[Greenbuilding] Weight of spray cellulose

Tue Feb 14 14:29:44 CST 2017

Hi, Sacie—

If the spaces are accessible, one option would be to make baffles to fit. These could be cardboard rectangles, scored along two edges which are then folded, and stapled in place. You can readily find examples of insulation contractors making these on the web.

Good luck,

Mike O’Brien

On Feb 14, 2017, at 11:29 AM, Sacie Lambertson <sacie.lambertson at gmail.com> wrote:

Thanks for the several responses to my query re the weight of dense pack cellulose and its potential for causing a bulge in the drywall.

Strapping the ceiling is precisely what I would like to avoid if possible.  ie This adds to the cost and complexity of the project.

Re weight, the question is, will 3 concentrated pounds of cellulose cause a bulge in the ceiling drywall?  (3.5 pounds/cu ft). The openings I'm talking about are less than a cubic foot in size.

I am assuming that is dry weight; wet would be heavier, n'est pas?

Opinions?

Thanks, Sacie

On Tue, Feb 14, 2017 at 8:19 AM, Clarke Olsen <colsen at fairpoint.net <mailto:colsen at fairpoint.net>> wrote:
You could strap he ceiling with 1x2, 12" oc. Side effect is flattening of the ceiling plane.
Clarke Olsen
clarkeolsendesign.com <http://clarkeolsendesign.com/>
373 route 203
Spencertown, NY 12165 
USA
518-392-4640 <tel:(518)%20392-4640>
colsen at taconic.net <mailto:colsen at taconic.net>

On Feb 14, 2017, at 8:59 AM, Bill Chaleff via Greenbuilding <greenbuilding at lists.bioenergylists.org <mailto:greenbuilding at lists.bioenergylists.org>> wrote:

> 
> From: Bill Chaleff <billarchtx at aol.com <mailto:billarchtx at aol.com>>
> Subject: Re: [Greenbuilding] Weight of spray cellulose
> Date: February 14, 2017 at 8:59:30 AM EST
> To: greenbuilding at lists.bioenergylists.org <mailto:greenbuilding at lists.bioenergylists.org>
> 
> 
> Dense -pack cellulose is installed at a minimum of 3.5 pounds per cubic foot.   That's the industry standard minimum to be "dense-pack."
>  
> Bill Chaleff A.I.A., Leed AP
>  
>  
> -----Original Message-----
> From: Sacie Lambertson <sacie.lambertson at gmail.com <mailto:sacie.lambertson at gmail.com>>
> To: Greenbuilding <Greenbuilding at lists.bioenergylists.org <mailto:Greenbuilding at lists.bioenergylists.org>>
> Sent: Mon, Feb 13, 2017 9:36 pm
> Subject: [Greenbuilding] Weight of spray cellulose
> 
> I have a situation where cellulose will be sprayed under an existing attic roof.  Thanks to a suggestion on this forum we are making ply gussets to extend the existing roof rafter to allow for at a minimum of 11 " of dense pack cellulose to be blown through netting against the spray foamed under roof.
> 
> My question is how heavy is 11" of sprayed dense cellulose?  At the perimeter of the space, where the extended rafters meet the floor joists over the rooms below, will the cellulose sag so much it will create a potential bulge problem on the drywall that will be covering the ceiling below?
> 
> The floor joists of the attic are old full 2x4s 16" apart.  Where the potential sag might occur therefore is a space that is about 14"x11".  The suggestion has been to take attach thin 2" wide plywood across the space, thus bridging it so the dense pack cellulose won't weigh too heavily and protrude into the ceiling space below.
> 
> However if we do this, we will obviously have to cover the entire ceiling this way before we put up drywall.
> 
> (The unseen dilemmas of rebuilding a very old house)
> 
> Thanks for all good opinions.
> 
> Sacie
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