When is copper the right material for flashing, and when is aluminum or galvanized acceptable?
Copper is the right specification when (a) the home's architectural value justifies a flashing material that lasts 80-100+ years, (b) the existing roof system is cedar shake, natural slate, or a system designed to outlast aluminum's serviceable life, (c) the home was originally specified with copper and replacement work should match, or (d) the visual character of the home calls for the patina copper develops over time. Aluminum is acceptable for standard architectural shingle replacements on suburban homes where the flashing's expected service life matches the shingles' (~25 years). Galvanized steel is rarely the right call in modern roofing; it's been displaced by aluminum on the budget end and copper on the premium end. For estate-class homes, the cost differential between copper and aluminum at the flashing scope is small relative to the project total, typically a few thousand dollars against the project total, and the longevity, visual character, and appropriateness to the architecture make it the right call. We default to copper recommendations on cedar shake, slate, and historic-architecture projects.
How long does copper flashing last?
Properly fabricated and installed copper flashing typically delivers 80 to 100+ years of service life, outlasting most other components of the roof and frequently outlasting the cedar shake or slate it accompanies. The longevity depends on a few specifics: copper thickness (16-ounce minimum for most residential applications; 20-ounce for harsh exposure or coastal-style conditions), proper soldering at all overlaps and detail work (sweat-soldered joints rather than mechanical fasteners alone), and isolation from incompatible metals (copper develops galvanic corrosion when in direct contact with aluminum, so any transitions need proper isolation). Cedar shake's natural acidity also reacts with copper but in a way that produces patina rather than degradation, a benefit, not a problem. We've worked on estate homes with original 1920s and 1930s copper flashing that's still functional today; the failures we encounter on heritage properties are almost always at the underlying substrate or other components, not the copper itself.
What copper roofing details do you fabricate and install?
Full scope: copper valley flashing (open-valley and closed-valley designs), step flashing at wall intersections, counter flashing at chimneys and parapets, chimney crickets (saddle structures behind chimneys to divert water), pipe flashing and vent collars, drip edge and rake metal, and standing-seam copper accents on bay window roofs, dormer cheeks and tops, oriel projections, porch roofs, cupolas, and small section roofs. We fabricate components in-house for straightforward profiles and work with regional metal shops on custom sections: anything requiring an architect's drawings, ornamental detail, or matching of historic profiles. Soldered copper gutters and downspouts are also part of the scope on estate-home projects where the roof drainage system is part of the architectural design.
What's the difference between 16-ounce and 20-ounce copper, and which should my project use?
Copper is specified by weight per square foot, 16-ounce copper is approximately 0.0216 inches thick, 20-ounce is 0.027 inches. For most residential roofing applications in Chicagoland (flashing, valleys, accent roofs), 16-ounce is the standard specification and delivers full expected service life. 20-ounce is appropriate where the copper is exposed to higher mechanical stress (areas with heavy foot traffic, harsh wind exposure, or where aesthetic-grade thickness is preferred), on standing-seam roof sections that are the primary roof material rather than an accent, and on certain historic preservation projects where the original specification was 20-ounce or heavier. We specify the appropriate weight for each project component, sometimes 16-ounce for valleys and step flashing combined with 20-ounce for visible standing-seam accents.
Does copper need maintenance?
Copper requires almost no maintenance; that's one of its key advantages. The natural patina that develops over 5-15 years (from bright copper to brown, eventually to the characteristic green of full oxidation) is protective; it doesn't need to be cleaned, sealed, or treated. The few maintenance considerations: keep copper clear of debris that traps moisture (leaf accumulation in valleys), don't allow water from incompatible metals (aluminum gutters above copper details) to drain across the copper for extended periods, and inspect soldered joints periodically for any stress cracks (rare but possible on older systems with extreme thermal cycling). Compared to cedar shake's annual inspections, periodic treatments, and selective replacement, or slate's eventual flashing-failure restoration cycle, copper is the lowest-maintenance component on a premium roof system.
What does copper flashing or copper accent roofing cost?
Copper flashing scope on a typical cedar shake or natural slate roof project (full valleys, all step flashing, chimney work, and standard penetration flashings on a 4,000 sqft home) typically adds about 10 to 15% to the project versus aluminum flashing at the same scope. Standing-seam copper accent roofing (bay window, dormer roofs, porch roofs) is priced by the section: profile complexity, soldering scope, and substrate prep drive it more than area does. A copper bay window roof is a smaller job than a porch roof, and full standing-seam main-roof sections are a different order of project again. We scope each one on site. We provide written estimates with copper weight specifications, scope breakdown, and fabrication source for every project: copper work is specification work and the proposal should reflect that.