Housing...Inside and Out

May 5, 2000
When Should You Paint?

Hot sun, wind, rain, hail, dust and extremely cold weather will gradually deteriorate even a good quality exterior paint. Exterior finishes wear at various rates. Natural finishes need renewing every year or two by applying a fresh penetrating coat when wear begins to show. Stain finishes are very durable and should last as long as five years.

Paint only after most of the old film has weathered away. If paint is applied too often, coating thickness may build where it requires costly removal with paint and varnish remover.

When repainting, use the type of paint originally applied if it can be determined. A different type of paint may be incompatible and may fail to wear satisfactorily.

There are many causes of poor paint wear. Most common are vapor condensation problems that occur in houses without insulation and proper vapor barriers. Other causes are rain or other water behind siding, an improperly applied priming coat, too frequent repainting or use of an incompatible type of paint when repainting.

Find the cause if trouble develops. If it is due to springtime blistering, the house may need better moisture proofing. Where water gets inside walls from the roof, locate leaks and examine the gutters. If water penetrates joints and the exterior wall covering, treat the lap and butt joints with a water repellant preservative before repainting.

Whatever the cause, find and correct it before repainting. A quick painting to cover unsightly failures is no short cut. It may only make matters worse by building the paint coat to a thickness that results in cross grain cracking. When this happens, all paint must be removed, and the work must be done over again.


Written by Dr. Francis Graham (Retired)

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