Updated September 2026 by Chris Horton. A method for reading two roofing bids that describe different roofs, not a verdict on materials. How we estimate costs
A homeowner asks a shingle contractor and a metal contractor to quote the same house and gets two numbers that are wildly apart. The instinct is to decide whether metal is worth the premium. The better question is whether the two bids are describing the same project at all, because in almost every case they are not, and the difference is hiding in fields neither bid filled in. This page is a scope-normalisation guide, not a lifetime cost showdown.
Metal roof is not one specification
The first source of confusion is a language problem. Asphalt shingle is a reasonably narrow product family: strip, three-tab, architectural or laminated, with a small number of premium designer lines on top. Two shingle bids are usually comparing recognisably similar products, and the interesting differences are elsewhere on the bid. When both bids are for architectural shingles, the architectural shingles quote decoder covers those differences line by line.
Metal roofing is not a product family in the same sense. Under one umbrella label a homeowner will be quoted any of several materials (steel with a metallic coating, aluminium, copper, zinc, or occasionally stainless), any of several profiles (standing seam with mechanical or snap-lock seams, exposed-fastener corrugated or ribbed panels, or stamped metal shingle and tile), any of several coating systems (bare Galvalume, polyester, silicone-modified polyester, or a full PVDF finish), and any of several attachment methods (through-fastened panels, hidden clips, or a nailing flange for metal shingles). The service life, wind rating, warranty length and installed price all sit downstream of those choices.
The Metal Roofing Alliance and the Metal Construction Association both publish material describing this range and the specification questions that follow from it. The practical consequence is that two contractors can quote a metal roof for the same house and describe two genuinely different products at two genuinely different prices, both of which may be honest bids for what they wrote down.
Once that is on the table, comparing an asphalt bid against a metal bid becomes a two-step exercise. First, force each bid to specify what it is actually installing. Then compare the two like-for-like scope lines, item by item.
The asphalt vs metal bid normalisation matrix
Print or copy the matrix below. Read the asphalt bid into the first column. Read the metal bid into the second. Where a cell is blank on either bid, it is not equivalent to the other side, it is an Unknown, and it goes on the questions list before any totals are compared.
1. Roof and deck assumptions
| Scope line | Asphalt bid — what it should state | Metal bid — what it should state |
|---|---|---|
| Measured roof area | Squares or square feet, and whether measured on the roof, from satellite imagery, or from plans. | Same, plus how eave overhangs, ridge caps and panel end laps were counted. |
| Pitch and complexity | Slope range, number of stories, valleys, dormers, hips. | Same. Some metal profiles have a minimum slope stated by the manufacturer; the bid should confirm the roof meets it. |
| Sections included | Which slopes and structures (main house, garage, additions, porches) are inside the price. | Same. Also whether any low-slope section will be roofed in a different metal profile or a different material. |
| Existing layers to remove | Tear-off or overlay explicitly. Number of assumed layers with a unit price for extras. | Metal over shingles is an option in some jurisdictions with the right substrate, but it is a different job than tear-off to deck. The bid should state which. |
| Deck condition and replacement | Included sheet count, thickness and material, plus the unit price for extras beyond the allowance. | Same, and stricter: many metal systems require a continuous, sound deck or specific plywood thickness for fastener pullout. A bid that is silent on deck standards is Unknown. |
2. Underlayment and moisture control
| Scope line | Asphalt bid | Metal bid |
|---|---|---|
| Underlayment product | Felt (15 or 30 lb) or a named synthetic. The specific product matters for warranty stacking. | A synthetic, high-temperature synthetic, or self-adhered membrane rated for the panel type. Underlayment specification is one of the areas where metal manufacturer documents most often diverge from shingle practice. |
