Metal Roofing 101: Why Panel Choice Drives Everything Else
A metal roof is the longest-lived, most weather-resistant cladding you can put on a building short of slate or clay tile. It will outlast two or three asphalt-shingle replacements, shed snow and hail without damage, and recover almost all of its scrap value at the end of a 50-year life. But unlike shingles — where you pick a colour and a warranty tier and the rest is identical — metal roofing splits into four distinct families with very different material lists, install methods, costs and design tolerances. Getting the right material list begins with picking the right panel.
Standing seam is the premium choice for visible residential and architectural commercial work. Panels are flat with raised vertical seams (typically 1" to 2" tall) on each edge; the seams snap or are mechanically folded together over hidden clips screwed to the deck. Because no fasteners pierce the panel field, the roof has no failure-prone gaskets, can move with thermal expansion, and lasts 40–60 years. Coverage widths are 12", 16", 18" or 24" — narrower means more seam lines (a more traditional look) and more material per square foot; wider means cleaner aesthetics, fewer clips, and lower labor cost. Exposed-fastener panels (R-panel, PBR, 5V-crimp, corrugated) are screwed through the panel face into the deck or purlins with neoprene-washer screws, spaced 12" on field and 6" on edges. They cover 24"–36" per panel, install fast, and run $4–$7 per square foot for material — but need a screw-replacement pass at 15–20 years to keep gaskets sealed. Corrugated is the classic wavy profile, still common on agricultural and rustic residential. Stamped metal shingles mimic asphalt, slate or wood shake in 12–14 sqft panels and install one course at a time.
For any of these families the takeoff math is the same: figure the actual sloped surface area (plan-view × pitch multiplier), add waste, divide by panel coverage to count panels, then list every piece of trim (ridge cap, rake / gable trim, drip edge, valley flashing, hip cap), closure strips at every ridge and eave, fasteners by panel type, and underlayment by square. This calculator does all of that in one pass for multi-slope roofs (gable, hip, complex), and outputs a complete shopping list you can hand to your supplier — including weight (for the structural engineer) and cost.