Just because you can use exterior paint inside doesn’t mean you should
Interior paints and exterior paints are formulated differently.
Exterior paints have VOCs that pose health risks.
Outdoor paints perform differently indoors.
If you’re wondering whether you can use exterior paint inside, you’re probably not alone. No doubt, there are plenty of folks out there who think if interior paint is good for their walls, then exterior paint must be better. And while this may be a reasonable assumption, it’s not necessarily a good one.
So, before you decide between flat, satin, and semi-gloss paint, you’ll have to figure out what type of paint is best for indoor surfaces. Interior and exterior paints are formulated differently and therefore perform differently. In order to paint your room like a pro, it’s important to understand the basic differences between the two types of paint and why you may want to steer clear of using outdoor paint inside.
The color application of exterior and interior paints is the same as the color application of interior paint, so yes, technically, you can use outdoor paint inside. But just because you can, that doesn't mean you should.
Because they’re intended to sit out in the elements, exterior paints often have more pigment added to them. And while these pigments yield a paint with excellent color saturation and durability, they also tend to have more volatile organic compounds or VOCs, which are extremely hazardous to your health.
VOCs are a group of chemicals that are often found in the products we use in the building and maintenance of our homes, including paints, paint strippers, cleaning supplies, pesticides, and assorted building materials.
Some of the more common VOCs are:
Benzene
Ethylene glycol
Formaldehyde
Methylene chloride
Tetrachloroethylene
Toluene
Xylene
1,3-butadiene
As exterior paint dries and cures, it off-gasses or releases VOCs into the air. And while the smell will be quite strong, that would be the least of your worries. The problem here is that VOCs are extremely hazardous to your health.
According to the United States Environmental Protection Agency (EPA), exposure to VOCs can lead to:
Irritation of mucous membranes (eyes, nose, and throat)
Headaches
Nausea
Loss of coordination
Damage to the kidneys, central nervous system, and liver
To make matters worse, if you’re using an exterior acrylic latex paint, it will continue to emit VOCs even after it dries. Interestingly, VOCs are so harmful that oil-based paints (known to emit a host of VOCs) have essentially been banned in certain states with high ozone levels.
If exterior paints are used as intended (outdoors), they’ll emit their VOCs into the air, no harm, no foul. If you use exterior paints indoors, however, you can see where there’s a problem.
In contrast, manufacturers often use organic pigments for interior paints that contain little to no VOCs, making them safe for indoor use.
Exterior paint requires sunlight to cure, so if you use it indoors, it will probably feel like, well, waiting for paint to dry. And the more time your paint takes to cure, the more chances there are for it to get scuffed and smudged and require touch-ups.
Remember, too, that exterior paints are designed to withstand the elements, not the vacuum, kids, or pets. So scratches will stick out like a sore thumb, and stains will be harder to clean if you can clean them at all without disturbing the finish.
Over time, exterior paint will not wear the way interior paint is designed to do, and you’ll likely find yourself with the same DIY project in a year or two.
Most interior paints are acrylic latex. These pains are water-soluble, and they’re made to be washable. Exterior paints, on the other hand, are usually waterproof, which makes them far more difficult to clean up in the case of a spill or splatter.
While indoor and outdoor paints appear similar on the surface, they're engineered differently and yield different end results. The main difference between interior and exterior paints is the binding resins, pigments, and additives contained within each.
Exterior paints are formulated without rigid binding resins so that they’re able to expand and contract along with outdoor temperature fluctuations. From scorching heat and punishing sunlight to frigid temperatures and the moisture that comes with rain, snow, and sleet, exterior paints are designed to withstand it all (within reason, of course).
These paints tend to be highly water-resistant. They often contain additives that block ultraviolet light (to help them resist fading), and some are even formulated with additives to prevent mold and mildew. And while these additives may yield rich exterior paint colors that protect your siding and other exterior services, they can be quite harmful, but more on that later.
While outdoor paint is formulated to withstand everything Mother Nature can throw at it, indoor paint is formulated to withstand whatever you and your family can throw at it. Courtesy of rigid resins, interior paints can beautifully withstand the bumps, scratches, and scuffs that come with daily life, and they’re easy to clean.
Paints intended for indoor use also contain additives that reduce drying time and distribute the pigment evenly. And they’re specifically formulated to resist staining, fading, and yellowing.
You shouldn’t use interior paint outdoors, because it is not durable enough to withstand the elements. Thanks to weather-resistant chemicals, exterior paints are created to handle extreme cold, heat, snow, rain, and UV rays, so they stand up against the test of time. If used outside, interior paint will crack and peel, and certainly won't hold up as well as paint meant for exterior surfaces.
People either love painting or they hate it; there are no in-betweens. If you’re not on team DIY for this one, you can always hire painters in your area to do it for you.
Sara Coleman contributed to this article.
Manufacturers use a different process and formula for exterior paint versus interior. The exterior formula has to withstand elements like temperature, UV lighting, moisture, wind, and debris. Interior paint doesn’t need to be as tough, only exposed to dust, scratches, dents, scuff marks, and the like.
Exterior paints contain more volatile organic compounds, or VOCs, making them dangerous when used indoors. Without the free ventilation of the great outdoors, it can take longer for the fumes to dissipate than interior paint. While you may notice the smell lessening more quickly, you should be wary of paint fumes inside for 48 to 72 hours after it dries.
Exterior paint contains a higher level of VOCs, which can be dangerous if you’re exposed to it for a long period of time. The good news is that paint’s toxicity reduces significantly once fully dried and cured. Do not keep open exterior paint cans in your home, basement, or garage, exposing your household to harmful chemicals over time.
