Porcelain tile in bathroom (underlayment question)

I'm in the planning stages of redoing the bathroom, the major project to be putting porcelain tile on the floor. The existing floor is vinyl tile - you know those industrial looking things you find in every supermarket, convenience store and school!). The tile was there at move-in 6 years ago, although I don't know if they are original to the house (1970's). I am assuming that once I remove the tiles, I will find hard glue and some sort of plywood - 1/4 luan paneling maybe?! Assuming that this is in good shape (not rotting), will this be a suitable base for laying the tile, or will it be absolutely necessary to remove it as well and replace with cement backer board??
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

*In a 1970's house it is quite possible that you will find multiple layers of flooring. Take it all off to the subfloor. Repair the subfloor if needed and then install 1/4" or 1/2" hardibacker cement board.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Inspection first is important..... Find out what is going on..... Backer Board is a recommended surface although that needs to be on at least 3/4" exterior grade T and G ply, glued well, and nailed and or screwed. Joist should be in good shape too. You can cut along the wall edges, and remove the field ply that is there, but block all perimeter......necessary.
Also the older tiles may have asbestos in them..... It was used in tile manufacture and I think on the internet you can google to find out when that was used and then not used...... I have looked it up in the past. 70's is ringing a bell...... Tile is usually pretty hard, but will dust and flake.....and if asbestos one should be very cautious with mask and plastic bag disposal..
I just finsihed a tile entry with 3/4 " t and g ply then thin set on the hardiboard. I even used some thin set to trowel the top joints with fiber tape..... Came out very nice..... Good Luck with your project. john ----- Original Message -----
Newsgroups: alt.building.construction Sent: Monday, July 06, 2009 12:49 PM Subject: Porcelain tile in bathroom (underlayment question)

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Floor must be rigid or the tiles and grout may crack as it flexes slightly when walked on. It's typically necessary to stiffen floors with a additional layers of plywood and propretary board such as Hardibacker board depending on what it's like. Use a flexible adhesive and the right kind of spreader as well.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ok, so I think we're ready to go this weekend. I've picked out my tile and the grout is on order! A few questions before I get started. First, cement backer board. I haven't stripped out the old tile/ flooring yet so I'm not sure what I'll find, but assuming everything is "average" what size should I use for backer board? Is 1/4" sufficient or should I be using 1/2"? The cost difference is negligible so that's not the issue here. I'm wondering about height difference in the new floor. Also, while I've read quite a bit about the installation and I think I have the basics down, there are some "technical details" that most how to books/sites don't really touch on...
- screws for the underlayment - what type of screws should I be using and how many? I read somewhere that using thinset under the backer board isn't really to secure it to the floor, but rather fill in any slight irregularities in the subfloor. Thus, I would need adequate numbers of screws to firmly secure it to the subfloor? Do the screw head need to be covered with an additional layer of thinset (i.e. cover them like you would on drywall and then apply thinset for laying the tile)?
- fiberglass tape on the joints - is this the same "adhesive backed" fiberglass tape they sell for drywall applications? I usually use paper rolls for this, but I know I have a few rolls of the fiberglass kicking around.
I'm sure there will be additional questions, but this is what is on my mind right now. I'm pretty excited to tackle this project and very excited to see the outcome. Thanks for all your help thus far.
Kevin
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.