Is Copper Roofing a Good Choice for a North Carolina Home?

Copper roofing is usually used as an accent on the parts of a house people look at most: front porch roofs, bay windows, entry canopies, dormers, cupolas and turrets. A full copper roof is possible but rare on homes, because copper is a premium material. In the Interlock line, about 98% of roofs sold are aluminum and the rest are Solid Copper, which gives a sense of how specialized copper is.

Copper accents suit many North Carolina house styles. They appear on Victorian and Queen Anne homes in Wilmington's historic district, on Colonial Revival and Georgian homes in Raleigh and Durham neighborhoods, on coastal homes in Beaufort and Edenton, and on newer custom homes around Charlotte and Chapel Hill where a copper bay roof sets off a slate-profile main roof.

A common combination is an aluminum slate or cedar profile on the main roof with a copper porch or bay roof. That works well as long as the copper drains away from the aluminum, as explained below. For the full set of options, see Interlock roof profiles.

Copper weathers through a series of colors before it reaches the familiar green. The Copper Development Association describes new copper as a natural salmon pink that passes through russet and chocolate browns before reaching a blue-green or gray-green patina. In the first weeks, especially in humid or rainy weather, it can show iridescent pinks, oranges and reds before settling into a uniform brown.

How fast the green patina arrives depends on the air and, above all, on moisture. The Association reports that the patina generally forms in about five to seven years in industrial and seacoast atmospheres and in about 10 to 14 years in rural atmospheres with little airborne sulfur. It calls the dwell time of moisture on the surface the critical variable. Horizontal surfaces patinate fastest, then sloping surfaces, then vertical ones.

North Carolina's humid climate keeps surfaces damp often, which tends to move copper along. A copper porch roof in a sheltered spot under trees may stay brown longer than an exposed one facing the ocean breeze. Every copper roof weathers at its own pace, which is part of its appeal.

Copper holds up well on the coast, and seacoast air is one of the environments where it develops its patina fastest. The Copper Development Association notes that once the sulfate patina is fully formed, it is highly resistant to all forms of atmospheric corrosion, which extends the service life of copper roofing and flashing. The earlier brown oxide films are much thinner and less protective, so the first years are the ones where copper is still settling in.

The bigger coastal concern with copper is what it does to other metals. Salt water is a strong electrolyte, and the Metal Construction Association warns that copper has a very severe corrosive effect on steel, aluminum and zinc, and that copper salts can quickly stain and corrode roof surfaces they drain onto. On a beach house with aluminum or galvanized gutters, railings and trim, the drainage path from any copper surface needs careful thought.

Copper runoff can also stain light-colored siding, stone and concrete with green streaks. Plan where the water goes before the copper goes up. See salt air and metal roofs for more on coastal exposure.

Copper can be combined with an aluminum roof, but water must never flow from the copper onto the aluminum. The Metal Construction Association's bulletin on dissimilar metals gives the example of a copper roof or pipe draining onto a zinc-coated steel surface, and it states that copper has a very severe corrosive effect on steel, aluminum and zinc. The same applies to an aluminum roof below a copper accent.

In practice, that means:

• Put copper below aluminum, not above it. A copper porch roof below an aluminum main roof is fine, because aluminum runoff onto copper is not the problem.
• Give copper its own gutters and downspouts, in copper, discharging away from aluminum surfaces.
• Separate the metals where they meet with compatible flashing and isolation materials, and use fasteners suited to each metal.
• Watch old copper, such as copper chimney caps, valleys or flashings left from a previous roof, that might drain onto the new one.

These details are routine for an experienced metal roofer but easy to miss for someone who mostly installs asphalt. Ask how the drainage will be handled before you sign.

Solid Copper is real copper; Copper Penny is a color. Interlock offers Solid Copper as its own roof option, made of copper that weathers through brown to green over the years as described above. Copper Penny is one of the painted colors on Interlock aluminum roofing, giving a warm copper tone on aluminum panels with the Alunar 70% PVDF finish.

The practical differences:

• Appearance over time. Solid Copper changes color and eventually patinates. Copper Penny keeps its painted copper look, changing only slowly as any paint does.
• Drainage. Solid Copper needs the drainage planning above. Copper Penny is aluminum, so it does not create copper runoff.
• Warranty. Both carry the Guardian Lifetime Limited Material Warranty from Interlock Roofing: Solid Copper and painted Interlock aluminum alike. On Copper Penny aluminum, the Alunar coating is also warranted for 30 years.
• Cost. Solid Copper is the premium option in the line; ask for both on the same estimate to compare.

If you love the look of new copper and do not want it to change, Copper Penny may suit you better. If you want the living, changing finish, choose Solid Copper.

Historic districts and HOAs often look favorably on copper accents, but you still need approval before installing them. In a local historic district, North Carolina law requires a certificate of appropriateness before the exterior of a building is altered, and the statute counts the kind and texture of building material as an exterior feature. Copper porch and bay roofs are a traditional detail on many older North Carolina homes, which can help an application, but the commission decides.

HOAs vary. Some subdivision guidelines restrict roofing to specific materials and colors, while others are flexible on accents. Submit the location, size and material with photos of similar homes, and get written approval before signing a contract. See HOA approval for a metal roof in NC.

If the house is in a local historic district, talk to the commission staff early, before you finalize the design. Bring drawings or photos showing where the copper goes, how it drains and how it meets the rest of the roof, since those are the details a review is likely to ask about.

Caring for a copper roof mostly means leaving it alone to weather and keeping its drainage clear. Do not try to scrub off the brown or green layers; they are what protect the copper. Clear leaves and pine needles from copper valleys and gutters so water drains freely, and check that downspouts still discharge away from aluminum, stone and light siding.

Have flashing and soldered seams checked periodically along with the rest of the roof, especially after hurricanes and severe thunderstorms. Our guides to pine needles and debris on metal roofs and roof damage after a hurricane cover what to look for.

Metal Roof NC, an authorized Interlock aluminum roofing dealer, installs Interlock aluminum roofing and Solid Copper, and can plan copper accents alongside an aluminum main roof. See our aluminum roofing page and the Interlock roofing page for more.