For homeowners and property owners holding two or more proposals

Three roofing quotes are usually three different projects.

Steep-slope residential · replacement and re-roof proposals

A price is only comparable to another price when both describe the same work. Almost none of them do, and the gap between them is where the second bill comes from.

30-second answer

How do I compare three roofing quotes?

Normalize scope before you compare price. Write the same line items down one page — measured area and how it was derived, layers removed, deck allowance quantity and unit price, underlayment and ice barrier, flashing replaced or reused, ventilation, disposal, permit, warranty, payment schedule, exclusions — and fill in what each proposal actually says. Compare the blanks first.

Safety first

Nothing on this page requires you to go up on the roof or into the attic to check what a bidder told you.

Everything a proposal claims can be checked from the ground, from a window, from photographs the bidder took, or by asking the bidder to write the claim down. Falls are the leading cause of death for workers in residential construction, and those workers are trained and equipped. Verification is a paperwork exercise. Keep it one.

Urgency is also the most common sales instrument in this trade. A real emergency is a hazard you can observe — active water intrusion, a sagging ceiling, missing covering after a storm. A discount that expires tonight is not one.

If a bidder has told you the roof or ceiling may be about to give way, or if water is running from or near a light, a fan, or an electrical panel: leave the area, keep people out from under it, and call your electric utility or 911. That is not a bid-comparison problem, and it does not wait for a third quote.

Learning paths and saved lessons

At a glance

The short versionSection link

Every figure on this page is arithmetic or a scope statement. This page publishes no cost range, no price per square, and no service-life number.

What you are actually comparing: Scope. Price is the output.Two proposals for the same address routinely describe two different projects. The price difference is usually the scope difference, and it is usually recoverable in writing before anyone signs.
Scope dimensions on this page: 15, each with its own reference row and worksheet lineArea and its derivation, waste, layers, deck allowance, deck re-fastening, underlayment, ice barrier, flashing, ventilation, penetrations, disposal, permit, product and assembly, warranty, and payment and exclusions.
The most common hidden divergence: Deck replacementAn allowance needs both a unit price and an included quantity. A unit price alone caps nothing; a quantity alone prices nothing. This single line moves more final bills than any other.
The unit that makes areas comparable: Roofing squares of roof surface, with waste shown separatelyOne square is 100 sq ft. Order area includes a waste allowance for cuts and is a larger number for the same roof — comparing one bidder's surface area against another's order area is the most common false comparison in roofing.
What a blank means: Not “included”A silent line item is a decision that has been moved from the contract to the crew on the day, or to a change order after tear-off.
What a low bid usually is: A smaller project, not a cheaper contractorThe NRCA's own consumer guidance puts it as “Keep a healthy skepticism about the lowest bid… Price is only one criterion for selecting a roofing contractor.” This page assumes good faith and looks for the missing scope first.
Number of bids worth gathering: Enough to see the spread, few enough to normalize properlyTwo proposals cannot tell you which one is unusual. Six will not be normalized, because nobody does this fifteen times. Three is the number most people can actually finish.

Tradeoffs

This page's advice — normalize scope before price — and where it is wrongSection link

The position here is that a written, itemized, like-for-like scope comparison beats a price comparison. That is not universally true, and pushed too far it does real damage.

Best when

You have two or more proposals with a meaningful spread and no obvious reason for it.
The proposals are one page each and mostly consist of a brand name and a number.
The house has known unknowns — an old roof, a suspected second layer, a soft spot, an unvented or partly vented attic, a chimney.
Someone has quoted a price per square, because a per-square price is meaningless until the two areas are on the same basis.
An insurance scope is involved, because an insurer's scope and a full replacement scope are two different documents and the gap between them is yours.

Think twice if

You are using the worksheet to force every bidder into your template. Good contractors write scope in their own language, and a competent proposal that answers a question differently is not a worse proposal.
You are normalizing upward to the most expensive bid without deciding whether you actually want that scope. Adding a ventilation change to Bid A because Bid C had one is not a comparison — it is a purchase.
The spread is small and the difference between the bidders is who will still be trading in six years. Normalization cannot measure that, and past a point it is a way of avoiding the harder judgement.
The building is a rowhouse, an addition, or anything low-slope, where the assembly rather than the line items is the real question and a shingle worksheet will mislead you.
You are treating unpriced items as free. A blank is an unbounded exposure, not a zero, and the arithmetic on this page deliberately refuses to fill one in.

What changes the answer

Who is paying. An insurance-funded scope, a lender-funded scope, and cash change which line items are even negotiable.
What your jurisdiction requires at a re-roof — ice barrier, deck re-fastening, permits, inspections — because a bid that omits a required item is not cheaper, it is incomplete.
Whether any bidder is proposing a recover rather than a tear-off. That is a different project and cannot be normalized against a tear-off at all.
The age of the building. Pre-1978 painted surfaces bring federal lead-safe work practice requirements into scope; pre-1990 shingles, felts, and mastics may contain asbestos, which is a testing question before it is a roofing one.
How long each proposal is held open. Material and labour prices move, and a quote from four months ago is not comparable to one from this week even if the scope matches exactly.
Whether you can get the bidders to re-quote against a normalized scope. That is usually a better use of the worksheet than adjusting their numbers yourself.

The mechanism

The price difference is usually a scope differenceSection link

This is the whole idea. Everything below is an application of it.

Nine scope items on one roof, against three proposals. The cells are not a judgement about the bidders — a cell is empty only because the proposal does not say. Every cell is repeated in words in the reference table below, and the arithmetic consequence is worked in full in “A worked normalization”.Original diagram, Understanding Roofing.

A roofing proposal is a description of a project with a number at the bottom. Most homeowners read it in the opposite order, and the number is the only part of the document that is directly comparable to the other two. That is the trap: the number is comparable, but it is not measuring the same thing.

A re-roof is not one job. It is a stack of separable decisions — how much of the old roof comes off, what happens to the wood underneath, what goes down before the covering, which of the sheet-metal details get replaced, whether the attic’s air path changes, who hauls the debris away, and who stands in front of the building inspector. Each of those is a line a contractor either carries in the price, excludes, or leaves out of the document altogether.

Three estimators walking the same roof will make different assumptions about every one of them, and they will not tell you which assumptions they made unless the proposal makes them write it down. The National Roofing Contractors Association’s consumer guidance says the same thing from the trade’s side: “Insist on a written proposal and look for complete descriptions of the work and specifications, as well as start and completion dates and payment procedures.”

Assume good faith and look for the missing line

It is worth being precise about what a cheap bid usually is. In the great majority of cases it is not dishonesty; it is a smaller project. The bidder assumed one layer instead of two, assumed the deck was sound, planned to reuse the step flashing, left the existing vents alone, and did not carry a permit fee. Every one of those is a defensible professional judgement. None of them is visible in a price.

That is why the useful question is never “why is this one so cheap?” It is “what is in the expensive one that is not in this one, and do I want it?” Sometimes the answer is that you do not — the expensive bid included a ventilation change you have no evidence you need. Sometimes the answer is that the cheap bid has moved a decision from today, when you have three bidders competing, to the fourth morning of the job, when you have one crew, an open roof, and no leverage at all.

Normalization has one honest failure mode

Some things genuinely cannot be normalized. Where a bidder has not priced something, the correct entry is not a guess — it is the word “unpriced”, carried through the arithmetic as an unbounded exposure. A worksheet that quietly fills those in with the other bidders’ numbers produces a tidy table and a false conclusion. The bid with the blanks is not the bid with the average cost of the blanks. It is the bid where you find out later.

