PREVENTING & RESOLVING EXTERIOR PAINT PEELING PROBLEMS
Exterior paint peeling is seen when a dry paint film loses adhesion with the underlying finish or substrate. It can be localized or widespread, random or repetitive. Substrate condition and preparation are essential for the coating to develop a strong adhesive bond to the surface.
PREVENTING EXTERIOR PAINT PEELING PROBLEMS
Substrate integrity should be sound and intact. If this is not the case, removal of the existing layers may be required before prep work can begin.CLEAN
All surfaces need to be free from dust, grime and contamination. This includes dirt, chalking and mildew. Scraping, sanding, wire brushing and pressure washing are all methods used to clean and prepare surfaces for painting. Project specific techniques will need to be determined. Be sure to let the surface dry thoroughly before painting, as paint cannot adhere to a wet surface.
DE-GLOSS
A previously painted substrate with sheen does not promote good adhesion of the next coating of paint. Dull the glossy surface using sandpaper (120-150 grit), making sure to remove all sanding dust. When the surface is clean and dry it is ready to be painted.
SURFACE AND AIR TEMPERATURES
Temperatures play a major part in the drying of a paint film. Hot surface or air temperatures may cause a coating to dry too quickly, not allowing the film to establish an adhesive bond with the substrate. Cooler temperatures (less than 50 degrees) will slow down the drying process causing the coating to emit dryer components without actually drying. A poor adhesive bond will result in peeling. It is usually best to paint when surface and air temperatures are 50°F-90°F.
MOISTURE
Another major factor in the drying and adhesion of a paint film is excess moisture. This will slow down or extend the drying time of a coating. If the underlying paint, primer or substrate was not thoroughly dry, the next coat may have trouble bonding. Exposing the substrate to high humidity shortly after painting could negatively affect adhesion and create appearance problems as well. This is often seen on older homes with inadequate vapor barriers and insulation in the exterior walls. Interior humidity actually permeates the wall cavity and condenses on the back of the outside wall, leading to peeling of the exterior paint.
RESOLVING EXTERIOR PAINT PEELING PROBLEMS
Surface adhesion must be inspected. Depending on conditions, underlying finishes may be where the problem begins. Testing adhesion in other random spots of a peeled surface should be done to assess the overall adhesion. Re-prepping surfaces after removal of existing coats will require the area be roughed and cleaned again before re-application.
Refer to “Preventing Exterior Peeling” for the proper steps and precautions to ensure a successful painting experience. If you suspect interior humidity is the problem, either lower the inside humidity (using vents, etc.) or create a non-permeable vapor barrier to keep the humidity out of wall cavities.
The information in this document is for general informational use and is not all-inclusive. Since application variables are a major factor in product performance, this information should serve only as a general guide. Valspar assumes no obligation or liability for use of this information.