Exterior House Painting in High Humidity
Humidity soaks your clothes and makes your hair a disaster, but it can wreak havoc on the aesthetics of your exterior paint as well. In fact, humidity is one of the most common problems when applying exterior house paint.
Ever walk out of your door and wonder if you’ve taken a wrong turn and ended up in a swamp? The summer humidity in the South has a way of doing that.
The good news is that humidity doesn’t have to prevent you from painting the exterior of your home. It does require a few additional precautions but it can be done.
Here’s what you need to know about exterior painting in high humidity. Take a look!
Why Humidity Can Cause Problems with Painting
Some exterior house painters have tried to paint in high humidity while using the wrong products, ending with a sticky result. Wonder why? It’s simple science.
Most paints include water alongside a solvent. For the paint to cure and form a hard surface, the water needs to evaporate before the solvent does. With oil-based paints, the same is true: the oil needs to evaporate before the solvent does.
Without getting too technical, higher humidity makes water evaporate at a slower rate. That causes the solvent to evaporate before the water or oil, which means your paint will not fully cure.
How Humid Is Too Humid to Paint?
It’s true that you can use exterior paint at more humidity levels than most people think, but there’s still a limit.
The ideal humidity level for painting is between 40% and 50%. If you’re indoors, it’s easy to attain that level with a dehumidifier. When you’re outside, though, it’s not as easy. If necessary, you can paint in up to 80% to 85% humidity.
Does Humidity Affect Materials in Different Ways?
As we discuss more about painting in high humidity, keep in mind that we’re referring to materials other than uncoated wood. Uncoated wood is far more susceptible to moisture than coated materials are.
The humidity levels above and the tips below work well for coated materials. When it comes uncoated wood, it’s a better plan to wait until a drier time of the year like the fall. Humidity forecasts may help you identify windows that will give you the dryness you need.
Tips for Painting in High Humidity
While it’s possible to paint at higher humidity levels than you may have thought, there are tips you should follow to make it more successful. If not, you may find yourself with a curing problem and you may need to strip the paint and start over.
To keep problems to a minimum, follow these tips.
Paint While the Heat Is Rising
Timing is key when it comes to painting your home in humidity. In particular, you want to pay attention to heat patterns.
The best time to paint your house is a few hours before the day reaches its peak temperature. The peak temperature tends to hit in mid to late afternoon, but you can check the hourly forecast for your painting day to make sure.
If you start to paint too early in the morning, the home may still be holding moisture from the overnight dew. Aim to paint in late morning is the dew or humidity is high. This gives the dew time to dry but the heat will still be rising for several hours.
As the heat rises, it helps the paint dry at a fast pace.
Test the Surface Moisture Beforehand
While we’ve been talking about humidity in the air, moisture in the material you’re painting will affect the result as well. To be sure a surface is dry before you start, there are ways to test it.
If you’re painting uncoated wood, scuff-sand a small area. You want to be able to blow the dust away with ease. If you can’t, give it more time to dry.
For non-wood surfaces, press a rag to the area and see if there’s any moisture on it. Be sure to use a light color that shows moisture with ease.
Paint In the Order the Sun Warms
It sounds like a line from The Lion King but it’s true. To make sure your painting surfaces are as dry as possible, start in the area that the sun hits first in the morning.
In general, this means you’ll start on the east side of your house and work toward the west side. Keep in mind, though, that trees and other shade-creators could affect this.
Control Indoor Humidity
Most of what we’ve discussed has related to painting your home’s exterior. However, even interior painting may take some extra thought when it’s humid outside.
In some cases, your HVAC system might take enough humidity out of the air to create great painting conditions. Don’t take it for granted, though. Measure your home’s humidity and if necessary, buy, rent, or borrow a dehumidifier while you paint.
Don’t overlook humidity that isn’t related to the weather, either. Need to paint a bathroom? Avoid using the shower or tub too soon before or after you paint.
This may seem obvious, but if it’s possible to bring any of the painting surfaces inside, do so. For example, if you’re painting a door, it’s better to remove it and set up a painting area inside instead.
Use Thin Coats
This is an important trick to use when you’re painting in high humidity whether you’re indoors or outdoors. Instead of one or two moderate to thick coats, opt for several thin coats. Thin coats of paint will dry at a faster pace, which means they’re more likely to cure without issue.
Getting a Great Paint Job in (Almost) Any Humidity
Conventional sources may say not to paint unless you’re in that ideal humidity range of 40%-50%. For those of us in Raleigh, though, we’d never have the time to get it all done.
In truth, you can paint in humid weather. You just need to know the limits and follow some extra precautions.
For more guidance about painting in high humidity and other painting details, reach out to our painting experts.