Underlayment choice


I am wondering when laying a lifetime shingle (i will be using CertainTeed Landmark Premium), what underlayment is generally used? Do most of you stick to a good 15# or make the upgrade to 30#? Synthetic? From my experience the synthetic is only practical when you have to be dried in for a long time without shingles, like on a big new construction job.


Never felt that felt made any difference. If the roof is right, underlay is moot.


felt is very important as it is the roofs last layer of defence against wind driven rain along with many other reasons. best to use an ASTM 30lb or 15. synthetics are new and not time tested.


[quote=“RooferJ”]felt is very important as it is the roofs last layer of defence against wind driven rain along with many other reasons. quote]

Got to make you wonder if you think about that. In Fla, the houses seem to all be covered with 3 tabs. Just think, every 6" across and 5" up, on the entire roof, a bare 2" headlap is protecting the whole roof.

A little tidbit to share here. At least 5 dimensional roofs I looked at last year leaked. Each leaked at a butt joint. The felt rotted out there by staying wet and each one, a large area of plywood rotted out too.

No felt, the leak would have been evident early and less damage.

Me. I have no butt-joints on my roof. Shame on me! I Dutch-Lapped the whole thing with Elk’s blessing. I seem to remember cutting all the wrinkles out of the felt whenever i found one…[/quote]


I prefer Roofers Select. It does lay flatter. And I can walk on it a whole lot better. Less fear of it ripping out under my feet.


I began using Gaf. Shingle Mate last year, and it lays so nice and flat that I can’t bring myself to go back to regular felt again…I also can say that if it gets wet, it is dry and flat in about 45 min. in the sun…
I normally rip 3 ft from the ridge on both sides, paper the ridge,and load the roof across the ridge on the 1st. day. Last year we had a passing thunder storm after I loaded 1,and it lasted for 2 days…when I got to the top of the roof(shingles were gone by this point)I lifted the paper to back slip the lower coarse of paper it was completely dry… This makes me feel secure in my choice of underlayment!
I began drying in all my jobs without fear of leaks from passing showers…(I always have tarps on hand anyway) I am no fool…


Hey Tinner. if you dutch lap GAF/ELK do you tell your custumers there is no warranty coverage with your installation method ? GAF will certainly not cover that kind of crazy work.


Yes. GAF,Elk said it was covered. Got a couple now near the beach areas. And a few others scattered around. Elk rep said, off the record, they prefer that. ( THey won’t put that in writing.)


BTW. I was with gweedo on this issue for years. Dutch lap looks horrible. So to speak.
In 30+ years of seeing all kinds of lapped shortcuts at walls, rakes, etc, i never saw a single leak caused by it. Never. It just looked so odd though. I wouldn’t do it on a 3-tab. Wouldn’t help them anyway. I’ve been seeing some mighty odd leaks on 3-tabs lately in the field areas. No holes. No damage. Just water migration. Lots in some areas. That’s why underlay is so important now. If I was using cardboard for my primary source of water proofing, I’d want underlay.

(Looks good on dimensiona shingles and gives them texture. I wouldn’t go over a doubled end. 2-layer part.)


im almost 100% GAF/ELK deck armour with no complaints and higher profits using it…[size=75]upsell[/size]