Better Isn't Always

sometimes what looks good on paper doesn't work too well in the shop

 

Representatives from sales and management don't always tell us everything we want to know. There are good reasons for this: We don't know what to ask; they haven't worked in the plant; and both parties sometimes assume too much.

Production workers generally haven't been prepared to pitch their products. They are more concerned with doing their own jobs, and those who are good are proud of the work they do.

Depending on plant rules, it isn't always possible to talk to those workers, but we had such an opportunity when the Mpls.-St. Paul Chapter toured the Artstone facility, where we met Dave Clancy, a.k.a. "Clancy."

Clancy is responsible for fabricating the metal anchorage used to hold precast stone in place. Undaunted by the combined might of specifiers before him, he expressed his own opinion about the types of materials we should be specifying for these unseen but essential components.

One of the important characteristics of anchors is corrosion resistance. The metal used must maintain its strength through the life of the building. In addition, it must not stain the stone.

Unfortunately, steel, the most commonly used building metal, rusts profusely, disintegrates quickly, and stains everything downstream.

To achieve a long service life, we have to protect steel from water. The most common way to do this is to apply a coating, usually paint or zinc. Though many would agree that hot-dip galvanizing is one of the best ways to protect steel, Clancy has a different opinion. Because the metal must be imbedded in the concrete before it is finished, and welded after, he reminded us there is more to think about than weather.

Hot-dip galvanizing has the following shortcomings.

  • The galvanizing is burned off during welding, so the finished product is only as good as the repair paint.

  • Welding generates toxic fumes; OSHA requires use of a respirator.

  • Lead time can be three to ten weeks, and labor costs increase.

Clancy suggested two alternatives:

  • Cadmium zinc coating, which results in better welds, less toxic fumes, and one to two week lead time.

  • Stainless steel, though it is not as cost-effective when used for welded connections.

Clancy also reminded us that welding destroys the zinc coating, which cannot be repaired to its original condition in the field. Regardless of the coating, the metal will corrode first at the welds. There is little to gain in using hot-dip galvanizing, and the problems caused during finishing make it more difficult to use.

2002 Sheldon Wolfe, RA, CSI, CCS, CCCA, swolfe@bwbr.com 
on the web at www.CSI-MSP.org 

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