efflorescence. is the vapor barrier compromised?
 

many of the inspection I perform where efflorescence is an issue I get asked where are the salts coming from. Well the answer is from moisture carrying the salts to the surface. The next question is the vapor barrier compromised? I have developed a simple test that can show this. If the vapor barrier is compromised soil will be exposed. It just so happens that soil contains Nitrates. Concrete does not. Go to a pet shop and buy a nitrate test kit. If the salts test positive than you have a vapor barrier puncture.

Frederick M. Hueston
www.stoneforensics.com
office 321 514 6845
Stone Inspection and Troubleshooting correspondence course
For more details see the training section at www.stoneforensics.com

Interesting Fred. Could a test positive for nitrates be from dirt on top of a properly functioning vapor barrier? :)

Dana

Yes it is possible, thats why you do several tests across the floor

outside deck?
 

have a friend /client
who's outside deck is showing signs of the white stuff.

its black slate laid onto of std dirta which in turn is on a 2" slab of concrete

other main issue is possible lime leeching coming from the concrete?
coming out on the fascia board
there is a drip cap on under the concrete slap but leeching is coming from under it as well

grout on the deck is still solid and the slate has not shaled at all.

but after several day of rain and it starts to warm up the deck shows signs of sweating beading coming up from the grout joints?

any thoughts?
two upper decks above have been red guarded.. and show next to no signs ??? but they are a little more protected from our BC weather

John
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.

thanks John
well client is so unhappy with it, that this year(summer sry spell) where going to use a high gloss concrete sealer / fila-wet to seal and see how that holds up
if the issue still presents its self year after then the slate & ditra is being taken off
and either hydro ban or red guarded will be put back in and new slate/ tile installed.