Why should you NEVER use a pressure washer on roof tiles... The problem is that with too much pressure, you are removing the granules. You need the granules to protect the roof from the sun; that is the primary purpose of the granules. After a good power wash, the roof will look great, but if too much pressure is used a significant part of the roofs' life has just been removed.
Algae staining begins with small spots which, over time, can develop into streaks. Algae stains, which are often mistaken for mold or mildew, aren't harmful to anything other than the appearance of asphalt shingles, but nobody likes the look. Algae spores are airborne and can quickly spread their way across an entire neighborhood or even a whole town. While they are not harmful to your health, algae growth can hurt the resale value of your home.
Moss adheres itself to the roof using root-like structures called rhizoids. These structures grow into the tiny cracks of the roof line and begin to break it apart. The moss also holds moisture which causes decay-forming organisms to get a foothold and rot your roof. Moss grows under the edges of shingles, loosening them and promoting the breakdown of the roof surface.
Mold is a fungus that is made up of multiple cells and gets energy from the organic matter it lives on. Mold reproduces in spores, which can be airborne and are not visible to the naked eye. When you can see mold on a house or sidewalk, you are seeing a “colony.” A colony is a single organism that grows in long branching cells called hyphae.
Mildew is a surface fungi that can easily be identified as a patch of gray or even white fungus that is lying on the surface of a moist area. Mildew thrives in moist environments and feeds on organic materials, including the oils in alkyd-based paints and cellulose thickeners found in many latex coatings.
An average 2000 sqft roof replacement can cost upwards of $10,000 - $20,000, while cleaning that same roof would cost less than $1,000. Try softwash and save thousands on replacement costs!