# OK to blow in insulation before drywall



## Miller257 (Jan 24, 2009)

I'm working on an addition for my house, I'm trying to get the heat going so I can keep working. I have 6 mil Poly on the ceiling (24 on center trusses). Is it ok to blow in the insulation on the poly (before I install the drywall) or will the poly sag too much.

Maybe blow in half now and half after the drywall.

Thanks


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## TaylorMadeAB (Nov 11, 2014)

If it's stapled well it will probably hold the insulation, but I wouldn't risk it. If starts to come loose you'll have a HUGE mess to clean up. 
Also if any lumps fall in between the trusses and the poly, your drywall won't sit nicely. 
You'd be surprised how much heat just the poly will hold in, don't worry about the insulation yet.


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## Bummie (May 11, 2007)

Don't risk it. Get the board up on the ceiling and screwed off before blowing insulation. TaylorMadeCon is right about the poly holding heat!!


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## brhokel606 (Mar 7, 2014)

TaylorMadeCon said:


> If it's stapled well it will probably hold the insulation, but I wouldn't risk it. If starts to come loose you'll have a HUGE mess to clean up.
> Also if any lumps fall in between the trusses and the poly, your drywall won't sit nicely.
> You'd be surprised how much heat just the poly will hold in, don't worry about the insulation yet.


I totally agree, the poly should hold it but if it doesn't, you are screwed. It is guaranteed that insulation will get between the poly and joist unless you use some kind of adhesive on the connection between the ploy and joist. Just poly for now, then throw up rock, worry about insulation after.


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## TNTRenovate (Aug 19, 2010)

6 mil poly stapled to kingdom come, you'll be fine.


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## Big Shoe (Jun 16, 2008)

Put batts in. :whistling


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## Randy Bush (Mar 7, 2011)

Poly on ceiling? Never see that here. I would rock first.


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## TNTRenovate (Aug 19, 2010)

I've also seen netting used on the ceiling.


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## Texas Wax (Jan 16, 2012)

TNTSERVICES said:


> 6 mil poly stapled to kingdom come, you'll be fine.


It works, but hanging rock on the lids after the insulation and poly has sagged over time .... Lids bites, lids with sagging insulation not fun


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## hdavis (Feb 14, 2012)

Pick up some .031 plastic (or maybe .07) and put it over the tops of the joists. That will more than double the R value that the single layer of 6 mil is giving you. Get rid of it before you blow the attic.

Or, strap the ceiling down and blow it now. Or ,blow it now and strap before hanging the drywall. Or, blow it now and fight hanging the lid.

Just a few options...


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## Golden view (Feb 16, 2012)

Texas Wax said:


> It works, but hanging rock on the lids after the insulation and poly has sagged over time .... Lids bites, lids with sagging insulation not fun


Exactly


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## Golden view (Feb 16, 2012)

Randy Bush said:


> Poly on ceiling? Never see that here. I would rock first.


Poly on ceilings in considered standard in certain climates and required in certain areas.


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## Golden view (Feb 16, 2012)

It took me an embarrassing number of times to learn that doing anything out of order is pretty much never worth it. If you already have the poly up, you're ready to hang the lid.


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## TNTRenovate (Aug 19, 2010)

Texas Wax said:


> It works, but hanging rock on the lids after the insulation and poly has sagged over time .... Lids bites, lids with sagging insulation not fun


Not dating is ideal but if you have to do it you do it. It's more of a it'll work, not that is recommended.


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## Xtrememtnbiker (Jun 9, 2013)

TNTSERVICES said:


> Not dating is ideal but if you have to do it you do it. It's more of a it'll work, not that is recommended.



What's dating got to do with anything Rob? :whistling


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## Miller257 (Jan 24, 2009)

Thanks for the reply's guys, I'll wait. Weather has been my friend this year.



> It took me an embarrassing number of times to learn that doing anything out of order is pretty much never worth it. If you already have the poly up, you're ready to hang the lid.


ehh not quite, it's an addition so I still have to blow out some walls and get some LVL's installed.


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## TNTRenovate (Aug 19, 2010)

Xtrememtnbiker said:


> What's dating got to do with anything Rob? :whistling


Tipitop school of typing


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## Morning Wood (Jan 12, 2008)

I guess you don't do strapping in your neck of the woods. If its strapped it should be fine.


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## blacktop (Oct 28, 2012)

2 ft on center ?? And you want to strap poly and blow insulation on top? That's the dumbest chit I've ever heard of In my life!! 


What planet do you people live on??


And If you do go this route ...The board will need to hung a day or two after the insulation is blown In.. or your screwed ! 


So why bother ?


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## hdavis (Feb 14, 2012)

blacktop said:


> 2 ft on center ?? And you want to strap poly and blow insulation on top? That's the dumbest chit I've ever heard of In my life!!
> 
> 
> What planet do you people live on??
> ...


Strapping would be 1X3 16"OC - maybe plywood rips, maybe furring strips run perpendicular to the joists. It's fast, easy and is not uncommon up here and very common in old houses. You can leave the lid off for months if you want, no problem..


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## fjn (Aug 17, 2011)

hdavis said:


> Strapping would be 1X3 16"OC - maybe plywood rips, maybe furring strips run perpendicular to the joists. It's fast, easy and is not uncommon up here and very common in old houses. You can leave the lid off for months if you want, no problem..






As far as I'M concerned, 1"x 3" strapping is the only way to go. Gives you a flatter ceiling and makes hanging the rock easier.:thumbsup:


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## muskoka guy (Nov 16, 2013)

fjn said:


> As far as I'M concerned, 1"x 3" strapping is the only way to go. Gives you a flatter ceiling and makes hanging the rock easier.:thumbsup:


We always strap on 16 inch o/c., 6mil poly, then insulate before ceiling is applied. Quite often we use v joint for ceilings which qualifies as a ridgid ceiling. If it is just drywall, you would have to strap or add braces on top of the bottom chord in order to meet the requirements of the maximum unbraced bottom chord spec in the truss data sheets. Maybe because we have snow load up here that it applies to us. Do you consult your truss specs concerning max. unbraced bottom chords. Do you add braces on top of the bottom chord. Do you not have to worry about unbraced bottom chords due to light or no snow loads.


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## Morning Wood (Jan 12, 2008)

Put the poly up before the strapping.


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## vff9 (Dec 1, 2008)

I agree with both fjn and Muskoka. ...poly and strap and then insulate ceiling. Electricians don't always like it having to run there wires through the poly but they get used to it ; -)

Sent from my SM-G900W8 using Tapatalk


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## Texas Wax (Jan 16, 2012)

Miller257

Wow Wawatosa, must have missed that.

If it's permitted, in >Wawatosa< ... Check with the inspector before doing anything "out of sequence". Like covering vapor barrier with drywall before inspection. The BI, in the past anyway, was a prickly stickler for details-procedures. kind of guy.

Enjoy the spring like Christmas.


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