| Ice and water barrier | Where it goes (eaves, valleys, penetrations) and how far up the slope, referenced to the local code minimum. | Same principle. Some metal systems specify full-deck self-adhered membranes in cold-climate applications rather than perimeter-only; the bid should say which the manufacturer requires. |
| High-temperature rating | Not usually required. | Dark metal roofs can reach surface temperatures a standard synthetic underlayment is not rated for. A metal bid should state a high-temperature underlayment where the panel and colour call for it. |
| Vapour and condensation strategy | Rarely called out on a shingle bid. | Metal assemblies over conditioned space sometimes call for a specific membrane, batten cavity or vent strategy to manage condensation. If the roof geometry and climate warrant it, the bid should address it. |
3. Flashing, edging and penetrations
| Scope line | Asphalt bid | Metal bid |
|---|---|---|
| Drip edge and gable edge | New drip edge, colour, gauge. | New matching gauge and colour drip edge or gable trim from the same panel system, not a shingle drip edge on a metal roof. |
| Valley detail | Open or closed-cut, ice-and-water lined. | Open metal valley with the correct hem, width and underlayment, matched to the panel system. |
| Chimney, wall and step flashing | New or reused, each named. Counterflashing and sealant separately. | Same, plus whether flashings are formed from matching coil stock or supplied by the panel manufacturer as system parts. |
| Pipe boots and vents | New rubber or lead boots for stacks; new box or ridge vents as required. | Metal-specific pipe boots (silicone or EPDM) rated for the panel profile, or purpose-made curbs and flashings for the exact profile. |
| Skylights | Replaced, reflashed or excluded, named individually. | Same, plus whether flashing kits are ordered from the skylight manufacturer for the specific metal profile. |
| Transition and dissimilar-metal detailing | Not usually required. | Metal roofs sometimes touch flashings, gutters or copper penetrations that are galvanically incompatible. The bid should state whether isolation is included where those junctions exist. |
4. Field material and system
| Scope line | Asphalt bid | Metal bid |
|---|---|---|
| Product identifier | Manufacturer, product line, and colour. Not just brand, and not just a warranty length. | Manufacturer, panel profile name, substrate (steel, aluminium, copper, zinc), gauge or thickness, coating (Galvalume plus a paint system such as SMP or PVDF/Kynar), colour and colour family. |
| Accessory system | Whether starter, ridge cap and hip-and-ridge are the same manufacturer as the field shingle. This is often what unlocks an upgraded manufacturer warranty tier. | Whether trims, closures, clips or fasteners, sealants and touch-up paint are all supplied by the panel manufacturer or a matched system. Mixing profiles across manufacturers usually voids system warranty. |
| Attachment method | Nail count per shingle (4 or 6) and any enhanced pattern for wind rating. | Whether panels are through-fastened (exposed fasteners with washer gaskets) or attached with concealed clips. Fastener spec, spacing, and whether clips are floating or fixed to accommodate thermal movement. |
| Seam and closure detail | Not applicable. | For standing seam, whether seams are mechanical (single or double lock) or snap-lock, and end laps, transitions and ridge closures accounted for. For exposed-fastener panels, ridge closures, end closures and stitch fasteners at overlaps. |
| Ridge and hip cap | Manufactured hip-and-ridge shingle product, or field shingles cut on site. Different price, different warranty standing. | Manufactured ridge cap with vented or solid closure, matched to the panel and to the ventilation plan. |
5. Ventilation
| Scope line | Asphalt bid | Metal bid |
|---|---|---|
| Exhaust | Ridge vent or other exhaust product, named. | A ridge vent designed for the metal profile, or an equivalent exhaust strategy. Cutting a shingle-style ridge vent into a metal ridge is not a specification. |
| Intake | Soffit vents, baffles, and whether existing intake is adequate. | Same. |
| Balance statement | An explicit statement that the finished system is balanced. Inadequate ventilation is a named exclusion in most manufacturer warranty documents. | Same, and often referenced explicitly by the metal panel manufacturer’s installation manual. |
6. Warranty structure
| Scope line | Asphalt bid | Metal bid |
|---|---|---|
| Manufacturer material warranty | The specific tier being offered, and whether it is a standard limited warranty or an upgraded system warranty conditional on accessory use and certification. | Substrate warranty (steel with metallic coating) and paint or finish warranty (fade and chalk) as separate documents with separate terms, plus the coverage table (prorated vs non-prorated period, colour-uniformity language, coastal exclusions). |
