Can You Use Exterior Paint on Interior Walls?

When decorating your home, you’ve probably noticed that there are different paints for inside and outside the home. Many people wonder whether the two are interchangeable and if you can use exterior paint on interior walls.

Technically, it is possible, but it is not advisable. Exterior paints tend to contain more fungicides to prevent mold. These compounds can lead to respiratory problems when used in the home. The increased levels of acrylic ingredients in exterior paint also create strong, lingering odors.

Exterior paints are designed to withstand the elements, so the ingredients used are very different from interior paint. Even if it might be more economical to use the same paint inside and outside, it can be incredibly dangerous to use exterior paint inside. Read on to learn more about the dangers of exterior paint, and which types of paint to use where.

What is the Difference Between Exterior and Interior Paints?

All paints are made from the same basic components; resins, additives, solvents, and pigments. Paints are made wet by the solvent, which then evaporates, causing the paint to dry. The rest of the components are left on the wall.

The pigment is what gives the paint its color and the resins bind the paint to the wall. Finally, the additives give the paint various properties, depending on what it is used for.

The pigments and solvents are very similar in exterior and interior paint, but different resins and additives are used. Exterior paints need to be able to withstand harsh weather conditions and problems like mold, so they need to be made from different compounds.

Most exterior paint contains acrylic polymers, which are very hard to break down. Acrylics bind strongly to surfaces, making them resistant to damage from the elements. They also create a strong smell when they dry. Exterior paint also contains fungicides that prevent mold growth within the paint film’s pores or cracks.

Although both interior and exterior paint contain volatile organic compounds (VOCs), exterior paint has much higher levels. The paint typically contains about 30 times more VOCs than interior paint. Exposure to high levels of VOCs such as benzene, trichloroethane, and formaldehyde can lead to serious health problems.

The different ingredients in exterior paint make it more durable, less likely to crack, and able to withstand mold and mildew. However, they also make it unsuitable for interior use.

What Happens if You Use Exterior Paint Inside?

Technically, exterior paint will look fine if you use it indoors. It will still dry ok, but it will emit a lot more odors. The VOCs in exterior paint will still continue to smell strong, even after the paint is dry. Exterior paint is also more prone to scuffs and scratches, even though it is more durable overall and less likely to crack. Exterior paints may not hold up well against regular household cleaning products either. Abrasive cleaners used regularly on interior walls or by scrubbing with abrasive sponges will eventually damage the finish of exterior paint. We do have a guide on cleaning mildew from exterior paints here. 

So, if you use exterior paint inside, you will be stuck with a strong smell that is tough to get rid of and the finish on the paint will not be as smooth as it would be if you used proper interior paint. There are also a number of serious health dangers caused by using exterior paints inside.

Are there any Dangers to Using Exterior Paint Inside Your Home?

From a health perspective, you should never use exterior paint inside your home. The higher concentration of fungicides and acrylic materials pose serious risks to those with respiratory problems such as asthma or allergies. These compounds can cause side effects such as nosebleeds, dizziness, headache, and rashes. They are particularly harmful to pregnant women and anybody with an existing respiratory problem like asthma.

Enamel and oil-based paints are particularly dangerous because they release high levels of VOCs. These VOCs break down and create ground levels of ozone that can be particularly harmful. These types of paints have been banned in many places for this reason.

How Could You Remove Exterior Paint from Interior Walls?

If you have exterior paint on interior walls, it is advisable to remove it. Attempting to cover the exterior paint with normal interior paint will only make it very difficult to remove later on. It can also cause damage to your walls and health problems for your family.

Start by scraping away any loose paint. If it is particularly old, you may find it comes away quite easily. Any remaining paint can be removed using lye or caustic soda mixed with water. This mixture is strong enough to remove hardy exterior paint but it can be very toxic, so be cautious and wear gloves and masks while using it.

Apply the caustic soap to the paint using a mop and let it sit until it is completely dry. At this point, you should notice the paint peeling and cracking, and it should scrape off easily. Once all of the paint is removed, use a sugar soap solution, which you can buy from any good hardware store, to clean the walls and prepare them for a fresh coat of paint.

What Types of Paint Should I Avoid Using Inside My House?

As a general rule, avoid using any exterior paints inside your home. In particular, look out for ingredients such as Teflon, titanium dioxide, and acrylic resin. These types of paint are particularly dangerous because they release high levels of VOCs that can cause serious health problems.

If you would like to repaint any interior walls or ceilings that have already been painted with exterior paint, then look for paints designed specifically for indoor use. There are many different varieties on the market nowadays so it shouldn’t be too difficult to find one that is suitable for your needs.

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Exterior Paint Inside FAQs

Can I use exterior paint on the inside of my front door?

It is not advisable to use dedicated exterior paint on interior doors, even the inside of the front door. It will still release toxic fumes into the home, so you need to find paints that are suitable for indoor use. You can buy paints that are labeled ‘interior/exterior’ which means they are suitable for indoor use but also durable enough to withstand being used outside.

Can you paint furniture with exterior paint?

Furniture that is going to be used in the home should not be painted with exterior paint. Instead, use a dedicated furniture paint and let it dry somewhere with plenty of ventilation, so it does not release fumes into your home.

Can I use exterior paint inside my garage?

It is still dangerous to use exterior paint inside the garage. There is not enough ventilation and the fumes can quickly build in such a confined space. Interior latex paint is still durable enough for the garage, and it’s perfectly safe.

Can I use exterior paint inside my bathroom?

People often assume that exterior paint is good for the bathroom because it is resistant to mold and mildew. However, exterior paint is dangerous in your bathroom. The best choice is to use tiles or another non-porous material. If you are using paint, buy a specific bathroom paint that has mold-resistant properties using safe ingredients.

Can I use exterior primer inside my house?

Exterior primers are not safe inside the house, just like exterior paint. They also take longer to dry which makes them impractical for use in the home. Interior latex primer is a much better choice and it is perfectly safe.

There is a reason why paints are labeled as interior or exterior. The requirements of the different paints mean that they’re made from very different ingredients. Using exterior paint in the home can lead to a number of health problems, so always follow the guidelines on any products you use and do not use them for anything other than their intended purpose.