Yes, we will do a partial roof cleaning. When we do a full roof wash, we provide a 2 year guaranteed clean warranty, meaning if any black spots return within 2 years we will come take care of it for free. We do not provide this warranty on partial roofwashes, because even if you can not see the algae on one side of the roof, it is still growing on that side. If all of the algae is not treated, it will grow back much quicker than a full roof wash.