My husband and I have decided to replace our kitchen floor and want to put down 18x18" porcelain tiles. The challenge is we live in an older home that is very unusually built. It is an all brick ranch built in 1961 with two 2x12's sandwiched together as joists every 6 FEET. These joists run the length (not width) of the home, over them the builder laid additional 2x12 perpendicular (like when building a deck) and then subfloor and the flooring which 90% of the house is hard wood floors.

We are getting mixed opinions on whether we can replace our vinyl kitchen floor with porcelain tile. If we lay a subfloor (1/4" or 1/2" plywood? ... or thicker) topped by cement board (1/4" or 1/2" ?) would that provide sufficient stiffness for the tile?

The floor we are replacing is just under 425 square feet.

Thanks

Easy and crude way to tell... sit a glass of water in the middle of the floor and have the heaviest member of the family walk across the floor... if you get much movement of the water its not a great idea.. if it sloshes at all forget it.

additional 2x12 perpendicular

How far apart are these? Are these stood on edge or laid flat?

They are laid flat like when you build a deck.

Update on our floor issue. A local tile setter came and looked at the floor. He says our house was "overbuilt" but still suggests we lay a 5/8" subfloor perpendicular to the FLAT 2x12's and then top that with 1/4" cement or backer board before the Magister 18x18" porcelain tiles! Isn't this a little over kill?

5/8 + 1/4" + 1/4" is more than an inch total. This floor butts up against an existing hardwood floor. I would like it to stay even, but also want it to be level and last.