Clay Product-Faced Precast Concrete Panels

Archive of Older Topics Archive - Product Discussions #2
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Importance Factor = High

We are currently involved in a project with brick faced precast. Currently, extruded cut bricks with kerf lines connecting the extruded holes are specified. The purpose of these lines is to enable the opposing brick faces to be split apart by simply tapping the end of the brick with a mason’s hammer. Both sides of the brick may then be used as facing veneer. Facing brick conforms to ASTM C 216, FBX.

Value Engineering is proposing the face bricks be deleted and substituted by thin brick of minimum 1/2 to 3/4-inch thick with backside of clay product units with a keyback or dovetail configuration in order to develope an adequate bond to concrete. Absorption rates have been accounted for for each product.

My urgent question is: Does anybody have thin brick failure experience (loss of bond and falling off precsat)?

I need some war or horror stories no later than Monday p.m. Pacific time. If yes, how was failure solved?

Thanks to all in advance.

Wayne

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Wayne,
What is your climatic region for the project?

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The San Francisco Museum of Modern Art is constructed with brick-faced pre-cast, though I don’t know whether it used thin brick or not. A quick google seach found that HOK was the architect-of-record–maybe they can assist.

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Thin set brick has been successfully used for years on precast tilt-up concrete panels.

You might check out www.tilt-up.org.

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Ascent magazine article “Designer’s Notebook: Clay-Product Faced Precast” that should be on PCI’s website, www.pci.org, has some helpful recommendations.

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Thanks all,

Doug, My project is in Seattle. Now in the new Marine Climate zone.

Paul, I have the Ascent mag article and all of the Designer’s Notebook Articles. Thanks for the tip.

I need news on failures.

Wayne

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Over here on the east coast, in the mid atlantic area one of the big fabricators in this (thin faced brick clad precast) is a company called Shockey. It is a popular system in some building types.

We don’t use it much, but we did have a project where the Owner wanted to entertain it as a cost reduction item.

The problem was that this was a complex project with lots of facade articulation, so only flat panel areas were really suiutable to their system. We had lots of standard masonry to integrate with. They had originally gotten the attention of the contractor and owner when they proposed their system - but when we tighened up some fabrication tolerances and joint widths so that the coursing aligned, it became much more expensive.

They wanted 3/4 inch ‘mortar’ joints between the brick (it is really not mortar, the precast mix fills the joints) but we required 1/2 inch +/- 1/16 inch. They also wanted 3/4 inch joint between panels and again, we wanted the 1/2 inch +/- 1/16.

So their proposal went away. We talked to several major precasters who also did this kind of work and the tolerances we wanted were not a problem, its just that using the 3/4 inch allowed them to be less expensive.

They have a sample specification that was fairly good…just make sure to modify the tolerances if necessary.

Most all of their work is thin brick. I don’t know of any of their failures, and I have no first hand knowledge of failures with the specific system. Any failures I have heard of I don’t recall any discussion whether it was thin faced units or not.

William

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Wayne - I’ve got no experience with the assembly you described (probably for a reason).

We would use Barkshire Panel Systems (not a precaster). Our architectural precast experience has been sketchy lately. We wouldn’t expect a precaster in our area (Concrete Tech; Central Pre-Mix Prestress) to fully appreciate the problems we encounter in the complex architectural applications (no offense to those companies - we use their products on many of our projects).

I don’t have a specific war story about thin brick in precast applications because “we don’t do that, that way”.

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Barkshire is out of business.

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Wayne - you might talk with John Tawresey at KPFF. He was involved at the Starbucks HQ remediation. Front desk number is 206-382-0600.

I recollect Barkshire was closed; but that’s who we used. They were expensive but did the job we asked them to.

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To Doug, John, Ron, Paul, William, and Anononymous,

Thanks for all of your help last week in providing information regarding failures of thin brick facing over architectural precast.

An associate spoke directly with Sid Freedman, Director Precast Concrete Services at PCI. Sid provided some information I thought I would pass along for your use:

PCI will be publishing a document in the near future that outlines the requirements for thin brick. Sid provided a draft copy of the document which is essentialy in final form (available on request). While not explicit, PCI will be recommending the use of thin bricks for facing materials on architectural precast over the use of soaps or half-bricks. To date they have received endorsment of these specs from major suppliers including: Endicott, Feldhaus, Summitville and Metro.

PCI has funded a study of vapor barriers used in conjunction with APC–report should be available in 2 weeks. The study is being conducted by Martha Vangeem at Construction Technology Laboratories in Chicago and evaluates the 4 different wall assemblies utilizing precast. The goal of testing is to evaluate optimum vapor barrier location in different climates. Will be interesting to see these results.

Half-bricks have greater abosorption and this has potential to further reduce bonding through crypto effloressence. This is in part the reason PCI is recommending the use of thin bricks.

Further the use of sealers is discouraged in these applications.

Use of half-bricks (soaps) generally requires the use of a self consolidating concrete–thin brick applications do not require this.
Sid feels that the use of a sandwich panel should be further explored for our project. The surface applied insulation in our project will be not be much more economical in his opinion.

According to Sid, the use of half-bricks is limited to Michigan–the rest of the world is moving to thin brick facing of precast due superior performance and economy. Seems to be some disagreement about this point in several of the circles my associate has been talking to. My associated is of the opinion it is clearly driven by financial interests as he has yet to hear of any catestrophic failures of thin brick facing assemblies.

Sid recommends the use of ASTM C1088 Type TBX thin brick over TBS which has lower tolerances. The same holds true for full size bricks under ASTM C216 - Type FBX over FBS.

He pointed us in the direction of Scott Systems (http://www.scottsystem.com/index.htm) who have proprietary brick inlay systems and test data showing results for freeze/thaw and bond strength. We are not sure how to interpret these results as the concrete mix and brick characteristics can play a significant role in the outcome. Also, we always question voluntary testing conducted by manufacturers. We will have to look into this further before we put all our eggs in this basket.

The document from Scott Systems is available for your review upon request.

I hope you find some of this information valuable.

My e-mail is wyancey@morrisonhershfield.com

Wayne