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RE: removing partition walls:

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This is an interesting question because it assumes that the original
structure was desiged with consideration to the interior partitions to
resist shear. I would doubt that to be the case unless you can verify the
connection of the interior partition which was removed to check it's
connection to both the foundation and roof (or floor diaphragm) above.
My guess is that if the interior wall is gypsum or plaster, it was not
considered in the lateral analysis - if one was even performed. I would
assume that, if shear was checked, the shear transfers would occur at the
exterior partitions. Therefore, I might disregard the interior partitions as
being anthing but dampers for the diaphragm.
However, if the connection above and below is positive, the wall sheathed in
plywood or the second floor partition extended and secured to the roof
diaphragm, I would want to replace it's capacity.

I have cut openings in exterior walls where I consider the stucco finish to
be shear value - especially if I can not verify if any plywood exists. In
this case I would run a calc to see what the actual shear is and check the
roof diaphragm to see what the capacity of the boundary nailing. If the
capacity of the roof is less than the demand, I would verify if the
remaining walls meet the nailed capacity of the roof and stiffen other
portions of the wall as needed.

In this case, I will have balanced the design shear or demand with the known
capacity of the diaphragm and upgrade only as necessary to meet the lesser.
One reason is the difficulty in trying to remove roofing to add boundary
nailing as well as the reason that you are not trying to provide more than
originally existed in the structure.

Dennis Wish PE

|-----Original Message-----
|From: BVeit [mailto:BVeit(--nospam--at)]
|Sent: Wednesday, March 11, 1998 2:43 PM
|To: seaoc(--nospam--at)
|Subject: removing partition walls:
|In small remodel jobs on old buildings, what's the standard of practice for
|restoring the shear capacity (if any) of minor partition walls that get
|Very often these are lath and plaster walls on post and beam foundations,
|liittle or no shear capacity to begin with.
|If one undertakes a rigorous analysis of the entire structure, the entire
|structure is found to be inadequate.  When upgrading the entire structure
|not part of the owner's scope, installing one shear panel, with new grade
|beam, hold-downs, etc. in the wall seems inappropriate.
|If one attempts merely to restore the capacity that was removed, simply
|plywood to the remaining portion usually satisfies this, in terms of
|distributing shear to the floor diaphragm.  (assuming floor joists above
|wall are adequate for dragging shear into the remaining panel.)
|Brian Veit, P.E.