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Backing Requirements for Lath ?

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I have a condition where I have attached a parapet to a platform framed wall. The parapet is laterally braced by a kicker back to the roof. I have a 1-1/4” wide x 16 gage strap (Simpson CS16) connecting the vertical face of the parapet to the studs below (a strap at each stud at 16”). Because of the end length of the strap on each end plus the depth of framing, the strap is about four feet long. The wall and the parapet face are sheathed in plywood.

 

The inspector claims that, when they install the lath for the stucco, the staples can’t penetrate the strap (which I agree) and therefore the lath won’t be connected to the framing.

 

Design conditions: 1997 UBC/2001 CBC; 100 mph wind, 6.4 km from the San Andreas fault (just in case any of that is pertinent to the question).

 

The question:

Is it mandatory that the staples go into framing members at 16” or is stapling to the plywood adequate? If one cannot staple into plywood sheathing (oops, I mean Wood Structural Panels, sorry APA), are there other methods of attachment (screws, etc.) which would be satisfactory into WSPs? If so (or if not), are there any good references related to the installation of metal lath? Usually, my design interests stop at the sheathing. The architect on the project is looking into this and I believe all involved would rather not have a structural solution (straps are already in, plywood installed, etc.).

 

I’ve specified straps before and I have never had this question come up. We (the contractor, the architect and I) have a good working relationship, so this is not a finger pointing exercise. We are just looking for a practical solution to the problem. The preferable solution is to tell the inspector to pound sand, but politely of course :o).

 

Thanks,

 

T. William (Bill) Allen, S.E. (CA #2607)

ALLEN DESIGNS

Consulting Structural Engineers

http://www.AllenDesigns.com

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