Expert: Dave Johnson - 9/30/2009

Question
I am looking at adding additional insulation in my attic, since my old insulation has seen better days. I have looked in to several types and decided that blown in insulation is probably the best bet due to not having to remove the old craft faced R13 that is in the attic.

The question is that since my home was built in 1977 and I have what looks like 2 by 6 ceiling joists what weight load can I safely add based on the rafter size?

Also, what is my ceilings strength since the dry wall was nailed in not screwed?

I have had to fix several nail pops when decorating so I am concerned that when I add the insulation the weight would cause an issue with the ceiling drywall coming lose, as well as that I have 2 by 6 instead of 2 by 8 rafters.

The span from the center load bearing wall to the outer wall is 13 feet on one side and 11 feet on the other.

Based on some articles I have read I think that is going to allow 10lbs per square foot. But, I do not know what weight R49, combined of R13 and Cellulose insulation, is per square foot. I also have some storage up there, not anything heavy but the usual junk.

Hopefully you understand my two concerns and can help.

Thank you

Martin

Answer
Hi Martin,
Is the ceiling strapped? If so, you have no worries.
Looks like you're going to put in about 10". That translates to around 700# for the area.
I'm not sure about the added weight to your drywall. So, short of doing the ceiling over,
you're taking a chance. Personally, I'd probably take the chance..
Best of luck,

Dave