Gypsum Board Shear Wall over 1/2" thick Sound Board

[Greatone76]

I have a situation where we have an interior shear wall that has 5/8" gyp board on both sides. The architect would like to use 1/2" sound board under the drywall. I know when you place wood panels over gyp board there is a reduction in shear capacity value. I would assume there is a reduction for our installation over the sound board as well. Does anyone know of a place where I could find a way to figure out that reduction.

 

[thaidavid40]

Is it possible to get the sound deadening you need on these walls only by some other means, so that the sound board doesn't affect the shear walls resistance values specifically?
Dave

Thaidavid

 

[Greatone76]

That's the point we are at determining if that is what is going to have to happen. If the reduction isn't something we can figure out we will have to change directions.

 

[thaidavid40]

I had another thought about how you might get around this obstacle. Why not use a steel-sheet shear wall panel (like the "Sure-Board" panels) against the studs. Then top that with the sound deadening board, and then the sheetrock layer? The steel sheets would only add about 1/8" to the overall wall thickness (almost unnoticeable in practice). You get to keep the tested ratings for the proprietary steel sheets shear values, the sound transmission class for the sound board, and the finish properties of the sheetrock. This seems a logical workaround to me, if it suits your purposes.
Dave

Thaidavid

 

[Heck83]

Greatone, you should send an email to APA and ask them directly. I think they will get you the answer you need. Are you also using OSB, because gyp only adds about 90 PLF of shear capacity alone. Can you put the gyp behind the soundboard? It seems like that wouldn't change the shear added by the gyp.