Interlock Standing Seam: Aluminum Standing Seam Roofing Explained
Quick answer
Interlock Standing Seam is a vertical-panel aluminum roofing system finished with the Alunar coating. Panels are 0.028-inch aluminum, 17 inches wide with a 1-inch seam, roll-formed in continuous lengths up to 26 feet, Class A fire and UL 2218 Class 4 hail rated, and backed by Interlock's 50-year transferable warranty.
What is Interlock Standing Seam?
Standing seam is the classic modern metal-roof look: broad vertical panels separated by raised seams that run from ridge to eave. Interlock roll-forms its panels from 0.028-inch aluminum with a ribbed contour for added strength, finishes them in the Alunar coating, and joins them with a lock-formed seam over concealed clips — so there are no exposed fasteners anywhere on the field of the roof. It installs on new construction or over an existing roof.
Specifications at a glance
Panels are 17 inches (43.2 cm) wide with a 1-inch seam height, manufactured to length in continuous runs up to 26 feet to minimize horizontal joints. They are secured with a combination of sliding and fixed clips that allow the metal to expand and contract, then lock-formed to the adjacent panel. The system installs over a minimum 1/2-inch sheathing with synthetic underlayment (a leveling underlayment can be added to reduce surface imperfections), at a minimum slope of 3:12 with ice-and-water or 4:12 with standard underlayment. Curved and tapered specialty panels are available for custom features.
Why homeowners choose it
Standing seam suits contemporary, farmhouse, and architectural homes where clean vertical lines are the design goal. Beyond looks, it is a high-performance roof: a non-combustible Class A fire rating is available, it meets UL 2218 Class 4 for hail impact, and the full interlocking connection with concealed clips resists wind and will not crack or split. It is lightweight, low-maintenance, available in a range of Alunar designer colors, and backed by Interlock's 50-year transferable warranty.
What to expect with installation
Authorized installers cover the deck with underlayment (optionally a leveling underlayment for a flatter finish), set a starter trim that acts as a water barrier, then clip and lock each panel to the next. Because the clips are concealed and the panels lock together, no fasteners penetrate the exposed weather surface. Minimum slope, underlayment, and clip spacing must follow Interlock's instructions to maintain the warranty.
Frequently Asked Questions
Does Interlock Standing Seam have exposed screws?
No. It uses a concealed clip system — sliding and fixed clips fastened to the deck — with the panels lock-formed over them. There are no exposed fasteners on the field of the roof, which improves both weather resistance and appearance.
What is oil canning, and is it covered?
Oil canning is slight visible waviness that can appear in the flat areas of any standing-seam metal panel. A leveling underlayment reduces it. It is a cosmetic characteristic that does not affect performance, so like all manufacturers Interlock treats it as aesthetic rather than a warranty defect.
Is standing seam good for hail and wind?
Yes. Interlock Standing Seam meets UL 2218 Class 4 — the highest hail-impact class — and its full interlocking, clipped connection is engineered for high wind, with the Guardian warranty covering 120 mph. A Class A non-combustible fire rating is also available.
What roof slope does it need?
A minimum of 3:12 with an ice-and-water underlayment, or 4:12 with a standard underlayment. Curved and tapered panels are available for specialty rooflines.
Sources
- Interlock Standing Seam Specification Manual — Product specifications
- ICC-ES ESR-1790 / UL 2218 Class 4 — Fire, wind & impact ratings
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Last reviewed 2026-07-11 · Reviewed by Scott Plumptree, Director of Marketing