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Unread 03-28-2016, 11:04 PM   #5
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jwmezzanotte's Avatar
Join Date: Mar 2010
Location: Prince Rupert BC Canada
Posts: 2,144
Ive had similar problems here with tile over ditra in exterior work. I feel like the waffles in the ditra hold a fair bit of moisture from our extended rain periods.

Have done some exterior work over hydroban and similar to what you experienced with Redguard I had much less of an efflorescence issue.

Ive been looking into it a bit more and am going to be using ditra drain vs ditra on a deck. Either tomorrow or the next day actually.
One issue though is that I dont have access to one of the suggested waterproofing membranes (dura deck tile deck was one)
Im going to be using Kerdi. Kerdi is not recommended for exterior use (per several schluter reps) however it is shown being used in the details for ditra drain.
Its a small project, so Ill be taking my chances (and quite comfortable with it)

The ditra drain will be a much better product for our climate I think. It allows any water that gets through the tile to drain out underneath the tile rather than having to evaporate back out bringing efflorescence.
The waterproofing layer is not the ditra drain, but the membrane below it. In my case I'll be using kerdi, though I'll mention again that Schluter recommends using something else.
I think that given how often it rains here theres still pretty good chances of efflorescence issues, but I do expect the ditra drain will make a big improvement.
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