Porcelain tile in bathroom

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
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Well, Assuming your underfloor and subfloor covering are reliable, I would use a hardi backer that would "feather out" where it meets the existing floor with tile thickness in mind. Using thinset on the floor prior to installing hardibacker is a good idea, and does help give the cement board a "bedding" I use 1 5/8 " gold drywall screws. I also have used an oversize bit-(junk bit) to give the bugle head of the screw a place to set so that it does not stick above the hardi backer and if you try to sink the screw it will break! Using a fiber tape on the seams and using some thinset ontop helps once again get the surface closer to level and does the same job as taping sheetrock. (filling the joint and somewhat connecting the sheets)
I also wet the floor prior to thinsetting the hardibacker. It helps keeping the thinset from loosing moisture prior to spreading.
Check the floor well prior to laying the hardi backer....If it squeeks, or moves, screw it down to the joist. Also take measures and screw the hardiboard to the joist.
john

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Perhaps lay down on the floor and look to see if it flexes as someone else walks about on it. If it does then consider taking it up, fix noggins between the joists to provide additional support and screw down WBP plywood before the hardibacker.
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On Jul 23, 10:55 am, "Cwatters"

A couple more questions on thinset mortar...
First, if I use a thinset under the backer board and screw it to the floor every 8", do I need to allow time for the thinset to dry before beginning to lay the tile? Also, what is the absolute minimum amount of time I have to wait before I can put the toilet back down!!! When I install the tile, I plan to do most of the floor on day one and leave a path of untiled floor to the toilet to do on day 2, so I'm not worried about walking on the tile before its ready, just being able to use the toilet...house full of teenagers who are not so sympathetic to the "remodeling bug"!
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I would let the thinset on the hardibacker set for one day. I would let the tile on the backer board set for one day. I would put a piece of ply down on the floor for use of the potty after that. you still have to grout.....so, you need one day for initial thinsetting. 2nd day for tile thinsetting 3rd day for grout setting... get a porta potti...for a day or 3? john

A couple more questions on thinset mortar...
First, if I use a thinset under the backer board and screw it to the floor every 8", do I need to allow time for the thinset to dry before beginning to lay the tile? Also, what is the absolute minimum amount of time I have to wait before I can put the toilet back down!!! When I install the tile, I plan to do most of the floor on day one and leave a path of untiled floor to the toilet to do on day 2, so I'm not worried about walking on the tile before its ready, just being able to use the toilet...house full of teenagers who are not so sympathetic to the "remodeling bug"!
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Rent a Porta-Potty for a week....You can't walk on it for ATLEAST 24 hours..I'd wait a little longer than 24 hours before installing the toilet....And who knows what "problems" you might run into when you start tearing up the floor....Thinking it will be done in ONE day is ridiculous for a first time DIYer and where are you gonna "GO" even if it does only take ONE day...Pretty long time to hold it...LOL......
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