What Are Aluminum Shingles? A Guide for New England Homeowners

What exactly is an aluminum shingle?

An aluminum shingle is a single roofing panel pressed from aluminum sheet and coated at the factory. Each panel is shaped to show several slates, shakes or tiles on its face, so a roof made from them reads as a traditional roof from the street. The Interlock® system is manufactured by Interlock Roofing at its plant in Delta, BC, and is Made in North America. About 98% of Interlock® roofs sold are heavy-gauge aluminum; the rest are solid copper. The panels are finished with the Alunar® coating, which carries a 30 Year Alunar® coating warranty. On the roof, the panels lock together on all four edges, and the fasteners are concealed under the next course. The result is a continuous metal surface that looks like separate pieces.

What styles and colors do aluminum shingles come in?

Interlock® aluminum shingles come in Slate, Cedar Shingle, Shake and Mediterranean Tile profiles. Slate is the most popular, and in New England it suits Colonials, Victorians and older brick homes that once had real slate. Cedar Shingle and Shake fit Capes, coastal cottages and farmhouses where wood was the original look. Mediterranean Tile is less common here but works on some Spanish Revival and modern homes. Interlock® also offers Standing Seam and solid copper roofs, which are different products from shingles. Colors include Black, Deep Charcoal, Hunter Green, Colonial Brown, Tudor Brown, Tile Red and Copper Penny, among others. If your home is in a historic district, check with your local historic district commission before you settle on a profile and color.

How are aluminum shingles installed?

Aluminum shingles are installed over a solid roof deck with an underlayment, starting at the eaves and working up the slope. Each panel's top edge is fastened to the deck, and the next course locks over it so the fasteners end up hidden. Side edges interlock with the neighboring panels. Trim, ridge pieces and flashing are fitted at every edge, chimney, wall, valley and vent. Cedar shingles, cedar shakes, concrete tile and natural slate are always removed first. A single layer of asphalt may stay only if an inspection finds it suitable. Rotted sheathing is replaced. Interlock® shingles need a roof pitch of at least 3/12. The flashing work is where experience shows, especially on New England houses with brick chimneys, several dormers and additions built in different decades.

How are aluminum shingles different from asphalt shingles?

Aluminum shingles differ from asphalt in what they are made of and how they fail. Asphalt shingles are a mat coated with asphalt and mineral granules. Over time, sun and freeze–thaw cycles dry the asphalt, granules wash into the gutters, and tabs crack or lift in high wind. Each replacement means a tear-off and a dumpster. Aluminum does not absorb water, does not lose granules and does not rust. Interlocking panels have no loose tabs, and Interlock® shingles are rated for winds up to 120 mph when installed to manufacturer specification. The trade-off is upfront cost: an aluminum roof costs more to install. Owners who plan to stay usually compare one long-lasting roof against the several asphalt replacements it would otherwise take.

Are aluminum shingles heavy enough to handle New England snow?

Aluminum shingles handle snow because of how they lock and fasten, not because of their weight. In fact, their low weight is an advantage. At roughly 0.4 to 0.7 lb per square foot, they put far less dead load on the rafters than slate or concrete tile, which leaves more of the framing's capacity for the snow itself. That matters on older Capes, triple-deckers and farmhouses whose rafters were never sized for heavy roofing. Snow can slide off a metal roof in larger sheets than it does from asphalt, so it is worth thinking about entries, decks and walkways below the eaves. Snow guards are an option in those spots. If your house has a history of ice dams, that comes from attic heat loss and ventilation, which we look at with you.

What warranties come with aluminum shingles?

Warranties vary by manufacturer, so read the actual documents. For Interlock® shingles there are two from the manufacturer. The Guardian Lifetime Limited Material Warranty covers the material and finish for the original purchaser while they own the home; it can be transferred once, and the second owner is covered to 50 years from substantial completion. The 30 Year Alunar® coating warranty covers the finish. Workmanship is not part of the material warranty. Every warranty has exclusions. One that matters here is ice damming, which is excluded from the material warranty because it comes from conditions in the house rather than from the roofing material.

Common questions