Flooring Tile - tile on wood subfloor (no backer)

I have a subfloor that is 1 inch thick with marble right on top. I plan to remove the marble and replace with porcelein tiles. Here is my problem. If I use cement backer below the tiles I will not have enough clearance for my fiberglass (can't cut it down) front door to open.

Can I place tiles on wood subfloor without the middel cement board layer? Isn't this they way it was done for decades prior to the creation of cement backer?

I have a subfloor that is 1 inch thick with marble right on top.

What is the composition of this 1" subfloor? Is it plywood 3/4" inch & 1/4", osb or something else?

You should not tile directly over plywood. You need to at a minimum put down 1/4" cement board or an uncoupling membrane like Schluter Ditra. But you need to answer the question above before we can tell you what to do for sure?

[QUOTE]Isn't this they way it was done for decades prior to the creation of cement backer?/QUOTE]

No. Before cement backer there were mud beds. Mud beds are still used today and are still the best way to go.

The subfloor is 19/32 ply with an additional 1/2 inch ply on top of it. The marble is on top of that. what shoudl I do since I have a clearance problem at the door? What is a Mud Bed?

You could use Schluter Ditra on top of the plywood. This is an uncoupling membrane that only adds about 1/8" thickness to your floor. This gets thinsetted to the ply with modified thinset. Then you thinset the tile to the Ditra with unmodified thinset. Check out http://schluter.com/english/products/2002/sectionf/overview-f/section-f.html

Tim - Im assuming that since you had marble on the floor previously that your floor meets deflection standards for ceramic tile.

I am assuing that it meets deflection standards, no marble crack in 5 years. Where woudl I see the standard?

Ho much thinset goes below and above the ditra? If the ditra is 1/8 inch how much additional thickness of thinset goes below?

Thanks for the help!

What size joists do you have, what is the spacing between the joists and low long is the unsupported span of the joists? You have to meet L360 for your porcelein tiles.

You can use 1/4" notched trowel to set the ditra. Because of its design, it will not be much more than 1/8" even with the thinset below. The size trowel to use to set the tile depends on the size/type of tile and how flat the floor is.

Look at this link for Ditra installation.http://schluter.com/english/products/2002/pdf/DitraHandbook(32)_052005.pdf

The joists are 2x10 and span 16 feet between supports. The joists are strange in the spacing in that they range from 14, 16, 17 and 19 inches apart in the area under the area that I wish to redo with porcelein. Where can I read about L360 standards?

16' unsupported span is not good. You need to do something to beef up the joist structure. Ideally you want to cut the unsupported span down to 12' or less. If this is over a basement you could put in a supporting wall in the basement (maybe build a closet for storage), or sister the joists to take some of the bounce out of the floor.

I use this site to check calculations when I need to. http://www.johnbridge.com/vbulletin/deflecto.pl