supporting a new tile floor- plywood depth, backer board depth?

I'm replacing a 3/4" tongue and groove rotted bath floor, and want to put in a tile floor. I've read different things in different books (and on different web sites) in terms of how to do the floor.
What I need to know is the appropriate thickness of plywood to use (and grade), and thickness of backerboard. Is 3/4" plywood and 1/4" backerboard more than I need? The studs are 16" on center.
My goal is to use the thinnest option that will still do a good job (I'd rather pay a little more for thinner underlayment if needed) to minimize some potential problems with toilet height, drum trap height, and clearance on the bottom of the bath door.
Anything will be firmer than the old rotten floor, but I want to make sure I'm not setting myself up for a lot of grout issues if the floor isn't firm enough.
Thanks! Keith
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
K Ruck wrote:

That will work, just make sure you use plenty of screw on both. I use ring nails. Drywall screws break!
Rich
--
"You can lead them to LINUX
but you can\'t make them THINK"
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
K Ruck wrote:

*That* is the minimum you need, not more than you need. Let this be your guide. http://www.ttmac.com/deflection_limitations.htm
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Ours is 3/4" "structurefloor" an engineered OSB type product which is attached to the 16" OC 11.5" TJI's by screws and construction adhesive. Over that, the tile guy glued and stapled (used almost 2 boxes ~10,000 staples) 3/8" ply and then tiled. In some of the $500K- 1M homes in the area, the General has him use a 3/8" dense medium grained chipboard (not MDF, Hardibacker or OSB) the name of which I can't recall right now, over the 3/4 stuff. The stuff is dense alright but has little structural strength. You can snap it with your hands. It runs about $ 7.00 a sheet so I went with the ply for a few bucks more for the added strength. Been in the house for over a year and it works for us.
BTW, Some of the "experts" here said the 3/8 wasn't adequate. I'm sure they'll sound off here.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Rudy once more attempts justification when he wrote:

Dear Rudy the Screwed homeowner, Technically, you don't have a clue what you're talking about. Your advice is flawed at best, and your ignorance shows every time you wail about using plywood or chipboard as you attempt to justify the screwing you got regarding your tile substrate.
<For the OP> The purpose of an acceptable tile substrate is not to provide structural strentgh. Structural strength is designed and built-in to the subfloor prior to the finish floor substrate. The finish floor substrate needs to supply an even, flat, and flex-free base for the tile or stone. The TCA, tile manufacturers worldwide, and every engineer/ architect, tile professional, etc, I've ever known or dealt with advises against using chipboard, particle board, luan, most plywoods, etc for tile substrates.
<For the screwed homeowner> $500K- 1M doesn't mean shit. To think that the price of the house (in todays world) means one is guaranteed that non-inferior workmanship and/ or materials will be produced throughout the house is absurd. Once again, your justification(s) for having an inferior tile substrate are worthless.
You're developing quite an inferiorioty complex about the inferior substrate your 'General' stuck you with Rudy. I bet we'll never here a peep out of you around here when the grout starts cracking. If this is a tract development, you and your neighbors will be screaming class action law suit very soon.

Always glad to help the ignorant, correct the morons that sound off here, and support and add to those that give correct advice based upon experience and knowledge of home building and repair. If that's an 'expert' then so be it and I am one. You're not.
Meantime, check out some decent attorneys and for pete's sake Rudy, quit showing us your ass about this topic every time it comes up.
-end of conversation-
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
G Henslee wrote:

geeee I hope I gave the right advice, would hate to get flamed by you. hahaha ... I do this type of work and yes I have had to replace bath floors which were installed wrong by Jose and Jos B. If the floor is not sturdy the grout will crack. 3/4" and 1/4" hardy should be ok if the floor joist are 16" on centers.
Rich
--
"You can lead them to LINUX
but you can\'t make them THINK"
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Evodawg wrote:

No chance Rich. This other guy and his "I got screwed with it so it has to be good" attitude doesn't cut it.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
G Henslee wrote:

Got cha, I came in late on the whole thread, so not sure what has happened in the past. ; )
--
"You can lead them to LINUX
but you can\'t make them THINK"
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.