I do not guarantee a specific time for Oregon moss not to return. Companies that do that are usually the start ups because they don’t know how it works yet. We guarantee our work, so if we say that we will apply 12 gallons of treatment, then we will apply 12 gallons of treatment. I have been doing this for 10 years and have learned that if not treated correctly, northwest moss will come back quickly. I would say that if you treat your roof two times a year you should be good, some houses take more then 2 a year but that’s rare. 2 a year is rare as well. Some people only need one treatment every 3 years to keep the moss from growing. The key is to keep an eye on your roof and stay ahead of the problem. If you see green, let me know and I will treat it before it turns to moss. It is the customers responsibility to keep an eye on the roof, checking for any signs of green or moss returning. A roof will turn green under the edges of the shingles before the moss starts to grow, which is an indication that it needs to be treated.
It is OK to have your roof cleaned and treated any time of year, but the months that are best for doing maintenance or treatment only (after we have cleaned your roof) are March through Early July and Late August through early November. Depending on the weather of course.
FYI: All products work about the same and wash off of the roof at about the same time, so it really doesn’t matter what you use as long as it is a registered moss and algae killer. I have tested most of them and have found Wet and Forget to be the most effective and safe. There are products that can be harmful to your roof so please consult a professional and do some research.
The cost for treatment is 50.00 per 3 gallon tank of mixed treatment applied. Most average size homes take 3 tanks or 9 gallons.