Painting the exterior or interior of a home is one of the most popular DIY projects for homeowners. A fresh coat of paint can transform the look and feel of a room or give your home’s exterior a major face lift. However, many homeowners find themselves asking – can you paint a house when it’s humid outside?
High humidity creates challenges for painting projects. Moisture in the air can negatively impact paint in several ways if proper precautions are not taken. As painting experts, we have painted numerous homes in high humidity areas. With the right preparation and painting products, you can absolutely paint a house during times of elevated humidity.
In this comprehensive guide, we’ll explain everything you need to know about painting in humidity. You’ll learn:
- How humidity impacts paint and painting results
- Ideal humidity range for exterior and interior painting
- Best practices for preparing surfaces for painting in humidity
- Tips for choosing the right paints and primers
- Application techniques to use when painting in humid conditions
- Precautions to take for proper paint drying and curing
- Pro secrets for minimizing problems with painting in high humidity
Properly understanding the effects of humidity and following these best practices will allow you to paint like a pro and end up with beautiful, long-lasting results – even when Mother Nature doesn’t cooperate!
How Does Humidity Affect Painting?
Before jumping into solutions for painting in humid conditions, it’s important to understand the ways that humidity can negatively impact a paint job.
Slow Drying and Curing
One of the biggest issues high humidity causes is slower paint drying times. Drying happens when the solvents in the paint (like water or mineral spirits) evaporate, leaving the paint adhered to the surface.
Curing occurs when the resins fully harden and bond together after the paint has dried. Curing makes the paint more durable.
When the air is humid, evaporation slows down dramatically. With exterior latex paints, drying time can be 2 times longer than painting in normal conditions. Oil-based paints can take up to 4 times longer to dry compared to painting in lower humidity!
Without proper surface preparation and painting techniques, slow drying leads to a variety of problems:
- Runs and sags – With excessive humidity, it takes longer for the paint to form a skin. This allows wet paint to sag and drip, ruining the smooth finish.
- Brush marks – In humid conditions, paint stays wet on the surface longer, which can lead to visible brush strokes in the finish.
- Contamination – Wet paint can pick up dust, bugs, and other contaminants that embed in the surface as it dries.
- Poor adhesion – If the surface underneath hasn’t dried fully before adding more coats, the paint layers may not bond properly leading to chipping/peeling.
Slow curing also causes issues by preventing the paint from reaching its designed hardness and durability.
Blistering and Peeling
Another common problem is blisters forming on exterior paint jobs several weeks or months after painting in humidity. This happens when moisture becomes trapped under the paint layers and creates bubbles as it tries to escape.
If the problem continues, the blisters can rupture and cause the paint to peel away from the surface.
Mold and Mildew
Excess moisture also provides ideal conditions for mold, mildew, and algae to grow if it gets underneath the paint. This not only looks unsightly but can deteriorate the paint and wood on exterior surfaces.
Improper Wood Stain Penetration
For wood surfaces like decks, railings, and siding, staining in high humidity can prevent stains from properly penetrating into the wood. This reduces protection and leads to premature fading/wear.
Ideal Humidity Range for Painting Projects
Now that you know why high humidity causes painting challenges, what is the ideal humidity range for painting the interior or exterior of your home?
Exterior Painting
For exterior surfaces like siding, trim, doors, shutters, fences, and more, the optimal humidity range is:
- 30-50% – This is ideal for proper paint drying and adhesion. 50-60% humidity is workable with proper preparation.
- 65-70% – Use caution when humidity is in this range. Slow drying issues are more likely. Take extra steps to prepare surfaces.
- 75%+ – Avoid painting in humidity above 75% if possible. Drying will be severely delayed with a much higher risk of problems.
Interior Painting
For interior rooms, the ideal humidity levels are:
- 30-50% – This is the perfect range for interior paint to dry properly without issues.
- Over 50% – Drying and curing will be slowed, increasing risk of problems like poor adhesion. Take extra precautions.
- Below 30% – Extremely dry air can cause flashing and uneven sheen. Lightly dampen surfaces before painting.
When humidity inside is too high, utilize dehumidifiers, fans, and air conditioning to lower it before painting.
Being aware of the humidity forecast and planning your paint project for dry days can help avoid issues. Now let’s look at solutions for prepping and painting for when high humidity can’t be avoided.
Preparing Surfaces for Painting in Humidity
No matter how quality the paint, improper surface prep will lead to lackluster results when painting in humid conditions. Follow these best practices:
Allow Proper Dry Time for New Construction
For new exterior surfaces like fresh wood siding or stucco, allow 1-2 weeks of dry time before priming and painting. Follow the manufacturer’s recommendations. Rushing the paint job risks trapping moisture under the new paint.