The reference

The 15 dimensions that make two roofing bids incomparableSection link

Read the fourth column first. It is the one that tells you what you are actually holding when a row is blank.

The 15 scope dimensions on which two proposals for the same roof routinely diverge, what a defined answer contains, and what silence usually means.
Scope dimension	What to write down for each bid	What a defined answer looks like	What silence usually means
1 · Measured roof area, and how it was derived	Roof surface area in squares, and whether it came from a field measurement, an aerial report, or plans.	A number in roofing squares of roof surface, with the derivation named: measured on the roof, taken from an aerial imagery report, or scaled from drawings. Complex planes, dormers, porches, and detached structures are listed or excluded by name.	Different bidders measured different roofs. Aerial reports estimate pitch from imagery and can miss a low porch, a dormer face, or a plane hidden under a tree. Until the areas agree, a price-per-square comparison is arithmetic performed on two different buildings.
2 · Waste factor and order quantity	Roof surface area and ordered area shown as two separate numbers, with the waste percentage stated.	“26.4 squares of roof surface; 29.6 squares ordered at 12 percent waste.” The waste factor is a material-ordering allowance for cuts at hips, valleys, and rakes — not extra roof.	One proposal quotes surface area and another quotes order area, and the second looks larger for the same building. This single confusion produces more false price-per-square comparisons than any other line on the page.
3 · Tear-off — how many layers are coming off	The number of existing layers to be removed, and the unit price if another one is found underneath.	“Remove all existing roofing down to the deck; one layer assumed; additional layers at a stated price per square.” The Department of Energy’s Building America Solution Center describes the baseline practice for an asphalt re-roof plainly: “Remove all existing roofing (shingles and underlayment) and replace any damaged wood sheathing.”	A second layer is discovered on the morning of the tear-off and priced while your roof is open. It is also worth knowing whether any bidder is proposing a recover — going over the existing covering rather than removing it — because that is a materially different project with its own code limits.
4 · Deck replacement allowance	The unit price per sheet or per board foot AND the quantity already carried in the price. Both numbers, not one.	“Six sheets of 7/16 in OSB included at $— per sheet; additional sheets at the same rate; unused sheets credited.” That is an allowance with a unit price and a quantity, so both parties already know what happens when the real number differs.	The most common hidden divergence in residential roofing. A unit price with no included quantity is not an allowance — it is a rate card for a change order you have not agreed to yet. A quantity with no unit price is worse: it caps nothing.
5 · Deck re-fastening	Whether existing sheathing is being re-nailed or re-screwed, and to what pattern.	Named as its own line, with a fastener and a spacing. BASC’s asphalt shingle guidance includes it in the re-roof sequence: “Inspect the roof deck attachment fasteners and re-nail as required to meet current requirements for nail type, size, and spacing.”	Usually that it is not happening. Some jurisdictions require deck re-fastening at a re-roof and some do not; where it is required, a bid that omits it is cheaper because it is smaller, and the inspector decides the rest.
6 · Underlayment	The underlayment product by name, and where each type is used if more than one appears.	A named product and its placement — field, valleys, penetrations, low-slope transitions. Underlayment is the secondary drainage plane under the covering, and the model code sets different applications for different slopes and coverings.	You are comparing an unknown against an unknown. It also hides slope problems: the 2024 IRC model text permits asphalt shingles only on slopes of 2:12 and steeper, and the underlayment application changes below 4:12.
7 · Ice barrier extent	Whether a self-adhered ice barrier is included, and how far up the roof it runs from each eave.	An ice barrier named as a product, with an extent in feet or courses, and with the jurisdiction’s requirement cited rather than assumed. Valleys, low-slope transitions, and wall intersections are stated separately from eaves.	In a cold climate, one bid may carry several hundred square feet of self-adhered membrane the other does not. Whether it is required at your address — and how far it must run — is set by your jurisdiction’s adopted code edition, its amendments, and its climate designation. There is no universal rule and no number on this page is one.
8 · Flashing — replaced or reused, location by location	New or reused, stated separately for drip edge, valleys, step, apron, chimney, skylight, and pipe boots.	A list, not an adjective. “New step flashing, new valley metal, new drip edge at eaves and rakes, new pipe boots, existing chimney counterflashing retained” is scope. Flashing is where roofs actually leak, and BASC’s re-roof sequence includes replacing flashing “around penetrations, at valleys, and at any roof-wall intersections as needed.”	Reuse. Reusing sound flashing is legitimate and common; reusing rusted or deformed flashing is not, and adopted reroofing text restricts it. A proposal that never mentions flashing has quietly transferred that decision to the crew on the day.
9 · Ventilation change	What exists now, what changes, and what happens on the intake side — not only the exhaust side.	Both halves. Exhaust and intake are quantified in net free area, which BASC defines as “the clear open area of a vent, taking into account the restrictions of the vent screening itself and the dimensions of the vent slots.” Most screened vents deliver about 60 percent of their gross opening.	Ridge vent gets added, intake does not, and the assembly is now pulling make-up air from the house. A bid that adds exhaust without adding intake is a smaller job than one that opens soffits, and the difference does not show up in the price line.
10 · Penetrations, accessories, and adjacent work	Pipe boots, vents, satellite and solar mounts, gutters, fascia, soffit, and anything being detached and reset.	Counted and itemized. “Seven pipe boots replaced; two turtle vents removed and decked over; satellite dish detached and reset; gutters not in scope.”	These are the classic mid-project additions. They are also where two bids diverge invisibly: one carries the solar array detach-and-reset and one assumes your solar installer will do it.
11 · Disposal	Container, haul-away, tonnage assumed, who pays overages, and where the debris goes.	Included with a stated basis, or excluded in writing. Roofing tear-off is a real waste stream: EPA reports that 600 million tons of construction and demolition debris were generated in the United States in 2018, with asphalt shingles named among the materials.	Occasionally that the homeowner is expected to provide the container. More often that the tonnage assumption is the bidder’s, and a second layer of shingles roughly doubles it.
12 · Permit and inspections	Who pulls the permit, who pays the fee, and which inspections are included in the price.	Named responsibility and named cost treatment — included, or a pass-through at cost. Whether a re-roof needs a permit at all, and what is inspected, is a local determination.	Either the fee arrives later as an extra, or nobody is pulling one. A contractor asking the homeowner to pull the permit is asking the homeowner to be the responsible party on the application.
13 · The product and the assembly, not the brand	The specific covering product, the starter and ridge products, the fastener and its pattern, and any rating being claimed.	A product line and colour, the starter course and hip-and-ridge products by name, the fastener pattern, and — where a fire, wind, or impact classification is being claimed — the tested assembly it belongs to rather than the shingle alone.	“Architectural shingles” is a category, not a product. Two bids naming the same brand can still specify different lines, different starters, and different nailing, and only one of them may match the assembly whose classification is being advertised.
14 · Warranty terms	Manufacturer document, workmanship term, registration deadline, transferability, and what voids each.	The actual documents, or their names and lengths, with the registration step and deadline stated. A workmanship warranty and a manufacturer’s product warranty cover different failures and are enforced against different companies.	A headline number on a proposal is usually a manufacturer’s product term, most of which may be prorated. It says nothing about who returns your call in year six.
15 · Payment schedule, closeout, and exclusions	Deposit, progress payments, the final-payment trigger, closeout documents, and the written exclusions list.	A schedule tied to events rather than dates, a final payment tied to completion and documentation, and an explicit exclusions list. Exclusions are the most useful paragraph in a proposal, because they are the only place a bidder writes down what they are not doing.	An unstated exclusions list is an exclusions list you discover later. Deposit, cancellation, lien, and payment terms are also governed by the law where the property is, which varies substantially and which this page cannot tell you.

