Is Using Exterior Paint Inside Okay?

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Have you ever wondered whether using exterior paint inside could be okay? Or did you finish the exterior painting and plan to use the paint in your bathrooms too? Although it might sound like a cost-effective solution, it’s not always advisable. Paint designed for exterior surfaces should not be used inside the house. They contain a higher concentration of harmful chemicals called volatile organic compounds (VOCs) and other binders and pigments than regular paint. 

And regardless of it drying quickly after application, exterior paint could emit toxic fumes, which is dangerous for your lungs. Besides, the paints can make people and animals sick, and the finish is often less appealing. This post will examine what exterior paint is and whether it’s safe to apply on indoor surfaces. We will also discuss mixing interior and outdoor paints and how you can safely do that. When you finish reading, you’ll better understand what paint is ideal for painting the outside of your house and whether it’s wise to apply it inside your house.

What is Exterior Paint?

Exterior paint is designed to resist blistering sun, torrential downpours, sandblast winds, and freezing cold. When applied on buildings, structures, or other exterior surfaces, it relies on its strength to last for a long time. It must resist weather and not allow mildew and mold to grow.

Better-made paints contain highly flexible resin binders which contract and expand with the surfaces they cover. It includes a blend of additives to help level the surface, protect it from damage, and fight dirt and moss from becoming a part of the finish. Most paints for the exterior are treated against UV light to help the colors of the pigments stay vibrant. Exterior paint contains more chemicals and is usually softer than you would find inside your house.

There is a good selection of oil-based and water-soluble paints for outdoor application. The oil and water-based paints are diluted with a solvent that causes the pigment to evaporate. The binders that hold the pigments and other additives in place hold the paint onto the surface. Such paints are usually offered with various colors and finishes and can be used with a roller, brush, sponge, or sprayer. Paints applied using water evaporate more quickly than oils, so they dry more quickly. Expect an increase in price for a high-quality paint that will last 10-15 years if applied as recommended.

Here are the key ingredients that make up exterior paints:

Pigments

Pigments can be organic or inorganically derived and give paints their color. White paint is composed of inorganically formed elements, like titanium dioxide. Organic pigments are derived from animals or plants, while inorganically produced pigments are derived from minerals. 

Organic pigment produces a better color than inorganic pigments, and inorganic pigments are more durable. The more pigment particles are used, the deeper and more opaque the color. The color pigments in exterior paints are specially crafted to resist fading when the sun, UV, or weather exposure.

Bases

Painting exterior walls with oil-based paints were common, but modern formulations allow water-soluble paints to be as good as oil-based paints. Tung oil, soybean oil, linseed oil, or other polymers are the components of the oil base; water serves as the base for water-soluble latex paints. Oil-based paint products give off more volatile organic compounds (VOCs) than water- or latex-based paints, but the two paints still contain stronger chemicals. Both types of base material are also offered in satin, gloss, semi-gloss, and enamel finishes.

Binders

Binders hold pigments and other additives to be applied to various surfaces. They are also able to withstand harsher conditions on the outside than the interior walls of houses.

Additives

Pigments, binders, and additives are spread and carried by mineral spirits in water-borne paints or oil paint. When you pour the water or spirits onto a surface, the paint is completely dissolved, and a dry paint film remains. Additives help paint thicken, level, fill holes, stick to surfaces, be waterproof, resist ultraviolet light, and resist mildew and mold. 

It can contain various fine particles, and it’s also possible to add colors to enhance its appearance. Some paints are also coated with artificial scents, which help to disguise paint chemicals in the air. Paint used on exterior walls has different additives than interior paint, which gives it the ability to withstand harsh environments.

Can You Apply Exterior Paint Inside?

You could have old spray paint leftover from painting your exterior structures and assume that because exterior paint holds up well against the elements, it would be good paint for the inside of your home. Even though your reasoning is sound, you must remember that exterior and interior paints are designed for different conditions.

Even though both kinds of paint have the same ingredients, like mildewcides and fungicides, they aren’t the same. Exterior paint contains a thicker formulation of tougher additives and binders to enable it to reshape and weather better than interior paint. Some exterior paints contain chemicals that can cause harm in enclosed areas, but these chemicals are less harmful outdoors. 

