It is very common to see multi-layer peeling on older homes and buildings. In most cases you can recognize this condition by examining the top and the bottom of the peeling paint chips or the color. Typically they will be different colors, and when measured for Dry Film Thickness the measurement is very thick when you consider the typical DFT for one layer of paint is about 1.5 mils.
The peeling is caused by a previous layer of paint loosing its elasticity and adhesive characteristics due to the age of the coating layer and moisture intrusion. Older coatings, especially oil or alkyd products, become brittle and crack due to constant expansion and contraction of the substrate. This is most common with wood substrates. Eventually, all layers of paint on top of the old brittle layer crack and peel. This failure is not a result of product quality defect in the last coat(s) of paint applied.
There are two ways to deal with this problem. The solution chosen will determine the longevity of the resulting paint job. The ultimate fix is the complete removal of all coatings down to the substrate, being sure to follow all existing precautions that apply to sanding dust and any resulting lead dust. Prep, prime and topcoat per selected product.
Warning! Removal of old paint by sanding, scraping and other means may generate dust or fumes that contain lead. Exposure to lead dust or fumes may cause brain damage or other adverse health effects, especially in children or pregnant women. Controlling exposure to lead or other hazardous substances requires the use of proper protective equipment, such as properly fitted respirator (NIOSH approved) and proper containment and cleanup. For more information, call the National Lead Information Center at 1-800-424-LEAD or contact your local health authority.
If total removal is not done, a scheduled maintenance program should be established, where by isolated spot peeling is annually addressed to prevent widespread peeling. This maintenance program should include pressure washing with bleach to kill mildew on exterior surfaces, scraping to remove any loose peeling paint, followed by sanding to the care substrate. Clean the surface and spot prime with the appropriate primer and top coat.