Tiling over plank subfloor [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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11-22-2009, 05:05 AM
I am new to this forum, so hopefully you can help me out here.

I have an older house (1956). It has a 1" plank subfloor with a standard 3/4" hardwood T&G floor. I have a 3' x 4' entrance way that currently has a stone (granite I think) flooring. I would like to replace the existing stone with a porcelain mosaic tile. I would also like to have the new tile flush with the existing hardwood floor. I would like to use Ditra if possible. Also, I plan to use additional hardwood flooring to border the tile. Unfortunately, I cannot see the subfloor from the basement under the foyer because the basement ceiling is finished (bought the house this way). I have been able to investigate the subfloor from other ares in the house.

My questions:
1. Is it possible to install a typical thickness tile flush to the hardwood flooring?
2. How do I install the tile on the subfloor without raising the tile above the hardwood floor?
3. What do I need to do use at the hardwood floor to tile junction? I saw a show that used some sort of acrylic sand caulking (or something like that). I heard that it is not a good idea to apply the grout against the hardwood floor (expansion and moisture issues).

I have seen/read a lot of information on installing tile, but they always assume that you have a plywood subfloor.

Any help would be appreciated.


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11-22-2009, 05:25 AM
Your picture doesn't look like granite, but that's besides the point.
About the only way we can answer any of these questions is if you start demoing the existing floor to see what we have to work with.

11-22-2009, 07:45 PM
What are the joist size, spacing and maximum unsupported span? If joists have deflection less than L/360, based on the answers to the questions above, then you'll need at least 1/2 plywood underlayment over the planks. Over the plywood you've got options, eg; CBU, Ditra, etc... Around the perimeter of the tile at hardwood, a color matched caulking or metal/plastic profile is commonly used.

Start w/the joist structure and we'll see where it leads.:)

11-24-2009, 07:01 AM
Thanks guys.

I will have to wait until I am ready to start the project to gather more information. I'll let you know what I find at that time.

One thing I was considering doing was replacing that section of planks with the plywood to reduce the height at that region (ripping the planks over the floor joists). Is that an acceptable procedure?

As far as the deflection was concerned, I didn't think it was that important since the area was so small. Then I realized that the deflection requirements may be to keep the tile from cracking or working themselves loose. Is that a correct assumption?

Thanks again - stay tuned.

11-24-2009, 08:36 AM
You will save some height, depending on what's there now. As it is, your plank subfloor must have 1/2" of plywood plus an underlayment, plus the thickness of your tiles, so I'm pretty sure that you'll need to remove the planks if you really want a flush tranistion. You will need to install blocking to support the edges of the plywood between the joists.

You are correct about the deflection issue.