Metal Roofing & Standing Seam Installation

Exposed fastener panels, the corrugated and R-panel profiles most people picture, are screwed straight through the face of the metal into the structure below. Every screw carries a rubber washer, and that washer is the seal. It is also the component with the shortest service life on the entire roof.

A standing seam roof carries no fasteners through its surface. The panels hang from concealed clips and lock to each other at a raised seam that sits above the water line, so nothing penetrates the plane rain actually runs down. That is the whole argument for the system, and it is most of why the two price differently.

Neither one is wrong. An exposed fastener roof over a shop, a barn or a covered porch is a sensible piece of building and will do its job for decades, provided somebody goes back and re-torques the screws when they start backing out. The mistake is buying an exposed fastener roof while expecting standing seam maintenance, which is none.

A steel panel forty feet long measurably grows and shrinks between a January night and an August afternoon. On a standing seam roof the clips are built for exactly that, so the panel slides against them and the seam absorbs the travel. Pin the same panel at both ends with fixed fasteners and the movement still has to go somewhere, so it goes into the fastener holes, which elongate, and into the panel itself.

Oil canning, the faint waviness visible across a wide flat pan in low sun, is worth naming because it alarms people who were not warned about it. It is a cosmetic characteristic of light gauge flat metal. It is not a failure, not a leak and not grounds for replacement, and striations rolled into the pan reduce how much of it the eye picks up.

Underlayment does more work under metal than it does under shingles, for a related reason. Metal sheds water quickly and then condenses on its underside when the panel goes cold at night, so the layer between the metal and the deck is managing water from both directions. A high temperature synthetic or a self-adhered membrane belongs there, and the felt that was acceptable under asphalt is not.

Service life is the reason people start asking about metal. On a properly detailed standing seam roof the coating is usually what ages rather than the steel, so the finish chalks and fades while the panel underneath is still structurally fine. Stone coated steel sits between the two families, with a granulated surface over a steel shell and the profile of tile or shake.

Price is the reason people stop asking. Metal costs more than architectural asphalt on day one, and the gap widens with complexity, because every valley, hip, chimney and skylight on a standing seam roof is a fabricated flashing rather than a shingle cut to fit. A simple gable is where metal comes closest to asphalt. A roof with six planes and three dormers is where it is furthest away.

Recovering an existing shingle roof with metal is possible and is sometimes the right call, but it is a code question before it is a preference. Layer count, deck condition and the jurisdiction decide it, and in Florida the answer is more often no than it is in Georgia. That gets settled before a scope is written, not after the panels are on site.