Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: Repairing Cracked Masonry

[Subject Prev][Subject Next][Thread Prev][Thread Next]
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
>
>
>
> ******* ****** ******* ******** ******* ******* ******* ***
> *   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> *
> *   This email was sent to you via Structural Engineers
> *   Association of Southern California (SEAOSC) server. To
> *   subscribe (no fee) or UnSubscribe, please go to:
> *
> *   http://www.seaint.org/sealist1.asp
> *
> *   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> *   send to the list is public domain and may be re-posted
> *   without your permission. Make sure you visit our web
> *   site at: http://www.seaint.org
> ******* ****** ****** ****** ******* ****** ****** ********
>
>
> ******* ****** ******* ******** ******* ******* ******* ***
> *   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> *
> *   This email was sent to you via Structural Engineers
> *   Association of Southern California (SEAOSC) server. To
> *   subscribe (no fee) or UnSubscribe, please go to:
> *
> *   http://www.seaint.org/sealist1.asp
> *
> *   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> *   send to the list is public domain and may be re-posted
> *   without your permission. Make sure you visit our web
> *   site at: http://www.seaint.org
> ******* ****** ****** ****** ******* ****** ****** ********
> 



******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 
******* ****** ****** ****** ******* ****** ****** ******** 


******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 
******* ****** ****** ****** ******* ****** ****** ********