Exterior of structures are exposed to the elements. As a result your exterior paint will fail. When will it fail depends on many factors including type of coatings applied, fluctuations and severity of local weather conditions, and nature and condition of the base surface. Here are few factors that cause the failure of your paint.
Failure to prepare weathered wood: As you know primer and paint don’t adhere to weathered wood. If you apply paint without properly preparing the surface, paint will peel off within a short time. Re-fresh weathered wood thoroughly by sanding or power washing before priming or staining.
Failure to smooth rough edges: Paint will not adhere to rough surfaces. Scrape surfaces thoroughly. Taper the edges of old paint by feather sanding. Be aware of lead and never sand any paint surfaces that contain lead. Hire an expert to deal with lead based paint.
Failure to use primer: Primer promotes adhesiveness and uniformity of the surface. It provides mildew resistance and prevents discolorations.
Failure to use correct type and quality of paint: Use the correctly designed paint for the job. Glossy paint is designed for metal surfaces and may not work properly on wood surfaces. Paints designed for indoors don’t work for exterior jobs.