Ceiling Joist (Drywall - No future rooms & limited attic storage) :
20 PSF Live, 10PSF Dead
#2 & Btr L/240
2X6 2X8
2X10 2X12
12" o.c. 16" o.c. 12" o.c. 16" o.c.
12" o.c. 16" o.c. 12" o.c. 16" o.c.
SPF 13-8 12-5 18-0 16-4
22-11 20-10 -- --
Hem-Fir 14-5 13-1 19-0 17-3
24-3 21-11 29-4 25-5

from http://www.admoyer.com/builderslibra...spancharts.htm (one of
many span table sites)

Renata


On Sat, 28 Jun 2003 16:19:19 GMT, 'nuther Bob
wrote:

On Thu, 26 Jun 2003 14:50:28 GMT, (Renata)
wrote:
Regardless of "formally loadbearing" 2x6 lumber can't span 17'.


You may have missed the point: In his house it already does. The
question is whether or not the wall was part of the structure
when the 2x6 was approved. If the wall is a formal part of the
structure, then they probably span half that distance as a true
load bearing member. If the wall is not part of the structure,
then it is probably still working to keep his ceiling from cracking.

If the 2x6's are "ties", then they are stressed horizontally and
not set up to handle a top load, just the weight of the
drywall below. It probably is not a good idea, probably does not
meet code today, probably did when it was built.

To further address the idea of making a truss type system up there -
you should realize that trusses are carefully engineered to handle the
situation they're placed in. Throwing in some 2x4s, and making it
look like a truss doesn't necessarily gain you the strength of a true
truss. Your safest bet (and probably easiest) is to add some 2x8s
along side the 2x6s (nail 'em together).

The idea of the phony truss is to provide some stability to avoid
wiggle in the 2x6 that would allow the ceiling to crack. Obviously
the 2x6 would have to meet code otherwise. You are right, you can't
engineer a truss system with a couple of 2x4's and some nails.

You probably do more damage to the ceiling by nailing in the 2x4's
with it all finished. Bolts would be needed at the ceiling end to
do it without causing more problems. They can be nailed to the rafters
at the top.

But, who know from here. Someone who knows structure needs to look
at it on site.


Bob