Floor prep for travertine tile

I am planning on installing travetine tile in a versilles pattern in my dining room (17' x 17').
The existing floor is 3/4" thick t&g plywood over engineered I-joists 16" on centers. I am planning on using 1/2" thick durrock (thinset & screws) then tiling. I used this method for smaller bathrooms in the house (largest 6' x 8'6") and the floors are very solid. I thought about using ditra, but they do not reccomend for natural stone. What do you think?

David,

NO, that does not meets any industry specs for subfloor system. You need more plywood and then you can use Ditra or 1/4" CBU or? But hold on.

Those I joists may not be up to specs for stone either. Can you get all the particulars of the joists, or call the manufacturer and make them tell you in writing what the "L" deflection rating is and at what load.

More from others later.

Jaz

What Jaz said, for stone, you need a floor that's twice as rigid. Maybe you got away with it in a bathroom or two because they are often stacked above each other and the traffic and loading isn't as heavy.

But this one?

I thought about using ditra, but they do not reccomend for natural stone.

Who doesn't recommend for natural stone? That should be a good one.

Your I joists should bear markings and with that info, call the manufacturer as Jaz said, and ask them what is the maximum allowable span to be at L/720 and build a closet wall below to cut the span to that amount, or, ask about fastening another 2x framing member to the bottom chord with full spread construction adhesive and screws to achieve the required rigidity.

You also need TWO LAYERS of plywood for a stone tile installation.