How to Install a Standing Seam Metal Roof

Homeowners choose metal roofs by color. Color is a coating line item. The panel family is the roof: it sets minimum slope, whether a seamer has to be on site, how long a panel can be, and how the roof handles movement.

Metal expands when it heats and contracts when it cools, and a roof panel sees a bigger daily swing than anything else on the building. Across a hundred-degree swing, a long steel run moves on the order of a quarter to a third of an inch. Aluminum moves about twice that.

One fixed point, everything else floats

Each panel gets exactly one fixed point where it is anchored and cannot travel. Everywhere else it rides on floating clips — two-piece clips whose upper tab slides in a track, resisting uplift while the panel slides along the slope. At the bottom, a hemmed panel edge hooks a continuous eave cleat, holding the eave line down without one fastener through the face. Set the sliding tab for the weather you install in: on a hot day the panel is near full expansion, so leave the travel toward contraction.

Where the fixed point goes

On typical residential runs the eave is the fixed point: the hem locked to the cleat holds the visible bottom line, and growth travels up-slope where it disappears under the ridge cap — which is why panel ends are cut short of the peak on purpose. On long slopes and low-slope commercial work the fixed point often moves to the ridge, so gravity is not dragging a heavy panel against the clips, and the eave gets a sliding detail instead. Very long runs are sometimes fixed near mid-span instead.

Standing seam does not lap in the field

There is no side overlap on a standing seam roof, because the seam is the lap. Panels engage edge to edge and the water line sits atop a raised leg, well above the drainage plane. Anyone quoting a standing seam sidelap dimension is describing a different product.

End laps, when the run beats the coil

The real overlap question is the end lap, and the right answer is to design it out — roll panels eave-to-ridge in one piece wherever slope length allows, which is what a portable roll former on site is for. When a run exceeds what can be formed, shipped or handled, the lap is a deliberate detail: several inches of upper-over-lower, a continuous butyl bead inside the lap, the lower end offset so the pans nest flat, a clip close to the joint on both sides, and slotted fastener holes so it can still move. A butted, caulked, unsupported end lap is a leak with a date on it.

Exposed-fastener panels — a different roof entirely

If your panel is corrugated or ribbed with screws through the face, overlap is a real field dimension: one full corrugation as standard, two ribs in high wind or at low slope, sealant tape in the sidelap where exposure warrants it, and the fastener placed to pull the lap tight without dimpling the panel. That is what most overlap advice online is about.

1. 1

   Square the roof before you trust it

   Measure both diagonals of every plane plus eave and ridge. Roofs are rarely square and a metal roof advertises it. Find the error first and split it between both rakes.

2. 2

   Set the module and check the last panel

   Divide eave length by panel coverage width. Sixteen and eighteen inches are the common residential modules; 12 in. on high-end work, 20 to 24 in. on commercial. Narrower panels cost more and oil-can less. If the math finishes on a two-inch sliver, shave an inch off every panel at the former so both rakes look intentional.

3. 3

   Dry in and flatten the deck

   No proud fasteners, no crowned sheathing — every deck flaw is legible through a metal pan. See underlayment for a metal roof for why felt is the wrong material here.

4. 4

   Set eave metal, chalk the first panel, then run one way

   Continuous cleat first, straight and tight, because every panel hem references it. Snap the first line square off the eave, not off the rake. Then hem, hook, clip, seam, repeat — and re-measure to the far rake every fourth or fifth panel. A sixteenth of creep per panel is invisible until it is an inch and a half of unfixable.

Nobody can quote one number for every roof. Four things set it:

• ●Panel width — a wider pan catches more wind per clip.
• ●Gauge and metal — 24 ga steel spans further than 26 ga; aluminum is softer and moves more.
• ●Design uplift — height, exposure and local wind speed set a pressure the assembly must resist.
• ●Where you are on the roof — the one crews skip.

Wind does not load a roof evenly. Air separating over the edges creates suction far higher along perimeters and rakes than mid-plane, and higher again in corners where two edge zones overlap. Spacing therefore tightens outward — often to roughly half the field spacing at corners — and the deck fastener may change too. Residential field spacing commonly lands between 12 and 36 in. on center, but treat that as a range the published table resolves, not a number to install from. Blow-offs start at a corner almost every time.

• ●Eave. Hem the panel bottom — a tight three-quarter to one-inch return — and lock it over the continuous cleat. The hem is structure, not trim.
• ●Rake. Panel leg turned up against a Z-closure, rake trim over it, hemmed outside and fastened into the fascia rather than face-screwed.
• ●Ridge and hips. Cut panel ends short, notch and offset the legs so they do not stack, turn the pan up an inch as a water dam, then closures, then a cap the panel can still travel under. A hip is the same detail on an angle, far slower, and routinely budgeted as if it is not.
• ●Penetrations. Keep pipes in the flat of a pan, never on or beside a seam. Bed a one-piece boot in butyl and fasten around its base; anything larger gets a curb.
• ●Crickets. Anything wide enough to dam water on its upslope side gets one, and snow piles against an obstruction faster on slick metal than you expect.

• ●Never cut with an abrasive wheel. A grinder throws hot filings that embed in the finish across the whole roof and rust into orange freckles within a season. Shears, a nibbler or a cold-cut saw — then sweep every panel, not just the ones you cut.
• ●Keep your weight at the seams. Walk flat-footed with your feet near the ribs where clips support the pan. A boot in the middle of a wide flat dents it permanently.
• ●Blue chalk, never red. Red is effectively a dye on a painted finish and will not wash off. Better still, mark the back of the panel.
• ●Carry panels on edge. Carried flat, long panels bow and take a set before they reach the roof. Never drag one across another, and store bundles pitched so water cannot sit between them.
• ●Striations and pencil ribs are structure. Fine lines or beads rolled into the flat stiffen the pan so it reads flat instead of rippling — the cheapest oil-canning insurance on wide panels or dark colors.