A zinc strip on a roof typically lasts 15 to 25 years, depending on the strip thickness, width, and environmental conditions, making it a long-term solution for moss and algae prevention. Zinc strips are usually made from rolled zinc metal, about 2 to 3 inches wide, installed near the ridge cap so that rainwater washes over the zinc and carries zinc ions down the roof surface. These zinc ions create an environment that is toxic to moss, algae, and lichen, inhibiting growth. The strip slowly corrodes and releases ions over time, which is why it has a finite lifespan. In areas with heavy rainfall, the strip may corrode slightly faster, lasting closer to 15 years, while in drier climates it can last 20 to 25 years or more. Higher quality, thicker strips from manufacturers last longer than thin, inexpensive versions. Effectiveness gradually decreases as the strip thins, so after 15 years you may notice moss beginning to grow again at lower roof edges furthest from the strip, indicating it is time to replace or add another strip. Some homeowners install a second strip halfway down large roofs for better coverage. Copper strips last even longer, often 20 to 30 years, and provide similar protection. Zinc strips are considered a passive, low-maintenance prevention method after cleaning an existing mossy roof and are recommended by roofing professionals.
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