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Re: Repairing Cracked Masonry

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Rand:

Practice makes perfect.  I am a moderately good typist.  I used to be a
pure "hunt and peck" and had to constantly look at the keyboard.  I can
now look at the screen and pretty much touch type.  The one thing that I
am still not good at is dealing with mistakes (i.e. mistyping
something)...ideally you are supposed to just go on and come back and fix
it.  I just instantly jump on the backspace key and fix it right away.
But, I got to where I am by just typing.  If you do it enough, then you
will start to remember where the keys are and slowly get faster.  It did
help me that I had a computer class in 8th grade that did a couple weeks
of typing lesson...that helped me learn to put my fingers in the right
place...but it took me YEARS to learn to NOT look at the keyboard all the
time.

As to your masonry problem, the foundation movement could certainly cause
problems for the masonry.  I would certainly expect some possible vertical
cracks at locations of local foundation movement.

I would also have to say that lack of attachment to the structure and
being unreinforced could potentially cause some ability for hte masonry to
move and crack under wind.  One of the things that I was wondering about
was whether or not the brick was adequately tied back to the CMU.  If not,
then the brick could be pushed/pulled by the wind such that it would crack
at spots.  But, if the overall masonry is not attached well and is
unreinforced, then it might be the complete masonry system that is moving.
Where the cracks are and their orientation would likely be a function of
the aspect ratio of the bay size and height, as well as whether you are
dealing with running bond (likely) or stacked bond (not so likely).

As to a MWFRS, I would say that there is a slight chance that you do
inadvertantly have one, on the lower levels at least.  If the CMU is up
tight to the steel frame, then it is likely acting as in-fill walls which
can provide some "shear wall" like capacity.  Generally, not the best of
things to do, but still can work, if in a more "brittle" fashion.  But, if
this is happening and the "in-fill wall" is getting significant load, then
this could also be the cause of some cracking and movement.

In the end, sounds like you got yourself a mess of a building!  ;-)

Regards,

Scott
Adrian, MI

On Wed, 10 Nov 2004, Rand Holtham, P.E. wrote:

> Alas Scott you have exposed my weakness...I am not much of a
> keyboarder...that is the reason for my brevity. ;-(     I suspect you are a
> good typist and I envy you for that. I'll try to sum up the whole situation;
>
> -8 story brick faced w/ cmu backup steel framed building on 9' deep spread
> footings in stiff clay (high PI)
> -Cavity space is filled w/ grout but cmu has water proofing membrane on it.
> What ties it has are corrugated metal type
> -Cmu is unreinforced and unconnected to structure but is grouted to floor
> beam above so I suspect the beam is bearing down on the wall enough to hold
> it in place.
> -no MWFRS
> -Several inches of foundation movement
> -and on and on and on.
>
> One big expensive mess up. We can underpin the foundation at the corners
> only because the building flares out at the bottom 2 floors except at the
> corners. But because for the nature of the building geometry. and actual
> movement this underpinning should thwart the movement from the foundation.
>
> But then there is the unreinf cmu that can only tolerate 6psf lateral
> loading and it needs to withstand 37 psf. and of course it needs to attached
> to the structure to transfer the lat load and to perform as a shear wall
> etc.
>
> Then there needs to be braced frames on the first to floors because the cmu
> wall stops at the 3rd floor. Then of course the brick system has so many
> flaws it needs to be taken off and rebuilt properly...so basically we need
> to rebuild the building from the inside out. Big Big bucks that the owner
> doesn't have!!!
>
> Since the fdn is the biggest contributor to the crack (which is causing a
> very leaky building) Well start there and fix the other problems later
> acknowledging that movement will still occur just not as much. But the
> cracks have to be sealed now (that is after all the main complaint). So I
> want to give them an option that will minimize he possibility of the caulk
> joint failing at least right away. By all rights the building should be put
> out of it's misery but that's not possible so we'll give it something to
> "manage the pain."
>
> And yes yes there is more....but do you know how long it took me to type
> that ;-) !!!
>
> Rand
>
>
>
>
>
>
>
> ----- Original Message -----
> From: "Scott Maxwell" <smaxwell(--nospam--at)engin.umich.edu>
> To: <seaint(--nospam--at)seaint.org>
> Sent: Tuesday, November 09, 2004 5:51 PM
> Subject: Re: Repairing Cracked Masonry
>
>
> > Rand:
> >
> > You have piqued my curiosity.  Are the 1" cracks vertical (this seems to
> > have been assumed by some but your original post was not clear)?  If so,
> > how high do they go?  Is the 1" crack width uniform through the depth of
> > the brick masonry?  How often are the cracks occuring?  Do you have an
> > idea of when they open up vs. when they close (i.e. seasonal, daily, etc)?
> >
> > Basically, I am wondering what is causing them.  As at least one other
> > person had suggested (James Cohen), it would be prudent to figure out what
> > is causing the movement before attempting a repair on the cracks.  In your
> > response to James, you seem to already be aware of this and have an idea
> > what is causing the movement in the cracks.  Now, however, I am
> > curious...are you willing to share what you think is causing the cracks to
> > move?
> >
> > I think that James' point is still well worth noting...if you know what is
> > causing the movement and "cure" that, then fixing the crack should be much
> > easier.  If the movement issues are solved, then the previously attempted
> > fix of caulking the crack should work (might still require a backer rod).
> > IF the movement issues cannot be "cured" then it is likely that there will
> > be no repair option that will work well.
> >
> > Regards,
> >
> > Scott
> > Adrian, MI
> >
> >
> > On Tue, 9 Nov 2004, Rand Holtham, P.E. wrote:
> >
> >> 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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