Common Problems Faced by Exterior Paint


Extremes in temperature, air pollution, expansion and contraction of building materials, or mold growth are some of the problems faced by the exterior surface of a home. These are related to improper preparation and application. 


Moisture penetration through a paint coat can result in cracking, peeling, discoloration and premature paint failure. They tend to be more apparent on edges and ends of boards and are observed where water is held on the surface, especially in heated and unheated buildings. Porous paints are particularly vulnerable to moisture penetration.

To eliminate most exterior water problems it is important that you ensure proper construction and maintenance. In cold climate, repeated thawing and freezing on the roof more water moves to the roof edge and an ice dam begins to build up, causing the melted water to penetrate the roof and drain into the exterior walls, and cause moisture and associated paint problems. This can be reduced significantly by insulating attics and proper attic ventilation. Condensation problems in cold climates are best prevented by installation of a continuous 6 mil polyethylene vapor barrier on the warm side of all exterior walls and ceilings.

Water vapour from inside a building can also destroy paint on the outside of a building by diffusing through the walls, i.e., water vapour from cooking, dish washing, clothes dryers, bathing and normal respiration by an average family of four can contribute three gallons of water per day to the humidity. If a vapor barrier has not been installed or if the vapor barrier is improperly installed, water vapour passes into the walls during cold winter weather and condenses to a liquid, eventually soaking into the siding and wetting the paint, causing blistering and peeling. 

This problem can also occur in the attic space, condensing on the gable ends and cause paint peeling there. Condensation from the attic side of the roof decking can slowly work its way down the side walls and cause paint peeling near the tops of these walls. To prevent this, the attic should be well ventilated. Gable roofs should have screened vent areas of at least one square foot per 300 square feet of ceiling area. Continuous slotted vents in hip roofs to allow air to enter the attic and ridge vents to allow its exit gives ventilation and reduces this problem. Always install a vapor barrier, over the soil in all houses with crawl spaces. This keeps moisture from moving out of the soil and up into the living space and then through the walls and ceilings. If there is no vapour barrier in the crawl space, then install it under new paneling or dry wall. 

Paint Blistering or Bubble

A blister is usually the loss of adhesion between the new and old layers. This usually forms after the paint has dried, the amount of time could be a day or even a year or more. A paint bubble occurs with the expansion of vapours or excess moisture on the surface during application, and usually forms before or during the initial drying phase.

Warm or Hot Surface

A bubble can also form when paint is applied on hot wall surface. The solvents, water for latex and mineral spirits for oil base, vapourize very quickly, while the paint dries quickly as well and form a film, becoming resistant to the transfer of the solvent underneath. Excessive thinning combined with heat will increase the chances of this condition occurring.

Avoid painting in direct sunlight or application to hot surfaces. Use paint conditioners such as Flotrol, for water base paints, or Penitrol, for oil base paint, to slow down the drying of paint when applied in hot weather and evaporation rates. 

Lifting Old Layers of Paint

Large blister or paint bubble can form when new paint film dries and shrinkcs, pulling the underlying layers and lifting them to the surface. For instance, if linseed oil was used to stain a wall previously, painting with latex or acrylic paint without a primer will cause this lifting of a paint layer when a new layer is added. The same result can happen when a home is originally painted with an oil base.

The only way to prevent this is to ensure proper preparation of the wall before painting the new coat of paint.