"Mongoct-- (sorry OP) If not using Kerdi shower pan, but just a mudbed/liner, can you use a topical membrane for a shower floor? I've posted previously, but it didn't catch your attention. I'm trying to understand this more as well... " Sorry if I missed your previous post. I seem to be hit and miss on the forums these days. I'm a little confused by the "mudbed/liner" comment and the desire to use it in conjunction with a topical membrane. So let me ramble a bit: I consider "liners" to be the CPE or CPVC thick shower membrane liners, the ones where you use a deck mud preslope, then install the liner over that with a clamping drain, then top the liner with another layer of deck mud, and you tile upon that. If that's what you're asking about, no I wouldn't use a topical membrane on top of all that. Here's what I consider to be a liner installation. Now back-tracking a bit: There are folk that use a topical membrane with a clamping drain, but they have to "dish out" the sloped mud bed as it gets close to the drain. It's sometimes referred to as the "divot method". That way the topical membrane will drain to the drain's weep holes. If you don't use a divot, then the raised part of the clamping drain can sort of act like a dam, causing water under the tile to pool around the drain. The area around the drain might appear perpetually wet. The divot method is not a technique I embrace. Nothing really wrong with it, it's just not my cup of tea. Here is a photo showing the "divot" carved out of the mud base: Virtually every shower I do is a one-off size or shape, so I'm almost always doing a sloped deck mud base. As to which topical membrane to use, when using Kerdi, I'll do a sloped mud pan and then cover that with Kerdi. If using Hydroban, then I'll still use a Kerdi drain in the sloped mud floor but then use Hydroban on the floor and walls. So if you want to use a topical membrane, then no , do not also use a liner within the floor. One membrane is all you want. Does that help?

All depends on how your floor system is constructed...joist size, span and how spaced. Also, Ditra can only be used for stone installations over wood when the floor system is double layer construction. You're going to have more than 3/8" when you're done with any tile installation. You have the thickness of the tile, the 1/8" thickness of the Ditra and any thickness the thin set motar layers will add to the formula. You will probably come in at about 5/8". Get what you want...if it means ordering a different wood product from a different source, then maybe that is what you may want to do. Lots of engineered flooring out there. I don't do enough of the stuff to give you brand suggestions, however Mirage, Mercier, Andersen are just a few to look for. Look at what the big box stores have and then find independent flooring retailers and see what they have. Lots of stuff is made overseas (China), so be aware and informed as to what you may be buying. Some folks are happy with engineered and some are not. Although color matching is pretty good these days, Lowes should not have shipped you product from different lots. Have you been to the Schluter site? Here is a link that might be useful: Schluter Ditra

Sure you can, but it will be a recipe for failure. IF it's not done properly. There are VERY few pros I've run into that I'd be comfortable with installing directly over plywood. There are several specs that MUST be followed to a "T" that are of no consequense with any other installation method, and for this reason, many pros won't even believe that it can be safely done. It can be, but your guy really needs to know what he's doing, and saying he's been doing it for 50 years doesn't constitute knowledge. He could've been doing it wrong for 50 years, playing russian roulette and just getting the empty cylinder. You can use a decoupling membrane such as ditra, but there is no paper you can use in place of either a membrane or cement board. I'd be willing to bet the stuff he's talking about is called "Tavy Thin Skin". It's a paper like material that came out about 4 years ago. When it first came out, Armen Tavy sent me about 100 square feet of the stuff, and the MASTIC used to put it down to try out. I threw the mastic out years ago, and use the paper for templating my custom designs. I would not trust going over it with tile if you paid me double and released me from all liability. The stuff's garbage, as far as I'm concerned. The Ditra, on the other hand, would probably be the way to go. It'll only raise the elevation an 1/8", so it shouldn't cause too many problems with reference to height. I used 3/4" plywood with a sheet of 1/2" plywood on top of that and it was not enough. This is exactly what I was talking about. Actually, what you described IS the recommended thicknesses and layers. BUT-- if it's not installed properly, you're going to have nightmares until the floor's torn up and redone. EVERYTHING YOU DO-- from how far you offset the joints in one layer to the other... which direction the grain of the plywood is laid in relationship to the direction of the joists... even what species of wood and grade the plywood is, right on down to the thinset you use (and regardless of manufacturer's claims, not every bag of thinset that SAYS you can use it over plywood, CAN be used-- not even close)-- ALL these things, and several others, are extremely important, and overlooking anyone of those, will be enough to make the installation fail, and drive you nuts looking for the culprit, because they're so subtle.

I'm getting ready to tile my kitchen. I'm leaning toward using Ditra uncoupling membrane instead of cement backerboard. We have 24" oc joists under 3/4" subfloor. The Schluter site says I can use Ditra XL over a single layer of 3/4 ply or regular Ditra over a double layer subfloor (3/4 and 3/8" layers). My question is, what is better/stronger? The single layer with Ditra XL or double layer with regular Ditra? Already assuming that my floor meets the L/360 deflection requirements for my tile. Ditra XL sounds like the better option as it would match up with 3/4" hardwood that is going in next to the tile, but if the double layer of ply is the stronger option, I'd go with that as we're putting in a granite island in the middle of the kitchen and a 36" bluestar range along the wall.