BobK207 wrote:
On Dec 6, 10:06 pm, Mike Paulsen wrote:
Aaron Fude wrote:
Hi,
If I have an 8'x8' wall and I will hang two sheets of drywall on it,
should I hang them vertically or horizontally or does it not matter -
Horizontal would be best. Vertical a close second. One each way a
distant third.

and why.
Horizontal seams are easier to finish and less likely to telegraph.

Drywall adds structural stability to the wall. Horizontally hung sheets
give twice the shear resistance as vertically hung sheets. (Although it
wouldn't be that big a factor on a 8' long wall.)

Mike-

I would beg to differ on your statement "Horizontally hung sheets
give twice the shear resistance as vertically hung sheets."

its just not true, an urban (or suburban) myth. Twice?

I don't remember where, but that's what I remember reading many years ago.
Here's one cite with similar claims:
http://irc.nrc-cnrc.gc.ca/pubs/bpn/61_e.pdf
"EFFECT OF INTERIOR FINISH ON RACKING RESISTANCE
Although not commonly considered as a structural component, interior
finish does in fact contribute substantially to the racking resistance
of buildings. According to Table 1, gypsum lath and plaster increased
the ultimate shear load of braced lumber-sheathed walls by five times,
while gypsum wallboard doubled it even though the latter was attached
only to the studs.
....
Wallboard orientation was also significant. When wall lengths were
increased to three times the wall height, horizontally applied gypsum
wallboard gave almost twice the shear resistance as the vertically
applied board, presumably due to the greater average distance of the
nails from the cut edges of the board."


Hung horizontally (& with the mid height seam unblocked) it would be
an unblocked diaphragm. Hung vertically, with the seam falling on a
stud, you'd have better continuity. No un-nailed edges, no unblocked
edges.

Agreed, which is why I said it wouldn't be that big a factor on an 8' wall.


The truth be told, drywall sucks as shear resisting material and the
whole discussion about drywall strength is rather silly.

http://www.gypsum.org/pdf/GA-229-08.pdf
"The following conclusions can be drawn from these tests:
....
2. Shear values for parallel application exceed those for perpendicular
application"

This test doesn't show anything approaching 2x. I'm neither an architect
nor engineer so the numbers don't mean all that much to me. Would it be
fair to say that horizontal beats vertical, but 2*insignificant is still
insignificant?

If you know of a good article or study explaining this further I'd
appreciate a link.

Thanks,

- Mike