| Workmanship warranty | Years covered, and who stands behind it: the contractor alone, or the contractor with manufacturer backing under a certification tier. | Same. Some metal panel manufacturers offer weathertightness warranties on specific standing-seam systems installed by certified contractors; if that is claimed, the tier and certifier should be named. |
| Wind rating | The label (for example, a numeric mph rating) and any conditions that must be met at install (nailing pattern, starter product, accessory brand). | The panel’s tested wind uplift rating, its test standard (for example, an ASTM or UL designation), and any clip spacing or substrate condition required to achieve it. |
| Registration | Who registers the warranty, and by when. An unregistered warranty can silently drop to a lower tier. | Same. On metal systems, the manufacturer sometimes issues the final warranty document only after a completion inspection or certified installer sign-off. |
| Exclusions to read before signing | Ventilation, algae, coastal proximity, tree overhang, colour uniformity over time. | Coastal or saltwater proximity, standing water, dissimilar-metal contact, chemical exposure, colour matching on repairs, and ventilation of the substrate. |
The roofing warranty guide covers the difference between a manufacturer material warranty and a contractor workmanship warranty in more detail, and why the two are not interchangeable.
7. Labour, cleanup and terms
| Scope line | Asphalt bid | Metal bid |
|---|---|---|
| Crew and installer certification | Any claimed manufacturer certification (contractor tier). Verify it on the manufacturer’s own contractor locator, not the logo on the bid. | Whether the crew is certified by the panel manufacturer for that specific system, especially where a weathertightness warranty is being offered. |
| Permits and inspections | Who pulls, who pays, and whether inspection is included. | Same. |
| Property protection and cleanup | Landscaping protection, magnetic nail sweep, final walkthrough. | Same, plus disposal of panel offcuts and swarf. |
| Timeline | Start window and days on site. | Same, with an allowance for panel lead time on custom colours or profiles. |
| Unit pricing and change orders | Per-square rate, per-sheet decking rate, per-boot pricing, and a written change-order clause. | Per-panel or per-square rate, per-sheet decking rate, and pricing for extra flashings or curbs. |
| Payment schedule | Deposit, progress, final, and what triggers each. | Same. Metal jobs sometimes include a deposit against panel order at the manufacturer. |
Do not compare yet
Two bids cannot be compared on price alone if any of the following is true. Treat each as a hard gate: send the bid back for specification before you look at the totals.
A bid that clears these gates is not necessarily a better bid. It is a bid that has become comparable. That is the whole point of the exercise.
How to read the two bids after normalisation
Once the matrix and the gates have been worked through, the difference between an asphalt bid and a metal bid usually resolves into three or four honest categories rather than one confused total. Naming them explicitly is often more useful than defending a preference.
The material category
A named premium architectural shingle system is a different product from a named PVDF-coated standing-seam aluminium system. Both are real, both are legitimate, and neither is a rebuttal to the other. This is where a homeowner’s expected time in the house, climate, and aesthetic preference are decisive, and it is the place where general lifetime and durability claims about “metal roofs” are least useful, because the range within the metal category is wider than the range between the categories.
The deck and structural category
A metal bid that includes structural or deck work an asphalt bid does not is not more expensive for the same job. It is a different job. Extra plywood, fastener-appropriate decking, or bracing at panel transitions is real work that should live on its own line rather than be baked into a headline metal price.
The system-completeness category
Bids that use the panel manufacturer’s own flashings, closures, sealants and fasteners are usually the ones eligible for the manufacturer’s stronger warranty tiers. Bids that mix parts across sources may be cheaper and may still be code compliant, but the warranty picture is different, and the difference belongs on the bid.
