Exterior Peeling Paint

Peeling paint is essentially an adhesion issue— the paint is not bonding to the substrate or to previous coatings. Trouble shooting the cause of the peeling is crucial if we are to solve the customer’s problem. Unless the cause of the peeling is identified and corrected, the problem will persist.

There are two types of peeling problems: inter-layer peeling (peeling between layers of paint), and peeling down to bare wood. Identifying the type of peeling is the first step in troubleshooting the problem.

Inter-layer peeling occurs when the bond between one coat of paint loses its bond to the previous coat. This will be evident when previous coatings remain on the surface, i.e., bare wood is not exposed. With few exceptions, inter-layer peeling is the result of poor preparation during a previous paint job. However, it remains necessary to identify the specific cause, that is, what steps in preparation were omitted or performed inadequately.

The most common causes for inter-layer peeling are painting over a dirty or chalky surface, or applying a latex paint over a hard, glossy oil paint. It is important to identify the extent and location of the peeling. Small, isolated areas of peeling represent a considerably different problem from extensive peeling. Isolated peeling may be caused by external factors (such as a leaky faucet or splashing from a downspout).

Peeling to bare wood is evidenced by the presence of bare, or primed wood. This type of failure is typically has three causes: insufficient ventilation of the house, the presence of excessive coats of paint, and the use of inferior paint. Again, the extent and location of the peeling is an important part of troubleshooting the problem.

When peeling is extensive, the first step is to inspect the ventilation system. Inadequate ventilation is common on older homes. A house should have 1 square inch of net free ventilation per square foot of attic space, evenly divided between intake and exhaust.

The next step is to determine the number and types of coatings previously applied to the house. As paint ages, it loses flexibility, resulting in stress cracks in the paint film as it expands and contracts. These cracks permit moisture intrusion into the substrate and/ or under the paint film. Complete failure can result quickly as the problem worsens.

In such cases, complete removal of all paint or replacement of the affected surfaces are usually the only viable corrective actions. The type of substrate will determine which option is more economically sensible.

Exterior Preparation

As with interior painting, proper surface preparation is crucial for achieving a long lasting paint job. A thorough cleaning to remove dirt and mildew is the first step in preparing exterior surfaces.

All loose paint and defective caulking should then be removed. Any rotted boards should be replaced, and all new and bare wood primed. Gaps between adjoining wood, or wood and masonry, should be caulked with an elastomeric sealant. Hardware and light fixtures which are not to be painted should be removed or properly protected, and all plants should be moved or covered.

Rusty surfaces, such as steel lintels and wrought iron, may require special preparation. All loose rust should be removed, and the surface then primed with a rust inhibiting primer.

As with interior paints, many manufacturers have developed new latex products which offer superior performance over oil base paints. A 100% acrylic latex paint should be used for exterior surfaces. Less expensive paints generally contain a vinyl, or vinyl-acrylic, resin, which is not as durable as a 100% acrylic resin and does not retain

Generally, paints offered for residential use are either alkyd base (oil) or water base (latex). The base indicates the solvent used to suspend pigments (coloring agents) and resins (binding agents).

Because they dry slowly, alkyd paints should not be used for exterior painting in warm, humid climates. The slow drying time gives mold spores more opportunity to attach to the drying paint film.

This, combined with the nature of the resins in alkyd paints, provides a near perfect environment for mildew. Latex paints are much more mildew resistant. While most high-quality paints now contain mildewcides, such additives will only inhibit mildew growth, not prevent its occurrence.

No paint job will last forever. However, the life of paint can be extended with the proper care and maintenance. Interior paint is generally not subjected to conditions as harsh as exterior paint. Maintenance usually consists of little more than occasionally cleaning to remove dirt, grease, or fingerprints. Scuff marks, scratches, and chips require touch up.

Exterior paint requires considerably more maintenance. Regularly removing dirt and mildew will not only keep the paint looking fresh, but will also prevent mildew growth from destroying the paint film. In addition, an inspection for rotted wood and cracked caulk should be conducted at least once a year.

Promptly replacing rotted boards and repairing cracked caulk will prevent more extensive and expensive damage.

Exterior Product Selection

Consumer magazines and television programs regularly test exterior paints. While these tests conducted can be informative and useful, the procedures for testing paints and other coatings cannot be accepted as the definitive statement on paint quality. Many factors must be considered when judging the quality of a particular paint.

For example, exterior surfaces in Houston are subjected to considerably different conditions than those experienced in northern climates. High temperatures and humidity, and mildew growth, are two factors more prevalent in southern climates. An alkyd paint may perform well in a northern climate, but will develop cracks and foster mildew growth in Houston.

A number of paint manufacturers have developed a reputation for producing superior products, and the cost of their products reflects this reputation. At times, this reputation has been aided by articles and reports. The durability of a paint is primarily determined by the type and amount of resin it contains. For most exterior applications, a 100% acrylic resin is recommended. An examination of the product data sheets of the highest quality paints made by leading manufacturers reveals that each contains approximately the same quantity of acrylic resin.

By this standard, there is little difference between these paints. Our experience confirms that these products perform equally well.

Proper surface preparation and application of the product according to the manufacturer’s specifications are as important as the quality of the paint.

The adage ‘you get what you pay for’ is not always true. Sometimes, savvy marketing can create an image of quality which doesn’t actually exist. In the case of paint, the contents of the can are more important than the quality of the label.