Moreover, exterior paint contains more volatile organic compounds (VOCs) and is more odorous than interior paints. The very nature of the material used in exterior paint causes it to cost more than quality interior paints.

Interior paint
Interior paint

In most cases, it is best to work in well-ventilated areas if you are applying exterior paint. Exterior paints release volatile organic compounds (VOCs) until completely cured; this can take up to two years when temperatures drop below freezing. 

Using exterior paint in temporary buildings like sheds, cabanas, or garages is okay as long as there is excellent ventilation and you are not planning to use them as a place to sleep. You may use exterior paint inside a house but not in a living area. Paints for indoor use are intended for walls and ceilings and are applied similarly to drywall. Interior paints dry faster than exterior paints and are more durable than other types of paint.

Furthermore, they can protect against scratches, scuffs, and abrasive cleaning agents. On the other hand, exterior paint is designed to be applied to all exterior surfaces, including wood, stone, metal, glass, and composite materials. Furthermore, exterior paint typically has a unique feel or texture that’s not pleasing when used inside.

Is it Dangerous to Use Exterior Paint Inside?

Painting interior walls with exterior wall paint is not advised for several reasons, including cost and appearance. It is also unhealthy for the painter. Working on interior walls puts you at risk of breathing harmful chemicals. Exterior paint contains volatile organic compounds (VOCs) and toxic chemicals that can cause problems such as asthma, allergies, and other respiratory problems.

Exterior paint is typically more flexible and softer than interior paint. It takes longer to cure exterior paints than interior paints, and the smells they produce often last well after the surface has dried. As long as the smells are outside your home, you shouldn’t have any problems with them once applied. But if you use them in an enclosed space, it could be very dangerous. 

It is harder to get mildewcide and fungicides in paints used on the exterior of houses than in paints used on the inside. Fungicides and Mildewcides in interior paints are different. Moreover, pigments and binders are produced with different ingredients that give the paint better resistance to weathering. Some painters use respirators to prevent breathing toxic fumes when spraying paint onto exterior walls or ceilings. Being dizzy or becoming light-headed while standing on a ladder to apply paint is a recipe for tragedy.

Applying paint to inside walls and ceilings with outdoor paint can cause harmful gases and fumes to escape into the air. VOCs help hold the pigment in paint, so it stays on the surface when applied. It is even more dangerous to use a sprayer to apply paint on surfaces rather than with a brush or roller because the fumes are rapidly emitted into the air.

Additionally, VOCs in paint and odors that come from painting outside houses are harmful to pets and humans. They may cause nausea, headaches, irritated eyes and throat, problems with how we breathe and feel, and problems for those with weakened immune systems. Long-term exposure can cause more severe illnesses and cancer. Fumes circulate in a house because of the heating and cooling systems often used in homes. Using exterior paint in ventilated home areas, such as outside the house, is much safer.

Moreover, it can take longer for the paint to completely cure in an indoor space. For example, if you painted the exterior walls of your garage five years ago, you may still smell the paint from time to time. Despite enough ventilation in the room, some days, fumes will hit you when you open the garage door.

FAQs

Can I Use Exterior Water-Base Paint in My House?

You could, but it is not usually the best choice. Most exterior paints are water-based, reacting with water even when wet. But many have a waterproof resin that makes them more resistant to weather. 

Can I Paint My Furniture with Exterior Paint?

Water-based or oil-based paint is best for outdoor furniture. Exterior paint usually lasts longer than most other types of paint, and it doesn’t need to be repainted.

What would you do if you accidentally applied exterior paint inside?

Did you mistakenly use exterior paint inside your house? Well, this may look a little silly, but it might or might not be dangerous, depending on the exact type of paint. You will need to remove it using some thinner or mineral spirits. Elbow grease and rubbing alcohol should remove the paint if it is water-based.

Final Thoughts

You could use exterior paint on the inside of your home, but it will take several weeks or even months for the paint to cure fully. It may still emit fumes even after your surfaces appear to be dry, which may cause people to feel irritated. Moreover, this paint is very soft and flexible hence not suitable for interior walls. If you use exterior paint on interior walls, ensure good ventilation and that the space is not a place where people or pets can sleep. Furthermore, exterior paint is a little more costly than interior paint.

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