Read this table one item at a time

1 · Measured roof area, and how it was derived

What to write down for each bid: Roof surface area in squares, and whether it came from a field measurement, an aerial report, or plans.
What a defined answer looks like: A number in roofing squares of roof surface, with the derivation named: measured on the roof, taken from an aerial imagery report, or scaled from drawings. Complex planes, dormers, porches, and detached structures are listed or excluded by name.
What silence usually means: Different bidders measured different roofs. Aerial reports estimate pitch from imagery and can miss a low porch, a dormer face, or a plane hidden under a tree. Until the areas agree, a price-per-square comparison is arithmetic performed on two different buildings.

2 · Waste factor and order quantity

What to write down for each bid: Roof surface area and ordered area shown as two separate numbers, with the waste percentage stated.
What a defined answer looks like: “26.4 squares of roof surface; 29.6 squares ordered at 12 percent waste.” The waste factor is a material-ordering allowance for cuts at hips, valleys, and rakes — not extra roof.
What silence usually means: One proposal quotes surface area and another quotes order area, and the second looks larger for the same building. This single confusion produces more false price-per-square comparisons than any other line on the page.

3 · Tear-off — how many layers are coming off

What to write down for each bid: The number of existing layers to be removed, and the unit price if another one is found underneath.
What a defined answer looks like: “Remove all existing roofing down to the deck; one layer assumed; additional layers at a stated price per square.” The Department of Energy’s Building America Solution Center describes the baseline practice for an asphalt re-roof plainly: “Remove all existing roofing (shingles and underlayment) and replace any damaged wood sheathing.”
What silence usually means: A second layer is discovered on the morning of the tear-off and priced while your roof is open. It is also worth knowing whether any bidder is proposing a recover — going over the existing covering rather than removing it — because that is a materially different project with its own code limits.

4 · Deck replacement allowance

What to write down for each bid: The unit price per sheet or per board foot AND the quantity already carried in the price. Both numbers, not one.
What a defined answer looks like: “Six sheets of 7/16 in OSB included at $— per sheet; additional sheets at the same rate; unused sheets credited.” That is an allowance with a unit price and a quantity, so both parties already know what happens when the real number differs.
What silence usually means: The most common hidden divergence in residential roofing. A unit price with no included quantity is not an allowance — it is a rate card for a change order you have not agreed to yet. A quantity with no unit price is worse: it caps nothing.

5 · Deck re-fastening

What to write down for each bid: Whether existing sheathing is being re-nailed or re-screwed, and to what pattern.
What a defined answer looks like: Named as its own line, with a fastener and a spacing. BASC’s asphalt shingle guidance includes it in the re-roof sequence: “Inspect the roof deck attachment fasteners and re-nail as required to meet current requirements for nail type, size, and spacing.”
What silence usually means: Usually that it is not happening. Some jurisdictions require deck re-fastening at a re-roof and some do not; where it is required, a bid that omits it is cheaper because it is smaller, and the inspector decides the rest.

6 · Underlayment

What to write down for each bid: The underlayment product by name, and where each type is used if more than one appears.
What a defined answer looks like: A named product and its placement — field, valleys, penetrations, low-slope transitions. Underlayment is the secondary drainage plane under the covering, and the model code sets different applications for different slopes and coverings.
What silence usually means: You are comparing an unknown against an unknown. It also hides slope problems: the 2024 IRC model text permits asphalt shingles only on slopes of 2:12 and steeper, and the underlayment application changes below 4:12.

7 · Ice barrier extent

What to write down for each bid: Whether a self-adhered ice barrier is included, and how far up the roof it runs from each eave.
What a defined answer looks like: An ice barrier named as a product, with an extent in feet or courses, and with the jurisdiction’s requirement cited rather than assumed. Valleys, low-slope transitions, and wall intersections are stated separately from eaves.
What silence usually means: In a cold climate, one bid may carry several hundred square feet of self-adhered membrane the other does not. Whether it is required at your address — and how far it must run — is set by your jurisdiction’s adopted code edition, its amendments, and its climate designation. There is no universal rule and no number on this page is one.

8 · Flashing — replaced or reused, location by location

What to write down for each bid: New or reused, stated separately for drip edge, valleys, step, apron, chimney, skylight, and pipe boots.
What a defined answer looks like: A list, not an adjective. “New step flashing, new valley metal, new drip edge at eaves and rakes, new pipe boots, existing chimney counterflashing retained” is scope. Flashing is where roofs actually leak, and BASC’s re-roof sequence includes replacing flashing “around penetrations, at valleys, and at any roof-wall intersections as needed.”
What silence usually means: Reuse. Reusing sound flashing is legitimate and common; reusing rusted or deformed flashing is not, and adopted reroofing text restricts it. A proposal that never mentions flashing has quietly transferred that decision to the crew on the day.

9 · Ventilation change

What to write down for each bid: What exists now, what changes, and what happens on the intake side — not only the exhaust side.
What a defined answer looks like: Both halves. Exhaust and intake are quantified in net free area, which BASC defines as “the clear open area of a vent, taking into account the restrictions of the vent screening itself and the dimensions of the vent slots.” Most screened vents deliver about 60 percent of their gross opening.
What silence usually means: Ridge vent gets added, intake does not, and the assembly is now pulling make-up air from the house. A bid that adds exhaust without adding intake is a smaller job than one that opens soffits, and the difference does not show up in the price line.

10 · Penetrations, accessories, and adjacent work

What to write down for each bid: Pipe boots, vents, satellite and solar mounts, gutters, fascia, soffit, and anything being detached and reset.
What a defined answer looks like: Counted and itemized. “Seven pipe boots replaced; two turtle vents removed and decked over; satellite dish detached and reset; gutters not in scope.”
What silence usually means: These are the classic mid-project additions. They are also where two bids diverge invisibly: one carries the solar array detach-and-reset and one assumes your solar installer will do it.

11 · Disposal

What to write down for each bid: Container, haul-away, tonnage assumed, who pays overages, and where the debris goes.
What a defined answer looks like: Included with a stated basis, or excluded in writing. Roofing tear-off is a real waste stream: EPA reports that 600 million tons of construction and demolition debris were generated in the United States in 2018, with asphalt shingles named among the materials.
What silence usually means: Occasionally that the homeowner is expected to provide the container. More often that the tonnage assumption is the bidder’s, and a second layer of shingles roughly doubles it.

12 · Permit and inspections

What to write down for each bid: Who pulls the permit, who pays the fee, and which inspections are included in the price.
What a defined answer looks like: Named responsibility and named cost treatment — included, or a pass-through at cost. Whether a re-roof needs a permit at all, and what is inspected, is a local determination.
What silence usually means: Either the fee arrives later as an extra, or nobody is pulling one. A contractor asking the homeowner to pull the permit is asking the homeowner to be the responsible party on the application.

13 · The product and the assembly, not the brand

What to write down for each bid: The specific covering product, the starter and ridge products, the fastener and its pattern, and any rating being claimed.
What a defined answer looks like: A product line and colour, the starter course and hip-and-ridge products by name, the fastener pattern, and — where a fire, wind, or impact classification is being claimed — the tested assembly it belongs to rather than the shingle alone.
What silence usually means: “Architectural shingles” is a category, not a product. Two bids naming the same brand can still specify different lines, different starters, and different nailing, and only one of them may match the assembly whose classification is being advertised.

