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:
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
Blue Grass, Iowa