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Dark Streaks on Roof Shingles

Posted on: June 15, 2016

If you are like most California homeowners who have shingled roofs, then you have at some point probably noticed dark spots or blackish steaks on some of the shingles of your roof and wondered what they are, and if in fact they are indicative of a potential problem.

Well, the good new is this: more often than not, those stains or streaks are an accumulation of algae or fungus and they pose no real danger to the shingles on your roof. Those colonies of algae form as a natural result of the moist environment on the shingles and consequently, while most asphalt shingle roofs have been treated with an algicide which will keep it free of algae colonies and stains for up to ten years, they reemerge as soon as the algicide wears off. Now while algae and fungus are not a huge threat to the integrity of your roof, a concentration of the spots could over time, eat into the shingles layers if not properly treated.

Another contributing factor to roof shingle fungus and algae relates to the fact that the levels of filler in the asphalt which are made up of crushed limestone, make it possible for algae and fungus to accumulate rapidly if the filler content is upwards of 60 percent of the total asphalt shingle. In other words, certain roofing manufacturers use more filler than others, and finding the manufacturers who uses the highest grade of copper coated granules in addition to one that uses less filler, can make a big difference in the vulnerability of your roof to algae and fungus.

Now when it comes to addressing the problem of how to deal with dark streaks on your roof after they already have accumulated, there are a couple of steps you can take to lessen the appearance of the stains and even help reduce the chances of them reappearing for a time. One quick way to start the process of at least preventing future algae from growing is by installing a zinc strip along the edge of your roof that will help by releasing a fungicide every time it rains, thus stunting the growth of algae on the shingles.

Additionally, you can also have the dark streaks removed by cleaning them off, but we can’t stress enough how important it is to take the correct and safe approach to this project it you do decide to take on this task yourself.

First and foremost, if you are going to clean the roof of your home you must come prepared with the right tools and the right plan. Some of the tools needed for this job include: a full body harness, ladder, garden hose, portable garden sprayer/ alternative pump apparatus, as well as some type of noncorrosive/nontoxic roof cleaning solution. Also remember that roofing experts advise against using any type of pressure washer or bleach, as they both could damage the shingles.

Prior to applying the cleaning solution with a sprayer, you should presoak the roof with water from the hose, as this will help slow down the process of evaporation drying up the solution when you spray it on. Typically, you want to start at the bottom row when applying the solution and make your way up the roof only once you start to see the runoff, making sure to use clean and even strokes. In addition to the cleaning solution, you can also take the next step of applying an algae stain blocking solution once the cleaning solution has dried.

Remember, if you do not feel safe or comfortable performing a roof cleaning project for yourself, do yourself the favor of calling your local roofing contractor to get the job done right!

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