Biocide Roof Wash

Me and my father have dabbled with softwashing but just wanted to ask for a bit of advice on roof cleaning. 

Got a customer who has a chalet type house which has some moss on it. Not loads and loads but enough. 

With a biocide can you just wash the roof and let Mother Nature take over or do you have to scrape it? If you treat first, when should you scrape? 

what sort of ratio is good for this time of year using DDAC 50 on a roof? 

We have the marshall roof scraping kit and large aluminium tower with support legs etc. 

We recently did a roof with bio but scraped it first , I think this is generally  way ones do it , if you don’t scrape it as it dies and comes off the roof and this will take months too happen it will keep filling the gutters up as well ,the one in the pictures we scraped then applied bio it’s now looking good with all growth dead 

Always scrape first. Customers will want to see some form of improvement straight away. 

Clarkus84 said:

Always scrape first. Customers will want to see some form of improvement straight away. 

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It’s an existing customer of 10+ years. So willing to trial it out. Got a few roof’s lined up now as well so it might be a new proper side line. 

Did the first part of the roof today and was quite impressed with the results. Will get some pictures up soon. 

I think i will scrape first then spray afterwards like everyone else does. 

I have got a job I sprayed with bio in Feb which will be scraped soon to see if there’s any difference.