HomeMy WebLinkAboutLetter (garage trusses) - 7/16/1998~% ,~~
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QIHK~lH
ON THE WATER
City of Oshkosh
Division of lnspecliou Services
215 Church Avenue
PO Box 1130
Oshkosh WI 54902-1130
GREG NOFFKE
NOFFKE LUMBER
1525 BOWEN ST
OSHKOSH WI 54901
July 16, 1998
Re: '~95 Kirkwood »-r.
Deaz Greg;
As you are awaze, our office has requested information regazding the bearing point of the mono pitched
gazage trusses at this address. Specifically, concerns have been raised to the adequacy of the 2x61edger
these trusses beaz upon and the method of attachment for this ledger. We have asked for structural
calculations to prove this ledger will support the loads applied. Based upon the information we have
received and reviewed to date, this ledger is not secured adequately to support the imposed loads. Until
we have received and approved information stating how this ledger must be secured to support the
trusses bearing upon it, this area may not be enclosed. Occupancy will not be approved until this
situation is resolved.
Steve Lichtwald has made attempts to supply us with the necessary information, but this information
does not prove the ledger is adequately fastened. His submittal included information on the Pasload
nails which were used, however the shear and withdrawal figures supplied to you by Pasload do not
show they have been substantiated by an independent testing lab in conformance with the requirements
of the National Design Specifications (NDS.) The information we aze obligated to use, without
independent testing results, are the figures supplied in the 1991 National Design Specifications for
Wood Construction, as this is the adopted standard for the State of Wisconsin Uniform Dwelling Code.
Based upon the figures used from the tables we faxed to Steve earlier this week, the method of fastening
does not meet the loading requirements. Table 12.3B shows a figure of 120# of shear value per 16d nail,
which after calculating 3 nails per stud in attaching the ledger to the garage wall, falls short on
supporting the 1075# per truss bearing upon this ledger. Additionally, this table is for a single ledger
member nailed to the wall, not two members as is the case on this site, thus these charts cannot be used
for this situation. By having two members, the rotational forces increase and the withdrawal forces
increase.
Also the calculations Steve provided to us on Wednesday, July 15, incorrectly applied the 16" spacing to
the fastener sheer value instead of applying it to the lineaz load. It is the linear load of 538# that should
be multiplied by 1.33 (the 16" o.c. framing factor) as this is the load that must be supported at each
stud/ledger connection point and the sheer value for the fasteners at each stud/ledger connection must
support this value.
Since the on site conditions aze not reflective of situations outlined in the building code or the NDS
manuals, structural calculations must be provided to verify the ledger is properly secured or what must
be done to properly support the ledger. If you want to take credit for the OSB gusset and the secondary
ledger, truss plans must be provided verifying the truss can be supported at three bearing points in
addition to the supporting calculations for the gusset and the ledgers (the ledgers must account for being
2 members wide versus a single member.) Also be reminded all submittals must specify the address of
the job, the concern(s) being addressed, the submittal must be cleaz and follow a logical procession (do
not make the reviewer jump to conclusions) and the submittal must be signed by the person preparing
the information.
As I explained to Steve Lichtwald and Bill Schlichting at this site on Tuesday afternoon, July 14, 1998,
the building code provides direction on standazd framing practices. However, the code also allows for
the use of alternate framing practices as long as the owner/builder can justify through structural
calculations the alternate will work. In this case, while a ledger may be a common practice, the code
does not provide details on how to attach the ledger to support the imposed loads. This is primarily due
to the number of variables that could be used in attaching the ledger: e.g. the spacing of the supporting
studs, 16" or 24" o.c., the depth of the ledger, the loads applied, etc. I also explained to these
gentlemen, an inspector has to be cautious not to become the designer. While a problem was identified,
an inspector for the City of Oshkosh cannot put himself/herself in the position of being the designer.
While we can assist with solutions for concerns specifically addressed by the code (such as header sizes
laid out in the code tables,) we cannot tell you how to fix an issue not specifically laid out by the code,
this is the responsibility of the designer, builder or owner.
I believe this office has been more than cooperative and patient on this issue. If you aze unable to
prepare this information or determine how this structural concern should be corrected to properly
support the imposed loads, you may desire to seek the services of a structural engineer or an architect.
While we cannot require information from an engineer or architect, it would certainly seem appropriate
in order to expedite this matter.
If you have questions or concerns, please call me at 236-5045.
cc: Bill Schlichting
Nicole Krahn, Building Systems Inspector
Sincerely