Zinc strips. Phew!
They don’t really work. I know they are presented as if they do, and people see them as a kind of DIY way to keep moss of their roofs, but when you really look into them, you’ll find issues that will end up costing you more money than they are worth.
Not only are zinc strips expensive, but you have to get up on your roof to install them yourself. 98% of roofing accidents happen in the transition from the ladder to the roof. So already, you’re taking a risk just by trying to do it yourself.
Zinc strips are usually installed on the ridgeline of the roof. When rain hits the zinc, it creates zinc oxide. If the zinc oxide concentrate is high enough, it doesn’t allow anything to grow. The problem is that distance is only about four to six inches away from the strip and then the moss takes off again! You’d have to put a zinc strip on every six inches of your roof, but there’d be so many holes on the roof that you’d ruin it.
The point is: zinc strips are expensive and they don’t work. The nails you attach them with put hundreds of holes on your roof, and as the wind works on that little strip of metal, they loosen and come off. Then you just have to go back and start again. They become a maintenance nightmare.
An alternative would be to gently clean the roof off with a machine made for roof cleaning, and then come back and apply a product that will go in every crack and crevice of your roofing material. It will change the pH of your roof so that it won’t support black rot fungus or moss. It may cost more initially, but it’s going to save you from getting hurt during installation and/or possibly ruining your roof.