14 · Warranty terms

What to write down for each bid: Manufacturer document, workmanship term, registration deadline, transferability, and what voids each.
What a defined answer looks like: The actual documents, or their names and lengths, with the registration step and deadline stated. A workmanship warranty and a manufacturer’s product warranty cover different failures and are enforced against different companies.
What silence usually means: A headline number on a proposal is usually a manufacturer’s product term, most of which may be prorated. It says nothing about who returns your call in year six.

15 · Payment schedule, closeout, and exclusions

What to write down for each bid: Deposit, progress payments, the final-payment trigger, closeout documents, and the written exclusions list.
What a defined answer looks like: A schedule tied to events rather than dates, a final payment tied to completion and documentation, and an explicit exclusions list. Exclusions are the most useful paragraph in a proposal, because they are the only place a bidder writes down what they are not doing.
What silence usually means: An unstated exclusions list is an exclusions list you discover later. Deposit, cancellation, lien, and payment terms are also governed by the law where the property is, which varies substantially and which this page cannot tell you.

The fourth column describes patterns, not accusations. A blank is most often an assumption a bidder made and did not write down — which is exactly why the fix is a written answer rather than a different bidder. Code references in this table are model or out-of-jurisdiction text; your authority having jurisdiction governs.

The expensive line

The deck allowance is where most quotes become billsSection link

Of the 15 rows above, this is the one that most often turns an accepted price into a different final number. It is also the easiest to fix, and it takes one sentence.

Nobody knows the condition of the wood under a roof until the roof is off. That is not a failure of estimating; it is the nature of the job. Sheathing rots where water has been getting in — around penetrations, along eaves, under a valley, over a bathroom vent that has been discharging into the attic for fifteen years — and none of it is visible from a ladder or from an aerial photograph.

So every honest proposal has to handle an unknown quantity. There are exactly three ways to do it, and only one of them is comparable across bidders.

A unit price with no quantity. “Decking replaced as needed at $— per sheet.” This looks like a protection and is not one. It caps nothing. Every sheet is an addition, negotiated after you have committed.
A quantity with no unit price. “Includes minor deck repair.” This prices nothing. “Minor” is resolved on the day, by the person holding the saw.
Both, plus a credit rule. “Six sheets of 7/16 in OSB included at $— per sheet; additional sheets at the same rate; unused sheets credited at that rate.” This is an allowance. It is comparable between bidders, it is bounded in both directions, and it removes the incentive to find damage that is not there.

Why it is the most consequential divergence

Two effects compound. The first is arithmetic: at a plausible sheet count, the difference between a bid carrying six sheets and a bid carrying none is a real sum of money that does not appear anywhere in the price comparison. The second is structural: the moment of discovery is the moment of maximum leverage imbalance. You have one crew on site, a roof that is open to the weather, no realistic option to stop, and no second quote. Whatever number is proposed then is the number.

A deck allowance agreed while three bidders are still competing costs nothing to obtain. The same conversation on the fourth morning of the job costs whatever it costs. This is the single highest-return question on the page, and it is one sentence long: how many sheets are in the price, and what is the rate for more?

Two related lines that travel with it

Ask about re-fastening in the same breath. BASC’s re-roof sequence includes inspecting the deck attachment fasteners and re-nailing “as required to meet current requirements for nail type, size, and spacing”, and some jurisdictions require it at a re-roof. A bid that carries it and a bid that does not are not the same job.

Ask also about documentation. Replaced sheets should be photographed and counted, and the count should reach you before the invoice does. This is the only line item on a roofing job where the quantity billed is decided entirely out of sight, and a bidder who offers photographs without being asked has answered a question about more than decking.

A worked example

A worked normalization: three bids, one roof, one basisSection link

Invented numbers, real method. Every figure below was made up to demonstrate the arithmetic — none of it is market data, a cost range, or a price for any roof.

One house. A 6:12 gable with a dormer, two storeys, field-verified at 26.4 squares of roof surface. Three proposals arrive. As written, they look like this:

Bid A — $14,600. One page. Names a shingle brand, says “24 squares”, says “flashing replaced as needed”, silent on layers, deck, ice barrier, ventilation, and permit.
Bid B — $17,900. Three pages. Layers stated, underlayment and ice barrier named, flashing listed by location, deck named at a rate per sheet with no quantity included, permit included, disposal excluded (“container by owner”), ventilation not mentioned.
Bid C — $19,400. Four pages. Every one of the 15 rows above answered, including six sheets of decking carried in the price with a credit for unused sheets, a ridge-and-soffit ventilation change itemized separately, and a written exclusions list.

The spread as stated is $4,800, and Bid A is cheaper than Bid C by 25 percent. Now take Bid C’s scope as the reference basis — not because it is the right scope, but because it is the only one fully described — and add back what the others do not include, using each bidder’s own numbers wherever they exist.

The same three totals before and after normalization. The $4,800 spread falls to $1,471, Bid B overtakes Bid C, and two of the three bars end in an open hatch because those bidders did not price the item at all. Numbers invented for this demonstration; the arithmetic is set out line by line below.Original diagram, Understanding Roofing.

Normalizing three invented bids to one scope basis. Every dollar figure is arithmetic invented to demonstrate the method — not market data, and not a price for any roof.
Adjustment	Bid A	Bid B	Bid C
Price as written	$14,600	$17,900	$19,400
Roof area on a common basis	Priced 24.0 squares against a field-verified 26.4. At Bid A's own implied rate of about $608 per square, the missing 2.4 squares are +$1,459.	Priced 26.4 squares. No adjustment.	Priced 26.4 squares. Reference basis.
Deck allowance to a common six sheets	No allowance and no unit price. Cannot be normalized: carried as an unbounded exposure.	Rate per sheet stated, zero sheets included. Six sheets at Bid B's own $95 rate is +$570.	Six sheets included at $88, unused sheets credited. No adjustment.
Flashing on a common basis	“Flashing replaced as needed.” Bid C itemizes the same work at $940, so +$940.	Flashing listed by location and included. No adjustment.	Flashing listed by location and included. Reference basis.
Ventilation change	Not mentioned. Bid C itemizes a ridge-and-soffit change at $1,150, so +$1,150 to reach the same scope.	Not mentioned. +$1,150, same adjustment.	Ridge-and-soffit change itemized at $1,150. Reference basis.
Permit fee	Not mentioned. Cannot be normalized: carried as unpriced.	Included.	Included.
Disposal	Included.	Excluded — container by owner. Cannot be normalized: carried as unpriced.	Included.
Normalized to Bid C's scope as written	$18,149, plus an unpriced deck allowance and an unpriced permit	$19,620, plus unpriced disposal	$19,400
Then the owner declines the ventilation change on all three (−$1,150 each)	$16,999	$18,470	$18,250

Read this table one item at a time

Price as written

Bid A: $14,600
Bid B: $17,900
Bid C: $19,400

Roof area on a common basis

Bid A: Priced 24.0 squares against a field-verified 26.4. At Bid A's own implied rate of about $608 per square, the missing 2.4 squares are +$1,459.
Bid B: Priced 26.4 squares. No adjustment.
Bid C: Priced 26.4 squares. Reference basis.

Deck allowance to a common six sheets

Bid A: No allowance and no unit price. Cannot be normalized: carried as an unbounded exposure.
Bid B: Rate per sheet stated, zero sheets included. Six sheets at Bid B's own $95 rate is +$570.
Bid C: Six sheets included at $88, unused sheets credited. No adjustment.

Flashing on a common basis

Bid A: “Flashing replaced as needed.” Bid C itemizes the same work at $940, so +$940.
Bid B: Flashing listed by location and included. No adjustment.
Bid C: Flashing listed by location and included. Reference basis.

