Roll roofing vs shingles lifespan

[Arky217]

I need to roof a 2000 sq. ft. shop economically. The roof is 5/12 pitch, plain roof, no valleys, dormers, etc.
I would be well satisfied if the roofing lasted 20 years.
My local hardware store has 20 year and 25 year rated fiberglass shingles.
They also have 90# roll roofing.
Even with a 6" overlap, the roll roofing is slightly less than half the price of the 20 year shingles, (also much faster and easier to apply).
My question is: What would be a realistic life expectancy of the shingles and of the roll roofing.
Also, if I go with the roll roofing, should I apply 15# felt under it as is commonly done with shingles ?

Thanks,
Arky

[Redoverfarm]

Not real sure what the life is on the rolled roofing.  You might scroll through this site and see if anything mentions it. These people have been in the buisness for years and i think i even bought some 30# from them before.  If not you might also check with Ownes Corning, Certainteed and others. Personally I would use felt under the rolled roofing.  It would probably prolong the life of the roofing.

http://www.johnsmanville.com/default.htm

[mvk]

Arky
I have a roll roof on part of my old house it's 30 years old. I have to fix or replace it but I got my money's worth. Most people don't like how they look, mine is about a 2/12 so you can't see it. I have coated it twice once with the silver coating and then last year with black stuff after taping all the seams. didn't hold .  Had it stopped leaking I would have coated it with silver again this summer.

I've seen shingles last that long too. Not sure why some roofs don't last. Oak leaves and pine needles in shade where moss and stuff grows seems to do them in in NH. I don't see the new shingles drying out and curling anymore?

Mike

[OldDog]

one word fix:

metal!