In my experience, nothing really beats getting up there once a year and brushing the moss off by hand. It’s a pain, but I’d rather do that than mess with chemicals or hope a strip does the trick.
That lines up pretty closely with what I’ve seen on older roofs in the PNW, especially those shaded north faces. Zinc and copper strips are supposed to leach ions that inhibit moss growth, but in practice—especially in areas with heavy rainfall and persistent shade—they just don’t seem to keep up. The streaking is a real downside too. I’ve seen some roofs where the runoff from zinc left these weird silvery trails that never really faded, and it looked almost worse than the moss.
I’m always a bit skeptical of “set it and forget it” solutions for moss, at least in this climate. The only folks I know who’ve managed to keep their roofs mostly clear are the ones who get up there every spring and fall with a stiff brush or plastic scraper. Not fun, but it works. Chemicals are a whole other can of worms—most of them aren’t great for runoff into gardens or storm drains, so I get why people avoid them.
Copper does have some theoretical advantages over zinc (it’s more effective at lower concentrations), but like you said, the price difference is hard to justify unless you’re dealing with a high-end roof or historic property where appearance is everything.
Mesh guards for valleys are underrated, honestly. I put some in after losing patience with constant clogs from fir needles and maple seeds. They’re not perfect—you still have to clear debris off the top—but they do keep the valleys from backing up and causing leaks.
If anyone’s curious about alternatives, I’ve heard of folks experimenting with “green” roof coatings that claim to inhibit moss without harsh chemicals, but haven’t seen convincing long-term results yet. For now, seems like elbow grease is still king... at least until someone invents self-cleaning shingles that actually work in our weather.
I get where you’re coming from, but I’ve actually had decent luck with zinc strips on my place (asphalt shingles, south Seattle). They’re not a miracle fix, but after I put them up a few years back, the moss slowed down a lot—at least on the sunnier side. The streaks are kind of ugly, yeah, but I’ll take that over scraping every season. Maybe it’s just less shade on my roof? Either way, I’m not ready to write off strips completely, especially for folks who can’t or don’t want to climb up there all the time.
Zinc strips can be a mixed bag, honestly. I’ve seen them slow moss down, but like you said, they’re not magic—especially if your roof’s got a lot of shade or north-facing slopes. The streaks bug some folks, but I’d rather have those than a moss carpet. If you’re not keen on climbing up there every spring, strips are way better than nothing. Just make sure they’re installed high enough on the ridge so rainwater actually carries the zinc down the shingles... seen a few folks miss that step and wonder why nothing changed.
Had a job last spring where the homeowner put zinc strips halfway down the roof, thinking it’d cover more area. Ended up with moss still thriving below the strips and some odd streaks up top. If you’re gonna use them, I always recommend running them right along the ridge—rain’s gotta wash that zinc all the way down. Also, if your roof’s shaded most of the day, you might still get patchy results. Sometimes a combo of strips and a gentle cleaning every couple years works best, especially on older shingles.
If you’re gonna use them, I always recommend running them right along the ridge—rain’s gotta wash that zinc all the way down.
That’s exactly what I’ve seen too. Zinc strips halfway down just don’t get the job done. I get why folks try it—maybe thinking it’ll “double up” on coverage or something—but the water just doesn’t carry enough zinc far enough down unless it starts at the top. I’ve noticed those weird streaks too, especially on older roofs where the granules are already a bit loose.
I wouldn’t say zinc strips are a magic fix anyway, especially if you’ve got a lot of shade or trees dropping stuff all year. Where I’m at (PNW), moss is relentless. Even with strips right at the ridge, you still get patches where it clings on, especially under overhanging branches. Like you said, sometimes you just have to get up there and do a gentle clean every couple years. I know some people worry about damaging shingles, but if you use a soft brush and avoid pressure washing, it’s usually fine.
One thing I’d add—if your roof’s got a low pitch or valleys where water slows down, those spots seem to stay wetter and grow more moss no matter what. Anyone else notice that? I’ve seen homeowners get frustrated after spending money on strips and still having to deal with green fuzz in the corners.
Anyway, sounds like you did what you could with what the homeowner wanted. Sometimes folks have their own ideas and you just have to roll with it... but yeah, ridge placement is key if you’re going to bother with zinc at all. Don’t let it get to you—some roofs are just stubborn no matter what tricks you try.