Hot summer sun, wind-driven rain, hail, dust, and snow and ice gradually take a toll on even the best finish. How frequently the finish should be renewed is governed by the rate at which it weathers away.
As pointed out, a paint maintenance program is determined by the kind of paint used in the first paint job. The basic rule is paint only after most of the old paint film has weathered away. Always remember that coating thickness can build up dangerously if paint, especially oil-base paint, is applied too frequently. Abnormal behavior spells trouble and possibly costly removal of oldpaint by blow-torch or by paint varnish remover.
Paint that starts to crack and peel from the wood indicates that a serious moisture problem may be involved. It may indicate two conditions (1) either a primer was used that was sensitive to water and perhaps too porous to provide adequate protection from rain and dew or (2) moisture from cold-weather condensation or ice dams is excessively wetting the walls and the siding.
Quality latex paints properly applied to old painted surfaces are proving to be excellent refinish systems. Latex does not always bond well to chalked surfaces, and because of its porosity it holds rain and dew. In turn, this moisture can penetrate the paint film and produce an abnormal peeling problem. When repainting chalky surfaces with exterior latex, therefore, it is advisable either to remove the chalk by sanding, scrubbing, or steel wooling or to apply a new coat of oil-base primer over the chalk. Recent developments in latex paint formulation have greatly improved performance over old paint. Thus it is important to read the directions on a label carefully before applying latex over old chalky paint.
Penetrating natural stains are easy to renew. Fresh finish is simply applied when the old finish appears to need it. As with the first finishing job, any excess of stainor oil should be wiped off, so that formation of a surface coat is prevented.
When to Paint
You can easily ruin your paint job if you forget to consider the weather. Excessive humidity or extremely cold weather can cause you trouble. If humidity is high, check the surface before painting. If you feel a film of moisture on the surface, wait for a better day.
Exterior painting is not recommended if the temperature is below 50º or above 95ºF because you may not be able to get a good bond. This is especially critical if using latex paint.
Latex and water-base paints allow more freedom in application than oil-base paints. They can be applied in humid weather and to damp surfaces. But for best results with either type of paint, do your painting when the weather is clear and dry and the temperature is between 50º and 90ºF.
Don’t paint in windy or dusty weather or at times when insects may get caught in the paint. Insects are usually the biggest problems during fall evenings. Don’t try to remove insects from wet paint; brush them off after the paint dries.
Start painting after the morning dew or frost has evaporated. Stop painting in the late afternoon or early evening on cool fall days. This is more important with oil-base paint than with latex paint. In hot weather, paint a surface after it has been exposed to the sun and is in the shade.
Ideally, the north side of the building should be painted first part of the morning, the east side later in the morning, the south side in the first part of the afternoon, and the west side later in the afternoon.