Can You Use Exterior Paint on The Inside?

Imagine how many times you have had to repaint the walls in your home because they keep peeling or getting discolored. As you wonder about a long-lasting solution, you remember that only the interior that has been bothering you; the paint on the exterior has never shown any need for a do-over. It has served you for over ten years and still looks fresh, so you start asking yourself if you can use the exterior paint on the inside and do away with the regular paint jobs. As logical as it may seem, you might want to stick to the interior paint for the indoors, and here is why.

Understanding the Difference between Interior and exterior paints

Primetime explains the difference in exterior and interior paints. As per the article, both paints contain solvents, resins, additives, and pigments. Pigments are the colors bound to the surface by resin; resin can be composed of silicone, acrylic, or latex solvents. On the other hand, solvents, which are either water for latex paint and mineral spirits for oil-based paints, cause the paint to be wet. The solvent evaporates as the paint dries. Additives usually give the paint some additional qualities such as mildew resistance, easy application, and easy to clean.

Since the lasting ingredients in any paint are the resin, pigment, and additives, the resin determines how binding the paint is to the surface. Paint meant for the outdoors has to withstand harsh conditions such as extreme changes in temperature. As the exterior surface expands and contracts under different temperatures, the exterior paint has to look good constantly. Therefore the resin used is flexible and the additives included have to prevent mildew from rain and fading from sun exposure. On the other hand, since the indoors are not exposed to such weather conditions, the interior paint resin is rigid. As a result, they are easier to clean.

Why You Should Not Use Exterior Paint for the Indoors

As much as you may want to save some money thinking that the exterior paint will be more durable than interior paint, there are few risks that you have to factor in, and they include:

  • Volatile Organic Compounds (VOCs)According to Medium, VOCs are usually referred to as paint fumes and can stay in a room for at least six months, causing sick building syndrome. There is a reason why homeowners are asked to look for somewhere else to stay as their house is being repainted. The fumes can cause headaches, nausea, and dizziness, especially if the room is not well-ventilated. The symptoms can progress to more serious issues such as vision and memory impairment depending on how long and frequently you are exposed. Research has shown that after painting, the indoors’ levels of organic compounds can be 1,000 times more than the outdoors, especially a few hours immediately after the job is completed. Although the fumes are mainly released within 48 hours in large amounts, they continue to be emitted for years in smaller amounts making exterior paints dangerous for your health if used indoors. You should note that interior paints also contain VOCs; they don’t release fumes in the same way as exterior paints, but still, ventilation is important to be on the safer side.
  • Flammability – The flammability of paint is dependent on the solvent used. Water-based solvents are not flammable, whereas oil-based solvents and aerosol paints are. According to To Canvas, aerosol paints are flammable because of the pressurized propellants in the can that are useful for the can to work and give the spray paint a uniform coating. On the other hand, oil-based paints are flammable; thus, the best options are latex paints and acrylic paints, which are not flammable.
  • Fungicides – Exterior paints are made to resist mildew development from moisture exposure since they contain additives like mildewcides and fungicides. You could think of applying paint to prevent mildew growth in your bathroom, but the chemicals could do more harm than good to your health. They have a strong smell that makes it hard to breathe and trigger allergic reactions.

Should You Use the Exterior Paint on the Inside?

According to, you can use exterior paint on the inside of your house so long as you take care. One of the things you have to be concerned about is the ventilation. VOCs can cause respiratory issues; therefore, ensure that you have adequate ventilation that includes open doors and windows and turned-on fans. Even after you have finished the paint job, leave the doors and windows open as the outgassing process continues. Also, to reduce VOC exposure risk, choose water-based paints as opposed to oil-based ones since the former has smaller traces of volatile compounds.

Since the outgassing processing continues for at least six months, you should look for a place to live for the next six or more months. If you must go back to the house, ensure that you have a face mask while you are inside and keep the leftover paint tightly-covered. The best way to be on the safer side is to choose the right paint, which means reading the ingredients. It could not just be about inhaling the VOCs; you could be allergic to some volatile compounds, and you cannot be sure of what the paint is made of until you read the ingredients. However, finding a paint that discloses every ingredient is rare; thus, you might want to stick to paint meant for the interior and avoid putting your health at risk with exterior paints.

If the main reason you are opting for exterior paint is for your bathroom to benefit from the mildewcides, you have other options. You can prevent mildew and mold growth by reducing moisture accumulation by turning on the fan as the shower runs and keeping it on for at least 20 minutes after you are done. An open window also plays a huge role.

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