23'x10' ceiling on three-season porch with rafter's 16"OC.
Help me understand. Everything I read says that I should run the
sheets parallel to the joists for strength. I can do that by
minimizing butt joints using 4x12x1/2 sheets.
I can avoid butt joints all together by using 4x10x1/2 sheets parallel.
I have checked the nailing edges and they fall on rafters. What am I
giving up strength wise running parallel to rafters? What else
haven't I thought of yet? Thanks tom

wrote:
23'x10' ceiling on three-season porch with rafter's 16"OC.
Help me understand. Everything I read says that I should run the
sheets parallel to the joists for strength. I can do that by
minimizing butt joints using 4x12x1/2 sheets.
I can avoid butt joints all together by using 4x10x1/2 sheets parallel.
I have checked the nailing edges and they fall on rafters. What am I
giving up strength wise running parallel to rafters? What else
haven't I thought of yet? Thanks tom

Don't have a real number, but w/ 16" O/C, I'd not worry w/ 1/2" or
thicker. I'd go the parallel direction w/ those dimensions for the
elimination of the butt joints and it eliminates the other length-wise
seam if use 4x12 the other way. If I do the seam-counting right in my
head I get you would have 46-ft edge and 14-ft butts (assuming stagger
sheets to not have a full-width butt joint) or 50-ft of edge seams the
other way w/ the 4x10's.

The only other thing I'd check is how close the tolerances are on the
rafter spacings as if they're just 2x material you only have 3/4" when
you split them so there's not a lot of slop for the joints. It also
will take getting the first sheet lined up pretty carefully so it stays
online going forward as you've got a total of five seams to make work.

wrote:
23'x10' ceiling on three-season porch with rafter's 16"OC.
Help me understand. Everything I read says that I should run the
sheets parallel to the joists for strength. I can do that by
minimizing butt joints using 4x12x1/2 sheets.
I can avoid butt joints all together by using 4x10x1/2 sheets parallel.
I have checked the nailing edges and they fall on rafters. What am I
giving up strength wise running parallel to rafters? What else
haven't I thought of yet? Thanks tom

Everybody gets all wedgied up about drywall butt joints and its true
they often don't look too good even with careful mudding. My technique
is make a taper on the butt joint end just like the edges using a small
body grinder. Do it outside to keep the dust controlled, then bring the
panels inside and hang them. I use fiberglass tape, sometimes two
layers, well bedded for strength, and setting type mud. Eliminating
extra steps of fill, dry and sand I believe actually saves time and the
dead flat joints eliminate problems with things like crown moldings and
certain light patterns from windows.
The usual caveats of good workmanship apply when dealing with reduced
panel thickness. Works on corners, too, where you absolutely,
positively, must have a 90 degree angle. HTH

Joe

Joe

If the framer was worth his pay, the joists should be 16" oc and the joints
should fall fine. I know that's wishful thinking in many cases, so when
you pick up your drywall, grab a few 2x4 as well and if you come across the
one joist that isn't at 16, screw a nailer on the side of the offending
joist and be on your way.


"dpb" wrote in message
ups.com...

wrote:
23'x10' ceiling on three-season porch with rafter's 16"OC.
Help me understand. Everything I read says that I should run the
sheets parallel to the joists for strength. I can do that by
minimizing butt joints using 4x12x1/2 sheets.
I can avoid butt joints all together by using 4x10x1/2 sheets parallel.
I have checked the nailing edges and they fall on rafters. What am I
giving up strength wise running parallel to rafters? What else
haven't I thought of yet? Thanks tom

Don't have a real number, but w/ 16" O/C, I'd not worry w/ 1/2" or
thicker. I'd go the parallel direction w/ those dimensions for the
elimination of the butt joints and it eliminates the other length-wise
seam if use 4x12 the other way. If I do the seam-counting right in my
head I get you would have 46-ft edge and 14-ft butts (assuming stagger
sheets to not have a full-width butt joint) or 50-ft of edge seams the
other way w/ the 4x10's.

The only other thing I'd check is how close the tolerances are on the
rafter spacings as if they're just 2x material you only have 3/4" when
you split them so there's not a lot of slop for the joints. It also
will take getting the first sheet lined up pretty carefully so it stays
online going forward as you've got a total of five seams to make work.

On 2 Jan 2007 08:45:58 -0800, wrote:

23'x10' ceiling on three-season porch with rafter's 16"OC.
Help me understand. Everything I read says that I should run the
sheets parallel to the joists for strength. I can do that by
minimizing butt joints using 4x12x1/2 sheets.
I can avoid butt joints all together by using 4x10x1/2 sheets parallel.
I have checked the nailing edges and they fall on rafters. What am I
giving up strength wise running parallel to rafters? What else
haven't I thought of yet? Thanks tom

That seems strange to me, since everything I've read (which
admittedly isn't much) says that you'll get less sagging
if you run the sheets perpendicular to the joists, so that
each panel spans as many joists/rafters as possible.

--Goedjn