Knowledge Base · Installation & What to Expect
Aluminum Roofing Fasteners: Why Concealed Beats Exposed
Aluminum roofing uses two fastening methods: exposed fasteners — screws driven through the panel face and sealed with rubber washers — and concealed fasteners — clips and interlocks hidden beneath the panels. Concealed systems like Interlock's last far longer, because they have no exposed gaskets to fail and they let the metal expand and contract freely.
Technically reviewed by Scott Plumptree, Director of Marketing · Updated 2026-07-12
At a glance
- Exposed-fastener panels are screwed through the face; each screw's rubber washer is a future leak point
- Concealed-fastener systems hide clips under the panels — no gaskets, no face penetrations
- Concealed fasteners let aluminum expand and contract without stress or screws backing out
- Interlock's four-sided interlock is a concealed system, which is why it carries a lifetime warranty
What is the difference between exposed and concealed fasteners?
Exposed-fastener roofing is screwed straight through the face of each panel, with the screw heads and their rubber (EPDM) sealing washers visible on the surface — the look of a typical corrugated or ribbed barn roof. Concealed-fastener roofing hides its fasteners: panels attach with clips or interlocking legs tucked under the next panel, so nothing penetrates the weather surface and no fastener is visible. Standing seam and interlocking shingle systems, including Interlock's, are concealed-fastener by design. It is the defining quality difference in metal roofing.
Why do exposed fasteners fail over time?
Because their weak point is built in. An exposed-fastener roof relies on hundreds or thousands of rubber washers to seal each screw penetration, and rubber is the shortest-lived part of the assembly. Sun degrades it, and the daily expansion and contraction of the metal works the screws loose, so washers harden, crack, and back out — typically starting in the 10-to-15-year range. Every compromised washer is a potential leak, which is why exposed-fastener roofs need periodic re-screwing and rarely carry lifetime warranties.
Why are concealed fasteners better?
Three reasons. First, watertightness: with no fasteners penetrating the exposed surface, the single biggest leak source on metal roofs is eliminated. Second, movement: concealed clips let the aluminum expand and contract freely, so there is no stress building at the fasteners and nothing working itself loose. Third, longevity and looks: a clean face with no visible screws lasts longer and looks architectural. This is why concealed-fastener systems like Interlock's are backed by transferable lifetime warranties while exposed-fastener panels are not.
What fasteners should be used with aluminum roofing?
Fastener metal matters as much as fastener placement. Aluminum should be secured with compatible fasteners — aluminum or stainless steel — never bare or ordinary steel, because dissimilar metals in contact and moisture can drive galvanic corrosion at the connection. Quality systems specify compatible concealed clips and fasteners engineered for the panel. Interlock's system uses concealed, corrosion-compatible fastening throughout, so both the fastening method and the fastener metal are chosen to last as long as the aluminum itself.
Common questions
Can you use steel nails or screws on an aluminum roof?
You should not use bare or ordinary steel fasteners on aluminum. Dissimilar metals plus moisture can cause galvanic corrosion at the fastener, staining and weakening the connection. Use aluminum or stainless steel fasteners specified for aluminum roofing — or better, a concealed-fastener system like Interlock's that uses compatible fastening by design.
Do concealed-fastener roofs cost more?
Usually yes, upfront — they are engineered systems that cost more than screw-through utility panels. But over the roof's life the math favors concealed: no periodic re-screwing, no washer-driven leaks, and a far longer service life. You are paying once for a lifetime roof rather than repeatedly maintaining an exposed-fastener one.
How often do exposed fasteners need to be replaced?
On an exposed-fastener roof, the rubber washers commonly need attention somewhere in the 10-to-20-year range, and many roofs eventually need a full re-screw as washers age. A concealed-fastener system like Interlock's avoids this maintenance cycle entirely, because there are no exposed washers to degrade.
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