Just saw this one...
Ilene, this product is designed for concrete masonry units to minimize
moisture absorption.  Usually, there is a separate block admixture that is
added at the precast plant and then the contractor is supposed to add the
product you mention to the mortar.  We've tested for its presence but have
never done any sort of perm testing.  However, given its intended
application I would steer clear away from this one.

In my opinion, Type N mortar is already dense enough and in some cases too
dense.  The glazed surface of the terra cotta may be "impervious" but the
interior is not.  I don't think it would be a good idea to seal the interior
masonry on all five sides unless you could guarantee that no moisture would
ever get into the masonry from behind or along cracks....EVER.

John

-----Original Message-----
From: The listserv where the buildings do the talking
[mailto:[log in to unmask]] On Behalf Of Ilene R. Tyler
Sent: Wednesday, April 08, 2009 12:35 PM
To: [log in to unmask]
Subject: [BP] Grace's Dry-Block

 New thread: does anyone know this product - Grace's Dry-Block II Mortar
Admixture? Can it be used as a mortar additive to Type N mix for
pointing glazed terra cotta to improve water repellency of the mortar?
I'm concerned about trapping moisture in the assembly, and causing more
damage than already occurs with the failed mortar. 

Thought I'd throw it out there for you all to chomp on...many thanks.


QUINN EVANS | ARCHITECTS 
Ilene R. Tyler, FAIA, FAPT, LEED AP
v 734.663.5888

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