Exterior paint is long-lasting, comes in a range of shades, and is often much cheaper to buy than interior paint, so you won’t be the first to wonder if you can use exterior paint inside your house. I have a few cans of leftover exterior paint, and I’ve considered using them rather than buying new paint for indoors. What harm could it do, I thought – it turns out, there’s a reason it’s best used outdoors.
Exterior paint uses a different combination of pigments, additives, binders, and Volatile Organic Compounds to keep the paint flexible and prevent mildew and stains. These changes make exterior paint unsuitable for use indoors, and they can be potentially hazardous and have an inferior finish.
It turns out that a simple swap of paints is not that simple after all. Exterior paint is designed to be used in outdoor weather conditions, and these changes in the way it’s made mean that its use as interior paint is not recommended. We’ll go through why it’s best not to use exterior paint inside your house and places where you can use exterior paint well.
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Can You Use Acrylic Exterior Paint Inside?
Exterior paint is different from interior paint because of the different ways they need to function. Inside your house, you need durable and stain-resistant walls that can easily be wiped down and cleaned. You do not want paint that allows chemicals into your air, which may affect your health and breathing.
Exterior paint is usually an acrylic latex blend (much like most interior paints) but has added resin to make it more flexible. This added latex allows the paint to shrink and expand without cracking – a necessary detail when dealing with changing temperatures and weather conditions. But the added latex does have a drawback that makes it bad for use indoors.
The same properties that allow the paint to adapt to the climate without cracking also allow the Volatile Organic Compounds (or VOCs) to be released into the air. These compounds are chemicals that will affect how the air smells and, in some cases, trigger breathing issues.
So, if you want to avoid a house that smells like paint and chemicals and keep your air cleaner, you should avoid using outdoor paints on indoor surfaces. Avoiding exterior paint inside is vitally important if you suffer from breathing issues such as asthma, where air quality is crucial.
Can You Use Masonry Paint Inside?
Masonry paint is another name for exterior acrylic paint. Because masonry paint is designed specifically for outdoor use, it has properties that allow it to be durable and waterproof and to go on easily to almost any surface.
While these benefits seem like they would be great for use indoors – especially in rooms like kitchens and bathrooms with more moisture – they are not suitable.
The fungicides and chemicals used in masonry paint to help protect it from UV damage are not ones you want to be breathing in. When used outdoors, these chemicals are released into the atmosphere, which will dissipate. However, when used indoors, the chemicals will be trapped in the air inside, are potentially hazardous, and may cause illness, bad smells, or breathing issues.
Can You Use Exterior Paint in Your Bathroom?
What if you want the benefits of exterior paint, like being waterproof or preventing mildew, but for use inside?
Look for the following indoor paint solutions:
- Paints designed for bathrooms and kitchens, which have an eggshell finish and are more water-resistant when dry
- Additives designed to be added to interior paints, such as mildewcides like this: https://www.amazon.com/Advance-Mildewcide-1-38-MfrPartNo-78902S/dp/B009YO2AG0
With these specialized interior paints, you can get the benefits of masonry paint without the worries of excess VOCs released into your house.
Can You Use Enamel Exterior Paints Inside?
Some exterior paints are made with an oil base rather than a water base. Water-based acrylic paints are generally easier to clean up, as tools and brushes can be washed in water. However, oil-based enamel paints need to be used with turpentine as a brush-cleaner and to wipe any drips or spills.
Enamel paints have toxic fumes, and in many states, they are banned for use both indoors and outdoors. With such a potential hazard, even if you live in an area where oil-based paints are not illegal, I would recommend you never use them to paint inside.
As enamel paints release a lot of toxic VOCs into the air, they are awful for the ozone layer. If possible, avoid using them at all, even for exterior applications.
Can You use Exterior Paints Inside a Garage?
Even though you may not be in your garage as often as you are inside your house, it is still inadvisable to use exterior paints in your garage. You would avoid using exterior paints in any indoor area for the same reasons – the release of excess VOcs and the tendency to be easily scuffed.
Instead, use interior latex (water-based) paint to paint the interior of your garage. Use latex paint to paint walls and ceilings, as it is less harmful to you and the environment. Because it is water-based, it easier to clean up and thin down with additional water if necessary.
Use Interior Washable Paints Inside
Surprisingly, although exterior paints are made to be tough and to withstand the harshness of outdoor conditions, they are not great for keeping clean from scuffs and other marks.
If you’re concerned about high-use areas that need washable paints, look at the modern range of new washable interior paints. These days, they come not only in high-gloss paints but also in matt ones, opening up even more decorating opportunities.
Many favorite brands of paints have a vast range of interior paints designed for high-traffic areas to withstand cleaning and scrubbing away grubby fingerprints, pawprints, and other marks.
Conclusion
Avoid using acrylic exterior paints inside, as their chemical makeup makes the paint more flexible. This change increases the excess gas and chemicals they release into the air and makes them unsuitable for interiors.
Despite their durability against temperature changes and weather, exterior paints tend to mark easily, so it’s better to use interior paints designed to be washable. Avoid using enamel/oi-based paints for interiors and exteriors, as they are particularly harmful to the environment.