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RE: Interior residential walls - clearance from concrete????

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Check (1994 UBC) section 2317.8, page 2-829. This is subject to
interpretation, IMO

|~|
|~|I am designing a custom home in the desert where the slab
|~|changes elevation
|~|by one foot. The Architect wants to frame the bearing walls on
|~|the low side
|~|of the slab so as to simplify the finish on the walls down to the plate.
|~|I was reminded that there is a requirment for a 1" clearance between the
|~|concrete and the wood - which makes the finish on the high side
|~|difficult.

I have not seen the 1" rule. The first question is what is "an impervious
membrane", If you have one, and a 3" slab and no water splash, then I would
say you can put untreated studs and sill plates in contact with the concrete
even though I would never detail it that way. To be safe I would consider
using bituthane under the sill and behind the studs try to detail a vent
space or use PT studs and sill
|~|
|~|Can someone point me to the code (UBC) section that stipulates a
|~|1" clearance
|~|for concrete on the inside of a residence where a moisture vapor
|~|barrier is
|~|applied below?
|~|
|~|Also, can I substitute builders paper between the studs and
|~|concrete stem
|~|wall at the elevation change and bring the wall closer to the concrete?
|~|
|~|Finally, what is the basis for this requirment if there is no
|~|expectation of
|~|moisture permeating the slab?

My opinion is that concrete can retain moisture or condensation can
potentially occur through the temperature and moisture gradients.

Jeff Smith

|~|
|~|Thanks in a advance,
|~|Dennis S. Wish PE
|