Ventilation change

Bid A: Not mentioned. Bid C itemizes a ridge-and-soffit change at $1,150, so +$1,150 to reach the same scope.
Bid B: Not mentioned. +$1,150, same adjustment.
Bid C: Ridge-and-soffit change itemized at $1,150. Reference basis.

Permit fee

Bid A: Not mentioned. Cannot be normalized: carried as unpriced.
Bid B: Included.
Bid C: Included.

Disposal

Bid A: Included.
Bid B: Excluded — container by owner. Cannot be normalized: carried as unpriced.
Bid C: Included.

Normalized to Bid C's scope as written

Bid A: $18,149, plus an unpriced deck allowance and an unpriced permit
Bid B: $19,620, plus unpriced disposal
Bid C: $19,400

Then the owner declines the ventilation change on all three (−$1,150 each)

Bid A: $16,999
Bid B: $18,470
Bid C: $18,250

Every dollar figure in this table was invented to make the arithmetic legible. Nothing here is a market rate, a national average, a price per square, or a figure that should be quoted anywhere. The method is the content; the numbers are scaffolding.

What the exercise actually produced

The stated spread was $4,800 — a third of the cheapest bid. Once all three proposals describe the same project, the spread is $1,471, and the order has changed: Bid B, the middle bid as written, is now the most expensive of the three. Bid A is still the lowest, but it is the only one carrying two lines nobody has priced. Whether it is genuinely the cheapest depends on how many sheets of decking come off and what the permit costs, and neither of those is knowable today. That is not a defect in the arithmetic; it is the actual state of the information.

Now look at the last row. Having put all three columns on the same basis, the owner went back to the ventilation change Bid C had proposed, decided there was no evidence the attic needed it, and struck it from all three — $1,150 off each. The ranking does not move, and that is the point: a line every bid now carries identically cannot change the ranking, which is exactly why it had to be added to all three before it could be declined by all three. Normalizing is not the same as buying. Every row is an include-or-exclude decision, taken deliberately, before any price is compared.

Notice also what did not happen. Bid A’s missing deck allowance was not filled in with Bid B’s $95 rate or Bid C’s $88 one. Doing that would have produced a tidier table and a false conclusion, because Bid A has not agreed to either rate. An unpriced line stays unpriced, and it travels with the bid as a risk rather than a number. The most useful output of this whole exercise is usually not the adjusted totals at all — it is the short list of things two of the three bidders never addressed, which you then send back to all three and ask them to price.

The uncomfortable one

What a suspiciously low bid usually meansSection link

Almost always: a smaller project. Occasionally: a business problem. Rarely, and last on the list: bad faith.

A bid that comes in well under the others is the most common reason people look for a page like this one, and the instinct is to ask what the contractor is hiding. That is usually the wrong question, and it makes the conversation adversarial before it has produced any information.

Work down this list in order. It is roughly the order of frequency, and each item is checkable against the proposal in front of you rather than against the bidder’s character.

It is a smaller project. Fewer squares, fewer layers, no deck allowance, reused flashing, no ventilation change, no permit fee, no ice barrier, disposal excluded. Every one of these is a line on the worksheet, and between them they account for most low bids.
It is a different product or assembly. A different shingle line, a lighter underlayment, a builder-grade starter and ridge, a different fastener pattern. Same brand on the letterhead, different bill of materials.
It is a genuinely leaner cost structure. Small crew, no salesperson, no branded truck fleet, owner on the roof, low overhead. This is a real and legitimate reason to be cheaper, and it is why “lowest bid” and “worst bid” are not synonyms.
It is a scheduling or cash-flow price. A gap in the calendar, a slow season, or a job that finishes a supplier volume target. Ask when the work would happen; the answer is often the explanation.
Something is not being carried that should be. Workers’ compensation is the one that matters most, because liability for an injury on your property is not a paperwork question. NRCA’s guidance asks for both liability and workers’ compensation certificates, in effect for the duration of the job, and verification means contacting the insurer named on the certificate.
The price is an entry point. A low number that becomes a larger one through change orders after work starts. This is the case people fear, and it is the case the worksheet defends against directly — because a change order needs an unpriced line to grow into.

The one pattern that is not a scope question

There is a version of a low bid that no amount of normalization fixes: a price offered in exchange for signing today, with a large deposit, on a document that does not describe the work. Pressure and vagueness travel together, and they travel together because a described scope is harder to leave.

Safety first

A deposit is the point of no return. Treat it like one.

A federal rule gives buyers a right to cancel certain sales solicited away from a seller’s place of business — 16 CFR Part 429 covers sales of $25 or more made at a buyer’s residence and allows cancellation “at any time prior to midnight of the third business day after the date of this transaction.” That rule also carries express exclusions, including one for buyer-initiated repair or maintenance work, and many states have their own home-solicitation statutes with different scope and different deadlines.

Whether any of it applies to a specific roofing contract is a legal question, and this page does not answer it. If you are in that situation, the useful step is to read the contract you signed and speak to your state or local consumer-protection office — not to rely on a general description of a federal rule.

Do not pay a deposit for work you cannot see described in writing, and do not sign anything on a doorstep to hold a price. If a proposal cannot survive a night on your kitchen table, that is information about the proposal.

And the mirror image

A high bid deserves the same treatment. Sometimes it is a larger project: more scope, a better assembly, a crew that will be there for eight days instead of three. Sometimes it is an access or complexity assumption you can check. Sometimes it is a sales organisation with a marketing budget priced into the roof. The worksheet does not care which direction the spread runs; it asks the same question of every column.

Considerations

What changes this on a real buildingSection link

Code and jurisdiction

There is no nationwide building code for site-built houses in the United States. States and local governments adopt model codes, amend them, and set their own effective dates — which is why the same provision moves between section numbers from one edition to the next. The model International Building Code’s restriction on recovering an existing roof rather than tearing it off is Section 1512.3 in the 2024 edition; NRCA’s technical staff were describing the same restriction as Section 1511 in 2019. None of it is law anywhere until a jurisdiction adopts it.

What a complete adoption record looks like: the Texas Department of Insurance requires windstorm certificate of compliance applications to be certified against the 2024 IRC or the 2024 IBC starting 1 April 2026 — a named jurisdiction, a named edition, a named effective date, and an official page that says so. That is the standard to hold a bidder to when they tell you something is “code”: which code, which edition, adopted by whom, and from when. A bidder who can answer that is worth listening to on the rest of the proposal.

That matters for bid comparison in one specific way. Where a jurisdiction requires something at a re-roof — an ice barrier, deck re-fastening, a permit, a mid-work inspection — a proposal that omits it is not a cheaper proposal. It is an incomplete one, and the difference surfaces as a change order or a failed inspection.

Every code reference on this page is model text, or an out-of-jurisdiction adoption quoted to show that requirements exist and vary. The Texas adoption above governs windstorm certification in that state's designated catastrophe area and nothing else; it is an example of a record, not a requirement anywhere else. Record your own jurisdiction, its adopted edition, its amendments, and the effective date, and confirm with the authority having jurisdiction before treating anything here as a requirement where you live.

Climate

In a cold climate the ice-barrier line is often the single largest material divergence between two bids, because self-adhered membrane is expensive and the extent is a judgement. In a hot-humid climate the divergence tends to move to ventilation and the attic assembly. Ask each bidder what climate assumption their scope is built on, and whether it comes from the adopted code, the manufacturer’s instructions, or their own practice.

Whether an ice barrier is required at your address, and how far up the roof it must run, depends on the adopted code edition, local amendments, the climate designation, and the assembly. There is no universal rule.

