The argument, stated plainly
The version of this fight that shows up on adjuster forums almost every season goes like this: the desk adjuster's estimate has 10% waste, the contractor's estimate has 15% or 20% on the same roof, and both sides are pointing at the difference as proof the other side is padding or shorting the claim. Neither side is necessarily wrong. Waste factor is not a fixed line item like tax or a code-mandated allowance; it is a percentage the estimator applies to cover cuts, overlap, and material that cannot be used off a full course because of how the roof is shaped.
The disagreement usually is not about whether waste exists. Both sides agree shingles get cut and some of that cut material is scrap. The disagreement is about how much scrap this particular roof generates, and that number depends on the roof's geometry, not on a rule either side can cite chapter and verse.
What actually drives the waste number
Waste goes up with anything that forces a cut instead of a full course run. The main drivers, in order of how much they typically move the number:
Facet count. A four-facet hip roof lays shingles in long, mostly uninterrupted runs. A twenty-facet roof with dormers and additions forces a cut at almost every course on almost every plane.
Hip and valley length relative to total roof area. Hips and valleys both require cutting shingles at an angle, and valley material in particular is often cut and discarded rather than reused. A roof with a high ratio of hip and valley linear footage to total squares wastes more per square than a simple roof of the same size.
Cut-up and small facets. Small, irregular facets (over bay windows, small porch roofs, turret sections) generate a high percentage of waste per facet because a full bundle rarely lays down clean on a small odd shape; you cut most of it and use a fraction.
Starter, ridge cap, and hip cap consumption. Some estimators fold accessory consumption into the field waste percentage; others price it as a separate line. Confirm which convention the estimate you are reconciling against uses before comparing percentages directly, because a 12% field waste with separate accessory lines is not the same total consumption as 15% waste with accessories folded in.
It is judgment, not a code
No building code specifies a roof waste percentage. No Xactimate® price list forces a default. The waste field in Xactimate® and the equivalent entry in Symbility® are both editable by the estimator on every estimate; the software will calculate material quantity from whatever percentage you type in, but it does not supply that percentage for you (see the vendor documentation in the sources below for how the field behaves).
That means a 10% estimate and a 20% estimate on the same roof are both the output of a human decision, and the way to resolve the disagreement is not to argue about who is right in the abstract. It is to put the roof's actual facet count, hip and valley footage, and cut-up in front of both sides and let the geometry make the case.
Practice ranges by roof complexity
These are common practice ranges observed across residential estimating, not a published standard and not a code minimum. Use them as a starting point to sanity-check a number, then adjust for the specific roof in front of you.
| Roof complexity | Typical facet count | Common practice range | Why |
|---|---|---|---|
| Simple gable or hip | 4 to 6 facets | 10% to 12% | Long, uninterrupted courses; few cuts; minimal hip and valley length |
| Moderate, some dormers or additions | 8 to 14 facets | 12% to 15% | More hip and valley cuts and at least one break in roof plane |
| Cut-up, many small facets | 15 to 25 facets | 15% to 20% | High ratio of hip and valley length to total area; frequent short courses |
| Turrets, curves, highly irregular | 25+ facets, non-rectangular | 20% and up | Almost every piece requires a cut; standard course length rarely applies |
These ranges describe practice, not policy. A roof that is technically in the moderate facet-count band but has an unusually high valley-to-area ratio can justify a number toward the top of the next range up; document why.
How a measured report grounds the number
The fastest way to move the conversation from opinion to evidence is a facet count and hip and valley length pulled from a measured report rather than eyeballed from a curb or a measured roof report. A measured report lists total facets, total hip and valley linear footage, and total squares for the specific structure, so instead of saying 'this looks cut-up to me,' you can say 'this roof has 18 facets and a hip and valley length of X feet against Y total squares,' and point to where that places the roof in the practice range table above.
Sketch My Roof roof measurement reports list facet count, hip and valley length, and total squares on the report, which is exactly the data an adjuster or contractor needs to defend a waste percentage instead of just asserting one. Ordering one report by address, before the estimate is written, means both sides are arguing about the same set of facts.
If you are the one reconciling a supplement, pull the facet count first. A contractor claiming 20% waste on a report that comes back with six facets and short hip and valley runs is a conversation worth having. A contractor claiming 20% waste on a report with twenty-two facets and a long valley run is simply describing the roof accurately.
Documenting the decision
- Cite the facet count and hip and valley length from a measured report, not an estimate
A measurement source is evidence; a description like "complex roof" without numbers is an assertion that invites the same disagreement again on supplement review.
- Note whether accessory consumption (starter, ridge cap, hip cap) is folded into the waste percentage or priced separately
Comparing a 12% field waste that excludes accessories against a 15% that includes them looks like a 3-point gap that is not really there.
- State the material
Cut waste behaves differently across shingle types and other roofing materials; note what is being estimated so the percentage is read in context.
- Write one sentence of rationale in the estimate notes
"18 facets, valley length X ft over Y squares, waste set at 17%" resolves a supplement dispute in one line instead of a phone call.
Frequently Asked Questions
Is there a code or manual that sets the correct roof waste percentage?
Why does the contractor's waste number generally look higher than the adjuster's?
Does waste factor include starter strip and ridge cap, or are those separate?
What roof characteristics justify a waste percentage above 15%?
How can I settle a waste disagreement on a supplement without a site visit?
Sources
- Waste percentage is an editable estimator input in Xactimate®, not a software-supplied default: Xactimate® official documentation (as of August 2026)
- Waste percentage is an editable estimator input in Symbility®, not a software-supplied default: Symbility® / CoreLogic claims documentation (as of August 2026)
- Measured reports list facet count, hip and valley length, and total squares for the structure ordered: Sketch My Roof roof measurement service facts (as of August 2026)
- Reports are ordered by property address with formats for Xactimate®, Symbility®, and PDF: Sketch My Roof residential order page (as of August 2026)
