Roofing Estimate: Squares, Layers and Six Missing Lines

The word squares appears nowhere on it. The estimate says "Tear off existing roof and install new architectural shingles, labour and materials included," then a four-figure number. That is the whole scope. Nothing on the page says how big the roof is.

So the number is attached to nothing. Roofing is sold by the square, and until that quantity is on the page you cannot line the bid up against the next one, cannot check either against a measurement, and cannot tell whether a later change order is a surprise or a hole somebody left open.

So read the sheet along a chain instead: measured area, then quantity after pitch and waste, then money. Break it anywhere and the total stops meaning anything. Everything below is public documents held next to each other by somebody who holds no contractor's licence and inspects nothing. Code sections name the edition they were read in and the date they were read — 21 August 2026 — and nothing here is safe to treat as national, because a model code only governs where a jurisdiction adopted it and only in the form it was amended into.

The square, and the number that comes before it

A square is 100 square feet, and a bundle of shingles is a third of one. Hence Minneapolis setting its permit threshold at "less than one bundle of shingles (33 1/3 square feet of roof area)" in its re-roofing handout.

The trap is that the roof is bigger than the house. Roof area is the footprint underneath times a slope factor, and that factor is the square root of 1 plus (rise/12) squared.

Seven squares between the flattest and the steepest, on an identical house. Pitch does more than stretch the area: past 8/12 the crew cannot stand on the surface unaided, and at exactly 8/12 the ice barrier requirement changes. So a complete estimate carries three numbers, not one — roof area, the pitch (or predominant pitch), and the squares being priced after waste. If only one is on your page, the first question is which one it is.

What a waste percentage costs, in your own numbers

Aerial measurement made this checkable, because the report publishes the range itself. Open EagleView's sample Premium Report at the Report Summary page: 3,978 sq ft across 18 facets, predominant pitch 4/12. Then read the waste calculation table underneath.

Same roof, every row. 8.7 squares between the ends of that table. Multiply 8.7 by whatever your bid charges per square and you have the size of the disagreement, in your own currency, with no national average involved.

The instinct is to read the high row as padding. Usually it is not: that sample roof has 18 facets, 9 valleys and 14 hips, every one a cut that throws material away. The report's footnote adds that the table covers roof area only, and that "additional materials needed for ridge, hip, valley, and starter lengths are not included." So a bid built on 39.8 squares with separate hip-and-ridge and starter lines can be honest, and so can one built on 48.5 flat. What separates them is knowing which row the number came off.

If a report was ordered, ask for it; forwarding a PDF costs nothing. If none exists, take the footprint from the county assessor's record, multiply by the slope factor above, and see where the bid's squares land against it.

Layers move two prices at once

The 2021 IRC separates two jobs sold under one word. A roof replacement strips the existing layers to the deck. A roof recover lays new covering over old, and the code rules that out where the roof already carries two or more applications of any covering, where it is water soaked or deteriorated, or where the covering is slate, clay, cement or asbestos-cement tile. In the 2024 IRC the recover rules have been lifted into a section of their own, R908.4, with those three prohibitions listed as exceptions — same substance, different number to quote at the counter. Minneapolis puts the local version plainly: overlays over one existing layer, subject to those conditions and to the manufacturer's instructions.

On your bid the layer count moves two lines at once: tear-off labour rises per square with each layer, and the tonnage roughly doubles.

The tonnage is kitchen-table arithmetic. A construction-waste brochure for builders and solid-waste planners, Recycling Asphalt Roofing Shingles into Paving Materials, puts shingle roof replacement waste at "at least 2 to 5 pounds per square foot of roof area," varying with layers and shingle type. Apply that to 3,978 sq ft: one layer is near 4 to 10 tons.

Gate rates are public. Lycoming County, Pennsylvania publishes a 2026 landfill fee schedule effective 6 April 2026: construction and demolition waste at $55.00 per ton from a commercial hauling enterprise, $69.80 per ton for an individual resident, $30.00 minimum on every transaction — and a line at the foot of the block noting the rates apply to waste generated in counties that name this landfill in their solid waste plans, which is a reminder that even a gate rate has a catchment. At that gate one layer off that roof is roughly $220 to $550 in tipping fees alone, and a second layer doubles it, before container rental, hauling and loading. This is not your number and is not meant to be. It is the shape of the number: a rate per ton, a resident rate above the commercial one, and a floor on every transaction. Find your own county's schedule and the same three parts will be there. Which is why the layer count belongs on the estimate rather than in the crew's discovery on the first morning.

Decking is the line that has to carry a unit price

Nobody can see the deck until the old roof is off, which makes it the home of the worst sentence on a roofing bid: decking replacement as needed at market rate. Agreeing a unit price before signing costs nothing. The same conversation on a Tuesday morning with a stripped roof and rain forecast is a negotiation you will lose, and it arrives as a change order — the clause that reopens a fixed price. Four things make the line usable: panel thickness and type, the unit (per 4x8 sheet or per square foot), whether labour, fasteners and disposal sit inside it, and a count above which the contractor stops and telephones you.

