how to attach 2x4 to rafters?

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  #1  
Old 07-21-08, 10:31 PM
K
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how to attach 2x4 to rafters?

Hi There,

I'm getting ready to finish my attic and I was wondering if someone could tell me the correct way to attach 2x4's to my 2x6 rafters to add extra space to put R30 insulation? I finished an attic a few years ago and used metal binding strips but that attic was not permitted and inspected so I'm not sure if that was the correct way to do it.

Thoughts anyone?

Thanks,

Ken

BTW - This is my first post so you may be seeing more of me in the coming weeks as I'm about to start my project and I'm sure I'll have lots of questions.
 
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Old 07-22-08, 07:29 AM
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Why don't you want to use the standard attic inulation which I believe is R 21? Adding 2x4s is a lot of work. I don't think it's needed.
 
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Old 07-22-08, 12:51 PM
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Want R30

Here in North Carolina everyone I've asked regarding attic insulation the response is always put R30 between the rafters. With 2x6 rafters I need another few inches to get the depth for the air channel behind the insluation and be able to put R30 in there without squishing it in.

I'm just not sure the best way to attach the 2x4's so that an inspector isn't going to give me grief about it.

Ken
 
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Old 07-23-08, 08:43 PM
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For some reason I don't think the inspector would insist on R30 if he knows that it can't fit in between 2x6s.
 
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Old 07-23-08, 10:07 PM
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You might consider using spray on expanding foam insulation. It will give you a far superior R value and is environmentally friendly. Check the cost you'll find it is less expensive than you might think and there are many contractors specializing in these products.
Thanks for listening.
 
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Old 07-23-08, 11:27 PM
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Are you going to be using the attic for any thing?
If not, run your second layer of insulation perpendicualr to the first layer, use unfaced insulation or blown-in insulation. Your vapor barrier (faced insulation) should be closest to teh ceiling. Placing a secon vapor barrier will only trap mositure between teh two and that creates other problems.
 
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Old 07-24-08, 09:00 AM
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We plan on using the attic as finished space - one side a play room for the kids and the other side a craft room.

Regarding insulation - I may look into the blown insulation. As for just using regular R30, I wasn't suggesting that I use R30 with just 2x6's. I want to add 2x4's to the exsiting 2x6's to build out the rafters so that I have enough room for the R30. This is what the post was for - to find out the best way to attach the 2x4's to the 2x6's. Can I just use pieces of plywood to scab them together or metal mending plates, etc???

Ken
 
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Old 07-27-08, 06:39 PM
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In that case, if I was in this pardicament, this is what I would do.

You need to have a ventilation space beteen the underside of the roof and the insulation, even if its only 1" you need to have air movement.

They sell plastic things for ventilation. or you could attach 1x2 to each side of the 2x6 then install a 1/8" piece of the cheapest paneling you can find. That will give you 1 1/2" of airspace.

To attach the 2x4 you have several options.
5" long nails/screws/lag bolts. Drill a pilot hole through the 4" side (actually 3 1/2") and you may need to countersink the screw/bolt head so you have a flat surface for your drywall. Dont forget the vapor barrier. It is a lot of work, but doable in sections.
 
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Old 12-05-10, 02:04 AM
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wait what do you mean vapor barrier? Where are you going to put that?
 
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Old 12-05-10, 06:48 AM
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This is a really old post. Vapor barriers are used to prevent warm moist air from coming in contact will cold parts of the structure. When that happens, moisture can accumulate and cause rot. If you have a specific project you are working on and would like more information on what you should do, start a new thread.
 
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