Water-Based Exterior Paint: Can You Use It Indoors?

If you're wondering whether leftover exterior paint can be used inside your home, the short answer is yes, but it's not recommended. Exterior paint contains a higher number of volatile organic compounds (VOCs) than interior paint, which can be harmful to your health. While exterior paint will dry indoors, it may take longer and the finish may appear patchy and uneven. VOCs are released into the air as the paint dries and cures, creating a strong chemical smell. In an enclosed space, exposure to VOCs can cause headaches, nausea, loss of coordination, eye, nose and throat irritation, and damage to the kidneys, central nervous system, and liver.

Exterior paint is also less resistant to everyday wear and tear, such as scuffs and scratches, and is more difficult to clean. It's designed to withstand rain, sleet, snow, and direct sunlight, but this durability comes at the cost of increased chemicals.

So, while technically possible, it's best to avoid using exterior paint indoors, especially in living spaces, to minimise health risks and ensure a quality finish.

Exterior paint contains more VOCs than interior paint

While it is technically possible to use exterior paint inside, it is generally not recommended due to the potential health risks associated with the paint's chemical composition. Exterior paint contains more volatile organic compounds (VOCs) than interior paint, and these VOCs can be released into the air as the paint dries and cures, creating a strong chemical smell and potentially causing health issues for those exposed.

VOCs are chemicals found in many building materials, including paint, that can off-gas fumes for weeks, months, or even years after application. They can build up indoors and have harmful effects on human health, including irritation to airways, headaches, nausea, and damage to vital organs such as the liver, kidneys, and central nervous system. Prolonged exposure to VOCs has also been linked to an increased risk of developing asthma or allergies.

Exterior paint is designed to withstand harsh weather conditions, such as rain, intense heat, UV radiation, and freezing temperatures. To achieve this level of durability, exterior paint contains more VOCs and other powerful chemical components. When used indoors, these chemicals are trapped inside the home, posing a risk to the health of occupants.

In addition to the health concerns, there are other reasons why exterior paint is not ideal for indoor use. It may take longer to dry and cure indoors, resulting in a patchy and uneven finish. Exterior paint is also not designed to withstand the everyday wear and tear of indoor environments and may be more prone to scuffing and scratches.

While it may be tempting to use leftover exterior paint for indoor projects to save money or reduce waste, it is important to prioritize the health and safety of you and your family. It is recommended to use interior paint, which contains fewer VOCs and is specifically designed for indoor environments, to minimize potential health risks.

Interior paint is more rigid and withstands abrasion better

Interior and exterior paints have different compositions and are designed for different purposes. Interior paint is made to withstand abrasion and resist staining, whereas exterior paint is designed to withstand weather conditions and temperature changes.

Interior paint is formulated to withstand abrasion and resist scuffing and scratching. It is made with more rigid resins that don't scuff or scratch easily and can be cleaned with soap and water. This is especially important for indoor spaces where there is regular foot traffic, pets, and children. Interior paint is also designed to be more delicate than exterior paint as it occupies the same space as people. It can also withstand the wear and tear of everyday life, such as oils, indoor humidity, staining, and abrasive damage.

Exterior paint, on the other hand, is designed to be flexible and withstand significant temperature changes. The resins used in exterior paints are softer and more flexible, allowing them to expand and contract without cracking. This flexibility is crucial for exterior paint to survive the ill effects of moisture and temperature changes. However, this flexibility comes at the cost of being more prone to scuffing and scratches when applied indoors.

The different compositions of interior and exterior paints also affect their respective drying times. When used indoors, exterior paint can take significantly longer to dry and cure compared to interior paint. This extended drying time can affect the appearance of the finished product, resulting in a patchy and uneven look.

In summary, interior paint is designed with more rigid resins to withstand abrasion and resist scuffing and scratching, making it better suited for indoor environments. Exterior paint, on the other hand, uses softer and more flexible resins to withstand temperature changes and outdoor elements.

Exterior paint takes longer to dry and cure

While it is technically possible to use exterior paint indoors, it is not recommended. One reason for this is that exterior paint takes longer to dry and cure when used inside.

Exterior paint is designed to withstand a wide range of weather conditions, from rain and snow to intense heat and sun. To achieve this durability, exterior paint contains resins that allow it to expand and contract with changing temperatures, preventing cracking. However, when used indoors, these same properties cause exterior paint to take significantly longer to dry and cure compared to interior paint. The extended drying time can affect the final appearance of the paint, resulting in a patchy and uneven finish.

The drying and curing process of exterior paint is also crucial for indoor air quality. Exterior paint contains higher levels of volatile organic compounds (VOCs) than interior paint. VOCs are released into the air as the paint dries and cures, creating a strong chemical smell. In an outdoor setting, these VOCs dissipate into the open air. However, when used indoors, the VOCs become trapped inside the home, posing potential health risks to occupants. The prolonged drying and curing time of exterior paint indoors means that these harmful chemicals will continue to be released into the indoor environment for an extended period.

The specific drying time of exterior paint indoors can vary depending on various factors, such as temperature, humidity, and ventilation. It is important to follow safety precautions when using exterior paint indoors, such as ensuring proper ventilation and wearing respiratory protection.

In summary, while it is possible to use exterior paint indoors, it is not advisable due to the longer drying and curing time, which can affect the appearance of the paint and prolong the release of VOCs, potentially impacting indoor air quality and the health of occupants.

Exterior paint is not designed to withstand everyday wear and tear

While exterior paint is designed to withstand harsh weather conditions, it is not designed to withstand everyday wear and tear inside the home. This is because interior and exterior paints are formulated differently and, therefore, perform differently.

Exterior paint is made to be durable and withstand the elements, but it is not designed to withstand the same kind of wear and tear that occurs indoors. Interior paint, on the other hand, is made to resist oils, indoor humidity, staining, and abrasive damage from everyday life, including pets, cooking, cleaning products, and bathroom fixtures.

Exterior paint is also softer than interior paint, making it less resistant to scratches and stains. It is also more difficult to clean. The formula of exterior paint is designed to expand and contract with temperature changes, making it less rigid and more prone to scratches and other damage.

Additionally, exterior paint contains more volatile organic compounds (VOCs) than interior paint. VOCs are toxic chemicals that can cause a range of health problems, including headaches, nausea, loss of coordination, irritation to the eyes, nose, and throat, as well as damage to the kidneys, central nervous system, and liver. When used indoors, these chemicals are trapped inside the home, posing a risk to you and your family.

In summary, while exterior paint may seem like a good option for its durability, it is not designed to withstand the everyday wear and tear of indoor environments. It is also more hazardous to your health, making it a poor choice for interior painting projects.

Interior paint is washable and scratch-resistant

The sheen of the paint will also determine how washable it is. Semi-gloss and glossy paints can withstand moderate scrubbing. Lower-sheen paints, such as eggshell and satin, can only be very gently washed. Flat paints lose their finish quickly when scrubbed.

If you want to use a washable paint in areas such as children's bedrooms or hallways, ask your painting contractor for a durable, scrubbable paint. These areas are usually painted with less sheen and are not very washable.

If you are washing painted walls, use a soft sponge and scrub gently with warm, slightly soapy water. Avoid using magic erasers, as they can make the paint disappear.

Interior paint is also scratch-resistant. Exterior paint is more prone to scuffing and scratches when applied indoors. This is because exterior paint is designed to withstand weather conditions, not indoor wear and tear. Interior paint is made to resist oils, indoor humidity, staining, and abrasive damage.

Frequently asked questions