Metal, tile & flat
Standing seam vs exposed fastener: quantities, cost and life
Both are metal roofs; they are built, priced and maintained differently. The difference shows up in the screws.
Two ways to hold a panel down
Exposed-fastener panels (ribbed, PBR, R-panel, corrugated) are screwed straight through the panel into the purlins or deck, with a rubber washer under each screw head. The side laps are held by short stitch screws. It is quick, cheap and strong, and every screw is a hole in the roof sealed by a washer.
Standing seam panels are held by concealed clips fastened to the deck under the seam; the next panel’s edge locks over the clip and the two edges stand up together as the seam. Nothing goes through the panel’s face. Snap-lock panels lock by hand; mechanically seamed panels are folded together with a seaming tool; nail-strip panels have a fastening flange hidden by the next panel.
Counting them
Exposed-fastener panels are counted by coverage width (36 inches for most ribbed panels); standing seam by seam spacing (12, 16 or 18 inches), with no side lap to subtract. On the same 40-foot gable roof:
| Exposed fastener, 36 in | Standing seam, 16 in | |
|---|---|---|
| Panels per 40 ft eave | 14 | 30 |
| Panels, two planes, with 3% waste | 29 | 62 |
| Fasteners | about 2,000 screws through the face plus stitch screws | 600 clips, 1,200 clip screws, none through the face |
| Seams or laps | 26 side laps | 58 seams |
| Minimum pitch | about 3/12 (lower with sealant and long laps) | 3/12 snap-lock; ½/12 mechanically seamed |
The screw count on the exposed-fastener roof comes from the screws calculator: 29 panels with five screws per purlin row, nine at the eave and ridge, and stitch screws every 18 inches, about 2,220 with trim. The clips come from the standing seam calculator: one every 24 inches up each 18-foot panel.
Cost
Standing seam costs more in material (narrower panels, thicker gauge, clips, more trim detail) and roughly twice the labor. Published 2025 cost surveys put installed exposed-fastener roofing at about $800 to $1,500 per square and standing seam at $1,200 to $2,500, before tear-off.
The same 20-square roof in both systems
From the metal roof cost calculator, 26-gauge exposed fastener, walkable, one storey, one layer torn off at $150 per square, $40 underlayment, $300 permit:
- Exposed fastener: $16,820 to $29,540, $841 to $1,477 per square
24-gauge standing seam on a steep two-storey house in a high-cost region (factor 1.2), over the existing roof:
- Standing seam: $31,718 to $62,336
Gauge, pitch, height and region account for much of the gap between the two examples; on an identical roof the system difference alone is roughly 50 to 70 percent.
Life and maintenance
Industry life-expectancy surveys put exposed-fastener metal at about 30 to 45 years and standing seam at 40 to 70. The panels themselves often outlast both figures; what wears out on an exposed-fastener roof is the washers. UV hardens and cracks the rubber over 10 to 20 years, and screws loosen as the panels expand and contract daily. A fastener inspection at 10 to 15 years, replacing failed screws with oversized ones, is part of owning one. Standing seam has nothing to replace except sealant at the trim.
Spread over its life, the dearer roof can be the cheaper one, if you stay to use it. The lifespan and cost per year calculator does the sum, and how long roofs last lists the ranges.
Thermal movement
A steel panel 30 feet long grows and shrinks by about a quarter inch between a cold night and a hot afternoon. Exposed-fastener panels accommodate it by flexing at each screw, which is what slowly enlarges the holes. Standing seam handles it with expansion clips that let the panel slide; on panels over about 30 feet they are required. Nail-strip panels, with fixed flanges, are limited to shorter lengths for the same reason.
Leaks, repairs and noise
Where the two systems leak is different. An exposed-fastener roof leaks at screws, a failed washer or a screw driven at an angle, and at side laps that were not stitched or sealed; both are easy to find and cheap to fix, a new oversized screw or a bead of sealant. A standing seam roof rarely leaks in the field; when it does, it is at trim, penetrations or a seam damaged by foot traffic, and the repair needs someone with the panel maker’s parts.
Damage from walking is worth knowing about. Exposed-fastener panels can be walked on the flats near the purlins; standing seam panels, especially wide ones, dent between the seams, and a dent can hold water. Neither system is noisier than shingles once there is a solid deck and underlayment under it: the drumming people remember is from panels on open purlins over barns.
Both need the same underlayment under them, usually a high-temperature synthetic, because metal gets hot enough in summer to soften ordinary felt. Both need the same attic ventilation; a metal roof over a poorly ventilated attic can drip condensation from its underside on a cold night.
Choosing
- Barns, sheds, garages, budget roofs: exposed fastener. Cheap, fast, easy to repair, and the fastener check is easy on a low building.
- Houses you will keep, low slopes, snow country: standing seam. No holes in the face, seams that shed water down to ½/12 (mechanically seamed), and the cleaner look.
- Steep, visible roofs where oil-canning would show: narrow standing seam panels (12 inches) or panels with striations.
Either way the panel arithmetic, slope length and coverage width, is the same, and metal roof panel maths covers it. The panel calculator handles exposed-fastener roofs, and what roofers charge per square sets both prices against asphalt, tile and slate.