AZPW Maintenance Services Roof Cleaning FAQs


Black staining is caused by the growth of algae and fungus spores that land on your roof, (Staining is not caused by pollution, soot or jet exhaust). These spores need three things to grow: heat, moisture and some kind of nutrient. The nutrient comes from dirt and the shingle itself, primarily the limestone filler used in manufacturing the granules. Shingle roofs are manufactured with different degrees of quality. Pricing is one way to tell the quality of a roof and the manufacturer’s warranty is another. Most roofs applied by builders and roofing contractors are in the low to medium quality range. Higher quality roofs are generally found on expensive custom homes and where the owner has taken a special interest in the quality of the roof.


It is safe to guess that the vast majority of shingle roofs are medium to low quality with warranties that range from 15 to 25 years. The same shingle continues to get longer warranties. Manufacturer placed petroleum distillates, copper and zinc granules in varying amounts in and on the shingle prevent algae and fungus growth over varying periods of time according to uncontrollable variables. As the shingle ages and is subjected to the extremes in local weather, it deteriorates losing is granules and its fungus fighting capabilities. It is not uncommon for low quality shingles to exhibit a lot of algae/fungus staining in just three years while most roofs are stained partially or completely within the four to five year range. Black algae/fungus staining will first exhibit itself on the north side of the roof, then the west, south and east. Green algae staining is caused by close or overhanging trees. Either staining process will occur if you haven’t maintained and protected your roof with Shingle GuardTM or similar type product.


The answer is clean it immediately! Here’s why: As the algae and fungus grow on your roof, they eat away the base of the shingle and expand and contract with the outside temperature. This growth and movement loosens the granules, creating premature granule loss, dramatically shortening the life of your roof. A 25-year roof may not even last 15 years if nothing is done. A fungus-covered roof not only is an eyesore but it is unhealthy as well; do you want fungus spores all over, around and in your home? And what about those people with allergies? In addition, the fungus covered roof keeps under roof temperatures a lot higher by preventing the reflective capabilities of the granules from doing their job. These soaring under roof temperatures make your air conditioner work a lot harder and increase your electric bills sometimes as much as several hundred dollars a year. Finally, homeowner associations are becoming more abundant, primarily to maintain and enhance value of the individual homes and neighborhoods. You are not alone in the appearance of your home, therefore, at the first sign of algae/fungus staining, it makes good sense to clean your roof. This is not difficult to accomplish!


You can hire a professional company like AZPW Maintenance Service Co., Inc. that offers several roof-cleaning services designed to meet your needs and budget. You can clean your roof yourself and save labor costs but you need to think twice about that decision. Is it worth the risk of falling or damaging the roof to save a few dollars? You can purchase commercial grade roof cleaners at The Home Depot or Lowe’s or use bleach or pool chlorine, but these methods can leave you with a streaked roof, dead shrubbery and grass. Due to environmental and safety concerns, chlorine is not recommended. (Chlorine has no cleaning capabilities at all, it is only a bleach, and results are very temporary)


When your roof is clean the one thing you can count on is that it will get dirty again quicker, sometimes a lot quicker, than the first time. Why? Because your roof’s fungus fighting capabilities that have diminished over time and you have had granule loss. Did you clean your roof with chlorine? If so, your shingle life was shortened because it will dry out and crack the shingles and fungus will grow sooner. It is interesting to note that some manufacturers recommend that roofs actually be cleaned with bleach or chlorine—of course, they are in the business of selling shingles, therefore, the quicker your roof succumbs, the quicker they will be able to sell you a new roof.


There are many uncontrollable variables that help hasten algae/fungus staining. First, the fungus will always appear initially on the north side of the house and roof. This is because moisture stays there longer and, as noted above, algae/fungus needs three things to grow: moisture, heat and a nutrient. Other variables besides the direction your house faces are the type, grade and manufacturer of your shingles, whether you have a pond or pool nearby creating abundant moisture, and how hot and humid the weather is. Continuous warm weather promotes fungus growth. Also, if you have trees near your house and they shade the roof, that promotes quicker fungus growth. If you haven’t cleaned the leaves and pine needles off, that keeps your roof ripe for fungus growth too.

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