Thermal Movement Decides Everything
A metal panel expands when it warms and contracts when it cools, and in New Hampshire the range is substantial — a dark roof in July sun against the same roof on a January night. A 20-foot steel panel moves measurably between those two states.
Standing seam is designed around that movement. Concealed clips hidden under the seam hold the panel down while letting it slide. Nothing penetrates the weather surface in the field of the roof.
Screw-down panel is designed against it. Screws through the face into the deck, each with a neoprene washer under the head. The panel still wants to move; the screw stops it. Every cycle works the fastener and compresses the washer a little more.
That is the entire difference, and it is why one lasts 40–60 years and the other 25–40.
The Comparison
| Standing seam | Exposed fastener (screw-down) | |
|---|---|---|
| Fastening | Concealed clips; panel slides | Screwed through the face; panel restrained |
| Penetrations in the field | None | Hundreds |
| Cost installed | $12–$20 per sq ft | Roughly $5–$12 per sq ft |
| Service life | 40–60 years | 25–40 years |
| Wear item | Flashing and details | Fasteners and neoprene washers |
| Maintenance | Check details every few years | Fasteners need checking and eventually replacing |
| Appearance | Residential; narrow pans read period-appropriate | Agricultural; reads as a barn roof |
| Solar mounting | Clamps to seams, no penetrations | Requires penetrations |
| Best on | Heated space you intend to keep | Unheated barns, sheds, outbuildings |
Frequently: Both
On a rural New Hampshire property the right answer is often not one material but two.
Standing seam on the house. The assembly is heated, so thermal cycling is at its worst; the space below is finished, so a leak is expensive; and you intend to keep it for decades. Every factor points the same way.
Exposed-fastener panel on the barn. Unheated, so the cycling is milder. Nothing finished below, so a leak is an inconvenience rather than a repair bill. And the cost difference across a large agricultural roof is substantial — frequently the difference between doing it and not.
A contractor who specifies the same product for both buildings without discussing it has not thought about your property. So has one who insists on standing seam for a hay barn.
Metal shingles are the third option and get forgotten. Steel metal shingles run $8–$14 per square foot and are worth considering where a seam profile is wrong for the house — a period building with complex geometry, or a roof where the long clean runs that make standing seam economical simply do not exist.
Living With a Screw-Down Roof
- Fasteners are a maintenance item. Expect to check them, and at some point to re-screw with larger-diameter fasteners into fresh material. That is normal for the system rather than a failure of it.
- Look for backed-out screws standing proud of the panel, and for washers that have hardened, cracked or squeezed out. Those are the leak paths.
- Do not over-tighten. Crushing the washer is as bad as leaving it loose, and it is the more common error when a homeowner goes round with a drill.
- Watch where two panels overlap and at the ridge and eave closures — those details fail before the panel does.
- It is not a failed roof. A screw-down panel at twenty years with sound fasteners has years left. Replacing it early because standing seam is better is not a good reason.