Removing biological stains: a guide to clean exteriors

Biological stains don’t just affect the appearance of your commercial building’s exterior but can cause damage to the resiliency of the masonry itself. The following information will help you understand biological stains and offer effective cleaning methods and preventative measures.

Understanding biological stains

Some types of biological stains and their growth conditions are:

  • Algae and moss grow in consistently moist conditions caused by poor humidity or leaks that accumulate water on the wall render.
  • Lichen grows on roofs and is caused by the reproduction of algae and fungus. It can be blown onto the roof or fall from nearby trees.
  • Mold or mildew flourish when the ground around your building is consistently wet because of improper drainage, broken gutters, leaky faucets, or too much shade.

Effective cleaning methods

Here are some cleaning methods to remove biological stains caused by algae, moss, lichen, mold, and mildew.

Soft washing vs. pressure washing

Soft washing requires a cleaning solution but is better for delicate materials (including stucco). Pressure washing is suitable if you don’t want to use cleaning solutions. It can damage delicate materials, so it should only be used in durable areas without previous damage.

For algae, moss, and lichen

  • Remove as much as possible with a knife and stiff bristle brush.
  • Rinse with water for about 30 minutes.
  • Gently scrub with a soft bristle brush.
  • Rinse off with water.

For mold and mildew

  • Mix 3 oz. trisodium phosphate, 1 oz. powdered detergent, 1 qt. laundry bleach, and 3 qts. Warm water. OR mix 1 part ammonia with 3 parts water.
  • Scrub the affected area with the solution using a medium hard bristle brush.
  • Rinse with water.
  • Repeat these steps if necessary.

Preventive measures to avoid stain recurrence

You can treat the area with protective coatings or sealants to prevent the stains from returning soon. Removing close plant growth and reducing shade can also improve air circulation and sunlight exposure.

JK Industries offers a spectrum of exterior restoration services. Contact us if you need cleaning or restoration of your commercial property’s exterior.