] [Thread] [Date] [Author]

[smthengr(--nospam--at)sirius.com (Jeff Smith)]

>1.      The joists are being promoted, in part, upon their ability to provide
>relatively long spans (up to 60 feet).  Nevertheless, the joists are
>manufactured with absolutely no camber or crown.  There is no defined
>top and bottom.  Won't deflection be a significant problem?

Regarding camber, I had a discussion with the local rep a while back. My
recollection is that they use to camber wood I joists on a special order. I
believe the open web joists can still be cambered (anyone  know?). When
using long spans for a combination roof and ceiling joist, there can be
perceptable deflections. So if you want a dead level ceiling, you may need
to isolate the roof and ceiling, or furr it level after the majority of
dead load is applied. Floors have a much higher live load
deflection/performance criteria so dead load deflections may not be as
perceptable. I would think that *extremely* deep joists would be required
to control vibration with 60 foot floor spans.
Regards,

Jeff Smith. S.E.
phone: (415) 543-8651
fax: (415) 543-8679
email: smthengr(--nospam--at)sirius.com

Smith Engineering
27 South Park
San Francisco, CA 94107