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"What questions should I ask a roof cleaning company?"
Ask questions that help you understand a company's history, credentials, guarantees, and specifics about how they clean and protect your roof and property, e.g.: How long have you been in business? Can you provide references? Are you licensed and insured? Do you guarantee your work? Do you use sub-contractors? How will you clean my roof? Do you utilize pressure washing? What cleaning substances do you use? If you use chemicals, how do I know they are safe? Will you be able to get my roof completely clean, or will some black marks and other stains remain? How will you protect my landscaping? Do you provide a written estimate?
"What are the black streaks on my roof?"
Black streaks are a type of algae that forms from airborne spores. It can grow on any type of roof, but is most common on asphalt roofs containing crushed limestone, which fosters algae growth.
Roof algae thrives in damp places, so is most often found in: regions with moist or humid weather, on north-facing roof surfaces (which in the U.S., receive less sunlight), and, on shaded roofs that are shielded from sunlight.
Black streaks on your roof should be cleaned, because the algae can cause damage by breaking down the protective UV granules that prevent shingles from drying, curling and cracking. Fortunately it's easy to remove algae streaks from your roof.
Many DIY'ers use a solution of bleach, TSP (trisodium phosphate), and water…however, bleach/TSP solutions can damage nearby plants and trees so take precautions. Fortunately, eco-friendly roof cleaning options are also available. Also, when cleaning the roof yourself, avoid high pressure washing systems, which can damage shingles, wash away protective UV granules, and void roof warranties.
If you prefer to hire a service professional , any good roof cleaning company will be able to remove the algae.
Also, when it's time to install a new roof, be aware that algae-resistant shingles are now an option.
"Is pressure washing bad for my roof?"
Generally, pressure washing is only safe on metal or concrete roof surfaces, or if a low-pressure method is used by a professional.
Homeowners who opt for DIY roof cleaning should avoid pressure washing completely. The risks of pressure washing include: loss of UV granules that protect shingle roofing from harmful sunlight, broken or damaged shingles, voided roofing warranties (many don't allow pressure washing) and, danger to homeowners from pushback-pressure while standing on a wet ladder or rooftop.
If you have questions about the best way to clean your roof, contact an experienced roof cleaning professional, who can offer the best advice for your specific circumstances – including exactly what kind of cleaning solution should be used.
"What kinds of cleaning solutions or chemicals are used for roof cleaning?"
Broadly speaking, there are three kinds of cleaning solutions used today:
The purpose of eco-friendly solutions is to avoid using chlorine bleach, phosphates, lye, and/or any other chemicals that can harm plants and the environment. Many roof cleaning professionals now use non-toxic, non-corrosive, biodegradable products similar to shampoo – just be certain to get a guarantee that the algae, lichens, and moss will be eliminated.
Eco-friendly roof cleaning solutions can also be purchased by homeowners who prefer to handle roof cleaning as a DIY project.
Sodium Hypochlorite (Chlorine Bleach) and TSP
Chlorine bleach and/ trisodium phosphate (TSP) can be mixed into water at varying concentrations, for an effective roof cleaning solution. The mixture is typically sprayed onto the roof, and rinsed after 20 minutes or so.
While this can be an effective solution for removing algae, moss and lichen, it produces strong unhealthy fumes, can hurt landscaping, and will enter waterways.
If you're using a professional, be sure you ask if they are using bleach or TSP. And, whether you're using a pro or doing it yourself, make sure that nearby plants and trees are hosed down before and after the roof cleaning process when a bleach or TSP solution is deployed.
Chemical Solutions Used by Roof Cleaning Professionals
Roof cleaning pros use a variety of cleaning solutions, with or without standard or so-called "soft" pressure washing. Make sure you ask what solution they plan to use, and insist on a plan to protect plants and trees near your roof if they are using bleach, TSP or other chemicals that are potentially harmful.
"Will the cleaning solution harm nearby plants and trees?"
Any solution that runs off onto your plants and trees has a chance of harming them in some way. Solutions that include chlorine bleach, TSP, other chemicals, heavy metals or lye can be particularly harmful. To avoid damage when a chemical solution is being used, water your plants and trees before and after the cleaning. This helps prevent the accumulation of damaging salts and other harmful residues.
Eco-friendly, non-toxic s hampoos and detergents are a good – albeit more expensive – alternative that won’t harm your landscaping if properly rinsed. If detergent isn’t thoroughly rinsed from plants and trees, the foliage may develop brown spots and could eventually die.
Regardless of which cleaning solution is used, it’s a good idea to use tarps and downspouts to channel the runoff more effectively.