Hello-
I am about to embark on my first tile project. I know this question has been asked , but I want to be certain I get my underlayment correct.
I have a 110 year old house.
Joists are true 2 X 10, spaced 16" o.c.; span is 14 ';I do not know wood species
subfloor is 1 by 4 planks
I will be installing 2 inch hexagonal ceramic tile ( 12' X 12' sheets)in a bathroom.
What would be the best underlayment solution?
Ditra is available in my area and I am considering this option.
Is Ditra a good option for a novice?

Thank you for any advice.

Your joists should be fine, provided they are in good shape.

For the subfloor, I would add a minimum 3/8" ply screwed to the planks with no glue.

Ditra's specs call for a minimum 2x2" tile. Since yours are hexagonal, I'm not sure if that will work. Someone else might have a better answer for that, or you can call Schluter directly. 1-800-472-4588

The tiles I am installing are 2" Octagon with 3/4" black sqaures so I will check with Schluter. If Ditra will not work, what would be the best way to proceed? 1/2" Permabase cement board over 3/8" ply?

Thanks

I would install 1/2" underlayment grade plywood over planks due to the probability of slight cupping of the planks. Especially if the planks are not t&g.

Schluter has a 2" min for tiles over Ditra as Kevin mentioned. I think you could disregard that if you first fill all the squares with thin set and set the tiles the next day. This will void any warranty you might have expected. Me, I don't expect any warranty.

I believe Schluter's position is in regards to heavy loads such a heavy table legs on a small area. I'm sure they will stick to their recommendation as well they should. Otherwise any CBU is just fine. You do not need 1/2". I recommend 1/2" ply, then 1/4", 5/16" or 3/8" concrete backer.

Jaz

I am ready to install 1/2" ply over my existing subfloor. What type of ply do I need? Is cdx a no-no? My HD carries southern pine in 1/2" and a bc grade in 1/2".

I will then put down cbu w/ thinset and backerboard screws. If I need some levelling would I do that before or after the cbu?

Thanks

Go with the BC grade, stay away from the CDX sheeting.

Any leveling needs to be done after the CBU is down.