Asked on Jan 3, 2012

Is there a proper way to get mildew or black stains from my roof??

Peace Painting Co., Inc.Woodbridge Environmental


I had a new roof put on my house 7 years ago... had a tree incursion 4 years ago and a third of the roof was replaced (the insurance company would only cover that...) Now there are what I call mildew but are black streaks and stains on the roof mostly visible on the "older" portion.. What if anything can I do?
2 answers
  • These streaks are mildew caused by spores becoming trapped in fibrous part of the shingle. As you drive around you can see this more and more on many homes. You can clean this yourself if you are comfortable being on a roof, but its really a job best done by a company that does this type of work. They simply spray a chemical that will remove the stains. Some use a bleach solution others special chemicals that will not harm plants etc. In any case regardless of what they do or use, you need to rinse down all shrubs and grasses then cover with plastic while the job is being done. Once complete plastic is removed and plants and grass is watered down again. Depending on how bad your roof is will determine how successful they will be. Real bad stains can be removed to a point that it becomes difficult to see. While others may not even be removed at all. New shingles now come with a chemical in the shingles that help prevents this from occurring. Your fiberglass shingles you have on the house now did not contain these chemicals when they were installed. The reason why people are seeing this more often is that the materials they construct shingles out of are a lot different then those constructed over 25 years ago. The products that they use are causing this to happen. Once the roof is clean placing zinc strips along the top run of shingles so just about on inch of the metal is visible should help prevent this from coming back. Every time it rains a little amount of this zinc is released preventing the mildew from coming back.

  • Peace Painting Co., Inc.
    on Jan 3, 2012

    Michael, here is a roof we washed this last fall using a detergent from The Depot named 'Jomaps Roof and Deck Wash'. Whenever I have used it, it has removed all stains. You see we use a pressure washer, so, with care, the chemical will do the work, minimally impacting the shingles. If you have a ranch house it is easy, if not, you may need to call a roof washing company. It seems your insurance could help here. Best, Charles

    , The chemical kills and loosens the mildew, The pressure washer removes the stain
Your comment...