The larger version of the question depends on what your house was built with. The Minneapolis handout notes that shingles must be fastened to solidly sheathed decks or nominal 1-inch boards, that many manufacturers refuse boards wider than 6 inches nominal because of splitting, and that many hold gaps between boards to 1/8 inch. On a house with plank decking, "replace a few sheets" becomes sheathing the whole roof — a different job with a different number. Ask for a photograph of each sheet replaced, too: the deck goes back under underlayment the same day.

Six lines that go missing

Drip edge, in feet. The 2021 IRC at R905.2.8.5 says a drip edge "shall be provided at eaves and rake edges of shingle roofs," and the sample report turns that sentence into a quantity: 328 feet. Local wording can lag badly here, and the Minneapolis handout is its own illustration of the problem. Its drip edge line reads "Drip edge is not required by code unless specifically required by the shingle manufacturer's installation instructions." Its body says it is written against the 2015 Minnesota Residential Code, which adopts and amends the 2012 IRC. It is stamped Last Updated 05/2016. And the header of all three of its pages tells you to "refer to the 2020 Minnesota Residential building code for all requirements and exceptions" — the document is directing readers past its own contents. Meanwhile Minnesota Rules 1309.0010 incorporates the 2018 IRC, which carries R905.2.8.5. Which sentence governs your job is for the inspector named on your permit. What is not in doubt is that a bid with 328 feet of metal on it and one without are not the same bid.

The ice barrier, with its extent stated. IRC R905.1.2 requires, where there is a history of ice forming along the eaves as designated in Table R301.2, an ice barrier running from the lowest edges of all roof surfaces to a point not less than 24 inches inside the exterior wall line, with a longer run on slopes of 8/12 and steeper. Read the measuring point twice: 24 inches inside the wall, so a deep overhang pushes the requirement past a single 36-inch roll and into a second course. Your estimate should say how many courses run at the eaves, and whether valleys and penetrations get the same.

Ventilation, and whose rule is being followed. IRC R806.2 sets minimum net free ventilating area at 1/150 of the vented space, reducible to 1/300 only on conditions. The shingle maker sets its own bar: GAF's application instructions for Timberline shingles (a dealer-hosted copy, revision 4/12 — pull the current one for your shingle) require 1 square foot per 150, "reduced to 1 sq. foot per 300 sq. feet" when vents are balanced between eaves and peak. And Minneapolis says re-roofing does not oblige an existing home to reach the new-construction figure at all. Three documents, three answers, and most estimates compress the lot into "install ridge vent." Ask for the intake number too: net free area is a pair, and a ridge vent with no soffit intake is decoration.

Flashing, itemised as replace or reuse. Step flashing at walls, valley metal, pipe boots by count, chimney counter-flashing, cricket, kick-out. Minneapolis is blunt: existing flashing "shall be replaced when rusted, damaged or deteriorated," and roofing tar "shall not be used in lieu of approved flashing." Quantities again — the sample report lists 39 feet of step flashing and 90 feet of valley.

Disposal, including where the container goes. Per ton, per container, or a flat allowance — and what changes if a second layer appears. Then the questions that become repair bills of their own: where the container sits, what goes under it, and who pays an overweight charge.

The permit, and which inspections it buys. Minneapolis again: "A building permit is required for all re-roofing work, except repairs involving less than one bundle of shingles." A final inspection is required, and "an underlayment and/or ice barrier inspection is not required." Read those two together: the items with the most hidden cost, the ice barrier and the deck, are exactly the ones no public official will look at. Hence photographs, written into the contract. Whoever signs it should be verified in the state licence database before a deposit moves, and if the permit line comes with an offer to leave it off, that discount has a term attached.

Three of those six — drip edge, the ice barrier and ventilation — are the ones a bid is most likely to move into a box marked Optional Upgrades, and the code and the shingle warranty answer differently for each. That is taken apart in its own piece, county tables and warranty clauses included, along with the three places to look up which edition and which amendments actually apply at your address. Every citation on this page rests on that question.

Ten questions, in this order

Ask by telephone if you like, but get the answers on a revised written estimate.

1. How many squares are you pricing, before or after waste, and at what waste percentage?
2. Where did the measurement come from — aerial report, tape, satellite? Can you email it?
3. What is the predominant pitch, and is any plane 8/12 or steeper?
4. How many layers are up there now, and how do you know?
5. Is disposal per ton, per container, or a flat allowance, and what changes with a second layer?
6. Decking: price per sheet, what thickness, labour and disposal included, and at how many sheets do you call me?
7. How many feet of drip edge, eaves and rakes, in what metal?
8. How far up from the eave does the ice barrier run, and does it go into the valleys?
9. Which flashing is replaced and which reused — step, valley, boots, chimney?
10. Who pulls the permit, which inspections apply here, and will you photograph the deck and the ice barrier before they are covered?

Nine of the ten answers are numbers. A contractor willing to put numbers on paper has told you most of what you wanted to know, and once two estimates carry the same ten answers, the gap between their totals describes something real.