Moisture and ventilation

Ventilation is the line item most often quoted as a product (“ridge vent”) rather than as a system. The Building America Solution Center defines the unit that makes the two halves comparable — net free area, “the clear open area of a vent, taking into account the restrictions of the vent screening itself and the dimensions of the vent slots” — and notes that most screened vents deliver about 60 percent of their gross opening.

A bid that adds exhaust and says nothing about intake is a materially smaller job than one that opens soffits, adds baffles, and balances the two. BASC’s guidance for a conventional vented attic puts no more than 50 percent and no less than 40 percent of the required area high on the roof — a distribution it draws from a model-code edition it names, not a universal rule, and not a number to hold a bidder to without checking what your jurisdiction actually adopted.

Vented attics and correctly designed unvented attics are both legitimate. BASC frames the choice as where to put the thermal boundary, decided by climate, HVAC location, building configuration, and intended use of the space — not by a rule that more ventilation is always better. If a bidder proposes changing which one your house has, that is an assembly decision, not a roofing accessory.

Wind

Fastening pattern, edge metal, starter course, and deck attachment are the parts of a bid that decide wind behaviour, and they are almost never itemized. Enhanced packages exist and are real scope: the IBHS FORTIFIED Roof standard, for example, “requires roof decks to be sealed”, requires “ring-shank nails, installed in an enhanced pattern”, and requires “a wider drip edge and a fully adhered starter strip”. If one bid includes that and another does not, they are not the same product.

Wind performance is site- and building-specific — basic wind speed, exposure, height, geometry, pressure zone, enclosure, risk category, attachment, and the tested assembly all matter. A marketing mph number on a proposal is not a code determination for your building.

Hail and impact

An impact-resistant upgrade is a legitimate line item and a legitimate reason for one bid to be higher. It is also a line that is easy to advertise and hard to verify from a proposal, so ask for the product, the classification, and the test it comes from — and ask whether your insurer actually recognizes it, because the premium treatment varies by carrier and state.

“Class 4 impact resistant” describes how a covering behaved in a laboratory impact test. It does not mean hail proof, it says nothing about the flashings, and it is not a promise about a claim outcome.

Fire

Where a proposal advertises a Class A roof, the claim belongs to a tested assembly — deck, underlayment, and covering together — not to the shingle by itself. Two bids naming the same shingle but different underlayments may not be offering the same classification.

Fire classification applies to a tested assembly, not to a covering in isolation. If it matters to you, the question is which listed assembly is being installed, in full, on your deck.

Access and site conditions

Two identical roofs price differently for reasons that have nothing to do with roofing: stories, pitch, tree cover, driveway access for a dumpster and a delivery, a neighbour’s wall, a pool or a conservatory under the eave, staging over a public sidewalk. A higher bid from someone who walked the property and noticed those is not padding. Ask each bidder what access assumptions their price carries.

Age of the building

Two federal programs can enter the scope on an older house. EPA requires that “anyone paid to perform work that disturbs painted surfaces in homes, childcare facilities and preschools built before 1978 be certified” under the Renovation, Repair and Painting rule. Separately, older shingles, felts, and mastics may contain asbestos; EPA advises testing where material is damaged or “if you are planning a renovation that would disturb the suspect material”, and that samples be taken by a properly trained and accredited asbestos professional.

Do not disturb suspect asbestos-containing material to satisfy your curiosity about a bid, and do not accept verbal reassurance in place of testing. Whether either program applies to a particular job, and what state and local rules add on top, is not something this page can determine.

Warranty and repair

Warranty terms are the least comparable part of a proposalSection link

Three proposals will quote three warranty numbers that measure three different things. The number on the page is almost never the useful one.

Manufacturer product warranty: Covers the manufacturer’s product against defined defects, for a term that is frequently mostly prorated — the payable value declines after an initial full-value period. Compare the full-value period, not the headline. Ask which components are covered: starter, ridge, underlayment, and flashing are often somebody else’s products.
Workmanship warranty: The installer’s own promise, and the one most flashing and detail failures actually fall under. Its length is far less informative than the company behind it. A ten-year workmanship warranty from a firm that is two years old is a shorter promise than a five-year one from a firm that is thirty.
Enhanced or system warranties: Offered through manufacturers’ contractor programs, and they are genuine scope: they normally require that manufacturer’s accessories throughout, a credentialed installer, registration within a deadline, and sometimes inspection or maintenance. If one bid includes one and another does not, the two bids are buying different accessory packages, not just different paperwork.
The questions that make them comparable: Registration deadline. Transferability, and whether transfer costs a fee or is limited to one transfer within a window. What voids it — reused flashing, installation over an existing covering, unapproved repairs by others, and missing maintenance are common exclusions. And what the remedy actually is: replacement material only, or material and labour.

Repairability

The practical question behind all of it is who answers the phone in year six, and what happens when they do.

Ask for the callback process in writing. Response window, whether a diagnostic visit is chargeable, and who decides whether a leak is workmanship or product.
Ask what happens if the company is sold or stops trading. A workmanship warranty is only as durable as the entity that wrote it, and roofing companies change hands often.
Ask for the pre-cover photographs. Once the covering is on, the deck, underlayment, ice barrier, and flashing details are invisible. Photographs are the only evidence you will have about whether the scope you bought was the scope installed.

A warranty is a contract between a reader and whoever wrote it. What it covers, what voids it, whether it transfers, and how it is enforced are set by that document and by the law where the reader lives. Read the actual warranty for the product and the installer in front of you — not a summary of one, including this one.

Ask before you sign

Questions to ask an installerSection link

Each of these has a one-sentence answer from someone who has already made the decision, and a paragraph of hedging from someone who has not. You are listening for which.

How did you measure the roof, and what is the surface area in squares before waste?
This is the question that makes every other number comparable. A bidder who measured on the roof, a bidder who bought an aerial report, and a bidder who paced the driveway will give you three different numbers, and you need to know which kind you are holding.
How many layers do you expect to remove, and what is the price per square if there is another one?
A second layer is a second layer’s worth of tear-off labour and roughly twice the debris to haul. The price for it should be agreed while three bidders are competing, not on the morning it is discovered.
How many sheets of decking are included in the price, and what is the unit price for more?
The most important question on the list. Both numbers or neither: a unit price with no included quantity caps nothing, and an included quantity with no unit price prices nothing. Ask also whether unused sheets are credited back.
Which flashings are you replacing and which are you reusing?
“We replace what needs it” is not scope. A list by location — drip edge, valleys, step, apron, chimney, skylight, pipe boots — is. This is also the single most common silent divergence between two otherwise similar bids.
Is anything changing about the ventilation, and what happens on the intake side?
If the answer covers only exhaust, the bid is smaller than one that opens soffits and installs baffles. If the answer is that nothing is changing, that is a legitimate position — but it should be a stated one, not a silence.
Is an ice barrier included, how far does it run, and what requires that extent?
The answer should name a source: the adopted code, the manufacturer’s instructions, or their own practice. Any of the three is a real answer. “We always do six feet” is a practice, and it is worth knowing that is what it is.
Who pulls the permit, who pays the fee, and which inspections are in the price?
If a contractor wants you to pull the permit, understand that you are becoming the responsible party on the application. If nobody is pulling one, understand that unpermitted work is a disclosure item when you sell.
What exactly is excluded? Can I have that as a list?
The most productive question in the set. A bidder with a real exclusions list is a bidder who has thought about the job. A bidder who says “nothing” has either not read their own contract or is about to write a change order.
How long is this price held open?
Material and labour prices move. A validity window is normal and answering it is easy. It also tells you whether you are comparing three current prices or one current price and two stale ones.
Was this house built before 1978 or before 1990, and does that change anything in your scope?
Lead-safe work practices and asbestos testing are scope, cost, and schedule. A bidder who knows the federal rules exist and says how they handle them is answering a question about competence as much as about price.
Can I see the certificate of insurance, and can the certificate name me?
A certificate of insurance is evidence of a policy on a date, not a guarantee of coverage for your job. NRCA’s consumer guidance asks for both liability and workers’ compensation certificates, in effect for the duration of the work; verification comes from the insurer named on the certificate, not from the paper.

