How do you know when it's time to re-roof?

Shingles are rated by years of life expectancy, as you know, by your question. As your home was built 15 years ago, the most common rating was twenty years for a spec home. Custom homes tended to be in the thirty year range. Not knowing the area of the country, where the home is located, or the presence of hail damage, the best answer is; How does it look? A certified home inspector can examine it and give you an informed view. Generally, they don’t have a dog in the fight, and will give you a straight answer.

I found out the hard way – leaks started around sky lights (notoriously hard to seal 20 years ago.) And when I looked at lower level roofs from the top floor windows, I could see cracks starting in the shingles.

The shingle life can also be based on the pitch of the roof and the location of the home. A steep pitched roof, say 12 12 would tend to last longer than a 12 6 roof line. Plus if you are in a predominantly dry locale add a few more years. Lots of variables. I for instance have a 12 12 roof and live in a very wet locale. The 40 year shingles on this roof are the equivalent of 50 year shingles.

And my 25 year shingles lasted 15 years. After a tremendous imbroglio with the manufacturers, I got free replacements but had to pay for installation. It took more energy than I could muster today.

If you wait for a leak, then you’ll likely have more damage under the roof that needs to be repaired. I would call three different roofers and have them all out to the house to give a recommendation on when to replace and a quote. That way you’ll know about what you’ll have to pay and when you’ll need to do it.

Your insurance company may be persuaded to kick in something on a replacement, if you have had any windstorm or hail events in the near past.

Just an idea – When you do reroof, that is the time to upgrade your attic ventilation. The cooler and drier your attic stays, the better.