hi,
I am a newbie home owner with a huge problem. I have wood that is rotted on my front porch. After further investigation it is only the top wood that is rotted, not the bottom. The previous owner did not use concert board. So, here is my plan. Pull out the tile and the rotted wood, replace with wood but I don't know what thickness to use since the concert board will add thickness and it needs to meet up with the front door. And then use porcelain tile on top. Will this work, or is it more complicated?
Thanks,
Carrie

exterior installations are the most demanding when it comes to doing it right and making it last. It would help to know where you are located, because southern florida is a lot different from southern ontario.

I would recommend re-building the porch to make sure you have at least 1/8 inch per foot slope away from the house. Top it with 3/4 inch exterior plywood and Schluter Ditra, then tile. An alternative would be to use 2 layers of 5/8 inch plywood and then a liquid water proofing membrane such as redgard or Aquadefense.

pistolpete is right, need to know what climate zone your in.

Judging by your description of the porch, I'm assuming this is not over a living area.If it is, then there's a big difference in how you would need to proceed.

Sorry, we are in St. Louis. It is not over a living area. Quite honestly, I need the solution that we can do ourselves. I didn't expect this and don't have a ton of cash but I need it to be safe.
Thanks!

Please look at the Schluter Ditra detail in the attached link.
Page 16 is the detail for a deck such as yours.
http://www.schluter.com/media/DitraHandbook.pdf

You should be able to do it yourself.

Keep in mind that Hardibacker is not recommended for exterior applications. Go with a true cement board like Durock or Permabase rather than a fiber cement board.