Depends on average size house you’re doing. Figure about a gal for every 50sq ft of roof if it’s dirty and steep. Just because you have a hundred, don’t have to make a full batch. And don’t worry about some being left over. When you mix a new batch on top of it, then it brings it back to life. Also, can use for your drive post treatment. When I was batch mixing I had the cleanest drive in the county, lol.
