Flooring Tile - replacing hardwood floor w/ceramic

I am needing to re-do my kitchen floor which at this point is hardwood. my ORIGINAL plan was to remove the t&g oak down to the 5/8 plywood subfloor and toss in 1/4 hardiback and then the tile getting back up to the level that the remainder of the area is (3/4" over the 5/8 subfloor).

I have 2*10 joists 16" oc, longest span is about 9'.

seems now that this isn't enough 'subfloor' for the job but I have height issues due to clearances for doors, dishwasher, etc.

could I just put down 1/2" exterior plywood (in other direction than the 5/8, end seams away from joists, nailed every 8", 1/8 expansion joints all around) and then tile directly on that withOUT the backer board?

thanks.!

ront

If you run it a a 45º it may work. When tiling over plywood if you must, Your going to need a bigger notch then one normally would. You want 100% coverage without trowel ridges.

Reading an article here from the man himself Dave Gobis,Does'nt say anything o about laying tha panels on the diagonal just to offset the joints(i always lay the top layer perpendicualr to the one below).
7/16 is the minimum thickness for the top layer of plywood(exterior plywood only).

Also the thinset needs to be rated for exterior grade plywood(egp).It has a picture in the article of a 3/8 notch sitting next to a 12" tile.The size of the tile and the type of tile dictates what size notch is to be used not the surface that you are bonding to.

He also reccomends that the panels be nailed every 6" on the seams and every 8" in the field gapping the panels1/8 of an inch at the sheets butting up to one another,at the walls and cabinets1/4"of an inch.Nails not to be nailed into the joists.
There it is right from the horses mouth :cool:

The latest issue of FCI magazine, goes in depth about this subject.

It is not online yet, as I checked so I could link you to the nice article.
Very interesting read.
Check out www.FCI.com sometime.