Why is algae growth becoming more of a problem on painted surfaces and what to do about it?

The paint on your exterior wall is discolored and you ponder whether this is due to dirt or some form of mildew. In addition, you notice your roof shingles – especially in the areas that receive a lot of shade – showing a dark green discoloration. You begin to think that this problem is not due to dirt or mildew but algae growth. In this newsletter we focus on defects and remedies for algae growth.

There are a number of factors behind the increased incidence of algae. The growth in the use of cement-based substrates such as Hardy Board and stucco is the single most important reason. This is because algae are prone to grow on these cementitious substrates. In addition, homes in humid coastal climates such as the Florida, Gulf Coast Texas, the Carolinas and the Pacific Northwest are more likely to face problems from algal growth.

Please note algae are plants that require light to grow and, therefore, are only found on exterior surfaces. They are also most likely to grow on the north and east sides of homes. To ensure effective protection against algae growth and overall superior durability, we recommend you use a top quality 100% acrylic paint that is specifically formulated for exterior use and contains algaecide.

Q & A:

Q:What does algae look like on coated surfaces?
A:Typically, algae are identified by their distinctive green color. Algae can also appear black and can be an excellent food source for mold and mildew. Algae and mildew are often found growing together. For more information on surface problems, please visit our FAQ's section.

Q:Can an algaecide be added at the point of sale vs. during the manufacturing?
A:Algaecides need to be added during the manufacturing. It is best to request paint from your supplier that contains both fungal and algal protection.

Q: How can algae be cleaned prior to painting?
A: Apply a 3 to 1 solution of water and bleach. Protect your eyes and skin when applying this solution and allow 20 to 30 minutes before reapplying as needed. Be sure that the all growth and dirt are removed from the surface. Then rinse thoroughly and allow to dry before painting. For more information on surface preparation, please visit our infosheets section.

For additional information on Algae, please visit the web sites below:

http://en.wikipedia.org/wiki/Algae

http://www.botany.uwc.ac.za/algae

http://www.ucmp.berkeley.edu/greenalgae/greenalgae.html