Metal roofing

Typical lifespan

30–70 years

Installed cost per square

$900–$2500estimate

Weight

50–150 lb per square

Fire class

Class A over an approved deck and underlayment

Impact class

UL 2218 Class 4 available; note that metal dents without losing watertightness

How does metal roofing actually work?

A metal roof is a set of panels that shed water down their length, and the whole question is how those panels are held down. Exposed-fastener systems are screwed straight through the face of the panel into the deck, with a neoprene washer under each screw head doing the sealing. Standing seam joins panels at raised vertical seams using concealed clips, so nothing penetrates the weather surface at all. That single difference drives cost, lifespan and maintenance: an exposed-fastener roof has hundreds of gaskets that dry out and back out over twenty years, while a standing seam roof has none. Metal also expands and contracts far more than asphalt across a day, which is why standing seam clips are designed to let the panel move and why a panel fastened rigidly will eventually oval its own holes.

What drives the cost?

Panels are cut to length per run, so every valley, hip, dormer and skylight adds a cut, a flashing detail and time — complexity moves a metal quote further than it moves an asphalt one. The metal itself matters: steel is the baseline, aluminium costs more and is the right answer near salt water, and copper or zinc are architectural money. The coating is where two apparently identical steel quotes diverge, because a premium fluoropolymer finish holds colour for decades longer than an economy paint system. Then there is tear-off, decking replacement at a per-sheet price, and access. Underneath all of it, the exposed-fastener versus standing seam decision is worth more than every other variable combined.

What separates a good installation from a bad one?

On standing seam, the work is in the flashings and the clips: correct clip spacing for the wind zone, panels free to move with temperature, and properly formed transitions at valleys, walls and penetrations. On exposed-fastener, it is the screws — driven straight, to the right depth, in the pattern the manufacturer specifies. Overdriven screws crush the washer and start leaking early; underdriven ones never seal at all. Both systems need an underlayment rated for the temperatures a metal roof reaches, and both need a ventilation strategy, because warm moist air meeting a cold metal underside condenses and drips exactly like a leak without ever being one.

Where does metal roofing work well?

Best climates: High wind, heavy snow, wildfire-exposed areas, and hot sunny climates where reflectance pays

Worst climates: Coastal salt spray with the wrong alloy or coating; galvanic pairing with the wrong flashing metal

What maintenance does it need?

Standing seam is close to maintenance-free in the field; what needs attention is the flashing at penetrations and the sealant at transitions, on a multi-year cycle. Exposed-fastener roofs are different and the difference is the whole ownership story: budget to have the fasteners inspected and re-driven or replaced somewhere around the fifteen to twenty year mark, because the washers are the failure point long before the panel is. On either system, keep debris out of valleys, avoid walking the panels unnecessarily, and never let dissimilar metals touch — pairing the wrong flashing metal with the wrong panel sets up galvanic corrosion that eats the cheaper one.

What fails first

On exposed-fastener panels, the neoprene washers under the screws — they dry out and back out decades before the panel does. On standing seam, the flashing details and penetrations, not the field of the roof

When should you choose it?

Choose metal when you intend to keep the house long enough to collect on the lifespan, when you are in high wind, heavy snow or wildfire-exposed country, or when reflectance genuinely pays in a hot sunny climate. It is also the right answer on low-slope sections where shingles would not be watertight but a full membrane feels like overkill. Standing seam in particular is the covering to choose if you would rather never think about the roof again.

When should you think twice?

Reconsider if you are selling soon, because you pay the whole premium and the buyer collects the payback. Be careful in severe hail regions: metal dents without losing watertightness, several carriers treat those dents as cosmetic by definition, and some policies now carry an explicit cosmetic damage exclusion — read that endorsement before buying metal for an insurance reason. And on a very cut-up roof, the cost of all those cuts and flashings can push metal past the point where it makes sense.

What ratings does it carry?

Common mistakes

• Comparing an exposed-fastener quote against a standing seam quote as though they were the same product. They age completely differently and one has hundreds of gaskets in it.
• Buying metal for an insurance discount without checking. It is carrier- and state-specific, and a cosmetic damage exclusion can cut the other way on hail dents.
• Ignoring the coating. Two steel roofs at different prices are frequently the same steel with very different paint systems.
• Skipping the ventilation gap on a recover. Warm moist air on a cold metal underside condenses and does the damage of a leak without being one.
• Fastening panels rigidly. Metal moves with temperature far more than asphalt; a panel that cannot move ovals its own fastener holes.