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Re: light extrior wall

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John,

        I've done this a couple of times where my client was a cladding contractor.  My client wanted to have quite a bit of input into the type (brand) and spacing of fasteners used.

        Essentially, the fasteners we used have washers that "pull over" the head at a specified load.  There are some chronic problems with this type of fastener you should watch out for.

1.)    Your job will be to design a practical sized panel with a practical number of fasteners strong enough to resist the wind loading but not too strong to prevent popping off or to permit a structural failure elsewhere.

2.)   20 psf might be too close to the maximum possible wind loading.  Cyclic wind loading may "work" some fastenings and cause one or two fastener failures; then one or two more failures; then the panel pops off.  These can (probably will) become a high maintenance item; you may want to make this very clear to the owner and take precautions to limit your liability.

3.)    You may want to work closely with your cladding subcontractor.  If you can influence the decision try to pick the best subcontractor, not necessarily the cheapest one.  A better idea might be to have the panels supplier designed and specify the warranty you want for the fasteners.

4.)    Of course you'll want safety chains to contain the panels if they do fall off.

        Hope those comments will be helpful.

Regards,

H. Daryl Richardson

John Nader wrote:

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /> I am designing a mechanical room.  We are required to provide a pressure relief wall openings which will blow out when the pressure reaches 20 psf.  The wall cannot be heavier than 3 psf.  Have any one been thru this before? Thanks in advance for your help. John