The workmanship and certification category
A certified installer offering a weathertightness warranty on a specific standing-seam system is a different scope of coverage than a general roofing contractor offering their own workmanship warranty on the same panel. Both are legitimate arrangements. They should be compared as such, rather than treated as identical because both bids used the word “warranty”.
Once the two bids describe like-for-like scope, the compare two or three roofing bids tool and the roof quote analyzer walk each bid through the specification questions and write the follow-ups out for you. Nothing you type is stored.
Route completed scope into the roofing tools
The full UpgradeWorth roofing tool set is designed to sit downstream of a normalised bid, not to replace the specification work.
- Roof replacement cost in 2026 covers the underlying drivers behind a total, once the bid is defined well enough to have one.
- Roof replacement quote checklist is the single-bid version of this matrix, useful when only one contractor has been called.
- Roof quote analyzer steps a homeowner through six passes on one bid, producing a written list of follow-up questions.
- Compare two or three roofing bids takes two normalised bids and calls out where they say different things.
- Roof estimate scope checker is a fast pass for the specification lines a bid is most likely to leave blank.
- Roof repair vs replace observation tool is where to start if a full replacement was not yet warranted.
What this page deliberately does not do
It does not declare a national dollar-per-square figure for either system, and it does not report homeowner-quoted numbers from forums as market facts. Regional labour rates, panel and coil pricing, gauge and coating tier, roof geometry, tear-off scope and deck condition move both totals enough that averaged headline prices tend to mislead more than they inform. Where a specific number matters to a decision, the source is the local, written bid on the specific house.
It also does not rank asphalt against metal on lifetime, warranty length or resale value. Manufacturer material warranty documents on both sides are specific, are not identical between products, and have exclusions that a comparison paragraph cannot fairly summarise. When those numbers become decisive, they come from the actual warranty documents attached to the bid, not from a category-level claim.
Common questions
Is a metal roof always more expensive than shingles?
Usually, but not always by the same margin, and comparing headline totals without normalising the scope first will overstate the range as often as it understates it. The matrix on this page is designed to separate genuine material and system cost differences from scope differences that are not part of the material decision at all.
Does a metal roof last longer than a shingle roof?
Some metal systems, installed to the panel manufacturer’s specification with the correct coating and detailing, carry longer material warranties than most shingle products. That is not the same as a general “metal lasts X years” claim, because service life depends on substrate, coating, detailing, ventilation and climate. Read the warranty documents attached to each specific bid rather than category-level averages.
Can I put a metal roof over my existing shingles?
In some jurisdictions, over some substrates, with some panel systems, yes. In others, no. A bid should state whether it is a tear-off to deck or a recover, cite the local code position, and reference the panel manufacturer’s installation manual on whether a recover is permitted for that product. If the bid is silent, treat it as Unknown.
What is the difference between exposed-fastener and standing seam?
Exposed-fastener panels are through-fastened to the deck or purlins with washered screws that remain visible. Standing seam panels are attached with concealed clips or a nailing flange and joined at raised, interlocking seams. They are different products with different price points, different service lives, different aesthetics and different failure modes. Neither is a substitute for the other on a bid.
What about PVDF versus SMP paint?
Both are named finish systems used on painted metal panels. Their fade and chalk resistance, warranty length and price differ. If two metal bids appear close in total but one names PVDF and the other names SMP, that is a real scope line, not a rounding difference.
About the author
Chris Horton writes UpgradeWorth’s homeowner decision guides. He covers how replacement projects are scoped, quoted and warrantied, with a bias toward what a homeowner can verify in writing rather than what a salesperson says at the kitchen table. UpgradeWorth does not sell leads, rank contractors or accept placement fees.
Next: the single-bid checklist for when only one contractor has been called, the roofing warranty guide for the difference between the two kinds of warranty on either system, or back to the Roofing hub.