Shingle roof life expectancy?

The asphalt shingles on our home are approximately 20 years old. How do we determine how much life is left on our shingle roof without waiting for it to leak? I don't want to replace unnecessarily but also don't want to have major water damage. Thank you for your suggestions.
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Look for cracking, seperation, loss of the coating on them, Susan. If they become brittle it's time for a change. How much gravel do you notice in your gutters (if you have them?) This is coming off the shingles. Take a good look around the drip ledge at the ends of your roof. You should notice good square corners on the shingles. If they are rounded, you might be getting close.
Jim

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wrote (with possible editing):

What Jim said. I'd just like to add that shingles usually come with a manufacturer's designated life expectancy. I had older 20 year rated Bird asphalt shingles that were still fine after 27 years. We changed them only because we added an addition and were putting a new roof on that. Contrast that to the awful GAF fiberglass shingles that were put on an earlier addition. It had a rating of 25 years, but was leaking after 12 years. GAF had enough impediments so that we were never able to get anything out of the warranty. When we did the new roof, we went back to asphalt (IKO Chateau) with a 30 year rating.
-- Larry snipped-for-privacy@lmr.com

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And I'll point out that this is all highly climate dependent. For example, here in Phoenix AZ, 20 year rated singles rarely last much longer than 10 years, because they get the volatiles baked out of them (typical surface temperature for shingles in the Arizona sun can reach 180 degrees!) and turn brittle and crunchy, to the point where shingles can actually *explode* when the monsoon rains sweep in and splatter water onto those shingles. No kidding. And hey, we can fry eggs on our sidewalks in summertime too, and can make hot tea just by putting water and tea bags in a glass jar and setting it out on the sidewalk.
--
Eric Lee Green mailto: snipped-for-privacy@badtux.org


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Look for curled (cupping) shingles and bits and pieces of shingle on the ground, especially after a strong wind. Also if the grit rubs off under under your fingers.
Regards,
John
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