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Re: Wood shrinkage

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Use steel studs!


----- Original Message -----
From: <JPRiley485(--nospam--at)aol.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Friday, February 25, 2000 3:38 PM
Subject: Wood shrinkage


> Architect wants to build residential structure in Iowa.
>
>      4 stories (1 at grade, 3 supported)
>      Wood stud bearing walls
>      Approx. 15,000 sf per floor
>
> Fire safety issues have been hashed out between the architect and the
> building official.  The building official required the architect to hire a
> structural engineer on this project "because it is 4 stories."  For an
> essentially identical 3-story building, he was allowed to do the
engineering
> himself.
>
> My concern is with the following UBC section:
>
> SECTION 2308  -  WALL FRAMING
> Wood stud walls and bearing partitions shall not support more than two
floors
> and a roof unless an analysis satisfactory to the building official shows
> that shrinkage of the wood framing will not have adverse effects on the
> structure or any plumbing, electrical or mechanical systems, or other
> equipment installed therein due to excessive shrinkage or differential
> movements caused by shrinkage.  The analysis shall also show that the roof
> drainage system and the foregoing systems or equipment will not be
adversely
> affected or, as an alternate, such systems shall be designed to
accommodate
> the differential shrinkage or movements.
>
> It's probably within the architect's overall responsibility to coordinate
the
> building materials so that we don't buckle a plumbing pipe, or something
like
> that.  And hopefully, the "analysis" of the effects of shrinkage will not
> entail much more than a shrinkage estimate (by me) and an evaluation of
its
> effects on the various systems (by someone other than me).  Seem
reasonable?
>
> Estimating shrinkage:  I believe longitudinal shrinkage in
Doug-Fir/Larch(N)
> is negligible, possibly 0.1%.  The significant shrinkage occurs in the
stud
> wall plates and rim board.  In the Timber Construction Manual there is a
> formula for estimating shrinkage based on initial and final moisture
content.
>  And I found this shrinkage calculator on the Internet:
> http://www.woodbin.com/calcs/shrinkulator.htm    It boils down to
> establishing initial and final moisture content . . . help.
>
> John P. Riley
> Riley Engineering
> Blue Grass, Iowa
>