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Insulating Garage Ceiling


I hope you can help.

I have a 21' by 21' two car garage that I want to insulate and drywall. The problem is that the ceiling only has 3 Collar ties. I have priced installing more ceiling joists to fasten the drywall to but it is expensive.

I would like to find a less expensive solution to insulating the garage ceiling. I have two other options I am considering and would like your comments on.

Option 1:
- Could I just insulate the roof joists, with 3" paper barrier insulation, the joists are 2"x6" 16" OC. I would maintain a gap between the roof sheathing and insulation for air flow.

Option 2:
- Install 4'x8' by 3" thick rigid foam insulation. Fastened to the bottom of the roof joists.

Does code require something over the insulation (Drywall...Plywood) or can the insulation remain exposed and pass a building code inspection. I understand local code is different by locality. I am interested in national and your experience with your local codes as many are similar.

Your comments will be appreciated.
Thanks in advance


Re: Insulating Garage Ceiling

Hello..Hello is there anybody out there..there..there

Should this be posted somewhere else.
Can anybody point me to a place where I can see the building code myself? Is the code on line somewhere? Is there a site that deals with building code questions?


Timothy Miller
Re: Insulating Garage Ceiling

Consider calling your local building department and ask them what is code in your area. Then insulate and drywall if needed to meet code of add more insulation and exceed code...

Re: Insulating Garage Ceiling

In general leaving the face of insulation exposed to a room is not allowed. Their is a foil faced scrim fg insulation that can be left exposed because it meets flammability requirements. It would have to be supported on the sides with joists/truss chords. Can't say I would recommend it to be left exposed though.
Codes vary. Your local building department can tell you which code they use. It's probably on their website. The building codes are not usually available free. Local library might have a reference copy.

Re: Insulating Garage Ceiling

ed21 and Timothy Miller

Thank you both for your reply.

Several people have suggested calling the building code office. I just did not think they would be available to answer questions. I will give them a call.

Thanks again

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