Check Moisture Content
Use a moisture meter to check surfaces are below 15% moisture content before painting. For interior walls, a reading over 12% requires additional drying time.
Extend Curing Time on Previously Painted Surfaces
If repainting an existing surface, allow extra time for existing paint layers to fully cure before recoating. Wait at least 48 hours between coats.
Fill Cracks and Holes
Seal any gaps, cracks, or holes with exterior caulk or filler designed for high humidity areas. This keeps moisture from penetrating under the paint.
Remove Mold and Mildew
Clean off any existing mildew, mold or algae from exterior surfaces with bleach or special cleaning solutions. Rinse thoroughly before priming.
Sand Glossy Surfaces
For slick or glossy surfaces, sand to dull the sheen and create a texture for paint to adhere properly.
Prime Bare Wood
On unfinished wood, apply an oil or shellac-based primer before painting, even if using latex paint. The primer seals the wood from moisture.
Choose Primer Carefully
Select mold/mildew resistant primers for high humidity areas. Oil-based primers form a better moisture barrier but require safe use practices.
Proper prep gives the paint the best chance of adhering well through all the humidity. Now let’s look at choosing the right paint and application methods.
Selecting Paints and Primers for Humidity
Choosing paints or primers formulated to withstand humid conditions is key to avoiding issues. Consider these tips:
Use Exterior Paints for Interior Projects
For interior walls and ceilings, use paint labelled for exterior use. The resins flex and breath better than standard interior paints to prevent blistering.
Choose Mold/Mildew Resistant Paint
Look for exterior paints featuring mold and mildew resistance to avoid discoloration and deterioration in humidity.
Use Enamels for Trim and Doors
For interior trim, cabinets, and doors, oil-based or enamel paints are more durable and block moisture better than standard latex paint.
Consider Urethane or Epoxy for Specialty Surfaces
Using urethane, epoxy or lacquer paints on surfaces like kitchen cabinets and metal doors provide the best protection and durability.
Apply Primer Before Hangling Siding
For new wood siding, prime all sides before hanging to protect from moisture exposure as it acclimates to the humidity.
Oil-Based Primer Helps Block Moisture
An oil-based primer or first coatprovides extra moisture blocking on siding, trim, and other exterior surfaces.
Add Paint Additives
Paint extenders or anti-sag additives help exterior latex paints apply more smoothly to prevent drips, runs, and brush marks.
Choosing the right paints and primers boost performance. Next we’ll review application tips for achieving a flawless finish when humidity is high.
Painting Techniques for Humid Conditions
Careful application techniques are also key to overcoming the challenges of high humidity:
Avoid Painting in Direct Sunlight
The sun’s heat speeds drying, which causes brush marks and affects smoothness. Paint in shade or when overcast.
Use Light Coats
Applying thin, even coats allows paint to dry properly between layers. Heavier coats stay wet too long.
Allow Proper Dry Time Between Coats
In humidity, latex paint may take up to 24 hours to dry between coats. Check directions and test thoroughly before recoating.
Backbrush When Rolling
For siding and trim, backbrush after rolling each section to work paint into the surface and prevent drips.
Paint Early in the Day
Start painting first thing in the morning or early afternoon when sun, heat, and humidity levels are lower.
Watch Out for Rain
Avoid painting if rain is expected within 2-3 days. Humidity levels spike before and after storms.
Brush from Unpainted to Painted Sections
On trim or walls, brush from unpainted areas into sections with fresh paint to prevent lap marks as paint dries at different rates.
Cool Paints Before Application
In very high heat and humidity, cool paint cans in the shade or in air conditioning for an hour before painting to help slow drying.
Proper technique makes all the difference in combatting humidity. Keeping paint workable and wet edges blended prevents ugly lap marks, brush strokes, and drips.
Maintaining Proper Drying and Curing Conditions
Painting is only half the battle when humidity is high. Maintaining ideal drying and curing conditions after paint is applied ensures a lasting finish:
Allow a Full 2-4 Week Cure Time
Even when paint feels dry to the touch, allow at least 2 weeks, up to 4 weeks cure time before washing or exposure to rain for exterior paint.
Run Dehumidifiers if Needed
For interior painting, use dehumidifiers to keep humidity at or below 50%, especially for the first 48-72 hours as paint dries.
Create Airflow
Position fans to blow air over painted surfaces to accelerate drying when possible. This is critical for interior painting.
