Metal vs asphalt roofing
Metal and asphalt are the two most common steep-slope choices, and they differ in nearly everything that matters for estimating: how they are counted, what slopes they suit, how long they last, and what they cost.
How each is estimated
Asphalt is counted in bundles per square — three for 3-tab, four for architectural. Metal is counted differently: by panel coverage width, meaning how many panels of a given usable width it takes to cover the eave length, multiplied by the number of runs up the slope. The two materials use genuinely different math, which is why the metal calculator asks for eave length and panel profile rather than just area.
Slope suitability
This is often the deciding factor. Asphalt shingles need at least a 2:12 pitch, and really perform best at 4:12 and above. Standing seam metal, by contrast, can be installed on very low slopes — down to around ¼:12 with the right mechanically-seamed system — which makes metal the standard choice for low-slope residential roofs where shingles simply are not allowed. On a steep roof, both are options; on a shallow one, metal often wins by default.
Lifespan
Asphalt shingle roofs commonly last 20–30 years, with architectural at the upper end and climate, ventilation, and install quality all mattering. Metal roofs routinely last far longer — often 40–70 years for quality systems. Over a long enough horizon, metal's longer life offsets its higher up-front cost, which is the core of the cost-per-year argument that metal advocates make.
Weight and structure
Metal is light — an advantage when re-roofing over a structure of uncertain capacity, and far lighter than tile or slate. Asphalt is moderate. If you are switching materials, especially to a heavier one, confirm the structure suits the new load and expect a permit, since changing material changes both the dead load and the fire rating. See reroofing vs tear-off.
The trade-off, honestly
Asphalt wins on up-front cost, familiarity, and ease of installation and repair. Metal wins on lifespan, low-slope capability, weight, and water shedding, at a higher initial price and requiring trained installers. There is no universally right answer — it depends on your slope, budget, how long you will own the home, and climate. We do not publish prices for either, because they swing by region and product; use your own quote in the cost estimator.