# Help in deciding the underlayment for roofing



## homeroofing2 (Dec 26, 2012)

Our roofer offers Rhino Wrap Synthetic Underlayment as a standard. If we want "Certainteed Diamond" underlayment (we'll have Certainteed Landmark Pro shingles), it is considered upgrade. Is it worth the extra cost to upgrade to "Certainteed Diamond" underlayment? Need a decide asap. Appreciate a quick reply. Thank you!


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## joecaption (Nov 30, 2011)

#1 Go back and add your location to your profile.
Not worth the extra money, underlaymant is not what keeps a roof from leaking.
Only time it would do anything is if the shingle blew off.


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## homeroofing2 (Dec 26, 2012)

Thank you. Sorry I did not figure out how to add location to my profile. I am from PA.

Also do we need new pipe covers for the existing vent pipes when we have the new roof installed?


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## joecaption (Nov 30, 2011)

Alway change the flashings.
Make sure to have drip cap installed.
Got a picture of the roof?


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## joecaption (Nov 30, 2011)

Look toward the top right, see where it says your name? Give it a tap and add it there.


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## ParagonEx (Sep 14, 2011)

I use Rhino synthetic no matter the shingle being installed.

Just ask him to install the rhino with the landmark pros. It isn't a problem.


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## homeroofing2 (Dec 26, 2012)

Thank you!

also the contract has

1) for shingles, it will be installed with four 1 1/4" galvanized roofing nails.
2) for flashing, copper flashing will be installed at chimney. Aluminum flashing will be installed at all other abutting areas.

Is this detailed enough? Thank you!


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## kt82 (Jan 28, 2009)

re; I use Rhino synthetic no matter the shingle being installed.
Are synthetic "felts" walkable at 6/12 pitch? how does a morning dew 
affect walk ability?


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## ParagonEx (Sep 14, 2011)

kt82 said:


> re; I use Rhino synthetic no matter the shingle being installed.
> Are synthetic "felts" walkable at 6/12 pitch? how does a morning dew
> affect walk ability?


Yes. I can personally walk on synthetic underlayments up to a 9/12.

I'm not sure about morning few because we roof what we tear off the same day except for extreme cases.


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## wrongdave (Dec 19, 2012)

I wouldn't worry too much about the brand of synthetic underlayment. 

When I did my roof this summer I tried to research synthetic underlayments, and I couldn't find anything that says there is any significant advantage to synthetics versus felt, or any particular brand of synthetic versus another once the roof is complete. There are advantages for the installation itself, but once the roof is done, it's the quality of the shingles and installation that will make the difference on your roof. 

Unfortunately with these types of new building materials, it takes several decades before you know how well they worked. So come back and ask somewhere around 2030 or 2040 and you will get more informed answers.


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## Windows on Wash (Aug 30, 2011)

Polyethylene is not a "new" building material. In this application, it less than 30 years old, but hardly unknown commodity.

It is vapor impermeable, more so than felt, which is a benefit. Enough to make me choose a roofer over another that uses felt...no.


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## kt82 (Jan 28, 2009)

wrongdave said:


> I wouldn't worry too much about the brand of synthetic underlayment.
> 
> 15# felt in the Texas market is not even 15 lbs anymore.
> it is more like kraft paper with no oil in it
> ...


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## kt82 (Jan 28, 2009)

Windows on Wash said:


> Polyethylene is not a "new" building material. In this application, it less than 30 years old, but hardly unknown commodity.
> 
> It is vapor impermeable, more so than felt, which is a benefit. Enough to make me choose a roofer over another that uses felt...no.


I thought the shingle manufactures required the underlayment to be "vapor permeable" or the warranty was voided?


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## Windows on Wash (Aug 30, 2011)

Negative. 

Shingles don't need to dry out through to the plywood.


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## kt82 (Jan 28, 2009)

I was wondering where the water vapor between the underlayment and the OSB goes 
#15 has a metric perm rating of 37.7
#30 22.2
while a typical "peel and seal" membrane is rated at .05
which implies to me that no vapor will pass thru the membrane which is good right?
I guess I should get back and finish my taxes.


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## wrongdave (Dec 19, 2012)

kt82 said:


> why when I was younger and Certainteed used virgin paper
> and real tar ,never mind


and asbestos. Ah yes, the good ol' days.


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## Windows on Wash (Aug 30, 2011)

Yes.

If you have a vapor barrier layer at the plywood/osb, the moisture shouldn't even enter that layer between plywood/osb via solar drive or bulk movement.

No moisture, no need for breath-ability.


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