A common leaky area


The bottem of this valley needs at least 2 ply of asphalt saturated underlayment.

Those of you that think Synthetic is appropriate here are in for a very rude awakening in the future.


why is that?are you using your underlay as water proofing?



Those who say underlayment is unnecesary after the installation of shingles are fools.



i think Synthetic underlay (GAF DeckArmor is what I use) is more than appropriate here AND is way better than asphalt saturated granular “ice & water” garbage that everyone uses, to cut costs (by not using Grace. But even grace is not good enough.

Deck Armor is 5 feet of continuous coverage, that DOES NOT trap moisture like most synthetics. And I’ve been installing roofs in MA for 13 years, and ALWAYS use DeckArmor … and no rude awakening (just) yet!

The last pic is my own roof - so I put my money in the right places.

I do install metal only though - so a lot fewer nail holes and a much better roof - so no problems that you would normally face with asphalt shingles and ice dams / etc.


This is all the proof i need.
These pics are from one of my own roofs when i wanted to believe in synthetic.
Two month old roof.
Gaf Tiger paw on a 7/12.


Also multiple reports of leaking from other local roofers using much cheaper synthetic.
Roofers reporting leaks even while installing
Two plys of synthetic.

I wanted to believe in Synthetic also!!!
The real benefits to the installer are huge!!
More coverage, Super light, install super fast, no wrinkling…


Perhaps the old nails contributed to the end result?


Those were new nails.


Did super sorry owens corning DURATION shingles also contribute?
They sure did.


@roof_lover Tiger Paw is not breathable - it traps moisture, causing plywood rot … it creates a greenhouse effect inside your roof… DeckArmor is breathable - means all moisture from attic can escape (albeit slowly) …

I am ALWAYS against all other types of synthetic underlayments.

Like I said - in 13 years of installing DeckArmor I have no problems with it.

PS - this is NOT a sales pitch for GAF … it just so happens that deck armor is the cheapest breathable synthetic… the “green” breathable underlay is like 2 times more expensive


Does o.c. still have a solid tar strip in your area? In my area there were people reporting problems with them back when they did, but they changed them roughly 5 years ago. (It does look like a spotted tar strip from your pics though).


I bet the fascia wasn’t flashed. Underlay isn’t the roof, it’s a backup.


Underlayment IS part of the roofing system for sure.
Man shall not live by shingle alone.
Unless he just never keeps the same phone number.


No facial flashing here.
Decking, underlayment and shingles slide at least one foot under this rake rafter.


I remember thinking one ply of saturated asphalt underlayment would be enough to water-tight the Bottem of a valley.
It might be if it is not shaded.


First off, Wow 13 whole years! Congratulations old timer!
Second, all synthetic is garbage as far as waterproofing is concerned. The benefits are resistance to UV rays in the hot season. This is due to lack of asphalt. The drawback is due to the same thing, lack of asphalt means no seal around plastic caps. Underlayment for comp roofs is only meaningful until shingles are installed. Anyone who thinks otherwise check Canadian applications.


Those photos are of a field area on a 7/12 with OC Duration over Gaf ulay, in florida?

Was the whole roof showing similar moist areas around the shingle nails?

What time of year were these photos taken?


Excellent question!!!
You know your stuff!!!

Yes, it was in wide open field
But it was installed in dec in florida
(Still hot)
Pics taken in feb.
This did happen on a section during that part of the year where the Sun didnt rise high enough to really ever hit it.

I am taking these conditions into consideration.
It really does educate me on what these products would do on lower slopes and slopes constantly shaded by tree cover.


The owenscor i g duration shingle fails
Because the sure-nail strip is only double thickness on the lower portion of the sure-nail area.
The upper half is only single thickness.
The nails get driven too deep .
This whole area is a water trough.
Owens corning made this nailing area lower than the rest of the shingle making it a water trough.
Water gets under this fibrous Strip and traps it and keeps it from evaperating.
Exact thing that happened with the last generation of Durations.
I hope Owenscorning will delete this line of shingles immediately!!!
And if it wasnt for synthetic teaching me how un-waterproofing it really is, i wouldnt have learned how sorry durations really are!!


Wow, so do you figure that is driven rain getting up under the lap? Or heavy flows getting in at the sidelaps?

I am not surprised (at all) to see moisture penetrate that underlay, but I would not expect there to be so much getting through the shingle. I agree about that nail strip on the durations (never understood why they did not granulate this, unless it is to get around Malarky’s “Zone” patent), but this is worse than I would expect…