Standing seam or exposed fastener is what separates a roof that outlives you from one that needs re-screwing in a decade. Most quotes do not make clear which one you are buying.
Reviewed by Michael ThompsonMetal roofing installation means fastening formed steel or aluminium panels to a prepared deck over an underlayment, with the entire system - panels, clips or screws, trims, closures and flashings - working together to shed water and allow for thermal movement. The choice that matters most is standing seam versus exposed fastener: concealed-clip standing seam has no penetrations through the panel face, while exposed-fastener panels rely on gasketed screws that are a maintenance item with a finite life.
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Panel decision, made before anything is priced
Standing seam uses concealed clips and raised interlocking seams; exposed-fastener corrugated or ribbed panels screw straight through the face into the deck or purlins. The first costs substantially more to buy and install; the second has thousands of rubber-gasketed penetrations that will need attention.
Watch forA quote that says "metal roof" and a price, with no panel profile, gauge, or fastening system named. That ambiguity is where the margin lives, and it is the single most common way homeowners end up with a roof they did not think they had bought.
Substrate - tear off, or install over the existing roof
Metal can often go over one existing layer of asphalt using furring strips or a purlin system, saving tear-off and disposal. Full tear-off exposes the deck for inspection and repair, and produces a flatter, better-looking finished plane.
Watch forOver-shingle installation used to avoid looking at the deck. If the existing roof has been leaking, going over it entombs wet sheathing under a sixty-year covering. Ask what evidence there is that the deck is dry.
Underlayment - and why it is not the same spec as under shingles
Metal roofs get hot and cold, and condensation forms on the panel underside. A high-temperature synthetic underlayment is used, and in freeze climates an ice barrier at eaves and valleys. Some assemblies add a ventilated batten layer so the panel underside can dry.
Watch forStandard felt under a metal roof. It degrades at the temperatures metal reaches and it is a false economy on an assembly meant to last decades.
Measuring and forming the panels
Panels are cut to the exact rafter length, frequently roll-formed on site so runs are continuous with no horizontal joins. Trims, ridge caps, hip and valley flashings and closures are formed to match.
Watch forPanels cut with an abrasive chop saw. The hot swarf embeds in the coating and rusts, leaving orange freckles across a brand new roof. Nibblers or shears are the correct tools and a metal roofer will have them.
Fastening - and leaving room for movement
Metal expands and contracts appreciably along its length. Standing seam clips are designed to let panels slide; exposed-fastener screws must be driven to the right depth, compressing the washer without crushing it, in the correct position relative to the rib.
Watch forOverdriven or underdriven screws. Crushed washers fail early; loose ones leak from day one. On a large exposed-fastener roof this is thousands of individually judged fastenings, which is exactly why installer skill matters more than panel brand here.
Trims, closures and penetrations
Ridge, hip, rake, eave, valley and wall details are formed and lapped so water and wind-driven rain cannot get behind them. Foam or metal closures fill the profile at ridge and eave. Pipes and vents get purpose-made flashings, not adapted shingle boots.
Watch forSealant doing structural work. Correctly formed and lapped trims shed water by geometry; caulk is a secondary defence with a service life. A roof held together by sealant will start leaking about the time the warranty conversation gets difficult.
Walk-through, touch-up and warranty registration
The roof is checked for scratches through the coating, swarf, missed fasteners and trim gaps. You should receive the panel finish warranty, the manufacturer system warranty where applicable, and the installer's workmanship warranty separately.
Watch forScratches touched up with any handy paint. Coating warranties are void where the finish has been breached and repaired with a non-approved product. Ask for the manufacturer touch-up pen.
Metal roofing installs at a clear premium to asphalt - typically two to three times the price for a comparable roof, with standing seam materially above exposed fastener. Panel profile, gauge, coating and roof complexity drive it. Our cost guide breaks it down by system.
See the full metal roofing installation cost guide - by material, size and region →
Estimate your metal roof panel run and area → Squares and rafter length - the two numbers a metal quote is built from.
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| Option | What it means for you |
|---|---|
| Standing seam | Concealed clips, no face penetrations. The long-life option. |
| Corrugated / exposed fastener | Screwed through the face. Cheaper, and the screws are a maintenance item. |
| Metal shingles & stone-coated steel | Metal performance in a shingle or tile appearance. |
| Metal roof vs shingles | The comparison most people are actually running. |
| Standing seam vs corrugated | The decision this page turns on, side by side. |
| Metal roofing material guide | Gauges, coatings, alloys and finishes explained. |
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