Synthetic roofing underlayment?

I'm getting a new roof. One of the roofer is proposing to use a synthetic underlayment in place of the traditional felt. He showed me samples of felt and the synthetic and asked me to try to tear them. The synthetic didn't tear. It was a lot like Tyvec in the way it looked and felt and seemed similarly tear resistant.
However I'm wondering if the strength of the material is a significant issue. Perhaps the greater thickness of the felt, providing a softer underlayment for the shingles, would be more significant.
Does anyone have experience and/or opinions about this?
Thanks.
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On 06/20/2014 04:27 PM, Alan Meyer wrote:

Most roof leaks are the result of fly-by-night hacks improper installation of roofing materials.
I'd be more concerned with the skills and integrity of the roofer than using the latest and greatest whiz-bang material.
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On Friday, June 20, 2014 4:55:37 PM UTC-4, Al wrote:

felt and the synthetic and asked me to try to tear them. The synthetic di dn't tear. It was a lot like Tyvec in the way it looked and felt and seeme d similarly tear resistant.

layment for the shingles, would be more significant.

I agree. But there are some differences which can matter in some applicati ons. One difference is the synthetics can go on over the roof sheathing and be l eft there without shingles for a month or more. It's tuff, waterproof so wind and rain won't damage it. If you're in a hurricane area and lose a bunch of shingles, the synthetic has a much better chance of surviving and continuin g to protect.
Also felt ain't what it used to be. Like so many other things, they've fig ured out how to make it cheaper, use less oil, etc. If you put it on and get a good rain before the shingles go on, the 15# stuff can warp and you're scre wed. If a roofing crew is going to do it on a clear day, does it matter? And it's still significantly less than the synthetic, meets code, and is widely used. More felt is used than synthetic, that's for sure.
In the end it depends on how long you're going to live there, if any of the above are concerns, and how much you want to spend. The difference in cost isn't zero, but it's not a lot of money on a $7,000 job either. I'd sleep OK at night with felt for most applications.
It's also important that they apply ice dam product to the lower portions, going 3ft past where the heated wall starts. That's code now for climates where ice dams are a concern. That goes down instead of the felt/synthetic .
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I always call at least 3 contractors referred by a reliable source for any job over $200. Schedule them to come over an hour apart and then make a decision.
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Alan,

Once the shingles are on, it won't really matter.
I put a new roof on our house last year. I used self-stick ice and water membrane on our low sloped (3/12) porch roof, the roof valleys, and the lower three feet of all the eaves. Then I used 30 pound felt for the rest of the roof.
30 pound felt is a lot stronger than 15 pound felt, and doesn't bubble up in the heat the way the 15 pound felt does. It holds it's shape better too, so I found it a lot nicer to work with.
I don't recall the ratings now, but I know there were two different felts that were both called "30 pound". One was thicker than the other and would be my first choice. But I used both with no issues. Either is a step up from 15 pound felt.
I wouldn't bother with the synthetic stuff, especially if it costs more. There may be advantages, but traditional felt has worked well for generations. It will work for you too. :)
Anthony Watson www.mountainsoftware.com www.watsondiy.com
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On 2014-06-20 4:27 PM, Alan Meyer wrote:

Normally we apply CertainTeed products, the felt paper works fine... they also sell a "DiamondDeck" synthetic crap but I've never needed it.
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