On Sunday, February 7, 2021 at 10:35:55 AM UTC, AnthonyL wrote:
Over the past year or so quite a lot of moss has grown on my garage
roof. It is pretty much a very big sponge.

I've had some success by shovelling a few spades at a time into a big
container full of water and then gently fishing out the moss with a
rake. But that's nowhere near 100% effective.

Ideas and what should I do next?

--
AnthonyL

Why ever wait to finish a job before starting the next?

Sprinkle it with bioligical washing powser. I did find an alternative liquid solution which I also found effective on our drive . Label reads " Bac 50" from R&D Laboratories Ltd., Unit U, Enkalon Ind. Est., Antrim BT41 4LJ

Apparently it is C10-C16 Alkyl Dimethyl Benzyl Ammonium Chloride (50%) Perhaps you could run some up yourself.

So far it is just as effective as the biological washing powder but perhaps easier spread. (Diluted and sprayed with a garden pressure sprayer.) Prior to this the washing powder was the only effective solution I could find. Lasted a few years. All other 'Moss Solution' products were useless. They required the removal of the dead moss. I found it very hard to shift even with a Stihl power brush attachment on their split boom system and using a spade threatened damage to the tarmac on the drive,