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Fwd: Re: floor deflections, was: Re: building code minimums for wood frame

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Jeff Smith wrote:
> >General comments to the many opinions raised about the issue of "code
> >minimums"...
> >Although I'm not an attorney, I don't believe that a client can
> >successfully sue an engineer for designing above code minimums
> >particularly if the design engineer can prove that his design was
> >warranted by calculations, etc. For example, the code requirement for
> >live load deflection is L/360. Based on my experience, this criteria
> >will produce a "soft" floor in a residence with long (>18') spans. My
> >preference is to use L/400. I cannot even conceive a qualified expert
> >witness being able to successfully debate this issue.

I once worked for an engineer whose number was something like S.E. 00006
and had an office policy regarding floor deflections.  He said that in
addition to checking code minimum L/360 deflection we should limit the
deflection of a single joist to 1/16" when 200 lbs (his weight was 200
plus pounds) is applied at mid span of any joist weather it is 10 ft
long or 20 ft. long.  There was no code justification for this. It was
based upon his observation that deflections become noticable to a second
person standing next to someone bouncing on a floor if this deflection
exceeds 1/16 inch.  When ever I have concerns about deflection I will
still run a quick check to see if his criteria is being meet.

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Richard Lewis, P.E.
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