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Old 11-08-2019, 12:56 AM   #1
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Extra weight on roof?


I have a room with an open beam ceiling (1 story) that I want to add 4" rigid insulation with 1/2' drywall finishing. Beams (3 1/2' X 5 1/4") are 32" (on center) apart. Should it be able to handle the extra load?
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Old 11-08-2019, 07:09 AM   #2
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Re: Extra weight on roof?


There's no real load to insulation, BUT 32" OC won't work for sheetrock. It will bow and eventually fail. You need to have an attachment point at 48" for standard size sheetrock. So your best bet would be to install perlins flat across and between your beams at 16" OC after you install your insulation. Either that or run 1x4 strapping at 16" oc under the beams perpendicular to the beams, then insulate and install sheetrock.

Not sure rigid insulation is your most economical, nor the best for this application. You will need 5 1/2" R19 kraft faced (with the paper down) for an easier installation. Installing foam boards, even if you can find 4" will require edge sealing with spray foam for a complete seal.
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Old 11-08-2019, 07:50 AM   #3
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Re: Extra weight on roof?


Quote:
Originally Posted by CutinCorners View Post
I have a room with an open beam ceiling (1 story) that I want to add 4" rigid insulation with 1/2' drywall finishing. Beams (3 1/2' X 5 1/4") are 32" (on center) apart. Should it be able to handle the extra load?

Maybe. Maybe not.



What is the run (length from bearing point to bearing point)?


The insulation only should not be a problem but the drywall and whatever else you have to add might be.
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Old 11-08-2019, 01:08 PM   #4
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Re: Extra weight on roof?


Sorry I forgot to mention the drywall of course. Insulation is light as a feather. In Los Angeles by code you have to finish with 1/2' drywall. You can visualize the size of the room from this exterior picture. A bathroom and hallway are further away. Another room is to the left.



And yes I would be adding wood to keep the drywall from bowing.


It would be easier to insulate the top but the quote I got (3K to 3.5K) is just too far out of my budget,

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Old 11-08-2019, 03:32 PM   #5
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Re: Extra weight on roof?


Sorry.



My reference books don't accept visualization as a measurement. In order to compute ceiling load and roof load for a given span one must have accurate measurement of the span. 2x6 16" CC has a pretty low rating.
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Old 11-08-2019, 04:18 PM   #6
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Re: Extra weight on roof?


Do you only want to do one room??
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Old 11-09-2019, 10:29 AM   #7
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Re: Extra weight on roof?


You're in sunny LA. I assume it is exposed T&G bead board to span the 32"? Is it still presentable with the exposed beams or all bad so you want to cover it all up with drywall? What are your goals with the 4" thick rigid?
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Old 11-09-2019, 03:28 PM   #8
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Re: Extra weight on roof?


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You're in sunny LA. I assume it is exposed T&G bead board to span the 32"? Is it still presentable with the exposed beams or all bad so you want to cover it all up with drywall? What are your goals with the 4" thick rigid?
Tongue and groove 2 X 6's on top of the beams, yes. I like the look of the open beam ceiling, but a roofer quoted me between 3K and 3.5K to insulate from the top. I wish I knew how to insulate on top of the existing room. I'd do it myself. But that's why I'm considering insulating from the inside. This room is usually about 6 degrees colder than my other rooms. It's a lot of effort to heat this room. On a cold night, 68 degrees would be "warm" for this room.

The reason for finishing with drywall is because I was told that this is the code requirement. I wish I could skip the drywall.

I've insulated the other 2 bedrooms. I finished those with drywall. But those rooms are a bit smaller.


4" thick for max R value.
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Old 11-09-2019, 04:02 PM   #9
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Re: Extra weight on roof?


I would put up the foam and just strap across the joists with 2x4s and drywall.
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Old 11-10-2019, 08:53 AM   #10
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Re: Extra weight on roof?


Quote:
Originally Posted by CutinCorners View Post

The reason for finishing with drywall is because I was told that this is the code requirement. I wish I could skip the drywall.

I've insulated the other 2 bedrooms. I finished those with drywall. But those rooms are a bit smaller.


4" thick for max R value.

I am fairly sure the requirement is for a 30 minute fire rating protection.


As I see exposed sprayed on foam in commercial buildings and have read that some of it is safe to leave exposed you may want to investigate that approach. It will cost more than DIY but may be significantly cheaper.
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