Control Temperature Fluctuations
Avoid wide temperature swings that cause condensation. Keep indoor temps 68-77° F for the first couple days after painting.
Delay Projects if Rain is Expected
On exterior paint jobs, pay close attention to weather forecasts. Delay projects if steady rain is expected soon after application.
Check Problem Areas
Inspect surfaces closely 2-3 weeks after application when painting in humidity. Look for blistering or bubbling, especially in areas that don’t receive direct sun.
Proper curing and drying produces a coat of paint locked in for the long haul. Your due diligence leads to long-lasting curb appeal and protection.
Professional Painter Secrets for Painting in Humidity
As experienced professional painters, we’ve picked up some invaluable tips and tricks for getting perfect paint results despite humidity:
Paint Small Sections
On siding or trim, paint just a few boards or sections at a time before going back to blend wet edges and prevent lap marks.
Use Latex Paint Additives
We keep paint additives like Floetrol on hand to mix into exterior latex paint when humidity is over 60%. It prevents brush marks and runs.
Only Apply Primer When Dry
We never start priming surfaces until moisture readings are ideal. Rushing causes poor adhesion and blistering down the road.
Pay Attention to Overhangs and Eaves
Overhangs and eaves retain more moisture and take longer to dry. We watch these areas closely when painting in humidity.
Spray Paint Problem Areas
For surfaces that retain moisture no matter the prep, we spray apply primer and paint. This prevents dripping and sagging.
Use Oil-Based Primer on New Wood
For fresh wood siding, an oil-based primer helps force moisture out from the wood while blocking absorption into the top coats.
Monitor Conditions Continuously
We check humidity, dew point, temperatures, and weather forecasts continuously when exterior painting to schedule coats accordingly.
Don’t be afraid to enlist a painting pro to help tackle a humid painting project! Their experience makes all the difference.
FAQs About Painting in Humidity
Many homeowners have additional questions about the best practices for painting their home exteriors and interiors when humidity is high. Here are answers to some of the most frequently asked questions.
Should I paint at night instead of the day?
Painting at night is actually not ideal. Although humidity is often higher after dark, temperatures are lower which causes condensation. This condensation gets trapped under the paint. It’s best to paint early or late when air temps are still warm.
Is morning or afternoon better for painting in humidity?
If possible, start painting in the morning when the surface is dry and temperatures are cooler. As the day warms up and humidity increases, stop painting by early afternoon maximum to prevent drips and runs.
How long does exterior paint need to dry before rain?
Most exterior latex paints fully dry and cure within 2-3 days without rain or dew. Oils take longer – up to 7 days. Check the manufacturer’s recommendations. Be sure to apply early if steady rain is expected.
Should I use a sprayer or brush and roller in humidity?
For exterior painting, backrolling after spraying is best to work paint into the surface. For interiors, brush and roller allow you to control paint thickness and blend properly.
How can I speed up paint drying time?
Using fans, dehumidifiers, and air conditioning helps. Oil-based primers also dry faster. But the most impactful step is proper surface prep so the paint adheres fast.
What is the maximum humidity to paint outdoors?
It’s best to avoid painting when humidity exceeds 75% as drying issues are almost guaranteed. Between 65-75%, take all the precautions possible. Ideally, keep humidity below 60%.
Should I use oil or latex paint?
On properly prepped surfaces, exterior latex formulats work very well and are easier to apply in humidity. Oils are more durable but come with safety considerations. For interiors, latex dries faster than oil-based paints.
Painting your home beauty shouldn’t be limited by humidity! While extra care must be taken, you can achieve stunning results. We hope these tips instill confidence to take on painting projects even when humidity can’t be avoided. Let us know if you have any other questions!
Conclusion
In summary, painting a house when it’s humid outside is definitely doable with the right preparation and techniques. The key steps include:
- Allowing proper dry time for new construction and recently painted surfaces
- Checking surface moisture levels and priming bare wood
- Choosing exterior grade paints and mold/mildew resistant primers
- Applying thinner coats, watching drying times, and starting early
- Maintaining proper drying and curing conditions after painting
- Enlisting a pro painter for stubborn humid conditions
While humidity can create challenges, careful prep work, moisture blocking primers, proper application methods, and suitable clean up conditions go a long way to ensuring you’ll end up with a beautiful and lasting paint job – rain or shine!
So don’t let high humidity keep you from giving your home’s exterior or interior spaces a fresh new look. With this comprehensive guide, you now have all the tips and solutions needed to paint like a pro despite the moisture in the air.