This might be kind of long, but I'd appreciate you reading it through.
Thanks.

I am going to bite the bullet and again replace a bathroom floor in May.

I have replaced the top surface once, about 18 - 20 years ago when I didn't
know what I was doing. Because I didn't then know what I was doing, I need
to do it again. I've gained a lot of knowledge since, but am always on
the look out for more.

Smallish bathroom, about 5' x 8".

Previously had really poor condition sheet vinyl over a particle board
underlayment.

Previously, I pulled the toilet and stored it in the back yard ( makes a
great planter!)

Stripped all the sheet vinyl from the floor up to the cabinate base, and the
shower pan. Removed any lingering vinyl adhesive with solvent, stripping
down to the particle board underlayment.

When I first replaced it, on the advice of the folks at Color Tile, I did
small tile (12" x 12" sheets) of 1" x 1" tiles. Thin set with a good notch
( 1/2 inch). Right over he particle board.

Surprise. After a lot of years of wear, many of the tiles are coming up.
Especially where there is some drip / moisture from the shower door when the
door is open.

Long to short, I have to pull all the tiles and re do.

I know I have a shower door problem re leaks. That I can and will deal
with before I do the floor. So, please ignore any shower door leak issues.

I also have a wierd bath room door access issue. The access from the master
bedroom to the bath is a pocket door. The pocket door didn't work when I
bought the house 30 yaers ago and still doesn't. The bedroom floor wall to
wall carpet. The bath has the afore mentioned tile. The pocket door is
both off its tarcks and won't clear either the WTW carpet, or the tile.

I am reluctantly willing to pull the wallboard off the bedroom side of the
pocket door to fix. I am not willing to pull the wallboard off the bath
side of the wall because that forms part of the tiled ( by the builder)
shower surround, and I'd really not want to have to replace the shower
walls. The tile on the walls still seem in good shape, and no leaks, etc
down into the family room below. My theory is if it ain't broke, don't fix
it.

I did have one leak onto the tile floor, from the toulet, after I did the
tile. This was about a year ago next June. Inside the toilet the
friggin' float arm broke off . The inlet valve thereafter opened, and the
inlet toilet valve kept allowing water into the tank. The tank totally
overflowed, with awter coming out of the lid. Of courese I was at work,
and when I got home after "X" hours, here was water everywhere. I sut off
the safety valve, got towels and the hop vac, and pulled up a lot of water
Wallboard on the ceiling of the family oom, under the bathroom, took a hit.
Oddly, the floor in the bath did not appear to suffer any additional
problems, no tile de laminating, etc. No where near any datile damage near
the toilet from the one time flood as compared to the damage by the leaky
shower door.

So, my questions a

1. Whats the conventional wisdom regarding thicknesses of underlayment /
underfloor and cement board in a bathroom before a tile application?

Is it 3/4 ply (outdoor ply, marine ply, regulay ply, whatever?) plus 1/
4" cement board.

Is it 1/2 inch and 1/2 inch?

Is it /8 and 3/8?

What has worked for you?

My gut thought is that I need at least 1/2" ply plus whatever.

I also think I have to do an autopsy of the current floor to find out
how much room I have inder it, i.e. I need to know the thickness of the
present particle board underlayment.

2. The Orange Borg sells lots of 1/4" cement board. Lurking here, I read
a lot of negatives about cement board for bathroom underlayment. I hear a
lot of positives about hardyboard as an underlayment. Around here
(Portland, Or.) here there is a lot of favorable comment about Hardieplank
siding as a replacement for the LP or whoever crappy mold and nushrom
growing exterior siding.. Same company? Parallel product? Personal
experiences with hardy board vs. cement board?

3. Because this bathroom is so small, I like the look of the small tile (1"
x 1"). Is there any longvity benefit to the larger (6" x 6" or 12" x 12")
tile. I can cut the small stuff with a tile nibbler. I think I'd need a
tile saw for the 6x6 or 12x12. Any tile installation requires tile
cutting.

4. Underfloor heat. I have gas fired forced hot air. There is one vent in
the bath room floor. It gives adequate haet when I showere about 06:30 am,
as the set back thermostat kicks the heat up about 06:00. Still whil the
bathroom air is warm the floor is cold.

I have seen a lot of Home Time / This Old House shows with electric (not
water, electric) grids under the tile for heat.

Systems, brands, thoughts, etc.

Thanks for reading this maybe too long missive. I really would
appreciate your comments and suggestions.
--
Jim McLaughlin

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