I know this has been discussed in the past, but I did a search and did not find any direct answers before my patience ran out.
I am tearing out the vinyl flooring in a small main bathroom – the tile area will be about 4 feet by 9 feet. The subfloor is 2×8 tongue and grooved on 4x6s on 4 foot centers. The current vinyl is over some type of 3/4″ pressed board over the subfloor (rather poor construction method in that the pressed board disintegrates when it gets wet – which tends to happen in the bathroom beside the bath tub…)
I was planning on putting some plywood over the subfloor and then Hardi backer over that and then the tile. This is in the S.F. Bay Area so moisture from condensation has not been a problem.
What is the best construction sequence. I assume (even in the Bay Area) that I should put some type of moisture barrier – possibly between the subfloor and the layer of plywood? If I find any low spots, should the leveling compound be between the plywood and Hardi or on top of the Hardi? What should I do where the plywood and the Hardi butt up against the tub? (removing the tub would require removing a fair amount of tile on two walls to pull it out.)
What is the best moisture barrier for this application. Is Hardi-Backer the better choice than other cement board products? I am assuming that I don’t need a separation barrier, is this a reasonable assumption.
If I keep the ply, Hardi, and tile to 1/4″ each, the top of the tile should be about even with the hardwood floor in the hallway. Would it be better to provide thicker plywood and/or Hardi-backer even if it would raise the level of the tile? Is there any easy test to see how much give there is to a subfloor?
Any other hints would be appreciated.
Thanks
Replies
What's the span length on the 4x6's? For ceramic tile you don't want more than l/360, for stone no more than l/720 deflection. Makinig sure your deflections are within limits is the single most important thing to ensure a good job.
I assume you are removing all the press board.
I would level over the hardibacker. You don't have to use hardibacker, there are alternatives such as Ditra. Ditra can also be made waterproof. I would leave a space at the tub interface and caulk.
You can get a lot of good advice at the John Bridge forum.
First, I'm a DIY who has done tile so take this with a grain of salt and wait for the pro's. Second, this is a great site, but check out JohnBridge.com. At the JohnBridge.com site you can use the "deflectometer" to see if your floor construction is adequate for tile.
Hardie or other CBU does not add stiffness to the substrate. Thicker won't mean less deflection. Its purpose is for thinset/tile adhesion plus it won't degrade with water exposure. Remember, it won't deteriorate with moisture, but it will allow water to penetrate thereby endangering your pressboard.
Use the 1/4 CBU or Hardie plus thicker ply or even thicker ply then Ditra which will provide you a water impermeable layer. Your plan however will have a defect at the edge of the tub where water will be able to seep thru.
If I reread your post correctly, then you plan on removing the pressboard and replacing it with the ply. Is that correct? If that is correct, then check for the allowed spans for your floor, use the indicated thickness of ply after removing the pressboard, then use Ditra and Tile away. Then hope you or the kids don't splash a lot at the edge of the tub.
The mysterious pressboard substrate under the vinyl definitely has to go. I will check out the John Bridge site. Thanks.