How do roofers measure your roof? Squares and pitch
Contractors measure your actual roof surface, not your home's footprint, and the difference is bigger than most people expect. Pitch, overhangs, and design features all add area, so a 2,000 square foot house carries meaningfully more than 2,000 square feet of roof. We measure in squares, where one square equals 100 square feet of roof surface. That number drives how much material gets ordered and how many hours the crew spends up there.
Pitch is the slope of your roof, written as a ratio like 6/12, meaning six inches of rise for every twelve inches of run. A 6/12 pitch is a moderate, walkable slope. Get much steeper than 8/12 and the job changes: harnesses, staging, slower movement, more careful material handling. All of that is labor, and labor is money. Here's something I tell every homeowner: your pitch will surprise you more than anything else on the invoice. A roof that looks "a little steep" from the street is often a lot steeper once you're standing on it.
Complexity stacks on top of pitch. Dormers, valleys, chimneys, and skylights all mean more cuts, more flashing work, and more time. A simple gable roof on a ranch house is the fastest, cheapest replacement there is. A house with six roof planes and two chimneys is a different job entirely, even at the same square footage.
One easy credibility check: ask your contractor to show you the roof measurement report. Reputable outfits use satellite-based measurement tools and can hand you the actual numbers. If someone prices your roof by eyeballing it from the driveway, that's a red flag.
How much does material choice move the number?
Material is the single biggest lever on your total, and the range is wide. Three-tab asphalt shingles sit at the bottom of the price ladder and give you the shortest lifespan. Architectural asphalt shingles cost a step more and last noticeably longer, which is why they're the workhorse choice for most homes around the Portland metro. Standing seam metal costs a multiple of asphalt, and slate and tile climb from there.
For most homeowners, architectural shingles offer the best cost per year of service. But the premium materials aren't a ripoff; they're a different bet. Slate costs several times what asphalt does upfront and can outlast two or three asphalt roofs. Whether that math works for you depends mostly on how long you plan to own the house.
Two things worth knowing about material pricing. First, shingle manufacturers adjust prices regularly, so a quote from last year may not hold; get current numbers in writing. Second, material is only part of the bill. Premium products like metal and tile also need specialized installation, so the labor line rises along with the material line. For a deeper walk through material trade-offs and the full project budget, see our roof replacement guide.
Where does the rest of the money go? Labor, permits, and disposal
Labor is the biggest single slice of a roof replacement, typically around half the total or more. That's why two quotes using the exact same shingle can differ by thousands of dollars: you're mostly comparing crews, not materials. Location matters too. The Portland metro is not a cheap labor market, so expect local pricing to run above what national averages suggest.
A few line items show up on nearly every legitimate estimate, and their absence should make you nervous.
- Permits: most jurisdictions around here require one for a full replacement, and your licensed contractor should be the one pulling it. Unpermitted work can void your homeowner's insurance and haunt you at resale.
- Tear-off and disposal: removing the old roof and hauling it away is real work and real dump fees. On a full-size roof it adds up to thousands, not hundreds.
- Underlayment and accessories: ice and water shield, synthetic underlayment, drip edge, ridge cap. You'll never see them in the finished roof, but they're required for a code-compliant, warrantied installation, and cheap substitutions here shorten your roof's life.
What hidden costs show up after tear-off?
The number on your initial quote is rarely the final number, and the difference usually lives under the old shingles. Knowing what can surface lets you budget calmly instead of panicking mid-project.
Decking is the big one. Your roof deck is the plywood or OSB under everything, and nobody knows its true condition until the tear-off exposes it. Rot and water damage have to be fixed before new shingles go down; there's no honest way around it. Budget a contingency of at least 10 percent for this, and ask your contractor upfront what they charge per sheet so there's no drama later.
Code upgrades are next. When a permit gets pulled, the new roof has to meet today's building code, not the code from when your house was built. That often means upgraded ventilation, ice and water shield in the valleys and eaves, and specific fastening patterns. It's not padding; it's the law, and it's good for your roof anyway.
Flashing should be replaced during a re-roof, not reused. Old, corroded flashing around chimneys and skylights is one of the most common leak sources, and reusing it to save a few dollars is how a new roof ends up leaking in year two. And if anyone offers to lay new shingles over your old ones to save money, understand the trade: an overlay is cheaper upfront, but it shortens the new roof's life and can void the manufacturer's warranty. There's a reason most reputable contractors won't do it.
How do you compare quotes without getting burned?
Get at least three itemized quotes, and insist on the itemized part. A quote that breaks out materials, labor, permits, disposal, and accessories tells you exactly what you're paying for. A single-line total is harder to compare and easier to pad. When one bid comes in far below the others, don't celebrate yet; ask what's missing. In my experience it's usually the permit, the decking contingency, or a plan to overlay instead of tear off.
Ask for the measurement report, build a 10 to 15 percent contingency for decking and code items, and check credentials before you sign anything. A manufacturer-certified contractor can offer extended warranties that a non-certified installer simply can't, which affects the long-term value of the whole investment.
And if you're not sure the roof even needs replacing yet, start smaller. A professional inspection or a repair buys some roofs several more good years. When you're ready for real numbers on your actual roof, you can get an estimate and see the math for yourself. Price matters, but a roof done poorly costs more in the long run than a fair price paid to someone who does it right the first time.