Easymat

I saw a small bronchure mention this product Easymat. Is this a underlayment for waterproofing? Can I use that under my floor betweeen the plywood and Harie board for insusrance of wetness from a shower. (for a bathroom floor) Not sure if it adhesives or not. Haven't went out to look at it.

Nope! You have totally missed the purpose of that product. Waterproofing is not one of its uses.

It's pretty obvious at this point you are dead set on making this floor waterproof and though you normally wouldn't need it to be, making it waterproof won't hurt anything either.

YOU CAN ONLY WATERPROOF ABOVE THE CEMENT BOARD!

That is, if you've already purchased your Hardi, and have it cut to size, install into a bed of thinset, screw it down, tape your seems and then coat it with a topical waterproofing membrane. You keep referencing Home Depot's products, so that would mean you would use Redgard. On Hardi, I give it a primer coat of diluted redgard, 4parts water to 1 part redgard, since hardi is so thirsty, just a really thin coating, then I go at it full strength Redgard. Must be 47mils thick dry or just over 1/16" thick when dry. Use foam backing rod in your perimeter expansion joints to plug them up (found with weatherproofing stuff and used to plug deep joints before caulking) and Run the redgard over that and up the walls a couple inches, embed fiberglass tape in the wall intersections in your first coat. Lowes also sells a liquid waterproofing product from Laticrete called "Floor and wall watertight"

If you haven't cut up the Hardi yet, return it and buy Ditra. Find a tile shop near you that stocks Kerdiband and install the ditra and install Kerdiband over the seams and at the floor wall intersections. You could also order the Kerdiband from HD or online at [www.tile-experts.com] or [www.tileprotection.com]

If you use Schluter Ditra, you can use Versbond to install the Ditra to the floor but for Schluter's warranty, you would need to use a different thinset to install the tile. Head over to Lowes and get "Megabond thinset" to install the tile. Don't buy the jug of megabond additive.

You could also use Noble CIS as your underlayment in which case you would set the membrane and your tile with Versabond. You can order it from [www.noblecompany.com]

Noble Products or Schluter Products get used on the floor in place of cement board

We're almost into November, the wife and daughter will be back in December. They can't just run outside and go behind a tree, or if you live in snow country, proudly write their name in yellow in the snow.

Sorry, maybe I'm just stubborn, but get me straight.
Isn't the worry is the plywood, so why not just waterproof beyond the cement board with a felt paper or other polymill item? We know that water will go through the cement board, its be easier to install membrance at this junction. Read lot of threads that plywood will expand if moistures pass tru, that reason why I was worry about the waterproofing.
I know it a burden for my wife and kids, but dam sure didn't want any problem in the end.

Stubborn?

Water won't go through the cement board if the waterproofing is on top of it.

Water will go through where all the fasteners are driven through anything you try to use for waterproofing between the two layers.

Straight now?

Both those membranes I mentioned would take the place of cement board, by the way. By the time you add the price of cement board, special fasteners, and trowelable liquid waterproofing membranes, either Ditra or CIS will be cheaper and out perform cement board. It's all in one step and saves you all that time that way as well.

I'll also share this little bit of info with you, they are both polyethelene membranes! Poly sheet membranes for tile! Woohooooo! Looks like you could grab the brass ring my friend. The horse is about to pass, just reach your hand out and take it

We all will have "passed" by the time this job gets done.

Hey, if I knew how easy it look on the Ditra viedo, I would have start with this instead of the Hardie. Maybe I just throw away the cuttted Hardie now and get the Ditra. The viedo if true what I see is what I get this be a much easier for a unprofessional dyi. (sorry) I just want this job to go to bed. Isaw one thing;I wonder if it a problem if I installed my plywood wrong side up, but shouldn't matter if I use Ditra right?
With Ditra I wont have to worry about the screw of a Hardie board anymore, correct since the Ditra is bond by the thin set. The cutting of Ditra is so easy and clean.

You installed the plywood with the stamp facing up? That is probably the most fatal error you could have done. I'd suggest you stop reading now and start removing it now. Just kidding. As long as the face grain of the plywood crosses the joist, fine. Go with Ditra, when you flat trowel the thinset first to ensure full contact with the plywood, it will fill any small little voids around knot edges prior to combing your lines. Go for it and put this job to bed.

BLJACK: you scared me, I almost got a heart attack that I messed up again. Thanks! Now where can I find Ditra in my city? How much is it, I figure all I really need is 13 feet x 3' wide would work. I would run one long 80" x 31" then two 46" x36" and one 6"wide by 36" at the door opening.

Can I do it this way or is the small 6" piece would be too small?
What I have is a L shape area where the tile will fit into.
All the piece will run perpendicular to plywood grain. (I guess it dosen't matter)
I will use unmodified thinset on bottom and modified on side of tile.