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Steve Bednarski Posted: Oct 08, 2010 05:33 PM	Can I sandwich roof foam and lid from underneath?
Steve Bednarski Posted: Oct 08, 2010 05:34 PM	Sorry for the empty post. Shaky fingers. Anyways, I am wondering if anyone has done a combination of roof foam, and also sprayed the lid from underneath to sandwich the sheathing. I have to do a new roof, residential low slope, and am considering cathedralizing the rear of the house, under the low slope area. I would obviously like to fill those cavities also. I believe they are 2x6 rafters. Or, does anyone have any thoughts on what to look out for when trying something like this? Am located on the Lake Erie coast, zone 5. I also have my furnace/AC up in that attic. So, any ramblings will be much appreciated. Thanks, Steve
quentin Posted: Oct 25, 2010 08:38 AM	Never tried it but there is no reason I can see why not. Just make sure to maintain the coating on the roof and you should be OK. Or you can just do one of the two instead either way.
Daniel X Posted: Oct 26, 2010 02:26 AM	I don't see why you would want to... Are you looking to completely fill between the rafters and then on top of the deck as well?
Steve Bednarski Posted: Oct 26, 2010 07:20 AM	Sorry if I did not present that question well. The rear of the house is not accessible to spraying from the underside due to the low slope, maybe 2/12. The rear I could spray a foam roof onto. The front is accessible for the most part, and would spray the underside with 3-4" CC, my question lies in the area where the two would meet, ie the ridge. If I overlap the CC from underneath by 2-3 feet under the foam roof, does THAT area leave any reason to be concerned? Hope that helps. PS. Thanks for the replies.
quentin Posted: Oct 27, 2010 10:08 AM	I have done some jobs where there was overlap like that require but the foam was on the inside. Just a weird design and the only way we could figure to ensure it was sealed right. I see no reason it would be a big problem if done right with a good overlap. Keep an eye out for moisture near the overlap since other materials won't have the insulating factor and act as a thermal bridge is the main concern I would have.
SprayFoamSupply.com Posted: Oct 27, 2010 08:10 PM	I did a rental house that I own like that. It had a shed roof that met a 12 pitch roof at the top. I sprayed 3" foam roof on the outside over the shed roof and coated with acyrlic. Inside, I sprayed 5" of cc under the 12 pitch roof. I made sure that the foam under the 12 pitch roof was sprayed down far enough so that it went lower than the top of the shed roof. I know that it works because there is no snow melt where the two roofs meet. You should have no issues provided you make sure the foams overlap. George
Steve Bednarski Posted: Oct 30, 2010 07:37 AM	Thanks for the information everyone. I did not think it would be a problem, but wanted to get some more qualified opinions. George, that is good news to me as that solution is what I am aiming for. I do not want to be one of the insulators with high utility bills, like the mechanics with non running cars, the electricians that keep popping fuses, etc. This will help. Thanks again to all. Steve

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Comments

Steve Bednarski

Posted: Oct 08, 2010 05:33 PM

Can I sandwich roof foam and lid from underneath?

Steve Bednarski

Posted: Oct 08, 2010 05:34 PM

Sorry for the empty post. Shaky fingers. Anyways, I am wondering if anyone has done a combination of roof foam, and also sprayed the lid from underneath to sandwich the sheathing. I have to do a new roof, residential low slope, and am considering cathedralizing the rear of the house, under the low slope area. I would obviously like to fill those cavities also. I believe they are 2x6 rafters. Or, does anyone have any thoughts on what to look out for when trying something like this? Am located on the Lake Erie coast, zone 5. I also have my furnace/AC up in that attic. So, any ramblings will be much appreciated.

Thanks, Steve

quentin

Posted: Oct 25, 2010 08:38 AM

Never tried it but there is no reason I can see why not. Just make sure to maintain the coating on the roof and you should be OK. Or you can just do one of the two instead either way.

Daniel X

Posted: Oct 26, 2010 02:26 AM

I don't see why you would want to...

Are you looking to completely fill between the rafters and then on top of the deck as well?

Steve Bednarski

Posted: Oct 26, 2010 07:20 AM

Sorry if I did not present that question well. The rear of the house is not accessible to spraying from the underside due to the low slope, maybe 2/12. The rear I could spray a foam roof onto. The front is accessible for the most part, and would spray the underside with 3-4" CC, my question lies in the area where the two would meet, ie the ridge. If I overlap the CC from underneath by 2-3 feet under the foam roof, does THAT area leave any reason to be concerned? Hope that helps.
PS. Thanks for the replies.

quentin

Posted: Oct 27, 2010 10:08 AM

I have done some jobs where there was overlap like that require but the foam was on the inside. Just a weird design and the only way we could figure to ensure it was sealed right. I see no reason it would be a big problem if done right with a good overlap. Keep an eye out for moisture near the overlap since other materials won't have the insulating factor and act as a thermal bridge is the main concern I would have.

SprayFoamSupply.com

Posted: Oct 27, 2010 08:10 PM

I did a rental house that I own like that. It had a shed roof that met a 12 pitch roof at the top. I sprayed 3" foam roof on the outside over the shed roof and coated with acyrlic. Inside, I sprayed 5" of cc under the 12 pitch roof. I made sure that the foam under the 12 pitch roof was sprayed down far enough so that it went lower than the top of the shed roof. I know that it works because there is no snow melt where the two roofs meet. You should have no issues provided you make sure the foams overlap.

George

Steve Bednarski

Posted: Oct 30, 2010 07:37 AM

Thanks for the information everyone. I did not think it would be a problem, but wanted to get some more qualified opinions. George, that is good news to me as that solution is what I am aiming for. I do not want to be one of the insulators with high utility bills, like the mechanics with non running cars, the electricians that keep popping fuses, etc. This will help.
Thanks again to all.
Steve

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