Copper strips have always been kind of a mixed bag for me. I manage a handful of older properties, and on the ones with heavy shade and low-pitch roofs, algae is just part of the deal—like taxes or weeds in the sidewalk cracks. Copper does seem to outperform zinc a bit, but it’s not a night-and-day difference. I’ve noticed the same thing: you get cleaner streaks right below the strip, but anywhere water doesn’t flow, the algae just laughs and keeps growing. Not sure if it’s the “fancier” look or just wishful thinking, but I’ve had more than one owner convinced copper is some kind of magic bullet. If only.
I’d echo the caution about bleach. One of our tenants went full “DIY hero” with a garden sprayer and basically nuked half the flowerbeds. Now I just tell folks to use a weak solution and keep it off anything green they want to keep alive. The dish soap trick helps the mix stick, but I’ve never seen it last through a rainy spring either. Seems like as soon as you get a few weeks of damp weather, you’re back to square one.
Spray-on roof cleaners are another one I’ve tried, but honestly, the results never justify the price. Maybe if you’re in a drier climate, but here (Pacific Northwest), moss and algae treat that stuff like a snack. I’ve even had a roofer tell me he’s seen more shingle wear from repeated chemical treatments than from the algae itself, which is a little ironic.
At this point, I just set expectations low. If you’ve got a north-facing, shaded roof, you’re going to be doing some kind of maintenance every couple years, no matter what metal you use. Birds and squirrels seem to love the buffet, though... so at least someone’s happy.
you get cleaner streaks right below the strip, but anywhere water doesn’t flow, the algae just laughs and keeps growing.
That’s exactly what I’m seeing on my place. I put copper up last fall, and it’s like a racing stripe—clean under the drip, green everywhere else. I tried the bleach thing too (carefully), but even with tarps, my hostas took a hit. Honestly, I’m starting to think shaded roofs are just destined to look “lived in.” At least the birds seem to appreciate the buffet...
Yeah, that copper strip trick is kind of a tease—works great right under the runoff, but the rest just keeps getting slimy. I’ve got a north-facing roof with big maples overhead, so it’s always damp and shady. Tried scrubbing once, but nearly slid off... not worth it. Has anyone had luck with those zinc strips instead of copper? Or is it just more of the same story?