Thanks all this forum member, worth reading

For the roof, you will need something a lot more powerful. Some of you may know it as pool shock. This is made up of 12% by weight “Sodium Hypochlorite”. But because it’s as thin as water it will run right off the roof and not really have the time (five minutes) to do it’s job. So we have to thicken up a bit. The best way, add some liquid dish soap to the mix to help the SH stick to the roof for more than one second. You can go into any pool supply and ask for a gallon of shock, for about $4.00 per gallon. This is just a heavy-duty version of household bleach. And no Walmart does not sell this or the big box stores.

Pressure roof cleaning and roof shampo.

Chlorine is the way to go

I think you can use spray and forget or better still use wet and forget. they should save plant life better than using chlorine

I think using a right pressure washer is enough.there is no need to chemicals especially when you are cleaning the roof since the power of high-pressure water can remove all kinds of dirt. even for stubborn spots you can increase the pressure and it will work.