I purchased this initially at a local hardware store for use on my roof. The asphalt shingles were nearly covered with a thick layer of lichen and green mold. I had the roof scraped as best as possible, and then treated with the spray and forget at 7x dilution. Within weeks, the remaining lichen and mold began to fade, and a year later, the roof is still completely clean with NO new growth. At this rate, I estimate the roof will remain clean for at least another year or two, without an additional application. I have since tried it on my 50 year old cement and brick front stoop, which even the power washer could not get completely clean. Within weeks, almost perfect, literally like new. Don't bother bleaching or using other harsh chemicals. This is an excellent product: don't waste your valuable time (and money) on ANY other solution! I bought a bottle for my father-in-law to use on his patio, which is constantly needing power washing each year, to remove the black and green mold/mildew that grows in the shaded areas. We'll see how that works over the next couple of months, I'm guessing amazingly!

I saw this stuff advertised on late-night TV and bought a small bottle of it at Home Depot to remove a particularly nasty little patch of algae stain (under a tree) on my roof shingles. I applied it and waited...and waited...and waited. And finally forgot it. Four months later, the stain was gone...and the shingles were so clean, they didn't match the rest of the roof. So I'm getting ready to do the entire roof now. This stuff is perfectly named...Spray & Forget. You'll be pleasantly surprised with the results...but patience is required.

Dislike they do not sell a sprayer to work with the ROOF cleaner that needs a mixing ratio of 9:1. I finally found a sprayer on my own after hours of research. It is a Nu-Calgon coil gun #4774-0. It has 5 mixing settings, 3:1, 4:1, 6:1, 9:1 & 10:1. It can spray a fan pattern of 4' to 5' or a jet stream 25' with 60 psi water pressure. I purchased my at Supplyhome.com for $72.00 with shipping. It sprays the 25' jet stream when you don't install the foam wand or deflector. The sprayer is well made. It is also ideal for many other spraying options.

Spray and Forget is so easy to use. Just mix and spray. Over time it does a fantastic job of removing stains, mildew and mold as well as lightning the surface. We used it on our composite deck and used a lesser dilution and it worked quickly and completely removed the stains and mold and even after a few days we could see a change for the better. Over time the rain reactivates it and keeps it bright and stain free. Love it!

This stuff is amazing. At first, I balked at the price. But, it takes only 26 oz. of Spray & Forget added to my 2-gal. tank sprayer, and I can treat my entire roof (house + carport). Even better, it lasts much, much longer than other products.
For the sake of comparison: I used to use the powdered stuff in a tall skinny can; It took 2 cans (at $10 each), and a treatment would last only 6 months. (Plus, the powder could not be applied on breezy days.) So, I was spending $40/year.
With Spray & Forget, I'm spending less than half that. The label says treat every 12 to 24 months, and I'm a believer: I just did my second spraying, 12 months after the first, and there was no moss up there at all -- I'm sure I could wait at least 18 months between treatments.
Also, note that I live on the coast in the Pacific Northwest, and our house is pretty much surrounded by tall trees -- so we've got a constant moss and mildew problem. With Spray & Forget, problem solved.