Asphalt Shingles vs Metal Roofing
Two common roofing systems, compared on the basics
Two systems, different trade-offs
Asphalt shingles cover most pitched residential roofs in North America; metal roofing has grown from farm buildings into mainstream housing. Neither is universally better. The right choice depends on the roof's slope and shape, the climate, the budget, and how long the owner expects to keep the building.
Installation method
Asphalt shingles are individual overlapping units, nailed in courses starting from the eaves. Metal roofing is typically installed as larger panels or standing-seam sheets running from eave to ridge, fastened either through the panel face or with concealed clips, depending on the system.
Exposed-fastener panels
Corrugated and ribbed panels screwed through the face with gasketed fasteners. They're economical and quick to install, but the fasteners and washers need periodic inspection because thermal movement and UV exposure can loosen or degrade them.
Standing seam
Panels joined by raised seams that are snapped or mechanically folded together, attached with hidden clips that let the metal expand and contract. More expensive and more specialized to install, but with no exposed fasteners in the field of the roof.
A quick comparison
- Weight: metal roofing is generally lighter per square than asphalt shingles
- Typical lifespan: metal roofing often carries a longer expected service life than standard asphalt shingles, though both vary significantly by product tier and climate
- Installation: shingles are widely installed by most roofing crews; metal panel/standing-seam systems often require more specialized installation experience
- Estimating unit: both are commonly estimated in 'squares' (100 sq ft), though metal panels are also frequently ordered by specific panel length and width
| Asphalt shingles | Metal roofing | |
|---|---|---|
| Minimum slope (2021 IRC) | 2/12 (double underlayment below 4/12) | 3/12 lapped; ½/12 with lap sealant; ¼/12 standing seam |
| Unit of sale | Bundles (commonly 3 per square) | Panels cut to length, plus trim |
| Weight | Heavier per square | Lighter per square |
| Complex roofs | Forgiving — small units cut easily | More trim and cut waste at hips and valleys |
| Maintenance points | Granule loss, lifted tabs | Exposed fasteners (if used), sealant at trim |
Durability ratings worth checking
Marketing lifespans and warranty terms vary widely and aren't directly comparable. Independent test ratings are more useful when comparing products:
- Fire: look for a Class A rating (ASTM E108 / UL 790). Most asphalt shingles and many metal systems achieve it as installed.
- Wind: shingles are classified under ASTM D3161 and D7158; metal panel uplift is commonly tested to UL 580 or UL 1897.
- Hail: UL 2218 impact ratings run from Class 1 to Class 4, the highest. Some insurers offer discounts for Class 4 products.
How estimating differs
Both systems start from the same roof-area calculation: the roof plan, including the overhangs, × the slope factor, as Roof Area vs Floor Area explains. Waste allowances differ, though: metal panels often waste less on a simple roof but can waste more around complex hips and valleys if panels can't be reused after a cut, while shingles are more forgiving of irregular cuts since they're a smaller individual unit.
Shingles
Divide the sloped area by 100 to get squares, multiply by bundles per square, and add a waste allowance. The Roof Shingle Calculator uses 3 bundles per square and 10% waste by default. Starter strip, hip and ridge cap, underlayment, drip edge and nails are ordered separately.
Metal panels
Metal is counted along the eave. Divide the eave length by the panel's coverage width, round up, and order each panel to the eave-to-ridge length plus overhang. For a 40 ft eave with 36 in coverage panels, that's 40 × 12 ÷ 36 = 13.3, so 14 panels per side. Trim — ridge cap, eave and rake trim, valley flashing — is ordered by the linear foot.
Comparing costs without guessing prices
Prices vary enormously by region, product tier and season, so BuildNumerics calculators never embed a market price. The Metal Roof Cost Calculator and the Roof Replacement Cost Calculator take your own quoted rates, which lets you compare two systems on the same roof area with real local numbers. For longer-term comparisons, divide each installed cost by the service life you realistically expect, not the warranty headline.
Common mistakes
- Choosing exposed-fastener panels for a slope below 3/12 without lap sealant.
- Estimating metal by squares only and forgetting that panels are cut to length and counted by coverage width.
- Comparing a 'lifetime' shingle warranty with a metal paint-finish warranty as if they covered the same things.
- Installing metal over an existing roof without checking the manufacturer's and local code requirements.
FAQ
- Is metal roofing lighter than shingles?
- Generally yes. Common steel and aluminum panels weigh less per square than asphalt shingles, which is one reason metal is sometimes installed over a single existing layer where the manufacturer and local code permit it.
- Can metal roofing go on a low-slope roof?
- Standing-seam systems can go down to ¼ in per foot under the 2021 IRC (Section R905.10.2). Lapped exposed-fastener panels need 3/12, or ½/12 with applied lap sealant.
- How do you estimate metal roof panels?
- Divide the eave length by the panel's coverage width and round up to get panels per roof plane. Order each panel to the eave-to-ridge length plus overhang, then add trim by the linear foot.
- Which lasts longer, shingles or metal?
- Metal typically has a longer expected service life, but both vary a lot by product, installation quality and climate. Compare independent ratings for wind, hail and fire, and the specific warranty terms, rather than headline lifespan claims.
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Sources
IRC Sections R905.2.2 and R905.10.2 (2021 edition)
Asphalt shingles: 2/12 minimum, double underlayment from 2/12 up to 4/12. Metal roof panels: 3/12 for lapped, nonsoldered seams without applied lap sealant, ½/12 with applied lap sealant, ¼/12 for standing seam. Read in the 2021 Seattle Residential Code, Chapter 9, a local adoption of the 2021 IRC; applies only where adopted.
IRC Sections R905.2.2 and R905.10.2 (2021 edition) — referenceUL 2218 / ASTM E108 / ASTM D7158
Impact resistance, fire and wind classifications for roof coverings.
ARMA Residential Asphalt Roofing Manual (2014 edition)
1 square = 100 ft²; typically 3, 4 or 5 bundles per square.
ARMA Residential Asphalt Roofing Manual (2014 edition) — reference