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Re: Concrete Masonry Walls

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Yes, you would need movement joints.  Since the masonry is CMU, which is
concrete, it will shrink much like concrete does.

There are a variety of types of vertical movement joint for CMU.  There
are "special" blocks with square ends but with a vertical notch in the
middle of the depth.  That notch can receive a rubberized "gasket" that
is cross shaped with two opposite legs of the cross going into the notch
on either side of the movement joint.  Another type of vertical movement
joint that is commonly refered to as a Michigan joint (I believe it was
created here in is not just because we are arrogant,
although we are that too at times).  It is done with CMU block with
frogged ends (the "ears" that you commonly see at the ends of CMU that
basically look like another cell would be created if you put two blocks
next to each other).  The "cell" created with the frogged ends of the two
block is filled with grout, but a layer of building paper is put up
against the CMU frogged end on one side.  This creates a bond break
between the grout and CMU, which allows for the lateral longitudinal
movement (i.e. horizontal shrinkage), but the grout plug still create a
shear plane across the joint.  There are some others as well.

If my wonderful verbal descriptions don't help, then let me know and I can
likely get you some pictures.


Adrian, MI

On Tue, 5 Jun 2007 gskwy(--nospam--at) wrote:

> Someone asked me a question I couldn't answer (since masonry isn't my expertise):
> Say I want to build a building where the exterior walls are masonry (i.e. concrete block walls, not a masonry facade.)  The walls are structural, not infill for a framed structure.
> If the front and back walls are 200 ft long, I would need control joints wouldn't I?  How do you detail control joints in structural masonry walls ?
> Gail Kelley
> ________________________________________________________________________
> AOL now offers free email to everyone.  Find out more about what's free from AOL at

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