Painting in the Rain: The Lowdown

painting in the rain
January 18, 2017 Painting in the Rain

Just as you have just finished washing your car, it rains. “I should wash my car more often”, you say.  “We need the rain – but I should have checked the weather forecast.” Well, folks, it also applies to that DIY or professional painting job in the interior and exterior of your home. Always check the weather. The simple rule of thumb is to ask yourself, is the washing drying on the line, should I wash my car or should we have a Barbie this evening? If the answer is no – then follow some good advice from the experts on painting in the rain. Common sense, and listening to Mother Nature, will ensure you will not be disappointed with your paint job.

Ideally – when should you paint?

  • Watch the temperature both inside and outside as this will affect the performance of the paint.

  • Take note of the humidity – too high or too low will cause problems.

  • The wall temperature must be above 10°C throughout the painting process.

  • 15 – 20°C, humidity 70-80% and a very gentle breeze – perfect timing.

Temperature and Humidity– important components to take into consideration when painting your home

These go hand in hand when deciding how and when to paint.

  • The lower the temperature, the longer it will take for your paint to dry. Both externally and internally.
  • If the humidity is high, waterborne paints will be slow to dry. Of course, they will be easier to apply because the paint will be runnier, but the problem will be an accumulation of water sensitive compounds onto the paint.  The effect will not be a good one.
  • Low humidity dries out paint.  Not ideal as this will lead to a heavier application.
  • Low humidity plus high temperatures will cause the paint to dry too fast. Sometimes you may want to add a product that will slow the process – your paint expert will be able to advise which products can do this successfully.

Paint should only be applied to a dry surface

A painting surface will be damp or wet if it has been rained on or if the air has a high moisture content in the air or of course from the garden sprinkler being left on the outside.

  • After heavy rain, wait at least one full day before painting.
  • The surface should not feel in anyway wet or damp. Be careful here, as sometimes surfaces may feel dry, but if they are in any way porous they may be damp deep down inside – this can be the case with surfaces such as wood and masonry.
  • If you are in an area that gets a lot of dew in the mornings, be careful as this will affect the surface of the paint. Wait until later in the day when the temperature has warmed up and there is no impending sign of more moisture coming into the atmosphere.  Difficult in those unpredictable thunderstorm regions.

Exterior Painting if it is Raining – Points to Consider

  • Common sense will tell you that high humidity is a more important consideration when painting the exterior of the house than when painting the safer interior of the home.
  • If there is too much moisture in the air it will make the paint “blush” (it goes white) and it will leave moisture on the surface. So, if you continue painting under this high humidity or rainy conditions the water will get trapped in the coating. When the paint dries and you have a hot day the next day, the moisture expands in the finish and will cause blistering. This you do not want. Hence, painting on wet days can be a problem and should be avoided.
  • Remember if water lies on your pavement or path and is taking a long time to evaporate, it is best to leave your painting until it does. Rather concentrate on your interior painting project at this time.

Interior Painting if it is raining (again) – Points to Consider

  • Interior painting has no really limiting factors. Walls must be dry both to the touch and, as far as you can tell, from the surface.  Keep in mind that window sills, window frames, etc. will get moist if left open whilst it is raining outside – so leave those for a dry day.
  • The type of paint you are using makes a difference. If the paint is water-thinned it will not make any difference if it is raining or not as long as the temperature is warm enough.
  • It may be raining outside, but you will still need to check the most important factor: the temperature of the room. Paint if greater than 15°C; hold off if less than this.  Paint on another day.
  • To get turpentine or oil-based paints to dry faster, heat is required.  So again, wait for a better day if it is raining or about to rain – there is nothing worse than sleeping in a room where the cupboards have been painted with a turpentine based paint and they are taking a long time to dry.
  • Good ventilation is essential in the room you are painting – be careful of fumes. Ideally, paint when it is warmer and you are able to open up the room.

Summary

Avoid professional painter slogans like: “No weather is going to hold us back from painting your home – rain or shine, sleet nor snow.” The seasons, of course, can be stretched as far as possible particularly in our country, but there are certain times that it is just not possible or advisable to paint, particularly externally. The best time to paint is determined by temperature and humidity, and as long as you are safely within the right climactic boundaries, it can be considered the painting season. Cloudy or overcast conditions are ideal for painting, provided ….it is not raining and rain is not expected (again).

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