I'm a professional roofer of 15 years, and independent roofing contractor of 7 or 8?
Best method is.... get your credit card out and call me.
No, just kidding. I don't even do treatments.
I'm basically just recapping lots of stuff that's been said, but here's my professional opinion, if anyone cares:
Detergent doesn't really seem to work, and if the roof is steep or cedar, it just rolls off.
Finely powdered zinc sulfate sticks to anything and works really well at both killing and preventing, but it'll kill your grass, roses, tomatoes, and pretty much anything else you get it on... as well as blind you and burn your lungs, if you get it in your face. Be careful. Also, the instructions on the commercial versions say you can sprinkle on the hips and ridges, but I've found it works a LOT better when you give the whole roof a nice even coat. If you're not comfortable moving around your roof, don't do this.
Never pressure wash - destroys the roof!
Zinc strip requires fasteners - don't put nail holes in your shingles! The stuff only works for about 3-5 feet below where you put it in, so you'd need to install it about every 5 feet all the way up the roof, and that's super ugly and a hell of a lot of fastener holes to keep track of.
Most shingles come in "AR" algae resistant versions, these days.. it's about an extra $5-10 per 100 square feet of material, but seems to work for a good several years, maybe longer (I pretty much never see my roofs again, after I install them). Get up on your roof every spring and risk life and limb, or pay a little more when you get a new roof and not have to worry about it for a while?
Best method is.... get your credit card out and call me.
No, just kidding. I don't even do treatments.
I'm basically just recapping lots of stuff that's been said, but here's my professional opinion, if anyone cares:
Detergent doesn't really seem to work, and if the roof is steep or cedar, it just rolls off.
Finely powdered zinc sulfate sticks to anything and works really well at both killing and preventing, but it'll kill your grass, roses, tomatoes, and pretty much anything else you get it on... as well as blind you and burn your lungs, if you get it in your face. Be careful. Also, the instructions on the commercial versions say you can sprinkle on the hips and ridges, but I've found it works a LOT better when you give the whole roof a nice even coat. If you're not comfortable moving around your roof, don't do this.
Never pressure wash - destroys the roof!
Zinc strip requires fasteners - don't put nail holes in your shingles! The stuff only works for about 3-5 feet below where you put it in, so you'd need to install it about every 5 feet all the way up the roof, and that's super ugly and a hell of a lot of fastener holes to keep track of.
Most shingles come in "AR" algae resistant versions, these days.. it's about an extra $5-10 per 100 square feet of material, but seems to work for a good several years, maybe longer (I pretty much never see my roofs again, after I install them). Get up on your roof every spring and risk life and limb, or pay a little more when you get a new roof and not have to worry about it for a while?
