Expert: Dan Griffin - 4/7/2009

Question
QUESTION: For use in new residential construction inn California, I am trying to locate structural CMU block (for envelope walls) with ALL the following characteristics:
Split-face.
Integral Water Resistance.
Mortarless (dry-stack)
Can you advise me?
Bruce Dobbyn


ANSWER: Bruce, look in your yellow pages for brick or masonry wholesale or manufacturer.  If this doesn't work, stop at any commercial construction site and ask either who the mason is or his supplier.  These guys are NOT buying their materials at Home Depot.

You may be seeking the Holy Grail.  Split face - no problem.  Integral water resistance - usually silane or siloxane applied to the finish structure.  Mortarless system - problem!!  As far as I know this would require a parge coat of fiberglass on each face (Quickwall) that would ruin your splitface.  It may also be acceptable to grout all cells - a trick I've use several times for underground catch boxes, etc which might not be acceptable for structural work.

By contacting a CMU manufacturer, he can give you better information.

---------- FOLLOW-UP ----------

QUESTION: Holy Grail indeed!  
Thanks for your comments.  I should have said I was looking for a mortarless system available with split-face, like Haener or Azar.  But with Integral Water Admixture like Grace Dry-Block so that the exterior split-face is ready to face the elements without sealing or parging.  Also, I should have said  that the walls would require seismic zone 4 seismic resistance and therefore multiple bond beams and cells fully grouted with no no cells open for drainage - like standard mortared CMU or Faswall.
I have already gone down the road of AAC  (too weak for Zone 4, not accepted under IBC;  and Durisol (absorbtive, requiring exterior plaster or siding.  So, now I'm down to contemplating the split-face CMU with separate interior insulation wall.

Answer
Bruce, if you can get the look you are after with Haener or similar and feel comfortable with the work, I think I would head there.  Applying a water sealer is pretty simple and straightforward.  Quite common to perform with a pump-up garden sprayer.  If you are thinking basement, it will require much more extensive treatment than a sealant.