Curious about those ugly black stains and streaks are on your roof? Those stains are caused by a dark green bacteria, "Gloeocapsa Magma" (commonly called black mold). The bacteria accumulate over time because they "feed" on moisture and calcium carbonate. They begin to show their black color as they form a dark and hard UV-protective outer coating. It is believed that increased temperatures and humidity promote the spread of this bacteria.
The majority of shingles today are made with limestone as a filler. These shingles hold moisture longer than the paper/asphalt shingles that were used years ago and the bacteria actually use the limestone as a food source. That is, the bacteria are actually "eating" the limestone fillers that are a part of your shingles, thereby shortening the lifespan of your roof.
Once the stains become noticeable, they will become worse year after year. It is thought that the bacteria growth holds moisture within your shingles causing premature aging, rotting, and/or granule loss.
Never use pressure on your roof - it will cut the life of your roof in HALF!
Welch Power Washing can SAFELY remove the stains without removing any asphalt granules from your roof. We use a safe and effective method that is approved by ARMA (Asphalt Roofing Manufactures Association) to clean your roof.