What is the life expectancy of a metal roof?
Short answer. Metal roof life expectancy depends mostly on the metal and its coating: painted Galvalume or galvanized steel commonly lasts 40 years or more on a house, aluminum is similar and rustproof, and copper or zinc can last many decades beyond that. Paint finishes usually wear before the metal does, so a finish warranty for fading and chalking is often shorter than the roof's useful life.
By metal
- Galvalume steel: steel coated with an aluminum-zinc alloy. The most common residential choice; it resists corrosion better than plain galvanized in most conditions.
- Galvanized steel: zinc coated. Many older Georgia barns and porches have it, and it eventually rusts, starting at cut edges and scratches.
- Aluminum: rustproof and lighter, but softer and quicker to dent.
- Copper: develops a patina and can last generations, at a high price.
- Zinc: self-healing patina and long life, rare on Georgia homes.
Paint systems
Most residential metal is painted. PVDF finishes hold color and resist chalking better than lower-cost SMP, or silicone modified polyester, finishes. Finish warranties cover chalking and fading within set limits for set terms, so read them separately from the panel warranty.
What shortens life
- Scratches and cut edges left untreated.
- Debris holding moisture against panels.
- Dissimilar metals in contact or draining onto each other.
- Exposed fasteners that loosen and leak, which can rot the deck even while the panels are fine.
- Poor ventilation and condensation under the panels.
Thickness
Thicker gauges resist dents and stay flatter. 24 and 26 gauge steel are common for standing seam, and 29 gauge is common for budget exposed-fastener panels.
Compared with shingles
Architectural shingles typically last 20 to 30 years in Georgia, so a quality metal roof can outlast one or two shingle roofs. See metal roofing in Georgia and heat, humidity and roof life.