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Re: Repairing Cracked Masonry

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"If I insulted anyone's intelligence, I apologize"

no, no, not at all sorry if it sounded like I insinuated that...

Back to the expansion...If the brick is grouted to the block (as in this case) and the brick was expanding wouldn't the cmu be the one to crack? after the point at which it (the cmu) could no longer restrain the stresses from expansion. I'd think that cracks seen in an expanding wall will most likely occur in the retraining element such as the cmu wall in this case or a cross wall in another case

----- Original Message ----- From: "David Fisher" <dfisher(--nospam--at)fpse.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Tuesday, November 09, 2004 1:21 PM
Subject: RE: Repairing Cracked Masonry


Rand:

It is all a function of how the brick veneer is detailed.

In good ol' cavity wall construction, the CMU and brick
Are separated by the "cavity" and the two wythes are laterally tied by
Horizontal joint reinforcing (ladder type) to allow the wall to
Move "in-plane" each according to its own material properties.

If truss type reinforcing were used or the construction is composite, not
Cavity, then the gap in the naturally expansive material (clay masonry) can
Still occur if rigidly tied to the shrinking CMU.



I was not privy to the foundation movement issue when I first responded, but
My understanding always was that for uniform vertical cracks to occur, the
stresses in this case, tensile, are fairly uniform thru the depth of the
section.


Movements due to differential settlement or lateral displacement tend to
produce flexural or shear type deformations, resulting in "acute" crack
angles (flexure) or stepped (shear) mortar joints.


If I insulted anyone's intelligence, I apologize.





David L. Fisher SE PE
Fisher + partners
372 West Ontario
Chicago 60610

312.573.1701
312.573.1726 fax

312.622.0409 mobile

www.fpse.com

-----Original Message-----
From: Rand Holtham, P.E. [mailto:rand(--nospam--at)sigmaengineers.com]
Sent: Tuesday, November 09, 2004 12:51 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Repairing Cracked Masonry

Stan,

It looks like that's what they've used previously. These are large cracks
say 1" wide. The rebar will not fully restrain movement, it is after all
just a 1/4" rod but hopefully would add ductility to the joint and hopefully

restrian the movent that disloges the caulk. Yes there is a lot of hope in
that sentence. Point well taken though.

Harold,

I have my doubts too, that's why I posted... what do you mean develop a
mortar doesn't an epoxy mortar already exist?

David,

The Engineer who evaluated the problem 15 yrs ago had the same conclusion as

you did. But he neglected to notice the 4 to 5" of differential movement in the foundation and that there is no discrete lateral force resisting system.

Differential foundation movement alone can cause a variety of crack shapes
vert, horiz, stairstep then add the displacement from wind loading.

Now set me straight on the expanding brick...As the brick expands it creates

a 1" gap??? I thought you leave a 1" gap so the material can expand into
that gap without causing distress....(I'm with you that clay expands and
concrete shrinks over time but...)


Keep it coming this is productive, Thanks guys :>

Rand



----- Original Message ----- From: "David Fisher" <dfisher(--nospam--at)fpse.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Tuesday, November 09, 2004 12:15 PM
Subject: RE: Repairing Cracked Masonry


Sounds like "Mother Nature" has created a control joint where none
previously existed...

Is that true?

What, if anything, did the architect specify?



Since it's vertical and not stepped, it would appear to be the result of
thermal/moisture stresses and not structural issues...


As we know, clay expands when wet while Portland cement products (CMU)
Shrink over time.


If it's a naturally occurring control joint, its probably needed in
exactly
or
Nearly that spot.


Treat it as such: fill the gap with a compressible filler and backer
rod/seal the
Exterior side of the joint.



David L. Fisher SE PE
Fisher + partners
372 West Ontario
Chicago 60610

312.573.1701
312.573.1726 fax

312.622.0409 mobile

www.fpse.com

-----Original Message-----
From: Rand Holtham, P.E. [mailto:rand(--nospam--at)sigmaengineers.com]
Sent: Tuesday, November 09, 2004 11:49 AM
To: seaint(--nospam--at)seaint.org
Subject: Repairing Cracked Masonry

Lister,

For the sake of brevity I will condense a very complex problem into a
simple

question that I have no answer for:
I have a large crack (actually many large cracks) in the brick veneer on
an
eight story building. This crack allows water to penetrate the building
and
attempts to caulk have been unsuccessful as the crack moves thereby
dislodging the caulk. I am contemplating the addition of a small (say #2)
rebar in the grout joint  (grind out joint repoint with epoxy mortar or
other?) so that the reinforcing crosses the crack in essence stitching the
crack together. Then applying the caulk with the idea that the added
reinforcing will control the crack from movement beyond that which the
caulk

can tolerate. I can see extending the reinforcing 24" or 36" on each side
of

the crack This is not to stop the building movement but to facilitate
waterproofing the brick facing.

My simple question is--- will the rebar bond well enough to the brick and
mortar for this to be effective? Any thoughts will be greatly appreciated
~:-).


Rand



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