LB= Load-bearing

First question:
Can anyone tell me what weight my attic floor can bear?
2x6's, 16" apart, and the attic is about 28' wide where each joist is
about 14' long extending from the exterior LB-walls to where they
slightly overlap over the center interior LB-wall (the joist butt-ends
do not meet, the joists are 1.5" off-center from each other). The entire
attic is about 48' long, just joists & collar-beams with a bunch of flat
2x4's (I think) layed end-to-end on top of the joists from one end of
the attic to about the other end.

Anyone know the lb./sq. feet for up there?

Second question:
-I currently have faced-fiberglass insulation batts up there between the
joists, peeled it up and it says "Johns Manville - Super-thick 6 1/2" R-
22c.24F.19l" on it, why the three numbers? Which is it?

Third question:
-I would like to add unfaced insulation to bring it as close to R-48 as
possible, should I roll the new stuff out perpendicular to the existing
stuff to cover the joists to prevent radiant heat loss?

Fourth question:
-For the places where I'd like to put down the plywood, covering about
400 sq. ft. of the total 1400 sq. ft. of my attic circling around the
attic stairs opening (all the headers/joists are doubled-up for the
stairs btw), should I not bother with adding any extra insulation
because it would have to be compressed into 6" of space underneath the
plywood, thus negating a lot of the R-value, right? Should I just leave
the existing fiberglass there and not add any before putting down the
plywood?

Fifth question:
Cost: Any ideas for what it will cost for about 1400 sq. feet of R-30
insulation in NY? Home Depot or Lowes the best for large quantities?
Somewhere else better?


Thanks for the help, wasn't sure about newsgroup etiquette and whether I
should have broken this up to 5 diff. posts for each question?

On Fri, 8 Dec 2006 10:53:08 -0500, G wrote:

LB= Load-bearing

First question:
Can anyone tell me what weight my attic floor can bear?
2x6's, 16" apart, and the attic is about 28' wide where each joist is
about 14' long extending from the exterior LB-walls to where they
slightly overlap over the center interior LB-wall (the joist butt-ends
do not meet, the joists are 1.5" off-center from each other). The entire
attic is about 48' long, just joists & collar-beams with a bunch of flat
2x4's (I think) layed end-to-end on top of the joists from one end of
the attic to about the other end.

Span tables at: http://www.awc.org/pdf/STJR_2005.pdf

You've got 2x6s spanning 14', 16" o.c.,
so the answer is, "not much weight".
For L/240 (about 0.7" deflection)
with 10PSF live load, and 5 PSF dead load,
you can span 14'1"

That's just about enough (10psf) to
support you and a toolbox.







Anyone know the lb./sq. feet for up there?

Second question:
-I currently have faced-fiberglass insulation batts up there between the
joists, peeled it up and it says "Johns Manville - Super-thick 6 1/2" R-
22c.24F.19l" on it, why the three numbers? Which is it?

Third question:
-I would like to add unfaced insulation to bring it as close to R-48 as
possible, should I roll the new stuff out perpendicular to the existing
stuff to cover the joists to prevent radiant heat loss?

Fourth question:
-For the places where I'd like to put down the plywood, covering about
400 sq. ft. of the total 1400 sq. ft. of my attic circling around the
attic stairs opening (all the headers/joists are doubled-up for the
stairs btw), should I not bother with adding any extra insulation
because it would have to be compressed into 6" of space underneath the
plywood, thus negating a lot of the R-value, right? Should I just leave
the existing fiberglass there and not add any before putting down the
plywood?

Fifth question:
Cost: Any ideas for what it will cost for about 1400 sq. feet of R-30
insulation in NY? Home Depot or Lowes the best for large quantities?
Somewhere else better?


Thanks for the help, wasn't sure about newsgroup etiquette and whether I
should have broken this up to 5 diff. posts for each question?