Interlock Slate & Cedar Shingle: Aluminum Roofing Specs & Benefits
Quick answer
Interlock Slate and Cedar Shingle is a four-way interlocking aluminum roofing system finished with the Alunar coating. Each shingle is 0.019-inch (0.48 mm) aluminum with a 9-inch weather exposure, weighs a fraction of real slate or asphalt, is Cool Roof rated, and carries Interlock's 50-year transferable warranty.
What is Interlock Slate & Cedar Shingle?
It is an aluminum roofing shingle press-formed to look like natural slate or hand-split cedar shake, then finished with the Alunar coating system in low-gloss designer colors. What sets it apart is the four-way interlock: every shingle locks to its neighbors on all four sides, with no exposed fasteners, creating a continuous weather-tight surface with color-matched trims. Because it is aluminum rather than stone or wood, it delivers the high-end look without the weight, cracking, rot, or maintenance of the materials it imitates.
Specifications at a glance
Each shingle is 0.019-inch (0.48 mm) aluminum measuring 17 5/8 inches by 9 inches, with a 9-inch course-to-weather exposure. It installs over a minimum 1/2-inch solid sheathing covered with synthetic underlayment, at a minimum roof slope of 3:12 when using an ice-and-water underlayment (5:12 with standard underlay). The flexible ridge cap fits any ridge or hip angle and the system can even follow arched or curved roof lines. Cast-aluminum snow guards are available in matching colors. The finished roof weighs less than 7% of a concrete tile roof and less than 30% of asphalt.
Why homeowners choose it
The draw is a premium slate or cedar look on a roof engineered to last a lifetime. Aluminum cannot rust, so it thrives in wet and coastal climates; the interlocking design resists severe weather and wind; and the Cool Roof-rated Alunar finish reflects solar heat to help lower summer cooling costs. It is low-maintenance, roughly 95% recyclable, and light enough to install directly over most existing roofs — saving tear-off cost and keeping old shingles out of the landfill. It is all backed by Interlock's 50-year transferable Guardian warranty.
What to expect with installation
The roof is installed by authorized installers over solid sheathing with the whole deck covered in synthetic underlayment. The first course hooks into the eave starter flashing, and each shingle interlocks with the next using concealed aluminum or stainless fasteners, so nothing pierces the weather surface where it is exposed. Minimum slope and underlayment requirements must be followed to keep the warranty intact.
Frequently Asked Questions
Is Interlock slate real slate?
No — it is aluminum press-formed and textured to look like natural slate or cedar shake. You get the high-end appearance at a fraction of the weight, without the cracking, rot, or maintenance of stone or wood, and it will not rust because aluminum contains no iron.
Can Interlock Slate go over my existing roof?
Usually yes. Because it weighs under 30% of asphalt and under 7% of concrete tile, it can be installed over solid sheathing (often over an existing roof) without special structural work. Your installer confirms the deck and slope are suitable.
What roof slope does it need?
A minimum slope of 3:12 when installed with an ice-and-water underlayment, or 5:12 with a standard underlayment. It can also follow arched and curved roof lines.
How long does an aluminum slate roof last?
It is engineered as a lifetime roof and backed by Interlock's 50-year transferable Guardian warranty. Aluminum does not rust, and the Alunar coating is warranted 30 years against excessive fade and chalk.
Sources
- Interlock Slate / Shingle Specification Manual — Product specifications
- CCMC 10475-R — Interlock Cedar and Slate — NBC 2015 compliance
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Last reviewed 2026-07-11 · Reviewed by Scott Plumptree, Director of Marketing