Mildew - Causes & Solutions

Paint mildew can cause a serious problem for any homeowner. By the time mildew is visible to the naked eye, it has typically spread far more deeply or broadly under the surface of the paint and into the substructure of the building. Mildew can transform into mold very quickly, and mold can cause serious health problems for occupants of a building. It is critical to discover and remedy the causes of the mildew and thoroughly refinish the paint as soon as possible.

Causes of paint mildew

Paint mildew is almost always caused by excessive moisture. Such moisture can collect on the exterior of the paint surface, but most often mildew is caused by moisture gathering under the surface of the paint. Such moisture can collect from a leak or condensation on the water or drain lines in the interior of the wall where the paint mildew is forming. It can also penetrate the surface of the paint through unsealed cracks in the painted material or from flaking and checking in the exterior paint itself. It is necessary to address the source of the moisture before any refinishing efforts can succeed.

Solutions to paint mildew

After identifying and fixing the source of the moisture, removing existing mildew is essential before new paint is applied. Scraping and sanding the surface of the paint is the first step in removing mildew, but mildew spores too small to see with the naked eye can remain and regrow after new paint is applied. For this reason, it is critical to scrub the immediately affected area and any surrounding surfaces with a chemical to kill off any remaining mildew spores. A variety of products, such as TSP or Toughcoat, are sold as mold killers, but these products are not substantially more effective than household bleach. Once the mildew spores are eliminated, treat the surface with a mold-preventing primer and allow it to dry fully before applying new paint.

Paint mildew can lead to serious structural problems. To remedy the situation, it is necessary to address the underlying cause and thoroughly treat the affected area before applying new paint.

Priming is essential for better adhesion, sheen uniformity, mildew control and durability. 
Select a top quality interior paint in the color and sheen of your choice. 

Substrates, Primers

Substrate: Various 
Primer: Clean with Bleach & Water Solution 
Finish Coats: 550 Super Latex Interior Flat Wall Paint 
1610 Sat-N-Sheen Int. Low Sheen Finish 
1650 Acry-Plex Interior Latex Semi-Gloss 
1685 Dura-Poxy + Int./Ext. Semi-Gloss Acrylic En. 
1680 Dura-Poxy + Int./Ext. Gloss Acrylic En.