Insulation of metal roof

Doug Walker
11/5/2017
I am planning to install metal roofing over an existing shingled roof. Around here I typically see this done with 1 x 4 battens spaced 4 feet apart and with 3/4" rigid foam panels between. Are the foam panels a good idea or is it better to leave an air space? If leaving the air space for ventilation should you use foam closure strips to seal the openings at the bottom end of the roof panels? If using vertical battens followed by horizontal battens would you place the vertical battens along each rafter? Finally, I have seen one roofing expert on the the internet who says that 29 gauge metal rather than 26 gauge is the best choice for residential use. What say you? Thanks so much.
Dick Bus
11/5/2017
placing vertical wood battens over each rafter creating an air space which is called above sheathing ventilation will do more for you than adding 3/4" foam. Oakridge Labs has done an extensive amount of testing on this. you will need to allow for an intake at the bottom that is balanced with the ridge vent. This can be accomplished by leaving the drip edge 1/2" away from the fascia. Then cross fur this with 1 x 4 typically spaced 2'oc. in your high humidity I recommend using an .032 aluminum panel. But 26 ga is definitely better than 29 ga. thanks for planning on using metal for your reroofing project.
Doug Walker
11/6/2017
Thanks for the info. I am adding a patio cover with a shed style roof with rafters attached about 6 feet up on the existing roof. Is there anywhere I can find information on flashing such an addition and also on flashing around a chimney? Thanks again.
Info @windowsonwashington.net
An informed customer is our best customer.
11/7/2017
Flashing specifics and recommendations should be available from the panel supplier at the end of the day. Most companies will have decent pdf documentation to demonstrate the specifics of their panel. I would start there and then branch out on your search if they don't have anything available.
Joshua Wallace
11/22/2017
Do i need to remove gutters before installing metal roof
Todd Miller
Classic Products, Inc.
11/22/2017
It depends a lot upon how your gutters are hung and what type of drip edge / starter you're using. You want to make sure that water coming off the roof is directed into the gutters. It is not unusual for the gutters to not be removed.
Joshua Wallace
11/22/2017
But dont i need to put fascial then metal then gutter are the fascial wont go on
Todd Miller
Classic Products, Inc.
11/22/2017
A metal fascia is not a mandatory part of most roof installations but, yes, if you're installing fascia then the gutters need to come down.
Joshua Wallace
11/22/2017
Not fascia iam sorry i meant the gabletrim
Todd Miller
Classic Products, Inc.
11/22/2017
Your metal roof supplier will be able to help you figure this out. Normally the gable trim does not interfere with gutters.
Info @windowsonwashington.net
An informed customer is our best customer.
11/22/2017
Joshua, Totally depends on how the gutters are mounted up as Todd mentioned. As a general rule, we usually have to wind up removing them to get everything mounted up properly.
Guest User
1/5/2018
I was contemplating a metal roof over asphalt shingles. One, is it okay to do this and Two, I was told installation would require a wooden frame over the existing roof. Your advice would be greatly appreciated.
Todd Miller
Classic Products, Inc.
1/5/2018
Doug, I get asked this question a lot. I have created a short video and blog post to address my thoughts on it here: https://www.asktoddmiller.com/roofing-help-videos/metal-roofing-101/metal-roof-installed-battens/
Guest User
1/6/2018
A week or so after finishing installing a metal roof on our new pole barn construction, the contractor realized they forgot to install the AstroShield that we had requested as a barrier for condensation. Without telling us we found them at the site pulling up the panels and putting the strips of AstroShiel down and screwing the panels back down. Now the roof is scuffedup because of the wet sand on their boots and the roof doesnt quite lay flat and all the “ trim” parts no longer lay flat and are what I call wavy . I told the contractor that I consider this reworked metal not the new roof I contracted for. They also in their rush to do the did not tape the AstroShield. I consider this a reworked roof and not the new roof I contracted for. The contractor disagrees. Can metal that has been attached, be pulled up and put back down be considered new because of the properties of metal. Input about the ability of the metal to be reworked would be appreciated.
Info @windowsonwashington.net
An informed customer is our best customer.
1/6/2018
The short answer to your question is yes. Depending on the panel, it should be able to be removed and reinstalled if done properly. Walking on the roof with sand covered boots doesn't sound like folks were super careful here, but without seeing the roof I can't really comment intelligently on it.

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