Cellulose
user-1015969
| Posted in GBA Pro Help on
I am in the process of building a new home and plan on using cellulose insulation in the attic. I hope to insulate the attic to r-60 which I believe is about 17″ thick. My home has energy heel trusses (2×6 bottom chord) spaced on 24″ centers. I have 1/2 drywall glued and screwed every 12″ to the underside. Im worried about the weight of the cellulose on the drywall especially after it absorbs moisture from the air. Should I be concerned and if so what precautions should I take? Thank you.
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Replies
Ask and you shall receive: https://www.greenbuildingadvisor.com/community/forum/green-building-techniques/25580/58-drywall-sufficient-support-r-60-cellulose-ceiling
It's pretty common to install 1x strapping 16" o.c. to the bottom of the truss chords (shimmed flat) using screws or ring-shank nails, and install the gypsum to the strapping.
It is likely no contractor will take on the liability of installing more insulation than USG recommends without you signing a waver making yourself solely responsible for any all possible failures.
Prepare yourself mentally and offer it up front do not make them ask for one. Understand you are pushing them outside of their comfort zone.
Walta
Consider going with type X drywall it has fibers in the gypsum to hold it together and it is 5/8 thick.
Walta
R-60 blown cellulose is normal for my jobs and a recent one topped R-120, with no waivers from the installer; above 8-12" it's self-supporting. That said, my projects always have strapping 16" o.c. (standard in New England) and usually a vapor retarding membrane. I would be concerned with 1/2" drywall on any ceiling if only fastened 24" o.c. remaining flat.
I thank everyone for their answers. It seems that I jumped the gun a little. I didn't even consider the weight of the cellulose and have already hung the ceiling drywall. Is there anything I could do after the fact to support this weight. Maybe strapping on top of the joist to help carry the load? Any other suggestions would be welcome.
Thank you