Require these in writing before you compare any two prices

Roof surface area in squares, the derivation method, and the order area with the waste percentage shown separately.
Number of existing layers assumed, and a unit price per square for an additional layer.
A deck allowance stating both the unit price and the quantity included, and whether unused quantity is credited.
Whether the deck is being re-fastened, and to what pattern.
Underlayment product by name, and where each type is applied.
Ice barrier: included or not, with the extent in feet and the basis for that extent.
Flashing listed by location, each marked new or reused.
Ventilation: existing condition, proposed change, and the intake side stated explicitly.
Penetration and accessory counts — pipe boots, vents, detach-and-reset items — and what is excluded.
Disposal: container, tonnage assumed, and who pays overages.
Permit responsibility, fee treatment, and the inspections included.
The covering product line, starter and ridge products, and the fastener and pattern; plus the tested assembly behind any classification being claimed.
Warranty documents by name, with registration deadline, transferability, and remedy.
Payment schedule tied to events, the final-payment trigger, and the closeout documents that come with it.
A written exclusions and assumptions list.

What goes wrong

Misconceptions, and how a comparison goes wrongSection link

Common misconceptions

Common belief
Get three quotes and take the middle one.
What is actually true
The middle of three numbers describing three different projects is not a moderate choice; it is an arbitrary one. In the worked example on this page, normalizing the scope moves the middle bid to the top. Rank by scope first, and the position of a price in the list stops being the thing you are deciding.
Common belief
Price per square is the apples-to-apples number.
What is actually true
Only after two things are true: both bidders measured the same roof, and both are quoting roof surface rather than order area. Until then, dividing by squares divides one project’s price by another project’s area. Per-square figures are useful for arguing with a proposal, not for choosing between three.
Common belief
A low bid means the contractor is cutting corners.
What is actually true
Usually it means they are quoting a smaller project — one layer instead of two, sound deck assumed, flashing reused, vents left alone, no permit fee carried. Those are professional judgements, not misconduct. The failure is that they are invisible in a price, and the fix is to make them visible rather than to assume bad faith. The NRCA still advises “a healthy skepticism about the lowest bid”, and both things are true at once.
Common belief
A longer warranty means a better roof.
What is actually true
A warranty term is a commercial decision by whoever wrote the document. Most long manufacturer terms are largely prorated, and the failures homeowners actually experience — flashing, penetrations, detailing — are usually workmanship rather than product. Compare the full-value period, the exclusions, and the age of the company.
Common belief
If a proposal does not mention it, it must be included.
What is actually true
Almost never. A silent line item is an unallocated decision. It is allocated later, on a roof that is already open, by whoever is standing on it. That is the entire mechanism by which a quote becomes a bill.
Common belief
I should just tell every bidder what the others quoted.
What is actually true
Sharing a competitor’s price invites a bidder to match a number rather than a scope, which is exactly backwards. Sharing a normalized scope and asking all three to price the same list is the version that works, and it is the more useful thing to do with the worksheet than adjusting their arithmetic yourself.

How it actually fails

The deck allowance that is only a unit price: The proposal names a price per sheet and carries no quantity, so every sheet is an extra. On a roof where the deck turns out to be soft over a bathroom or along an eave, the allowance line becomes an open-ended addition negotiated with a torn-off roof over your head.What you can see: A single line reading “decking replaced as needed at $— per sheet.” Ask for the included quantity. If the answer is “we’ll see”, that is the finding.
Order area compared against surface area: One bidder writes the roof’s surface area and another writes the quantity being ordered, which includes a waste allowance for cuts. The second number is larger for the same building, so the second bidder’s price per square looks lower.What you can see: Two proposals for the same address whose square counts differ by about the size of a waste allowance, with no disagreement about which planes are in scope. Ask both bidders which number they wrote down — surface or ordered — rather than assuming one of them measured wrong.
The exhaust-only ventilation upgrade: Ridge vent is added because it is quick and visible; intake is not, because opening soffits is slower and sometimes needs a carpenter. The bid is smaller, and the assembly is now unbalanced.What you can see: A proposal that names an exhaust product and says nothing about soffits, baffles, or net free area on the intake side.
Flashing described with an adjective: “New flashing where needed” or “flashing replaced as necessary” reads like inclusion and functions as discretion. Whoever is on the roof decides, on the day, how much metal the price covers.What you can see: No location list. Compare against a proposal that names drip edge, valleys, step, apron, chimney, skylight and boots separately — the difference in length is the difference in scope.
The insurance scope treated as a replacement scope: An insurer’s estimate is a settlement document for covered damage, not a specification for a complete re-roof. Bidders who quote to it and bidders who quote to the building are answering two different questions, and the gap belongs to the owner.What you can see: One proposal whose line items and quantities mirror an adjuster’s worksheet exactly, including its omissions.
The stale quote: Two bids arrive within a week and the third is months old, held over from an earlier round. Material and labour prices moved in between, so the comparison contains a time difference disguised as a price difference.What you can see: No validity window on any of the documents. Ask each bidder how long the price stands, and re-date anything older than the others.
Normalizing to the most expensive bid by reflex: Every item that appears in one proposal gets added to the other two, so the exercise silently converts into a decision to buy the largest scope on offer. Normalization is meant to make the bids comparable, not to make them identical.What you can see: A worksheet in which every column has been filled in and no line has been struck out. If nothing was declined, no decision was made.

Sources and further readingSection link

Understanding Roofing / Published August 14, 2026 / Updated August 26, 2026

Scope and limitations

It publishes no cost range, no price per square, and no dollar figure for any line item.
The three bids in the worked example, and every number in them, are arithmetic invented to demonstrate a method.
They are not market data, they are not a range for anyone's roof, and they should not be quoted as one.
It cannot tell you which bid to accept.
Normalization ranks scope.
It cannot measure whether a crew is competent, whether a firm will still be trading in year six, or whether the person who walked your roof understood what they were looking at.
It cannot tell you what your jurisdiction requires at a re-roof.
Ice barrier, deck re-fastening, permit, and inspection requirements are set by your adopted code edition, its local amendments, and the authority having jurisdiction.
Code text quoted here is model or out-of-jurisdiction text shown to demonstrate that requirements exist and differ.
It cannot quantify how often each divergence occurs.
No public dataset separates residential roofing change orders by cause, and none of the frequency language on this page ('most common', 'usually') rests on one.
Those judgements are stated as editorial judgement and are open to correction.
It is not legal advice, and it makes no promise about cancellation rights, deposits, lien exposure, or the enforceability of any contract term.
Those vary by state and by the facts, and the federal cooling-off rule cited here carries its own exclusions.
This page needs review by a lawyer qualified in the reader's jurisdiction before it ships.
It cannot tell you whether an insurer will pay for a scope item, or how a claim will be settled.
That is a policy question and a jurisdiction question.

