Repair or replace? How do we decide on a roof inspection?

The 30% rule, in real numbers

Most of the repairs we do fall in a typical range of $350 to $2,500. Most asphalt replacements run $6,500 to $18,000. The 30% rule is how we weigh one against the other: once a repair would cost more than about 30% of what a new roof on that house would cost, the money is better spent on the new roof.

An example: On a $6,500 roof, 30% is about $2,000. If you're quoted that much to patch a roof that's worn out everywhere, you'll likely be paying for the next patch soon after, and the one after that. If the same $2,000 fixes a chimney on a roof with plenty of life left, it's money well spent.

The rule is about the roof as a whole, not the leak. A cracked vent boot on a 10-year-old roof is an easy, low-end repair. The same money spent on a roof that's bald on every slope is buying a few months.

Age helps you guess where you are. Older three-tab shingles usually wear out in about 15 to 20 years around here, and architectural shingles in about 25 to 30, if the attic is properly vented. But age is only a guide. The condition of the shingles is what decides.

What we look at before we make the call

1. Where the problem is. One spot (a vent boot, a chimney, a few shingles off a ridge) points to a repair. Leaks in more than one place, or a new leak every season, points to a roof that is wearing out.
2. The shingles on every slope. We look for granules (the sandy coating) worn off, shingles curling, cupping or cracking, and tabs that lift in ordinary wind. If that is on one slope, it is a repair. If it is on every side of the house, it is not.
3. The flashing. The metal where the roof meets a chimney, a wall or a skylight. This is where most leaks start, and on its own it is a repair.
4. The attic. Stains on the underside of the roof boards, soft or delaminated decking, daylight around nails, or frost on nails in winter. Soft decking in more than one spot changes the answer.
5. How many layers. If there are already two layers on the roof, any replacement is a full tear-off, and that feeds into the price we compare the repair against.

Then we show you the photos, tell you which side of the 30% line you are on, and if you need work, you get a free written, line-item estimate. If the answer is a roof repair, we say so. If it is a roof replacement, we show you why.

Can you just put new shingles over the old ones?

Sometimes it's allowed, and it is cheaper up front because there's nothing to tear off and haul away. As our FAQ says, we rarely recommend it. Here is the honest trade-off:

• It hides the deck. Rotted plywood or boards stay under the new roof, and nobody sees them until they fail.
• It hides the flashing. Old flashing at chimneys and walls usually gets reused or patched over, and that is where most leaks start.
• No proper ice barrier at the eaves. The stick-down membrane that stops ice dam water belongs on the deck, not on top of old shingles.
• It adds weight and usually shortens the life of the new shingles. They're laid over a lumpy surface that holds heat.
• It makes the next roof cost more. Two layers to tear off is more labor and more dumpster weight. Many townships cap a roof at two layers, so the next one is a full tear-off either way; ask yours.

Where an overlay can make sense: (Question for Jim: is there any case where you would put a layer over the old one, for example one flat existing layer on a sound deck, or a house being sold soon, and do you ever do it)

So when you compare estimates, check the first line: tear-off to the deck, or a layer over the top? Two quotes for "a new roof" are not the same job if one leaves the old roof on.

What we see when we inspect roofs around here

Our most common good-news call is a cracked vent boot. On a roof that's 15 or 20 years old, the rubber collar around the plumbing vent cracks and drips into the bathroom ceiling. It looks alarming, it's one of the cheapest repairs there is, and it doesn't mean the roof is done.

The second is chimney flashing covered in thick black roof cement. Someone patched it instead of replacing it, and it held for a season or two. Proper new flashing is a repair, even on an older roof, as long as the shingles around it are sound.

The post-war Capes, ranchers and splits in Willow Grove, Hatboro and Warminster are mostly on their second or third roof, and plenty of them have two layers from a re-roof back in the '80s or '90s. When those start leaking in more than one spot, we usually find the bottom layer has been holding water against the deck, and that tips it to replacement. On the older homes in Ambler and Abington with board sheathing, we look harder in the attic before we make the call.

We also see the south and west slopes wear out first, because they take the most sun. A roof can look fine from the front yard and be bald on the back.

(Question for Jim: roughly how often a free inspection ends in "just repair it" versus "it is time to replace", and what most often tips it)

One roof we told to repair, and one we told to replace

(Question for Jim: two recent inspections you are comfortable publishing, one where you recommended a repair and one where you recommended replacing: town, house type, roof age, what you found, and the price or price range of each)

For what a full replacement involves, see the scope and photos from a roof replacement in Warminster.

Getting the call made on your roof

1. Do the ground check first. Walk around the house with binoculars. Look for granules in the gutters, curled or missing shingles, and anything lifted at the chimney. Then go in the attic on a dry day with a flashlight.
2. Write down what you know. Roof age if you have it, past repairs, and where and when you have seen water. It helps us more than you would think.
3. Book a free inspection. We check the roof and the attic and show you photos. See roof inspection for what we look at.
4. Get the answer in writing. A line-item estimate for the repair, or for the replacement, or both if you are close to the 30% line, so you can compare.

When you don't need a new roof (or us)

If your roof is under about 15 years old and you have one leak, you almost certainly need a repair, not a new roof. If a home inspector flagged "granule loss" on a roof that otherwise lies flat and doesn't leak, that's normal aging, not an emergency; keep an eye on it and have it looked at every year or two. And if the only problem is overflowing gutters or a stain that turned out to be a bathroom fan or a sweating pipe, the roof is fine and we'll tell you that.

Related questions

How much does a roof inspection cost?

Ours are free. We check the shingles, flashing, vents, gutters and the attic, and show you photos of what we find. If something needs work, you get a free written, line-item estimate.

Should I repair or replace my roof?

Repair it if the problem is in one area and the rest of the shingles still lie flat and hold their granules. Replace it if the shingles are worn out all over, it leaks in more than one place, or the deck is soft. Our rule of thumb: once a repair would cost more than about 30% of a new roof, put the money toward the new roof.

Is it cheaper to put new shingles over the old ones?

Yes, up front, but we rarely recommend it. A second layer hides rotted decking and failed flashing, adds weight, and usually shortens the life of the new shingles. Tearing off to the deck lets us see and fix what is underneath.

How old is too old to repair a roof?

There is no fixed age; condition decides. Older three-tab shingles usually wear out in about 15 to 20 years and architectural shingles in about 25 to 30. A roof near the end of that range with worn shingles on every slope is usually past the point where repairs make sense.

Will you tell me if I do not need a new roof?

Yes. If the roof only needs a small repair, or nothing at all, that is what we will tell you, with photos. Replacement only makes sense once a repair would cost more than about 30% of a new roof.