If your 20-year-old roof is builder-grade 3-tab shingles, the honest answer is yes — replace it. In Michigan, 3-tab roofs realistically last 15 to 20 years — the top of the 15-to-25 range national guides quote rarely survives our winters — so at 20 yours is at or past the end even if it isn't leaking yet. If it's an architectural (dimensional) shingle roof, you may have 5 to 8 good years left — but only if it passes the specific checks below.
Why the Michigan discount? Southeast Michigan crosses the freezing line dozens of times each winter, and every freeze-thaw cycle lets water work into small gaps, expand, and pry at shingles, sealant, and flashing. Add ice dams at the eaves and attics that bake shingles from below in summer, and a roof here ages faster than the same roof in a milder state. Age sets the odds, though — condition gives the verdict. Here's how to read yours.
How do I check my 20-year-old roof without climbing on it?
You can learn most of what you need in twenty minutes with binoculars — or a phone camera zoomed in — and a flashlight. Start outside, from the ground, and walk the whole house looking for:
- Curling or cupping shingles — edges turning up or centers dishing mean the asphalt has dried out and lost its flex.
- Cracked, broken, or missing shingles, especially if more show up after every windy day.
- Bald or shiny patches where the granules have worn away and black asphalt shows through.
- Granules collecting in gutters or piling up below downspouts — a roof sheds heavily in its final years.
- Dark moss or algae streaks, which hold moisture against the shingles through every freeze.
- A wavy or sagging ridge line, which can mean soft decking underneath.
Then check the attic on a bright day with the lights off:
- Daylight showing through the roof boards anywhere.
- Brown water stains on the decking or rafters, especially near valleys, chimneys, and vent pipes.
- Insulation that's damp, matted, or crusted — old leaks leave a trail even when it's dry.
- In winter, frost on the underside of the decking or rusty nail heads — moisture is getting where it shouldn't.
Scoring it honestly: one or two mild ground-level signs on an architectural roof means watch it and re-check each spring. Two or more — or a roof that started life as 3-tab — means you're in the replacement window. Anything in the attic, or any sag, means get a professional inspection now, because water is already finding its way in.
Should I repair a 20-year-old roof or replace it?
Run the math before you patch. A small, isolated fix — a few wind-lifted shingles, a resealed pipe boot — for a few hundred dollars is reasonable on any roof. But once a repair estimate on a 20-year-old roof climbs past $1,500 to $2,000, it rarely pays off. You're buying maybe two or three years on shingles that are failing everywhere at once — $650 to $1,000 per year of borrowed time — and the next leak usually shows up somewhere the repair didn't touch.
Compare that to replacement. A typical 1,600-square-foot metro Detroit roof replaced with Owens Corning Duration architectural shingles runs roughly $9,700 to $11,100 all-in. Spread over the 20-plus years a properly installed architectural roof should deliver here, that's in the neighborhood of $450 to $550 a year — with a warranty behind it instead of crossed fingers.
One situation flips the calculus: selling within the next two years. Buyers' inspectors flag 20-year-old roofs almost automatically, and the result is usually a price concession, a repair credit, or a buyer's insurer requiring replacement before closing. A new roof with a transferable warranty removes the objection entirely — and you choose the contractor and the price instead of negotiating under deadline pressure.
What will my insurance company do about a 20-year-old roof?
This is the part that catches homeowners off guard. Across the industry, carriers have tightened up on roof age, and Michigan homeowners are seeing it at renewal. Many insurers now require an inspection before writing or renewing coverage on a roof older than 15 to 20 years. Many switch older roofs from replacement-cost coverage to actual cash value, meaning any future claim pays out minus depreciation — which on a 20-year-old roof can leave you covering most of a replacement yourself. Some carriers have added roof payment schedules that pay as little as 20 to 40 percent of replacement cost once a roof passes the 15-to-20-year mark, and some decline to renew around year 20 unless the roof passes inspection.
Before your next renewal, ask your agent three questions: Is my roof covered at replacement cost or actual cash value? Is there a roof age threshold or payment schedule on my policy? And would a class 4 impact-rated shingle like Owens Corning's Duration FLEX earn a discount? Sometimes the answers alone settle the replace-now-or-wait question.
Signs you can wait a few more years
Not every 20-year-old roof needs replacing this season, and we'd rather tell you that than sell you a roof. You can likely wait if:
- The shingles are architectural, lying flat, with edges still sealed down.
- Granule loss is minimal — no bald patches, only a light dusting in the gutters.
- The attic is clean: no stains, no daylight, dry insulation.
- It's a single layer over sound decking, with balanced soffit-and-ridge ventilation.
- Your area hasn't taken a major hail or wind event since it was installed.
If that describes your roof, put it on an annual schedule: a ground check every spring, clean gutters, and a look in the attic after the first hard thaw. And start budgeting anyway — at 20 years, the question is when, not if.
Frequently asked questions
Q: How do I find out how old my roof actually is?
Check your closing documents or the seller's disclosure, ask your city for past roofing permits, or ask longtime neighbors — subdivisions often reroof in waves. Failing that, a roofer can estimate age from shingle style and condition during a free inspection.
Q: Can I just put new shingles over the old layer?
Michigan code generally allows up to two layers, but a layover traps heat, ages faster, hides the condition of the decking, and can limit your warranty — we recommend a full tear-off. If your roof already has two layers, tear-off is required, and removing the second layer adds about $750 to a typical replacement.
Q: What does a replacement actually cost?
For a typical 1,600-square-foot metro Detroit roof with Owens Corning Duration shingles, plan on roughly $9,700 to $11,100 installed. Duration FLEX runs about 10 percent more, larger or more complex roofs scale up from there, and new seamless gutters add about $12 per linear foot.
If your roof just turned 20 and you'd rather know than guess, Guthix Roofing — a licensed and insured Michigan builder (License #262600716) based in Wyandotte, serving Wayne, Oakland, Macomb, Washtenaw, and Monroe counties — will give you a straight answer. Our instant quote tool measures your roof from satellite imagery in about a minute, and every number is confirmed with a free on-site inspection before anything is final. If the honest answer is that your roof has five more years, that's what we'll tell you. Questions first? Call (734) 360-0805.
