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Wood shrinkage

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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 

My concern is with the following UBC section:

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:    It boils down to 
establishing initial and final moisture content . . . help.

John P. Riley
Riley Engineering
Blue Grass, Iowa