| What Are Those Black Stains on a Shingled Roof? | Those black unsightly stains are algae. Algae appear as dark to black stains each shingle and usually covers a majority of the roof surface area, more predominantly on the lower portion of the roof where moisture content is higher and taper as they reach the ridge caps. |
| How Does a Roof Get Stained with Black Algae? | Algae can spread from one infected roof to another via airborne spores. These spores land randomly on a roof and take root. A Shingle is the perfect breeding ground for algae due to its porosity and constant moisture content. A protective sheath creates the dark to black color the algae forms in an effort to protect itself from the sun’s UV rays. |
| How Does Algae Grow? | Algae require moisture and proper temperatures to grow. Dew is the primary moisture source. Algae are found excessively in the Southeast of North America, but it can and will grow anywhere. The algae generally grow on the northern exposures of a roof since this exposure generally receives less sunlight. Algae are very well adapted to extreme conditions, meaning they can survive both extreme heat and extreme cold weather conditions. |
| What Is The Solution? | It is recommended to install Algae Resistant Shingles. These types of shingles have a specially formulated granule that inhibits algae growth, keeping your roof looking new and algae free for years. If installing a new roof is not an option, it is recommended to clean your roof with a special roof cleaning mixture. For more information click How To Clean Roof Shingles |
| What You SHOULD NOT do! | It is recommended by the leading roofing manufacturers to not power wash your asphalt shingle roof. Power washing shingle roofs can dislodge the granules, which can lead to premature shingle failure. The reflective shingles present in a shingled roof can both reflect the sun’s heat in the summer which will reduce cooling costs and can retain the heat in the winter thus reduce heating costs. |
| Where Can I get More Information? | Visit North America’s largest roofing manufacturer GAF for all the information you need. |
Removing Vanadium Stains
Vanadium stains should be removed prior to cleaning with hydrochloric acid. Vanadium stains are yellow, green or reddish brown discoloration commonly present
on newly laid bricks.
Steps for removal:
- Take sodium hypochlorite, the active ingredient in household bleach and pool chlorine. This is a a good treatment for mild stains.
- Sodium hydroxide, more commonly known as caustic soda is also a good treatment. Take 21 ounces per gallon of water.
- Spray or brush solution onto a dry wall. When stains disappear rinse the wall thoroughly.
- Oxalic acid is the most common removal method. Mix 2.8 to 5.6 ounces of oxalic acid per gallon of water. Apply mixture to dry wall. When stains disappear, neutralize the acid on the wall with 2 ounces of washing soda per gallon of water. Do not rinse off.
Removing Mortar Residue From New Bricks
- Mortar joints should be allowed to harden for at least 3 days
- Remove all large mortar dags with hand scraper
- Cover adjacent materials such as glass, metal and wood
- Saturate the brick wall with clean water
- Apply hydrochloric acid solution max 1:20 for light colored bricks and max 1:10 for dark colored bricks using low pressure
- Allow for sufficient dwell time
- Pressure rinse off acid solution with low pressure power water spray
- Repeats steps as necessary
- DO NOT use more than 1200 PSI for smooth bricks or more than 1800 PSI for textured bricks
- Use a 15 degree fan jet with nozzle no closer than 10 inches from brick surface
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