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Roof Cleaning 101

What will you find on your roof?

clean me roof

When it comes to roof maintenance most homeowners don’t take roof cleanliness into consideration. We typically think if our roof isn’t leaking than there isn’t any issue. However, leaving roof cleaning issues unchecked can lead to damage of shingles, shakes and tiles which can lead to premature aging of your roof. Below we have listed some of the most common troubles and causes which is provided by Roofers 911, as well as preventative measures and ways to treat and clean ones roof.

blackalgaeBlack Algae – Often misnamed ‘mildew’ or ‘fungus’, black algae is usually found on the shadier slope of the roof, or on an area shaded by a tree. The staining tends to be uniform, unlike the black streaking seen when asphalt shingles bleed-through. The black stain is actually dead organic debris from dead algae. There are shingles made with zinc or copper granules designed to inhibit algal growth. Another way to help avoid black algae is to trim tree branches overhanging the affected area, allowing more sunlight. There are also zinc or copper strips that can be tacked to the ridge that will cause algae- killing metal salts to wash down the roof when it rains. Some people pressure-wash the algae, but I feel this is detrimental to shingle integrity. There are plenty of chemical solutions to remedy this problem. It is best to contact a professional roofing contractor to help make the right choice, both for you and your roof type.

 roof-debris-blowingDebris Staining – Is a fairly common problem, especially on low pitched roofs with overhanging branches. Staining occurs when piles of debris, such as leaves or needles from coniferous trees collect on the roof. These piles retain water and can cause serious damage if not dealt with. Not only can algae and fungus originate here, but also actual plants. Moss, lichens, and other plant life can often thrive on a neglected roof. The main way to combat this particular type of problem is to physically remove debris from the roof by sweeping and/or washing plant matter from the roof. Care should be taken not to damage any shingles or other roofing material. Debris staining is a prime of example of how prevention can be far less expensive than repairs. It is far easier to remove debris from a roof than to fix the resultant damage if not removed.

black stainingBlack Streaking – When black stains occur on your roof in the form of streaks, it may be a case of ‘bleed through’. This occurs when the bituminous material in asphalt shingles begins to break down and bleed from the shingle. Unfortunately this is usually a sign of faulty materials, or older shingles in need of replacement. However, it can be hard to distinguish bleed-through from black algae which is listed above, and is why I always recommend seeking the advice of a trusted roofing contractor before making any decisions on course of action.


How can this be cleaned?

cleaning roof Most common roof cleaning methods include either pressure washing or a form of chemical solutions that contain Chlorine Bleach or Sodium Hydroxide and other not so environmentally safe products. Although these methods are sufficient products in cleaning your roof with minimal negative impact, the effects are temporary. However, each method has its benefits and drawbacks below is a list and comparison of the most common roof cleaning and treatment methods.

  • Chlorine Bleach:  When using this method  you need to ensure it is followed by a thorough rinse as well as make sure you use proper care to protect people and  the surrounding property from the overspray and runoff because it can be highly toxic. Although it it provides faster cleaning and minimal rinsing and therefore has less wear and tear on the shingles itself, it can be corrosive to your roof fixtures (boots, valleys, flashings, and underlayments).


  • Oxygenated Bleach: This method although more labor intensive and requires immediate rinsing is safer for your roof fixtures and has less of a negative impact on the environment.


  • Ammonium Compounds: Although this method is less damaging to roof fixtures and more environmentally friendly it is not EPA (environmental protection agency) approved, it is more labor intensive and requires immediate rinsing as well.


  • Pressure Washing: This process has the advantages of not using chemicals which can eliminate cost as well as be less damaging to the environment, it is very time consuming and cause force on the surface of the roof that can wear away the surface, therefore this process is usually only recommended on concrete barrel tile, or metal roofs.


  • Proprietary Soap: This method is both safer on the environment as well as on your roof fixtures however is more labor intensive and requires rinsing.


Although these methods are relatively safe and effective, repeated use can lead to premature aging of the roof due to high pressure or harsh chemicals and later can lead to costly roof leaks. By using a proper form of preventative maintenance you can eliminate the need for future cleaning as well as the damage that comes with it.

If  you come across any roofing issues during  your summer maintenance and are in the Puget Sound region of Washington State contact Chase Construction North West, Inc. today. We are Master™ certified contractor through GAF. We have been providing our region with expert commercial and residential roofing services for over 13 years. We provide services in Seattle, Tacoma, Federal Way, Renton, Auburn and all of the surrounding cities. Give us a call at (253) 544-3651 or fill out our free estimate form.

2 thoughts on “Roof Cleaning 101”

  1. Ridley Fitzgerald

    Thanks for the information about roof cleaning. I think we need to get ours cleaned soon, so this is great to know. It sounds like proprietary soap is the safest method, even if it is harder. We’ll just pay someone to get it done!

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