Can You Use Exterior Paint Inside?

Is there a half-full can of exterior house paint sitting in your garage or basement just begging to be used on a project? Or maybe there’s some leftover interior paint you’ve thought about using on the exterior of your front door?

If you answered yes to either of those questions, you’re not alone. Most DIYers have wondered whether they can use exterior paint indoors—or vice versa—at some point in their home improvement careers. The short answer is that you’re far better off only using paints for the applications they were designed for.

While you can technically use exterior paint inside and interior paint outside, doing so can result in more mess than you might think. Use the right paint for the right application, and you’ll avoid potential headaches. We checked in with painting professional Brandon Walker of ASAP Restoration, who helped us explain how to choose the right paint for your project.

First, here’s a short primer (sorry, we couldn’t resist!) on the types of interior and exterior paint we’ll be discussing:

• Acrylic latex paint is water-soluble when wet and emits minimal VOCs (volatile organic compounds). Manufacturers engineer most varieties to be washable and scratch-resistant.
• Interior acrylic latex paints are specifically designed for indoor use. They have very low VOCs and are quite affordable. The vast majority of interior paints are acrylic latex.
• Exterior acrylic latex paints have added resin to make them more weather-resistant. These resins result in higher VOC counts (and higher prices).
• Interior/exterior paints are designed to offer a balance between interior and exterior paints. They can be used either indoors or out.
• Oil-based paints are very durable but emit more VOCs than water-based paints and require turpentine or mineral spirits to thin or clean up. Once an industry standard, they now make up a minority of paint sales.

Can You Use Exterior Paint Indoors?

Technically, you can… but you shouldn’t! Exterior paints have resins designed to help the paint expand and contract (instead of crack) in extreme heat and cold, as well as additives to deter mildew, fading, and staining.

As a result of those resins, exterior paints also contain a higher number of VOCs than interior paint. This means that the paint’s off-gassing (the process of releasing fumes) will be smelly at best and potentially hazardous at worst. It’s especially concerning for people with allergies, breathing problems or chemical sensitivities. Even after it dries, exterior acrylic latex will continue to emit VOCs.

Some cities and state governments limit the use of paints with high VOCs. This varies with your local rules; for example, California varies on a county-by-county basis, while Delaware has a state-wide law.

Can You Use Interior Paint Outdoors?

No, you should never use interior paints on projects that will be exposed to the weather.

Interior paints don’t contain the resins, fungicides and other additives that make exterior paint durable. In addition, manufacturers don’t formulate interior paint to expand and contract with temperature changes. Interior paint is also not designed to withstand intense UV exposure from direct sunlight.

As a result, your interior paint will begin to crack and peel as the temperature changes. If it’s exposed to the sun, its color will quickly fade, and it will be prone to mildew growth if it’s in the shade. In short, interior paint won’t stand up to the elements. Use interior paints on your exterior projects, and you’ll be repainting them regularly.

Interior/Exterior Paints – Works in both Worlds

Interior and exterior paints have low VOCs but still contain strengthening resins that allow them to withstand rain and UV rays. They can be used indoors or out and can take a real beating.

The downside? They’re expensive. But if you’re going to tackle both interior and exterior work (or just want the convenience of storing less paint between projects), they’re a great option.

Brandon Walker says he likes to use interior/exterior paint on interior areas that will get more abuse, such as trim, door frames and baseboards. “This gives the paint used in these areas a bit of a longer lifespan with normal everyday use than an interior formulation would provide,” he says.

However, Walker avoids using interior/exterior paint in larger areas that won’t take as much abuse. “It isn’t necessary,” he says, pointing out that “it will cost more for coverage than an interior formulation. This includes pretty much any interior wall or ceiling.”

About the Expert

Brandon Walker is the resident paint guru at ASAP Restoration in Arizona. With over two decades of experience, he’s experienced everything from minor jobs to complete renovations.