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Lesson 3 of 3

The second roof
is the expensive one.

A roof is priced by the square and paid for by the year. The bid shows what the first roof costs. This page is about what the roof costs per year it keeps the water out, and it is written for the person funding the build as much as the person building it.

Run Your Numbers (615) 792-5156
The math the bid leaves out

Three costs that never make the spreadsheet.

The tear-off. The second roof does not go on an empty deck. The first one comes off, goes in a dumpster, and gets hauled away, and the deck gets repaired. That line is on every re-roof quote and on no new-construction bid.

The year it happens. A roof that lasts 20 years on a house you hold for 25 means a full re-roof on your watch, at year 20 prices, while the house is occupied. A roof that lasts 45 means the next owner's problem, and a listing that says so.

The bills in between. Insurance discounts for a Class 4 roof, a cooler attic under a reflective color, and the storm calls that do not happen. None of it is on the bid. Some of it is worth asking your agent about before you decide.

The question is not which roof is cheaper. It is what each roof costs per year it keeps the water out.

How to use this page

Bring two quotes. We do not put prices on the site.

Get a quote for the roof you are being told to buy and a quote for the one you would rather put on. Enter the price per square for each, the square count, and how long you expect to own the house. Then enter the service life you believe for each roof (the ranges are in the questions below), and what a tear-off and disposal costs per square in your county.

The calculator counts a replacement whenever a roof's life runs out inside your hold, charges the tear-off with it, and credits the unused life of whichever roof is still good when you sell. The result is what each roof costs over the hold, and per year of service.

It does not know which roofs you are comparing. It only knows arithmetic.

Cost Over Time

Two roofs, one house, your numbers.

Nothing you type here is sent anywhere. It runs in your browser.

The house

Roof A (the cheaper quote)

Roof B (the better quote)

Published ranges: 3-tab 15 to 20 years, architectural shingle 25 to 30, metal panel 40 to 60. Pick the number you would defend to a buyer.

Over 15 years

Roof A, day one
–
Roof A, replacements during the hold
–
Roof A, cost over the hold (net of unused life)
–
Roof A, per year of service
–
Roof B, day one
–
Roof B, replacements during the hold
–
Roof B, cost over the hold (net of unused life)
–
Roof B, per year of service
–
Difference on the bid
–
Difference over the hold
–

Fill in both quotes, both service lives, and the tear-off to see the comparison.

Cost over the hold = first roof, plus each replacement (new roof plus tear-off) that falls inside the hold, minus the value of the life left in the last roof when you sell (priced at that roof's installed cost). Per year of service = installed cost divided by service life.

Before You Price a Roof

Know what you are putting on the house.

Three short reads on shingles and metal. Written for the builder who has to answer to the money, and for the money.

Lesson 1 What you are paying for Gauge, substrate, coating, fastening, and cut length on metal. Layers, nail zone, and wind pattern on shingles. Each one you can check on a sample. Read it → Lesson 2 Read the spec sheet Coil tags, coating names, UL classes, wind ratings, and what "limited lifetime" means once you read the table. The words to look for in every roof warranty. Read it → Lesson 3 The second roof is the expensive one A roof is priced by the square and paid for by the year. Run your own two quotes against the years you will own the house. You are here

Frequently Asked

Roof cost over time, answered.

How long does a shingle roof last in Tennessee?
Longer in the shade than in the sun, and Tennessee has a lot of sun. Published service life for laminated architectural shingles is 25 to 30 years; 3-tab runs 15 to 20. Hot attics, poor ventilation, and south and west slopes shorten it. Most re-roofs we see come at 18 to 25 years. Metal panels are commonly rated for 40 to 60 years of service with the coating warranties to match, and the panel usually outlives the screws that hold it.
What does a tear-off cost when a roof is replaced?
It is the part of a second roof that is easy to forget. The old shingles have to come off, go in a dumpster, and be hauled away, and the deck gets inspected and patched before the new roof goes on. Ask a roofer for the tear-off and disposal line on a re-roof quote in your county and put that number in the calculator. A metal roof installed over the first shingle layer, where code allows it, can skip one tear-off entirely.
Does a metal roof lower insurance or energy bills?
Sometimes both, and it is worth asking before you buy rather than after. Many insurers discount for a documented Class 4 impact-rated roof, which includes most metal panels and impact-rated shingles. Light-colored metal with a high solar reflectance number keeps an attic cooler in summer, which shows up on the cooling bill in a Tennessee August. Neither is guaranteed; ask your agent and look at the SR number on the color chart.
Is a metal roof worth it on a house I am going to sell?
Run it with the hold period you actually expect. On a quick sale the extra cost is real and the long life belongs to the buyer, though buyers and inspectors notice a metal roof and it removes the "roof is 20 years old" objection. On a rental or anything you will hold long enough to face a re-roof, the second roof and its tear-off are yours, and the calculator on this page is built for that math.

Stop By the Desk

Let’s talk it through in person.

Bring your plans or just your questions. We’ll get you squared away.
119 Cumberland St, Ashland City. The coffee’s on.

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