All About Exterior Paint Problems

A coat of paint on the exterior of a home can do wonders to improve its appearance and hence its value. Albeit, appearance is important to the value of a home, enough can’t be said for the added benefit that paint offers to the lasting quality of a home.

Paint can protect a home against damage from moisture, ultra-violet and even structural pests. Unfortunately, the key to superior lasting quality involves more than just a coat of paint. Proper preparation, superior materials and quality workmanship are fundamental to a successful paint job.

Exterior painting is generally more complicated than interior painting due to the various environmental conditions to which a home’s exterior is subject. Blistering, peeling, chalking, rust and mildew are a few of the most common exterior paint problems.

Blistering is a condition on painted surfaces that resembles blisters on ones skin. Most blisters can be traced to a moisture problem. Water vapors attempting to escape are trapped by the paint resulting in a blister. Excessive heat, painting in hot weather, overly-thinned paints and poorly prepared surfaces can also cause blistering. New lumber that has been painted which has not had the opportunity to fully air dry is a prime source of blistering.

Prevent blistering by allowing new material to fully dry. A vapor barrier below the siding will help prevent moisture-related blistering. In-home moisture control and insulation at exterior walls can aid in preventing blistering.

Although peeling paint may begin as a blister, more often than not there are other factors involved. Too many coats of old paint is the most pervasive cause of peeling paint. Moisture or a poorly prepared surface that is chalky, dirty, greasy or slick can also cause paint to peel.

Peeling paint can be removed by using any of the traditional methods — sanding, scraping, power washing or by using a heat gun. We believe that the use of a torch (a most effective method) is best left to the painting professional due to the fire hazards involved.

Once all of the paint has been removed, bare wood and voids should be repaired with an high quality exterior grade vinyl spackling compound and sanded. More than one application may be required if shrinking occurs. Patches should be spot primed with a high quality oil base primer-sealer.

That powdery substance often found on exterior siding is called “chalking”. It is generally the result of a chemical breakdown of the ingredients in paint (pigment, binders and solvent) caused by environmental conditions. Chalking can also be caused by inadequate priming (especially over a porous surface), overly-thinned paint or applying the paint too thin.

Often, most chalking can be removed by washing the surface with a solution consisting of powdered laundry detergent and water. Vigorously scrub the surface with a clean cloth or nylon truck brush. If the chalking remains, the affected area should be washed using trisodiumphosphate (TSP) in accordance with the manufacturers directions. In addition to removing the chalking, the TSP should dull the finish which will necessitate a fresh coat of paint. In the case of heavily chalked surfaces, a “surface bonder” can be used in conduction with a primer to enhance finish coat adhesion.

Rust stains are unsightly and can be almost impossible to conceal. Spots of rust here and there are generally the result of deteriorating nail heads. Where possible, we suggest that rusting nails be removed and replaced with a new hot-dipped galvanized nail or ceramic coated construction screw. These fasteners are designed to resist rust.

Where it is not practical or possible to remove rusty nails, the heads should be lightly sanded with sandpaper or a wire brush and dabbed with a rust converter. Surrounding siding that may be rust stained should be treated with a shellac-based primer-sealer (stain killer) that is designed to resist bleed-through. A finish coat of paint can then be applied over the primer.

A painted finish that has many cracks and chips is called “Alligatoring”. This condition is frequently caused when a hard finish paint is applied over a soft paint or when flat paint is applied over a high sheen paint. Alligatoring is a sure sign that the surface is in need of some serious prep work which will most assuredly involve scraping, sanding, filling and priming.

Mildew seems to be a universal problem. Mildew loves dampness. Homes in heavily-wooded areas or that are surrounded by dense shrubbery are more susceptible to mildew. Trimming tree branches and thinning shrubbery is one of the most effective methods of dealing with a mildew problem.

Prior to applying new paint, existing mildew should be removed using a solution consisting of one-third cup of powdered laundry detergent, one quart of liquid chlorine bleach and three quarts of warm water. Add the bleach to the water first and then the detergent. Even though the solution is mild, be sure to wear rubber gloves, safety goggles and have plenty of ventilation. On exterior siding, the solution can be applied using a pump garden sprayer. Allow the solution to sit for approximately ten minutes, but don’t allow it to dry. Rinse with fresh water.

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