Exterior paint is not safe to use inside. While it’s usually a good idea to reuse leftover paint when possible, exterior paint differs significantly from interior paint, and you should not use it inside your house. Many paints contain additives that make the paint effective outside, but the same additives can harm your health when used in enclosed spaces.
Learn more about the risks of using exterior paint inside and what to do if you’ve accidentally used this paint for your indoor project.
What Is the Difference Between Interior and Exterior Paint?
Whether at the end of an artist’s brush or a painter’s roller, the composition of paint is the same. The four basic components are:
- Pigments: These give the paint its color.
- Resin: This is the binding agent that adheres paint to a surface and makes it solid when dry.
- Solvent: This is the carrier that keeps paint liquid until applied to the surface.
- Additives: These are extra ingredients to boost performance, such as anti-mildew agents.
Varying the formula adds properties ideal for specific applications. Exterior paint must be durable and weather-resistant to withstand the elements. It needs to adhere to different surface types and textures. Indoor paint doesn’t have to work as hard. Its purpose is decorative. While it should resist stains, it’s less hardy than external paint.
The most significant difference between interior and exterior paint composition is the resin. In outdoor paint, this binding agent is softer and more flexible. It resists UV rays and weathering. The resin in interior paint is inflexible to prevent scuffing. Additives also differ to make each paint type perform better in its environment.
What Is Interior Paint?
Interior paint beautifies and protects the inside of our homes. Its composition is safer for humans. Many paints emit low volatile organic compounds (VOCs). VOCs are gases released into the air by many household products and can cause harm when breathed in. Indoor paints have a lower VOC concentration, and most don’t contain fungicides.
Types of interior paint include:
- Latex: This water-soluble paint is fast-drying and easy to clean. Although less durable, it accommodates low-wear-and-tear areas.
- Acrylic: This paint is similar to latex and is also water-soluble. Acrylic’s higher polymer count makes it more durable (and expensive).
- Alkyd: This oil-based paint lasts longer than water-soluble paints but is slower to dry. Alkyd paint works well for higher-traffic surfaces like doors and floors.
Indoor paints come in various vibrant colors and finishes, from matte to gloss.
What Is Exterior Paint?
Exterior paint withstands the elements while enhancing the outside of your home. It faces UV rays, wind, rain and extreme temperatures. Its breathable formulation prevents water from getting trapped and causing mildew. Flexible resin allows the molecules to expand and contract according to the temperature. This elasticity also helps resist peeling, chipping and discoloration.
Types of exterior paint include:
- Acrylic: The composition of acrylic outdoor paint differs from indoor. Added chemicals make it more elastic and able to react to temperature changes.
- Latex: This is a cheaper alternative to acrylic that is quick drying. Like acrylic, it expands and contracts according to temperature.
- Oil-based: This option is less common than acrylic and latex paint due to higher fume emissions. Oil-based external paint suits well-ventilated outdoor areas. It shrinks less than water-soluble paints.
Weather-resistant outdoor paint contains more VOCs than interior paint. Its design lets it adhere to rougher surfaces like wood, brick, metal or stucco. External paint offers fewer color and finish choices than indoor paint.
Why You Should Not Use Exterior Paint Inside
You should never use exterior paint inside your home — the repercussions can be extremely serious. Always read the labels carefully when choosing paint. Select only products designed for your specific uses. Explore key reasons to avoid exterior paint indoors below.
Health Risks
Both interior and exterior paints include volatile organic compounds (VOCs), chemicals released as gases from the paint as it cures and dries. Exterior paints have significantly higher amounts of VOCs than interior paints since they are weather and fade-resistant. Some exterior paints continue to release VOCs for years after drying.
Manufacturers create paint to cure and settle outdoors. Using exterior paint in confined areas inside your home can lead to high concentrations of VOCs that cause various health issues when inhaled. Some VOCs are classified as carcinogens and can contribute to long-term health risks when individuals have prolonged exposure. Some health risks include:
- Irritation to the eyes, nose and throat
- Headaches
- Nausea
- Dizziness
- Damage to the central nervous system and other organs
Some exterior paints may include additional chemicals to improve their durability and resilience to weather, UV rays, temperature fluctuations and mildew. These additives can be dangerous to inhale, making many exterior paints unsafe to use indoors.
Performance
Most exterior paints stick to siding, stone, brick and other exterior materials. Interior paint, on the other hand, binds to drywall and other indoor surfaces. When you try to apply exterior paint to drywall, it may not adhere properly. You may see more deterioration, cracking and chipping than you would with interior options.
Many exterior paints require UV light to cure properly and outdoor airflow to dry effectively. If you use exterior paint inside, you could have extra long drying times, affecting the final appearance. Paint can become scuffed or smudged while drying, resulting in an uneven look and an undesirable texture on your interior walls.
If you have leftover interior and exterior paints, you may consider mixing them to use up the supplies. You should not mix exterior paint with interior paint, though. They have different formulas — mixing these different types of paint can affect performance and appearance, leading to faster fading, cracking and deterioration.
Wear and Tear
While most exterior paints are durable and resilient for outdoor use, they are unsuitable for indoor wear and tear. Interior environments deal with oils, staining, indoor humidity, scratches and other types of abrasive damage. Interior paint is suitable for this type of wear, but exterior paint is not. It is more likely to get scratched or damaged when used inside.
Interior paints are also washable, especially the types used for kitchens and bathrooms. Most exterior paints are often waterproof and designed to withstand the weather, making them more difficult to clean with indoor products.
