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Metal roof underlayment??

747mopar

747mopar

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Just curious as to what everyone's thoughts are on the subject? Around here this bubble wrap stuff is all the craze for putting under metal roofs. I don't get it, is it just another way to get money out of people or is it legit? I guess it's supposed to add R value which can't possibly amount to anything and it's going on a roof with a well vented attic?

Personally, I like good ol fashion tar paper.. anytime I pull a roof that's in decent shape (not leaking or exposing the tar paper) the wood underneath looks like new so it works.

Just trying to plan out replacing my roof which is 1/2" plywood over purlins then tar paper. If the paper still looks good I just might throw the metal right over it and be done.
 
747mopar said:
Just curious as to what everyone's thoughts are on the subject? Around here this bubble wrap stuff is all the craze for putting under metal roofs. I don't get it, is it just another way to get money out of people or is it legit? I guess it's supposed to add R value which can't possibly amount to anything and it's going on a roof with a well vented attic?

Personally, I like good ol fashion tar paper.. anytime I pull a roof that's in decent shape (not leaking or exposing the tar paper) the wood underneath looks like new so it works.

Just trying to plan out replacing my roof which is 1/2" plywood over purlins then tar paper. If the paper still looks good I just might throw the metal right over it and be done.
Click to expand...


I agree with you. Traditional tar paper uses petroleum as a binding agent, but also as a preservative....and its properties for maintaining in extreme cold and heat are also well know.....then there is the cost......waaaaay better.
 
We use peel & stick underlayment here which is expensive as hell and is better than tar paper when you have a shingled roof which will eventually leak and it will protect the plywood better. That being said a metal roof roof over #30 tar paper is just fine.
I had a shingled roof that needed replacing and I left the shingles on it ( they were the old 3-tab flat shingles ) and put new tar paper over them and new 1x4 purlins with blue foam board cut between then the metal roof.
 
Guess Im late to the game as I don t know what the bubble wrap stuff is. As I normally also just use tarpaper under my metal roofing metal, I did change over to some "new" stuff on the last one. My local seller said a lot of his contractors had starting using the black vinyl wrap. It was just like the white house wrap one uses on top of the sheathing and under your vinyl siding or hardy board or brick. Basically just a bit bigger than regular roll of tarpaper and much easier to lay down by yourself.
 
The only thing I can assume using the plastic vapor barrier is condensation buildup under the metal roof (cool house/hot metal/humidity), especially when you are putting the metal roof and furring strips over the old asphalt roof. I have seen the Tyvek used, but not heard of using some kind of bubble wrap. As far as an additional R rating, that is what the ceiling insulation (R30) is for.
 
The Bubble wrap junk is for Pole barn construction so the inside of the steel won't sweat,
not for putting on top of plywood on your house. I just had my roof done last year and did
all of my homework on products. I live in northern Illinois, same climate as yours, and I
used a fiberglass self-adhesive heavy paper under my architectural shingles by Owens Corning.
It should work well for your application too. Owens Corning High temperature peel and stick
underlayment.
 
Last edited:
I put 30# felt on everything but my sandwich.
 
The manufacturer usually specifies what underlayment they want under the metal. All the commercial jobs I specified either wanted roofing felt (tar paper) or snow and ice guards (peel and stick). Current building code requires snow and ice guard at the eaves to help stop water from backing up under the roofing.
 
I use one layer of 50 felt tar paper an another layer 30 then metal, the paper is what seals your roof the metal , shingle , tile is to protect the paper
 
Look in my build thread but I think what I used was called Titanium???

Seemed like it did a great job... .02
 
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