Can You Use Exterior Paint Inside Your Garage?


One of the best things I did to freshen up my garage was to paint the wall. It’s a great way to update your garage without doing a complete renovation. However, I wondered whether I should use interior or exterior paint, so I decided to do some research.

It turns out that there are some do’s and don’ts when it comes to painting these walls, including what type of paint to use and when to use it. 

Interior vs Exterior paints for garage walls

When painting inside your home, including your garage walls, always use interior paint instead of exterior paint. Exterior paint is meant for open spaces with good air-flow. It is specially formulated to protect your home from rain and snow, and contains chemical additives that can be toxic to your family if used inside.  

In the rest of this article, I’ll dive deeper into what type of paint you should use inside your home.

Then I’ll cover how temperature impacts the painting application and drying process, and why some garages are just better left unpainted. 


Is It Safe to Use Exterior Paint In Your Garage?

According to the United States Environmental Protection Agency (EPA), exterior paint should never be used inside your home. This includes your garage.

All paints, both interior and exterior, are made up of the same four basic components: resin, solvents, pigments, and additives.

It’s in those four components that we find the major differences.

The first difference is what type of resin is used to bind the pigment to the paint itself. This is what allows the paint to stick to your walls. 

The most common paint resins are acrylic, alkyd, and epoxy resins.

Epoxy resins are commonly used in flooring and sealants because of their high durability. However acrylic and oil-based (alkyd) paints are very common in homes.

In my case, I found out that my builder used an exterior paint in my garage. We decided to cover it with a fresh coat of Drylok paint to help waterproof and cut down on harmful fumes.

Acrylic Resin (Acrylic or Latex Paints)

Acrylic resin is a water-based paint that gives off relatively low amounts of volatile organic compounds (VOCs) while drying. Because of that, is extremely popular in both interior and exterior paints.

It’s easy to clean and dries quickly compared to oil-based paints. In fact, most acrylic paints dry in as quickly as 20 minutes.

If you mix an acrylic paint with an epoxy base you get what’s commonly called latex paint. Latex paints are very durable and great for your garage.

Epoxy paints fall under this category as well. However, you’re most likely to find epoxy used as a floor coating, or sealant because it adheres so well to porous surfaces like concrete. It is also corrosion-resistant, breathable, and easy to clean.

Alkyd Resin (Oil Based Paints)

Alkyd resin paints are oil-based and can be used inside or outside the home.

Oil-based paints are tougher than acrylic paints, and are typically used on areas that receive more wear and tear, like doors, window sills, or trim.

These types of paints are tricky because they can give off more VOCs than water-based paints. They also require the use of chemical paint thinners or turpentine to clean up or remove, which means more chemicals. 

Additives Can Make Exterior Paint Toxic

Air quality is critical with interior paints so another major difference between interior and exterior garage paints is the additives.

Interior paints are made with fewer chemicals and additives so they don’t adversely impact your health. By contrast, exterior paints are designed to withstand the elements, repel mildew and be chip-resistant.

All that comes through chemical additives. 

Exterior paints need to are rated to survive scorching summers, freezing winters, downpours, and a constant barrage of UV rays from the sun.

Chemical additives are combined with the resin and the pigment to help protect your home. These include mildew resistant chemicals, fungicides, anti-fading compounds, anti-chipping solutions and more. 

All those additives expel gasses during the drying process in a process called outgassing.

This is why you should always paint in a well ventilated area, and keep the area ventilated for up to 48 hours after you finish.

Although most outgassing happens within 48 hours painting, it continues in smaller amounts for several years. In an enclosed space, these gasses can be harmful to humans and pets.

That’s why you should never use an exterior paint inside your home or garage.   


Can You Use Interior Paint in an Unheated Garage?

As with any paints, one of the biggest concerns is the temperature of the room when you’re painting. In this case, it doesn’t matter whether you’re using interior or exterior paint on your garage walls.

The temperature is the key ingredient.

Unlike our living room, most garages aren’t climate controlled.

That limits when you can start a painting project.

You’re looking for that ‘Goldilocks point’ that’s neither too hot nor too cold during both the painting and drying process. If it gets too extreme in either direction, it can have adverse effects on your walls. 

When temperatures are too cold, a water-based paint will have a hard time adhering to the surface, making it much harder to dry properly.

If temperatures are too hot when painting with a latex paint, they won’t dry properly and can become gunky and too wet on your wall. This can lead to cracks and bubbles in your paint fairly quickly.

It is recommended that the temperature be be at least 50 degrees Fahrenheit (10 degrees Celsius) and not higher than 90 degrees Fahrenheit (32.2 degrees Celsius) for the entire painting application time and the drying process. 

Humidity also plays a part too. High humidity has similar effects to high temperatures. The paint can’t dry properly, which damages the finish.

During the painting process, manufacturers recommend that you control both the temperature and humidity levels. In colder climates, that means using an electric or propane garage heater in your garage. In warmer climates, you’ll want to invest in a portable air conditioner or garage dehumidifier.    


Should You Paint Your Garage?

So why don’t more people paint their garages?  

In most cases, this comes down to a simple cost savings for the home builder.

Paint best adheres to a clean, flat surface. Because most garages don’t have finished walls (drywall or other wall covering), it takes a lot more paint to get a good finish.

In existing homes, you’ll need to thoroughly clean off any dirt before you start painting. Also, if there are any imperfections on the walls, those will need to be fixed as well.

That adds additional costs that most homeowners just aren’t willing to pay.

In the end, it really comes down to personal preference and how much effort you’re willing to put in to have a great looking paint job. 


Conclusion

Never use exterior paint on your garage walls, or any other interior room. The best type of paint to use in your garage is an acrylic latex paint because it is durable, quick-drying, and easy to clean. I have some great recommendations for the best paints to use on your garage walls in this article.

You can use latex paint, even if you have a heated garage. You’ll want to avoid extreme temperatures during painting and drying, however. You may need to temporarily heat or cool your garage so it stays between 50 and 90 degrees Fahrenheit (10 to 32 degrees Celsius). 

Once you’ve decided to paint your garage, the next step is to figure out what color to paint it. While I recommend a simple white or light gray, there are many other paint schemes to choose from. We have a huge guide on how to choose the right color for your garage walls here.

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