Selecting a Contractor
National Roofing Contractors Association
That a buyer should insist on a written proposal with complete descriptions of the work and specifications, start and completion dates, and payment procedures; that liability and workers' compensation certificates should be obtained and be in effect for the duration of the job; and the direct quotation about keeping a healthy skepticism about the lowest bid.
Trade-association consumer guidance written by an industry body whose members are contractors. It is not adopted law, it is not a contract, and it does not define scope for any particular job.
Asphalt Shingle Roofs
U.S. Department of Energy, Building America Solution Center (PNNL)
The baseline re-roof sequence quoted on this page: remove all existing roofing (shingles and underlayment) and replace any damaged wood sheathing; inspect the roof deck attachment fasteners and re-nail as required for nail type, size and spacing; seal decking seams, install underlayment, and replace flashing around penetrations, at valleys, and at roof-wall intersections; drip edge at eaves and rakes; and an ice barrier along the eaves in cold-climate regions with a history of ice dam formation.
Best-practice guidance for builders, not adopted law anywhere. It describes a recommended standard of work, which is exactly why it is useful as a yardstick for what a proposal does and does not include — but a bid that departs from it is not thereby non-compliant.
Calculating Attic Passive Ventilation
U.S. Department of Energy, Building America Solution Center (PNNL) / Last updated 23 August 2021
The definition of net free ventilation area as the clear open area of a vent accounting for screening and slot dimensions; that most screened vents have about 60 percent free area; the 1/300 and 1/150 ratios; and that no more than 50 percent and no less than 40 percent of the required area should be high on the roof.
It cites the 2015 IRC as its ratio source. Ratios, exceptions, and the vapour-retarder conditions attached to them differ between code editions and jurisdictions, and this page does not treat any ratio as a requirement.
Vented versus Unvented Attic
U.S. Department of Energy, Building America Solution Center (PNNL)
That both vented and unvented attic assemblies are legitimate approaches, and that the choice is where to locate the thermal boundary — decided by climate, the need for living or storage space, building design and configuration, and the location of HVAC equipment.
Design guidance, not a code determination. Whether an unvented assembly is permitted, and under what conditions, depends on the adopted code and the specific assembly.
2024 International Building Code, Chapter 15 — Section 1512.3, Roof recover (MODEL code text)
International Code Council, ICC Digital Codes — the publisher's own edition of the model text / 2024 edition
That the restriction on installing a new covering over an existing one sits at Section 1512.3 of Chapter 15 in the 2024 edition of the model International Building Code.
MODEL code text. It is not the law in any jurisdiction until that jurisdiction adopts it, and adoptions amend. Section numbering moves between editions and differs between the residential and commercial codes. Confirm the adopted edition, its amendments, and its effective date with your authority having jurisdiction.
Reroofing by the book
National Roofing Contractors Association, Professional Roofing (Mark S. Graham) / 1 February 2019
The substance of the model code's recover restrictions — removal is required where the existing roof is water-soaked or deteriorated so that it is not an adequate substrate, where the existing system is slate or asbestos-cement, concrete or clay tile, and where the existing roof already carries two or more layers of any type of roof system — and that the provision was numbered Section 1511 in the edition current when the article was written.
Trade-association technical commentary on model code text, not adopted law, and written by an industry body whose members are contractors. It describes the edition current in 2019; the 2024 edition carries the provision at Section 1512.3, which is why both sources are cited here rather than one.
Adopted building codes for windstorm certification
Texas Department of Insurance
The worked adoption record quoted on this page: that windstorm certificate of compliance (WPI-1) applications must be certified in accordance with either the 2024 International Residential Code or the 2024 International Building Code starting 1 April 2026 — a named jurisdiction, a named edition, and a named effective date, published by the adopting authority itself.
Governs windstorm certification in the Texas designated catastrophe area only. It is not the building code for the rest of Texas, it is not the code anywhere else, and it is cited here as an example of what a complete adoption record looks like rather than as a requirement for any reader.
2024 International Residential Code, Chapter 9: Roof Assemblies — R905.1.1, R905.1.2, R905.2.2, R905.2.7 (MODEL code text)
International Code Council, ICC Digital Codes — the publisher's own edition of the model text / 2024 edition
That asphalt shingles are permitted only on roof slopes of 2 units vertical in 12 units horizontal or greater (R905.2.2); that underlayment application is set by Table R905.1.1(2), which varies with covering type, wind design, and roof slope — including a different application for slopes below 4:12 than for 4:12 and greater; and that ice-barrier installation is governed by Section R905.1.2 in areas with a history of ice forming along the eaves (R905.2.7).
MODEL code text, read on the publisher's own site. It is not the law in any jurisdiction until that jurisdiction adopts it, and adoptions amend. Confirm the adopted edition, its amendments, and its effective date with your authority having jurisdiction.
Lead Renovation, Repair and Painting Program
U.S. Environmental Protection Agency
That EPA requires anyone paid to perform work that disturbs painted surfaces in homes, childcare facilities and preschools built before 1978 to be certified, and that approximately three-quarters of US homes built before 1978 still contain some lead-based paint.
A federal program summary. Whether a specific roofing scope disturbs painted surfaces, which thresholds apply, and what an individual state adds on top are determinations this page does not make. Several states administer the program themselves with their own rules.
How do I know if I have asbestos in my home (floor tile, ceiling tile, shingles, siding, etc.)?
U.S. Environmental Protection Agency
That shingles and similar home products may contain asbestos; that testing is warranted where material is damaged or where a renovation would disturb the suspect material; and that samples should be taken by a properly trained and accredited asbestos professional.
General homeowner guidance. It does not identify which specific roofing products contain asbestos, and state and local rules on testing, notification, and disposal vary.
Sustainable Management of Construction and Demolition Materials
U.S. Environmental Protection Agency / 2018 data, Advancing Sustainable Materials Management fact sheet
That 600 million tons of construction and demolition debris were generated in the United States in 2018, and that asphalt shingles are among the materials counted in that stream.
A national materials-management dataset. It says nothing about the tonnage a particular roof produces, about disposal pricing, or about what any local transfer station charges.
FORTIFIED Roof
Insurance Institute for Business & Home Safety (FORTIFIED program)
That an enhanced roof standard exists and is defined as specific scope: a sealed roof deck, ring-shank nails installed in an enhanced pattern, a wider drip edge, and a fully adhered starter strip.
A voluntary above-code program run by an insurance research body. It is not a building code, it is not required anywhere by default, and designation involves an independent evaluation this page does not describe in detail.
16 CFR Part 429 — Rule Concerning Cooling-Off Period for Sales Made at Homes or at Certain Other Locations
U.S. Government Publishing Office (Code of Federal Regulations) / 2023 CFR annual edition
That a federal rule defines a door-to-door sale as one solicited away from the seller's place of business at a purchase price of $25 or more at the buyer's residence, that it gives the buyer a right to cancel prior to midnight of the third business day after the transaction, and that it carries express exclusions — including sales made after prior negotiations at a fixed retail establishment, transactions covered by 15 U.S.C. 1635, buyer-initiated bona fide personal emergencies with a signed waiver, mail or telephone transactions, buyer-initiated repair or maintenance of the buyer's personal property, and sales of real property, insurance, or securities.
Federal trade regulation, not roofing law. Whether it applies to a particular roofing contract, how its exclusions operate, and what additional or longer rights a state home-solicitation statute grants are legal questions this page does not answer. This is precisely the content that requires review by a qualified lawyer before the page ships.
Fall Protection in Residential Construction
U.S. Occupational Safety and Health Administration / Issued 16 December 2010
That falls are the leading cause of death for workers engaged in residential construction, and that conventional fall protection is required for residential construction work six feet or more above lower levels.
An occupational-safety standard for employers and workers. It is not homeowner guidance; the fact that trained workers use fall protection is a reason for an untrained reader to stay off the roof entirely, not a procedure to copy.

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