New Porcelain Tile floor in an existing unconditioned room..?

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Old 01-04-11, 04:07 PM
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New Porcelain Tile floor in an existing unconditioned room..?

So I have a 12' by 6' enclosed non-insulated sunroom entry on my mid '60's rambler. The following is the existing floor construction:

vinyl sheet, currently pealing up at all the edges
3/4" plywood subfloor
2x P.T. tapered sleepers @ 16" o.c.
6mil vapor barrier (i think, not sure though)
1/8-1/4" sloped conc. slab (the slab is an exterior slab and slopes away from the house as this sunroom was framed up and added at a later date).

my questions pertaining to use of a 12 x 24 porcelain floor tile are:

1. I should remove the existing vinyl, yes?

2. I should put down 1/4" fiber cement board, will hardie panels work?

3. With being an unconditioned space that is subject to humidity, do I need to add moisture barrier somewhere and if so where would i put it?

4. With being an unconditioned space that is subject to humidity and rapid temperature changes how should I deal with expansion and movement? Is there a specific type of grout or thinset or both that I should be using for this type of application? special edge conditions to consider or other expansion joints?

5. Can anyone point me to any other good resources for this specific application?

Thanks much,

Mike
 
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Old 01-06-11, 06:07 AM
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Welcome to the forums! I have done one sunroom type installation where there was no heat/cooling. It turned out great, but I was really reluctant to do it for the same reasons you have.
However, it hasn't budged in 2 years, nor has any of the grout cracked, so the customer is pleased. I look in on the room whenever I go there for other jobs.
With that said, however, I used 12x12 on the bias with a border tile to match. I believe you will be pushing the envelope with 12x24, mainly for the span restrictions quite often in sunrooms.
1/4" cbu, either made by Durock or the Hardiebacker will work fine. I like the Hardiebacker because it has screw placement divots and a grid to aid in cutting.
Embed your cbu in a layer of thinset and screw it securely. You could, and probably should use a vapor barrier, but I question the integrity of it once you drill a gazillion holes in it installing the cbu.

 
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Old 01-07-11, 10:01 AM
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Thanks for the info and the pic, looks good! I was wondering if you would explain in just a little bit more detail about pushing the envelope with a 12x24 and regarding the span restriction for a sunroom. My sleepers, or joists we'll say, will be running in the same direction as the long side of the tile. So the 12" side of the tile will be running the direction spanning over the 16" o.c. spacing of the joists. That said, do you think there will be additional deflection in the subfloor and cbu because of the unconditioned nature of the space? Thanks for any additional information.

Also, do you recall what type of grout and what type of mortar/thin set that you used on this application?

Thanks again for any advice.

mike
 
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Old 01-07-11, 01:42 PM
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Hey, Mike, My brain wasn't in gear. You are installing this on a slab with sleepers. You won't have much of a deflection using 16"oc. My installation was 10 above grade. You will need the cbu embedded in thinset. I used modified thinset (Versabond) and the customer provided the grout, and I can't bring up the picture of the box in my mind. It was a common sanded grout, off the shelf.
 
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Old 01-07-11, 02:10 PM
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Mike

Some questions.

How are the sleepers anchored to the slab? When you say tapered, is that to compensate for the slope of the floor? How solid is the floor, any movement when you walk on it, jump up and down on it? How long have the pt 2x's been there? I assume temperature changes are severe, you are in Washington, yes?
 
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