sub-floor thickness help

I am looking to install porcelain tile in my kitchen and great room.

My question is, do I need to add additional plywood for deflection.

My current subfloor is 1 1/8 inch thick, plywood.

My floor joists are 4 x 6, that are supported every four feet.

The distance between the joists is also every four feet.

I was going to use Ditra over the plywood, which I believe should be just fine, but I'm worried that I may need to increase the thickness of the sub-floor first.

Thanks in advance for any advice!

 

Schluter DITRA - Underlayment for Tile Installation | HomeFlooringPros.com

Scroll down to Wood Substrate.

 

I have no idea how that link is relevant the the question.

SSCMOC is located on the left coast where many homes are built in this unorthodox manner. The joists are 4x6" spaced about 48-50" o.c. and they span 48-50" o.c. There are no specs for that type of framing that I'm aware of. Best check with local experts to determine what the deflection specs are. The most critical is the deflection of the subfloor.

Saying that, I know that framing will work for ceramic tiles most of the time if done right. Is the subfloor ply one layer of 1 ⅛" or more than one layer? Is it in good shape with no large notches or holes? Any rot or sagging? It's always a good idea to add more ply if you can stand the added height. It should be fine with Ditra or even CBU.

Jaz