Managing Mold and Mildew

Mold and mildew are types of fungi that settle on a surface and thrive in warm and damp situations.  
Mold and mildew forms in many different colors, including blue, green, yellow, brown, gray, black, or white. It grows as a flat pattern on surfaces which may appear either powdery or downy, or it can be fuzzy in appearance. 

These fungi can cause health problems such as respiratory issues and headaches, also inflammation including pain in the joints, mental status changes, and extreme fatigue. Where mold is present structural damage to the surface can occur over time.

Where is it found?
Mold and mildew is quite common in damp, humid conditions out of direct sunlight. It can also be seasonal, with dry and wet cycles.

The fungi are not caused by the actual surface but occur when spores are attracted and thrive.  Rough and textured surfaces are more prone to growth because they tend to trap airborne dirt, spores, and moisture. Whereas smoother surfaces have less of a profile that would hold onto the contaminants. 

Removal of mold and mildew growth can be difficult on rough and textured surfaces, any previous coating or finish can be affected by the roots of the growth.  Damage to the coating or finish can result from overly aggressive cleaning.

Below are some steps for the successful removal of mold and mildew:

The following processes are recommended to see if the fungi can be removed without damaging any underlying finished surface.

  1.  Use a building or industrial cleaner in solution with water and scrub the surface. Then rinse off the residual dirt, mold or mildew, plus the cleaning solution before it can dry on the surface. The cleaning solution should have no more than 10% of household bleach added to the mix. (please note – the use of bleach products is completely prohibited on some projects) There is a range of industrial type mold and mildew cleaners and building cleaners such as “30 second” cleaners that may work. 


  1. If a standard cleaning does not work try ‘power washing”. Start at a low pressure and increase until the desired cleaning is attained.  The power washing can disturb the finish and can tear up the surface, so care must be taken.


  1. If chemical cleaning and power washing do not work the only alternative is power sanding and/or abrasive blasting.  Both of these methods will change the texture of the surface and also remove any applied coating or finish. Re-coating will be required.

More information on Mildew treatment on painted surfaces can be found in the MPI Repaint Surface Preparation Standard = MPI RSP-9 in the MPI Maintenance Repaint Manual 
Caution Note: 
Both bleach and TSP are corrosive. Rubber gloves and eye protection should be worn during mixing and application. Plants and shrubbery located near the work area should be protected from direct contact with the solution.

Products tested to MPI Green Performance and MPI Extreme Green have the lowest VOC, with proven high-performance. Look for these logo’s on the paint cans.
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