From: "Drew A. Norman, SE" <DNorman(--nospam--at)dnormanse.com>
Date: Fri, 06 Apr 2001 12:00:08 -0700
IMHO, the issue of what is "enforceable" in terms of deflection is less
important than the question of what is appropriate in your judgement as a
designer and what you owe your customer. Personally, I would check
deflection against a limit of 1/240th of the king stud's span (about an
inch). If I could do it without adding significant additional cost (e.g.,
by putting in a fourth stud), I'd try to get 1/360.
Because you indicate a brittle finish (stucco), I think that an engineer who
failed to make a deflection check in the instance you describe might be
liable to his or her customer in the event that the finish cracked due to
excessive deflection of the otherwise structurally adequate king stud
REGARDLESS OF WHAT LOCAL BUILDING CODES REQUIRED. Under most circumstances,
your contractual obligation is to abide by the standard of care normally
applied by reputable professionals in similar circumstances and based on my
experience (primarily in Southern California), I would say that the standard
of care around here DOES require a deflection check and a 1/240 max wind
load deflection as a serviceability standard.
----- Original Message -----
From: "Steve Hiner" <shiner(--nospam--at)folsom.ca.us>
Sent: Friday, April 06, 2001 11:14 AM
Subject: Exterior Stud Wall Deflection
> 1997 UBC 1611.5 sets "interior" wall deflection limits of L/240 for
> finishes and L/120 for flexible finishes (for 5 psf minimum out-of-plane
> Given an "exterior" sawn lumber king stud (actually 3-2x6's) that is 19'
> tall with 5' tributary width of wind loading (80 mph wind, exposure B,
> stucco finish). If the calculations show that combined axial & bending is
> satisfied ... would you check the stud's deflection as well?
> What kind of deflection limitation do you think is enforceable ... since
> the code does not appear to specifically address deflection limitations of
> exterior walls?
> Thank you for any input.
> Steve Hiner