Costs
Paint manufacturers use a different process and formula to create exterior paint for interior paint. Many exterior paints have high-quality ingredients that enhance their durability and heavy-duty performance. These ingredients can make exterior paints more expensive than interior options. Using exterior paints for the inside of your home can lead to high and unnecessary costs.
What to Do If You Used Exterior Paint Inside
If you’ve accidentally used exterior paint inside of your home, don’t worry. You can mitigate the health risks of the paint by following these few steps:
- Ventilate the room: You need to ventilate the room as much as possible by opening windows and using fans. This will preserve indoor air quality and push VOCs outside. Prevent odors and fumes from entering the rest of the home by blocking the door and closing air vents.
- Wear protective gear: As you ventilate the room and prepare to paint over the exterior paint, protect yourself against skin irritation and damage from VOCs by wearing the right gear. Gloves and a mask or respirator can minimize how much of the paint you interact with and the fumes you inhale.
- Apply interior primer: Once the exterior paint is fully dry, apply a high-quality indoor primer. This primer will seal the exterior paint and prevent odors and chemicals from spreading throughout the home.
- Repaint the walls: After priming the walls, you can cover them with high-quality interior paint. A new coat of interior paint can improve appearances while mitigating risks from harmful chemicals.
Following this process to seal and cover the exterior paint is critical to protecting your health. If you feel any discomfort or worry about doing this process yourself, you may want to work with a professional, such as The Ohio Painting Company. Professional assistance can also be beneficial when you have respiratory complications or illnesses that prevent you from completing the process yourself.
To support your household’s health, do not spend extended periods near freshly painted spaces. Take breaks by stepping outside to get fresh air. Plan your painting schedule around your family’s routines — choose times when the house is less busy to minimize exposure. Keep children and pets away from the painting area until everything is completely dry.
A painting professional has experience working with interior and exterior paints. They will know how to work with each type safely. As experienced experts, they can effectively prime and repaint your walls to ensure your home is safe and healthy. A trusted painting team can properly ventilate the room to protect the rest of your home from the exterior paint’s odors and fumes.
Best Applications for Interior and Exterior Paint
Choosing the right paint for the job is crucial. Interior paint contains less harmful chemicals and is more resistant to smudges. Exterior paint’s durability and weather-resistant additives make it suitable for outdoor surfaces. It’s important to understand the differences and avoid using exterior paint inside.
When to Use Interior Paint
Use interior paint on walls, doors, window frames and ceilings inside your home. The vibrant color options are ideal for giving the interior a fresh look. With a wider choice of finishes, you can find one that best suits the aesthetic and use.
When choosing the type of paint for your interior project, consider the use and traffic in the area. Latex paints are ideal for areas less prone to wear, like walls and ceilings. Acrylic is more durable, so it suits cabinets and doors. Oil-based paints are less common but complement higher-wear surfaces like floors.
A paint’s finish influences where you should use it. It affects a surface’s look and ease of maintenance. Examples of interior finishes include:
- Flat or matte: These finishes do not reflect light, making them ideal for hiding flaws. They’re challenging to clean, so they are better suited to ceilings and minimal-traffic areas.
- Eggshell: This is a popular choice with professionals and DIY painters. Its low-sheen, durable finish works well for most areas of the home.
- Semi-gloss: The most resistant to wear and tear, semi-gloss has a high-shine look. This option is ideal for doors, windows and trims.
While using indoor paint outside isn’t harmful, it isn’t recommended. This paint lacks the additives and pliable resin structure of outdoor paint and would likely crack when faced with harsh outdoor conditions.
Tackling your interior painting is a rewarding but complex project. Before grabbing your roller, it helps to read up on how to paint the inside of your home.
When to Use Exterior Paint
You can use exterior paint for any outdoor painting project. Examples include the exterior of your home, windows, doors, balconies and sheds. It withstands harsh weather conditions and improves the outward appearance of your home. Maintaining a well-kept exterior adds to your home’s value and curb appeal.
Water-based latex and acrylic paints work best for exterior projects. Their composition makes them flexible and breathable. They are also less likely to crack than oil-based paints and adhere well to most surfaces. Oil-based paint’s durability and simple cleaning work in high-traffic areas.
You have a few finish choices:
- Flat: The nonreflective surface may be ideal for hiding flaws in older houses. The paint’s porous nature makes it less durable and better suited to exterior siding.
- Semi-gloss: The higher sheen makes this finish easier to clean. It is more long-lasting than flat finishes and works well on window frames.
- High-gloss: This is the most reflective and resilient finish. It makes a statement but also shows imperfections. Use this finish on doors or shutters.
Avoid using exterior paint indoors, as it is designed and intended for outdoor use. Its chemical composition is ideal for weather resistance, not human inhalation. The higher VOC content, fungicides and other additives are advised for outdoor use only. Using this paint indoors carries health risks. Instead, stick to indoor paint inside your home.
Repainting your home’s exterior is no small task! You need to consider the right paint for the specific climate, the cost and the best time of the year to paint. Hiring a professional painting company eliminates the hassle of a large-scale painting project.
Get Your Painting Done With the Experts at The Ohio Painting Company Today
When used indoors, exterior paints can put your health at risk and make your walls appear less attractive. Sticking with interior paints is the best way to protect your family while ensuring your home’s interior looks beautiful.
The Ohio Painting Company has extensive experience performing interior and exterior paint jobs for homeowners throughout Dayton, Cincinnati and East Columbus. We pride ourselves on providing transparent, trustworthy and reliable services that ensure your satisfaction. We know how to use exterior and interior paints appropriately to beautify your home.
Contact us today to request an estimate for your next painting project.
