House-Painting-Before-Rain

How Rain & Damp Surfaces Effect Painting

If it rains within one hour after painting a home’s exterior, rainwater will leave watermarks or wash away any paint that has not dried. Painting over a wet surface decreases paint adhesion and causes the paint to dry more slowly.

Adverse weather forecasts are a constant consideration when painting outdoors – however, strategically, painting in covered spaces is the best way to prevent unpredictable weather conditions from ruining wet paint. Looking at the local weather radar is an excellent way to predict the potential for rain, equipping exterior painters to gauge adequate dry times before an evening shower settles in. 

Can You Paint When It’s Raining?

We get frequent evening storms in the summer here in Raleigh, NC. Painting in heavy rain or on surfaces that have accumulated moisture should always be avoided, regardless of exterior paint type. However, some acrylic exterior paint dry times are faster than others, enabling them to withstand moisture sooner. 

The potential for damp or rainy weather is nothing new to house painters, as most exterior painting projects face these conditions. However, knowing how to avoid getting caught when rain is forecasted will reduce the chances of the paint being negatively impacted.

Exterior-Painting-Light-Rain

Large overhangs on eaves and gable ends of a home provide covering and additional protection against rainwater. Light rain or drizzle is less likely to saturate siding and other areas directly underneath an overhang. Corner boards, window sills, and areas subjected to standing water will be affected the most by rain and should be painted, allowing ample time for the paint to dry before being exposed to excess moisture.

Painting During Rainy Seasons

Painting when there is rain or high humidity in the forecast can be tricky. Some seasons and specific regions are more prone to rain showers, forcing painters to work around these conditions – otherwise, exterior painting wouldn’t be possible during these times. 

There are many tricks that professional painters learn over time to prevent painting over wet surfaces while still being able to continue paint production during wetter seasons. But paint colors, products, and weather significantly affect the chances of successfully painting when a storm is imminent. 

When painting darker colors, siding, horizontal surfaces, metal, or wood staining, the conditions should be as dry as possible.

Painting Before It Rains

Painting a dry surface with the potential for rain can be nerve-racking. However, in our 20 years of experience, subtle paint degradation has been rare and never beyond repair. 

However, if the paint is exposed prematurely, it could suffer from weeping, known as “surfactant leaching.” So, just because the damage is not irreparable, it doesn’t mean it won’t cause a few completion delays and headaches. 

Furthermore, once dry, paint runoff can cause damage to other areas, such as roofs, driveways, and stained wood. So, painters should be cautious when painting above or near these areas when rain is forecasted.

Painting After It Rains

Applying paint too quickly after it rains can cause more issues than painting before it rains. Painting damp surfaces can cause bubbling and trap moisture in wood substrates, leading to wood rot and additional paint failure.

After a light rain shower, allow at least 4-12 hours of dry temperatures above 55 degrees in direct sunlight before continuing painting, and allow a minimum of 12- 24 hours after heavy rain. No brushing, spraying, rolling, or paint preparation should occur within 18 hours of pressure washing or after several days of constant rain.

Using Oil-Based Paint in Wet Conditions

While oil-based paints are not water soluble, like water-based paints, oil paints are affected when applied in wet conditions. Conventional oil-based paints should never be painted over damp surfaces unless they are specified to do so.

Oil paints take longer to dry; therefore, more time is needed to plan around temperate weather conditions. Soya Alkyds, a raw material in these paints, will suffer from streaks and watermarks when exposed to rain before it dries.

Priming Over Wet Surfaces

Paint preparations such as priming, caulking, and puttying should also be avoided in the rain. Although paint is over 50% water and will damp surfaces, lower surface moisture will allow the solvent to penetrate better, taking raw materials and bonding agents deeper within the surface. 

Painting and preparing a dry surface promotes better adhesion, allowing the best durability without any adverse effects on each part of the painting process.

Painting Indoors When It’s Raining

The potential for leaking doors and windows will impact interior painting the most. Painting inside while it is raining will create subtle application changes under certain circumstances. Interior walls that join exterior walls will also take longer to dry. 

Interior paint dries slower when it’s humid or damp outdoors as well. However, an increase in airflow will counter the effects of a rainy day for interior painting.

Conclusion

Just because there is rain in the forecast doesn’t mean the day is off-limits for house painting; it just means painters must know what they are doing and be cautious along the way. 

On the other hand, if water is dripping off your painter’s elbows and they are still painting, you may want to send them home.

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