Painting Exteriors in the Winter

In Houston, we can paint exteriors every month of the year. The real concerns when painting exteriors is temperature and moisture. Most of the exterior products that we use can be applied down to 35 degrees. Since we seldom get that cold, temperature is rarely an issue for the paint. (The painters are a different issue.)

However, at cooler temperatures the paint will not dry as quickly, and this slows further when the humidity is high. In this regard, temperature can be a concern.

Another issue is the dew point. We have experienced situations in which excessive moisture has accumulated on a painted surface overnight. Even though the surface of the paint was dry when we left the job, the moisture re-wetted the paint.

During the winter we are much more cognizant of the weather, since we have more than one concern. But with a few extra precautions and a conservative approach, we can paint exteriors year round.

Painting Bricks

Painting bricks can often be an effective way to improve the appearance of an older home. But special steps should be taken.

The bricks should be cleaned to remove dirt, algae, and mildew. A masonry primer should be applied to seal the bricks. If they are extremely pitted or uneven, a block filler may be needed to fill the indentations.

Bricks present some unique problems compared to wood. The porosity of the bricks and the alkalinity of the mortar can adversely affect the appearance and adhesion of paint. For example, highly porous bricks which are not properly sealed will absorb paint unevenly, resulting in a spotty appearance.

On older homes with significant damage to the bricks and mortar, painting can greatly improve the appearance. Caulk can be used to fill cracks, and once painted, are much less noticeable.

An elastomeric coating can be used to provide a water proof barrier that will also bridge any hairline cracks that develop later.

Moisture and Peeling Paint

Most peeling paint is caused by the moisture. This is particularly true of older homes without adequate ventilation. The problem is usually worst on the walls outside of high moisture rooms, such as bathrooms.

The moisture will migrate through the wall until it reaches the surface of the exterior siding. If that moisture cannot easily escape from the wood, it can push the paint film away from the surface. The problem tends to be worse on walls that get significant exposure to the sun.

When the sun hits the wall, the water expands. On older homes, it is likely that an oil base paint was used at one time. Oil paints do not “breathe”, i.e., allow moisture to move through the paint film.

In addition, on many older homes the overlap between pieces of siding has become sealed over the years. This prevents adequate ventilation of the wall cavity, which in turn keeps the moisture trapped.

Moisture takes the path of least resistance. This generally means pushing the paint film off of the surface. The problem is usually made worse on walls with direct sun exposure. As the sun heats the wall, the moisture vaporizes and expands.

The solution essentially involves improving the ventilation of the wall cavity. This can take several different forms.

One of the easiest is to simply break the seal between the pieces of siding. This may involve removing caulk and the build up of paint. While the gap between the siding boards may be a little unsightly to some, peeling paint is usually more so.

In extreme cases, it may be necessary to insert a small wedge between the boards. This will maintain the proper gap between the siding, and allow the moisture to escape.