Uplift Wind Loading Values [RE-wrenches]

[Bill Brooks]

Jeff and Pat,

If you have a copy of my course manual it shows that conservative estimates
of wind loading (for exposure on typical roofs) is 25lb./sq.ft. for 85mph
and about 55lb./sq.ft. for 120mph wind speeds. This agrees with Uni-Rac's
code compliance document. I also show a table of withdraw loads for
different types of wood. If you follow either Uni-Rac's or Pro Solar's
guidelines you will be just fine. If you are designing your own, use my
method or look at Uni-Rac's document (its 1.73 MB so if it might take a
little to download it if you have a slow connection, but it is well worth
it).

The URL is:

http://www.unirac.com/pdfs/tb103.pdf

Bill.

-----Original Message-----
From: Jeff Oldham [mailto:starpower4u at juno.com]
Sent: Wednesday, March 19, 2003 10:58 AM
To: RE-wrenches at topica.com
Subject: Re:Uplift Wind Loading Values [RE-wrenches]


I've run into this a lot actually, it can be very frustrating as the plan
checkers are starting to get outside of their jurisdiction. They should only
be concerned with attachment to the structure. From that attachment point on
up it should not be part of the review. They never require this information
for other roof mounted equipment like HVAC. Sure, they want to know how it
is attached, but when it comes to how are those feet attached to the unit
and how is the unit's chassis attached to the main frame/rails it is not
their responsibility. However, they seem to want to go to that level with
our mounts and inter-mount and PV attachment details with stamped calcs!

The magic number for UBC is 13#/sq.ft. more efficient lift than some
airplane wings!! I guess it's not just gravity it's the law! In any case the
inspectors and plan checkers should only be looking at lags/anchors and
structural members as you stated.

Arruuggg! Good luck.
-jeff


Jeff Oldham


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