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mdudu 03-01-2010 04:58 PM

drywall for vaulted ceiling
I have a vaulted ceiling in my living room. I've installed rigid foam boards in between the rafters which are 2x6's spaced 16" OC. I've been reading a lot about how to attach the drywall over that and my question is do I need furring strips or can I attach the drywall directly to the bottom of the rafters? That would be easier and, it seems to me, stronger but I have two concerns.

Firstly I'm worried that the 2x6's will provide a path for cold to flow down from the roof in the winter and that I could end up with the rafters' outlines being visible on the ceiling side of the drywall due to the temperature difference. Secondly, I read that the rigid foam expands a little and if I affix the drywall flat against it, it will eventually push out and dimple the screws.

The other idea I've read about is to thermally isolate the rafters from the drywall via a layer of thin foam board with furring strips over that. Then using long screws through the layers of drywall, furring strips, and foam into the rafters to affix them to the ceiling.

Is that overkill?

Thanks for any advice!


Scuba_Dave 03-01-2010 05:05 PM

Where are you located ?

mdudu 03-01-2010 05:33 PM

I am in the virginia suburbs of washington, dc

Scuba_Dave 03-01-2010 05:49 PM

Did you put in rafter vents in between the rafters for ventilation?
(pink vents in the picture)
How much rigid did you install between the rafters & did you seal each edge ?
You need about R-38 for a ceiling
If you are not near that then I would install 4x8 sheets of rigid foam across the rafters, then install sheetrock

Gary in WA 03-01-2010 09:06 PM

If you use the foam baffles, don’t forget to leave a 1” air space between them unlike Dave’s picture. It’s to remove trapped moisture.

As Dave said, you need a lot more R-value than in the 4-3/8" left in a 2x6 after the 1-1/4" deep baffle.

Be safe, Gary

mdudu 03-02-2010 12:24 AM

I used foam baffles, then two layers of 2" thick rigid foam at R-10 each which was just right to match the rafter depth. So it sounds like I should put another layer of foam board and the drywall up against that? If I just lay it perpendicular across the rafters and then screw the drywall up against it, will that hold up? especially considering that the ceiling is at a slant so there will be lateral forces on the screws?



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