TECHNICAL BULLETIN
Mold and Mildew
Exterior paints can support the growth of mildew, particularly after they have weathered for a couple of years. Flat paints, oil-based paints, and lower cost paints are more susceptible to mildew growth. Mildew is most likely to form on northern exposure and in shaded damp area. Where mildew is detected:
- Cover plants and grass in the area.
- Apply a 3:1 solution of water and household bleach to the mildewed area using a brush or garden type pump up sprayer. Wear eye and skin protection and a respirator. A test area is recommended to check for color fading.
- Allow solution to remain on the surface for 3 to 5 minutes then rinse completely and allow to dry before coating application. Do not add detergents or ammonia to the bleach and water solution.
Dirt and Chalk
Airborne dirt can accumulate on paint and darken it, and be a source of nutrients for mildew. Chalky pigment can be released from paint as it weathers, resulting in fading of colors and unsightly rundown. Both dirt and chalk can be removed by scrubbing or power washing.
Scrubbing is best done with a mild detergent and scrub brush, followed by thoroughly rinsing. Harsh alkaline cleaners such as TSP can reduce the gloss of alkyd paints and of some latex paints.
Power wash using an all purpose cleaner/degreaser. Care should be taken not to lift paint or damage the surface. This cleaning process could be done 1-2 times per year.
Efflorescence
Moisture from within or behind a masonry substrate can carry white powdery salts out, undermining the paint or disfiguring the surface.
- Remove any buildup of efflorescence using a stiff metal wire brush. Wear eye and skin protection along with a dust mask. If possible, identify and eliminate the source of water causing the efflorescence.
- Where necessary, prime with a latex masonry primer Sure Grip Exterior Acrylic Latex Primer and repaint.
Closely Monitor
It is important to monitor the condition of exterior paint in order to catch failures early, and thus minimize subsequent failures and to make redos more cost effective. In addition to assessing exterior paint for dirt, chalk, mildew, and efflorescence and treating as outlined above, check the paint closely for the following and repair immediately:
- Cracking or checking
- Blistering, peeling, and loss of adhesion
- Serious fading and loss of gloss
- Signs of rusting
For further information on maintaining exterior wood, contact your Diamond Vogel representative.