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Laying Ceramic Tiles

jimmiejp's picture

Laying Ceramic Tiles (post #195981)

I'm about to tackle laying ceramic tile in my foyer. Not having ever done this before, I would appreciate a little help as to the proper underlayment to use. My sub-floor is 5/8" plywood. At this point of course I'm attempting to decide which "cement board / backerboard" and the thickness required? Is it necessary for me to add another layer of plywood?


Many thanks in advance.........Jim

An equally important bit of info is the span of the joists (post #195981, reply #1 of 7)

under that floor.

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I'll get on it (post #195981, reply #2 of 7)

I'll get on it immediately!


thanks for the Info!...............Jim

underlay under tiles (post #195981, reply #3 of 7)

my understanding is that the substrate under ceramic tile should be 1 1/8 or 1 1/4, depending on what dogma you want to subscribe to.

What will your supplier warranty? Betcha it ain't just the 5/8 subfloor.  and if you've got lino, you may have particle-board underlay, which ain't in my book a recommended substrate for ceramic tile.


Besides if you install the tile directly on the 5/8 subfloor, the next guy who relaces tje floor (AND IT  MIGHT SOON  WELL BE YOU) might be wanting to find nasty annular reamers to stick where the sun don't shine, all the while cursing the mis-directed frugality of the previous installer....


In other words, do it right the first time....



Tile size (post #195981, reply #4 of 7)

Another factor is tile size.  The larger the tile the less flex it will withstand.

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 *Under ideal conditions

Couple of points (post #195981, reply #5 of 7)

1) as others have mentioned, you need a proper structural thickness of subfloor and underlayment. 1-1/8" of ply is the way to go, so you'd want 1/2" ply on top of what you have. Offset the seams and screw the 1/2" to the 5/8".

But wait, there's more...

2) Then you need to transition from wood to tile. This is usually done with cement board. 1/4" will work. Cement board offers no structural strength, so it doesn't count towards the 1-1/8" thickness mentioned above. If you use cement board, you use thinset between the underlayment and the cement board,m then nails or screws to secure the cement board to the unerlayment.

The thinset is not to bind the two together. That's that the fasteners will do. The thinset fills any micro-voids between the cement board and the underlanyment, preventing any vertical movement, and ensuring a long-lasting installation.

2a) Other transitional materials beside cement board: You can use a membrane like Ditra, or one of the others out there. Ditra can be use right over your 5/8" subfloor if it's T&G and if your joists are 16" on center. If not, then Ditra could be used over the ply/underlayment.

3) Then you tile over the cement board of Ditra.

4) Grout.

5) Drink beer.

There are 10 kinds of people in this world; those who understand binary and those who do not.

More on underlayment (post #195981, reply #6 of 7)

I have a situation with 3/4" AdvanTech as my subloor @ 24"OC.  If I add 3/8" ply to get me to 1-1/8" subfloor and then Detra AND use a tile under 12" do think this will work?

I might add that the 3/4" is sitting on 1-1/2" sleepers on a slab with 1-1/2" ridgid foam between the sleepers.


Was on vacation... (post #195981, reply #7 of 7) I missed your reply.

Ditra XL can be used over a 3/4" subfloor 24" on center with ceramic tiles. No need for the additional layer of ply.  If you want the second layer for added stiffness, have at it, then you can use regular Ditra.

Ditra specs can be found on the schluter website, I highly recommend you visit that so you know you;re building the proper sandwich and using the proper materials and thinsets, etc.

Best, Mongo 

There are 10 kinds of people in this world; those who understand binary and those who do not.