I suspect ceramic.>>
In response to OP's:
SNIP <<3. 1/4" thinset over wonderboard.
4. tile.
The concern they have is that water from the thinset

SNIP
I think it is safe to assume that most use the referenced thinset for ceramic. Vinyl, wood, pergo, etc. are usually not attached with thinset.
Robert
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This is all good advice from RicodJour. I would agree that thinsetting the cementboard (my preferred choice is hardibacker) gives the floor added strength and in a bathroom...added moisture resistance. Use high quality thinset.
I always like to wait an extra day before getting onto the newly installed subfloor. To get on it the next day gives it less than 24 hours to dry, which is just the beginning of the curing process. An extra day would make it at least twice as strong. There is a lot of stress on the subfloor during the tiling process.
Finally, my concern (without being there) is that a particle-board type material such as yours, in a bathroom, could be damaged, or even weakened with age and water seepage, especially around the toilet and where the tub and shower are. If your existing board is weakened, you must tear it out and restore the floor with plywood before installing the cement board. The cement board/ hardibacker board alone cannot support the tile. Technically you need 1 1/4" of flooring to support tile. Generally this is done using the 3/4" standard subfloor that is in most homes, with a 1/2" additional material such as cement board. 1/4" Hardibacker board has the same rated compression strength as 1/2" cement board (durock- wonderboard etc), so you can compromise the thickness some by using the 1/4" Hardibacker. The important point is that the entire subfloor must be very strong, and tightly bonded and screwed together to properly support ceramic/porcelain tiles.
You've taken the time to ask some detailed and specific questions, which is a good sign you're no dummy. Follow through with the advice given here and research the many good tile-forum websites and really understand what you are doing.
thetiler
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