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Author	Comments
Tim Heger Posted: Jan 21, 2007 09:04 AM	Log cabin roof I am building a log cabin and I need to put a roof over the exposed tounge and groove sub-roof. Right now the traditional method is to frame a 2x12 structure on top of the tounge and groove. The 4x10 rafters which support the exposed tounge and groove provide all the required support so the 2x12 structure is just to provide for the standard roll insulation. See photo's on blog site listed. My questions are: 1-Is there a spray foam solution that will provide the required R38 value that I can spray onto the existing structure? 2-If there is a product that I can use - what kind of framing is required (2x4, 2x6, etc) will I have to build over the existing sub-roof? 3-What foam product did you use and where can I buy it? Thanks, Tim
Thomas Kasper Posted: Jan 21, 2007 11:30 AM	I have done some built up roofs in the past. I use 2x6 lumber on end and screw them down to the roof rafters. You need long screws, I use ten inch screws and predrill the 2x6s. You can get a r-38 in that cavity with ridgid spray foam.
Tim Heger Posted: Jan 21, 2007 04:48 PM	Thanks for the reply - did you frame the 2x6's 24" OC?
Thomas Kasper Posted: Jan 21, 2007 05:24 PM	Yes the 2x6s were 24" oc with a tin roof on top of them.
Posted: Jan 22, 2007 08:16 AM	"Is there a spray foam solution that will provide the required R38 value that I can spray onto the existing structure?" yeppers!! closed cell ~r6.5 to an inch...most applicators will tell you 4-5" will be plenty of closed cell as you are ~94% thermal efficient with this product in this appliction... open cell ~r3.5/inch,,but i personally would apply in the 8-10" range to obtain good rvalue and great thermal performance... consider a layer of board stock under the tin roof,,over the top of the 2x12 rafters to stop the thermal bridge effect of the rafters... nice blog..frame on.. since you are
Gerry Wagoner Posted: Jan 22, 2007 08:55 AM	"1-Is there a spray foam solution that will provide the required R38 value that I can spray onto the existing structure?" Yes. "2-If there is a product that I can use - what kind of framing is required (2x4, 2x6, etc) will I have to build over the existing sub-roof?" 2x6 is adequate, as Tom suggested. Use Rigid foam (closed cell). "3-What foam product did you use and where can I buy it?" You will have to locate a contractor in your area. all the best, olger
Thomas Kasper Posted: Jan 23, 2007 02:09 PM	I think the built up roof is the most difficult and time consuming to do especially on a 12/12 pitch, but is very rewarding when finished. Have fun and be careful up there.

Author

Comments

Tim Heger

Posted: Jan 21, 2007 09:04 AM

Log cabin roof

I am building a log cabin and I need to put a roof over the exposed tounge and groove sub-roof. Right now the traditional method is to frame a 2x12 structure on top of the tounge and groove. The 4x10 rafters which support the exposed tounge and groove provide all the required support so the 2x12 structure is just to provide for the standard roll insulation. See photo's on blog site listed.

My questions are:

1-Is there a spray foam solution that will provide the required R38 value that I can spray onto the existing structure?

2-If there is a product that I can use - what kind of framing is required (2x4, 2x6, etc) will I have to build over the existing sub-roof?

3-What foam product did you use and where can I buy it?

Thanks,

Tim

Thomas Kasper

Posted: Jan 21, 2007 11:30 AM

I have done some built up roofs in the past. I use 2x6 lumber on end and screw them down to the roof rafters. You need long screws, I use ten inch screws and predrill the 2x6s. You can get a r-38 in that cavity with ridgid spray foam.

Tim Heger

Posted: Jan 21, 2007 04:48 PM

Thanks for the reply - did you frame the 2x6's 24" OC?

Thomas Kasper

Posted: Jan 21, 2007 05:24 PM

Yes the 2x6s were 24" oc with a tin roof on top of them.

Posted: Jan 22, 2007 08:16 AM

"Is there a spray foam solution that will provide the required R38 value that I can spray onto the existing structure?"

yeppers!! closed cell ~r6.5 to an inch...most applicators will tell you 4-5" will be plenty of closed cell as you are ~94% thermal efficient with this product in this appliction...
open cell ~r3.5/inch,,but i personally would apply in the 8-10" range to obtain good rvalue and great thermal performance...

consider a layer of board stock under the tin roof,,over the top of the 2x12 rafters to stop the thermal bridge effect of the rafters...

nice blog..frame on..

since you are

Gerry Wagoner

Posted: Jan 22, 2007 08:55 AM

"1-Is there a spray foam solution that will provide the required R38 value that I can spray onto the existing structure?" Yes.

"2-If there is a product that I can use - what kind of framing is required (2x4, 2x6, etc) will I have to build over the existing sub-roof?" 2x6 is adequate, as Tom suggested. Use Rigid foam (closed cell).

"3-What foam product did you use and where can I buy it?" You will have to locate a contractor in your area.

all the best,

olger

Thomas Kasper

Posted: Jan 23, 2007 02:09 PM

I think the built up roof is the most difficult and time consuming to do especially on a 12/12 pitch, but is very rewarding when finished.
Have fun and be careful up there.

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