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?
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.
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
One difference is the synthetics can go on over the roof sheathing and be l
there without shingles for a month or more. It's tuff, waterproof so wind
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
Also felt ain't what it used to be. Like so many other things, they've fig
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
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
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. :)
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