Tiling kitchen floor [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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10-04-2006, 07:18 PM
I wonder if you guys could give this a read and see if I'm doing anything wrong. I'm getting ready to put down 3/8 thick Italian porcelain tile on my kitchen floor that's 10' by 15'. The house is about 60 years old and has regular conventional 2X10 16 inch on center floor joists with 3/4 inch rough sawn boards run on the diagonal. I need to match up with 3/4 inch oak flooring in the dining room.

Here's what I was thinking; refasten the floor boards with 2 1/2 inch square drive deck screws. Lay down either 3/8 or 1/2 inch BC plywood with the plywood grain running perpendicular to the joists. Fasten every 6 inches with screws to the floor boards and not the joists. (should I glue down the plywood?) Layer Ditra over the plywood using Versabond thinset and tile over the Ditra. The Ditra site says to use unmodified thinset to set the tile. Can I use the Versbond since it's only a "slighly modified" thinset or does anyone have any recommendations on the best unmodified thinsets to use in this application.

Thanks in advance for your help. You guys have been great with my other projects.

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Tool Guy - Kg
10-04-2006, 07:45 PM
Hi Paul,
Your plan sounds good, providing that the joists meet Deflecto (http://www.johnbridge.com/vbulletin/deflecto.pl) standards for your tile.

No, don't glue the plywood down with anything like construction adhesive. That will create a new problem.

As far as the Versabond to set the tile. Yes, you can do it and it will work, but you will void your warranty because the that thinset is modified. John Bridge uses Versabond all the time like this and he's happy, even without the warranty. If you wanna recommendation for a good unmodified, you can use Tec's Full Set (http://www.tecspecialty.com/product_detail.asp?prodId=22). :)

10-04-2006, 07:47 PM
I'd use the 1/2", and don't glue it...gluing ply to dimmensional lumber is frought with likely complications. You didn't say how big the tile are. You'd probably be okay, but a good quality unmodified would work. Backbutter the tile to burn a good layer of thinset into it, and set them. The bigger the tile, the longer it would take for the modified to dry...it needs to do both dry and cure, where the unmodified only has to cure (in the absence of air).

10-05-2006, 07:44 AM
Thanks for your advice. The tile is in varying sizes and forms a 3 tile pattern. The largest piece of tile in the pattern is 18X18 and the next largest is 12X18 with the remaining piece being 6X12.

10-05-2006, 08:10 AM
In that case Paul (18" tile) you'll want to check every SF of floor after the ply is laid down, making sure is it flat. Using an 8' to 10' straight edge, personally I'd shoot for nothing more than 1/8" out over 10'. And with 1/2" ply over 60 year old dimensional lumber, I'd count on having some leveling work to do.


10-05-2006, 09:35 AM
2X10's, 16" OC, with 3/4 rough sawn boards on a diagonal..... what's the span of the 2X10's?

Doesn't having the 3/4's on a diagonal make the effective OC joist spacing more than 16"? Depends on the diagonal degree of course.

Just wanted to double check - the 3/4's on a diag kind of threw a yellow flag in my mind.