is gypsum board acceptable as diaphragm material

huangyhg

is gypsum board acceptable as diaphragm material?
i am designing a new condo building and have minimal shear wall area on the exterior face of the building.  the building has a center corridor which are shear walls and i want to transfer the roof forces back through the ceiling to the corridor walls.  is this acceptable?  i am looking at the ibc code which gives design values for walls but i don't see anything about diaphragms.
thanks.
this is a bit dated, however, the 1996 sbcci "standard for hurricane resistant residential construction" gives shear values for 1/2" gyp board used in horizontal diaphragm assemblies: table 304c2 gives a recommended shear capacity of 70 pounds per linear foot.
this is based on 1/2" thick material with 5d cooler nails or 1-1/4" drywall screws at 7"spacing at the edges and 10" spacing at intermediate supports.
for what it is worth i would not use drywall for a diaphragm (or a shear wall for that matter) in a damp climate.  the humidity makes it very soft where you can't hold a picture up with a nail.  
call it over convservative but that is my two cents.
i typically don't design using gwb as a horizontal diaphragm, but i do recognize that it is probably a pretty good one.
how else does the connection between the top of an end wall and the gable end truss above it work?  unless you brace the end wall up to the roof diaphragm, using diagonal   
in my area the nailing pattern is be hard to obtain.  we have used the ceiling 5/8" gyp interior diagrams at gables, but it takes extra efforts.
if interior gyp is getting damp, consider getting a new roofer.
add bracing in the trusses to transfer the forces down to the interior wall, or better yet take care of it at the exterior face of the building.  if your loads are minimal it shouldn't be hard to take care of it the normal way.
its always better to take the standard way out, especially in a litigious building group like condos.
why not sheath your wall with plywood and cover with 1/4" to 1/2" gyp.
mmin-  are your roof trusses light gauge or wood?  strictly speaking for either material i don't think ibc recognizes using gyp in a diaphragm.  the version i have (2000) lists only wood structural panels or diagonal sheathing as acceptable as a diaphragm for wood construction.  ibc doesn't say anything about diaphragms for light gauge framing(section 22). (might this be an oversight?  i think it is.) however hud has published test data on osb and plywood diaphragms in light gauge construction, see
my original design used a limited area available on the exterior face for a beefed up shear wall segment.  a site inspection however revealed that there was a large hole cut in these panels for process air for a heat pump unit installed behind it leaving the shear panel useless.  i am left with designing field modifications to correct this issue.  my hope is that by increasing the number of screws to the 5/8" gypsum i can provide a "simple" fix.
the trusses are wooden.  i have considered bracing from the ridge to the walls but the trusses have a truss at the ceiling level combined with the roof truss members.  i am not sure about fitting braces through the   
fyi
this topic is addressed in the 2003 version of the ibc - section 2508.5  there is an evaluation report by the gypsum association at
i would not use it in my area which is florida. during hurricanes and in many instances roof membranes are breached. this will create water leaks. the concern is if there is ever any water intrusion on the gyp board, then you will lose any rigidity.
regards,
lutfi