On Mon, 7 Sep 2015 12:09:42 -0400, "Mayayana"
wrote:

| . The floor as a sheet can't be very
| strong, given the waffle design
|
| Why cannot it be strong? You get full support on 50% of the tile area,
| evenly disributed - guaranteed. (assuming you can follow
| instructions)

And what about the other 50%? It sounds like the
finished product would have a great deal of flex, since
the top of the waffles will have just a thin layer of
thinset, and the sheet itself is very flexible.

You have obviously never used the product.

| It is NOT floating as a sheet. It is firmly bonded to the subfloor by
| a full contact thinset layer but with a small amount od "slip" built
| in to "decouple" the tile from the subfloor so any shift in the
| subfloor, within limits of course, is not transmitted to the tile,
| causing either the tile ot grout joint to fracture.

That doesn't make sense. I though the selling point
was that it floats

Not only have youi never used it you have not downloaded the
installation instructions to see how it is used.

. It can't be glued down and
also "decoupled". A small amount of slip built in?
Built in to what? Either it's stuck down with thinset
or it isn't.
Not onlky jhave you never used it or read the instructions, you have
obviously never even laid eyes on the product.
Concrete board, on the other hand, does
float.
It does? It is fastened down by both nails or screws AND thinset.,
with all joints taped and filled with thinset., and all joints need to
be properly staggered etc.
Your description doesn't make any sense
to me. You're describing a dense foam sheet preventing
cracks in grout and tile better than a sheet of concrete
board. (And as I said, the one job I've seen is already
showing problems in less than 6 months.)

It is not a foam product - as I said you've never seen the stuff - and
if it is failing in 6 months, it was not properly installed. If you
used concrete board the way you seem to think it is used it will fail
as well - every bit as soon.

| The selling points mentioned on that page are
| not convincing. "Even if your house shifts, your
| tiles won't". They're implying that a mortar bed
| or thinset on concrete board install will crack, which
| is not true.
|
| It sure is true. I've seen many tile on concrete slabjobs where the
| tile is cracked because the slab cracked. You see it in shopping malls
| all the time. It happened in our old office building (second floor of
| re-enforced concrete structure) and it has also happened in the
| building we are in now (a single story concrete "pad" construction.
|

I'm not talking about concrete slab. That's a different
situation. I'm talking about wood construction houses,
with plywood subfloor, where either a mortar bed or
concrete board are used. The OP does have a concrete
slab, but he hasn't mentioned anything about cracks.
The trouble he's having is with tiles coming up.

Ditra works even better on wood subfloors, with even more advantages
over cement board (which you would NOT use on a concrete slab,
generally speeking)

| They also make a claim about being
| waterproof. Waterproof is a main feature of tile.
|
| Tile may be waterproof, but grout most definitely is not.

Next time you step out of the shower, let yourself
drip a puddle and see if it runs down between the tiles,
soaking into the grout.

It definitely penetrates grout. That's why you need to seal grout.
That's why unsealed grout discolors and mildews.
ALL concrete products are pourous and none are waterproof. They may be
water resistant, butif you totally dehidrate a concrete product it
turns back to powder.

Why else do you need a water resistant or waterproof backer for tile
shower enclosures? Put tile on drywall, and the drywall turns to mud.