A lot of house painting is done in the fall. It seems like the best time to paint a house or do any outside task. The weather is cool, making it more comfortable and easier to do the work, and the days are still long enough to work into the evening. This is a bad thing. I recommend not painting outside after October 1. Low temperatures have an adverse effect on most exterior paints as they dry and set.
My Money Where My Mouth Is
I started my successful house painting business in 1970. Since then, I will not schedule any outdoor painting jobs after October 1. Some customers didn’t like it and would hire other painters to do the job. As soon as a year or two, there would be paint failure - the flaking and peeling and cracking of paint.
The houses had to be repaired and painted again. Or they would just repair the failed paint and touch up with the same color used on the house, with uneven results due to differences in fading and weathering. After many years of this, my customers found out that I was prudent in my decision and they hired me back.
If you read the paint can labels, they tell you at what temperature you can apply the paint. Most recommendations are 50 or 55 degrees Fahrenheit. It seems like a safe temperature to apply paint. Many fall days, it may be in the 70s in the daytime. But the paint goes through not only a drying of the paint, but also a chemical reaction has to take place.
Often the paint may be applied toward the evening, and the time needed for the drying and the chemical reaction goes into darkness. There are some low overnight temperatures at night in the fall, often as low as 28 degrees Fahrenheit. The drying and chemical reaction needs warmer temperatures than that. Let me explain the chemical reaction that takes place after paint is applied.
Two things happen during this process. The vehicle (either latex or oil) evaporates as the paint dries. This can be slowed by low temperatures, but that’s not the real problem. The second thing that happens is a chemical reaction within the paint. This cannot occur in the lower temperatures.
There are many chemicals added to your paint. I am not going to mention all the names, because you wouldn’t recognize them. Let’s just say that paints have catalysts that speed up the formation of polymers from paint resin. Molecules are rearranged as the reaction progresses, the polymers ending as chains of single molecules. If the temperatures are very low, it will be difficult for this process to take place.
Other Factors for Fall Failures
There are some other reasons not to paint outside. Certain types of windows need putty (glazing compound.) Putty takes a very long time to dry, especially because a large amount of putty has to be used, making it thick.
Putty also needs warmer temperatures to dry and cure properly, otherwise it will crack and have to be removed and replaced. And if you paint over it before it’s cured, the moisture escaping from the putty has to pass through the layer of paint, and both will fail. For a good, tight paint job, you also need to use a lot of latex caulk. Caulk also needs warmer temperatures to dry and cure. Primers need some warmth to dry as well.
Good Fall Projects
There are things that can be painted in the fall. Chief of these is to spray paint metal lawn furniture and other objects you may want to spray-paint. If started in the morning, the furniture would have enough time to dry.
Fall is actually the best time to paint indoors. On a fall day, you can open the windows for ventilation and drying. The cooler temperatures of the fall are much better than a hot, muggy day in the summer. If you are painting in the fall, it’s best to be painting inside.