So you’ve got a few cans of leftover exterior paint from your last house project and you’re wondering if you can use it for an interior wall. The short answer is maybe, but there are a few things you need to consider before slapping on a coat of outdoor paint inside.
While exterior paints are designed to stand up to elements like UV light and weather, they also contain chemicals to prevent mold and mildew growth that can off-gas in an indoor space. The sheen or gloss of the paint also plays a role in whether or not it will work inside your home.
Before you crack open that can of exterior paint for an indoor project, read on to learn what you need to know to do it properly or if you’re better off purchasing a can of interior paint.
Differences Between Interior and Exterior Paint
Using exterior paint inside your home may seem convenient, but there are some important differences to consider before you dive in.
Exterior paint is designed to withstand harsh weather conditions like extreme heat, cold, and humidity. It contains stronger resins and binders to prevent fading and damage.
Interior paint, on the other hand, is made to suit the controlled climate inside your home. It has fewer VOCs (volatile organic compounds) and a less overpowering odor.
The sheen is another factor. Exterior paint typically comes in glossy finishes to repel water, while interior paint has finishes like eggshell or satin that produce a subtle sheen.
A glossy paint indoors can make imperfections in your walls much more noticeable.
Application and cleanup also differ. Exterior paint requires a primer, and it is more difficult to apply and clean up. It can take longer to dry and requires more coats for an even finish. Interior paint, however, goes on more smoothly and dries faster.
Factors to Consider When Using Exterior Paint Indoors
So you found some leftover exterior paint in the garage and are wondering if you can use it for an indoor project to save some cash. The answer is maybe, depending on a few important factors.
First, check the label to make sure it’s latex or acrylic paint. These are water-based, so they release fewer fumes and VOCs that can be hazardous indoors. Oil-based paints, on the other hand, have strong odors and solvents that linger, so avoid those inside.
Second, consider the sheen. Flat or matte paints have little to no sheen, so they hide imperfections well and are easy to touch up.
Eggshell or satin paints have a soft, subtle sheen good for walls. Glossier paints like semi-gloss or high-gloss, are more durable and scrubbable but show more imperfections. For interiors, stick to flat, eggshell or satin.
Ventilation and priming are also key. Open windows to ventilate and run an exhaust fan to remove fumes. You may need to apply a primer first, especially if painting over a dark color. Priming helps with adhesion and provides an even base coat.
If the paint was stored properly in an airtight container, it should still be good for a few years. But if it has a musty smell or the consistency seems off, it’s best to buy a fresh can for indoor use. Your health and safety should be top priority.
Preparation Is Key
Preparation is key to successfully using exterior paint indoors. Before you start painting, take the necessary steps to ensure you’ll get the results you want.
First, thoroughly clean the walls to provide a smooth surface for the paint to adhere to. Wash the walls with a degreaser or TSP substitute to remove dirt and grime. Then sand any rough areas and patch any holes or cracks. Wipe away all dust with a tack cloth.
Next, apply a primer designed for both interior and exterior use. The primer will seal the surface and provide a uniform base for the topcoats of paint. For the best results, tint the primer to a shade slightly lighter than your final paint color.
Two coats of primer are recommended for bare drywall or if you’re making a significant color change.
You’ll also want to protect the floors, trim, and any adjacent surfaces from drips and splatters. Lay drop cloths, tape off trim, and consider removing outlet covers and hardware.
Ventilate the room well by opening windows and using fans to prevent fumes from building up.
When painting, use a brush to cut in edges and corners, then roll on two coats of paint, waiting 2 to 4 hours between coats. Exterior paint typically requires more coats to achieve an even finish. Add a clear topcoat like polyurethane to doors and trim for protection.
Clean up thoroughly when done using paint thinner or water and soap. Dispose of all painting supplies, drop cloths, and empty cans properly according to the product labels.
Proper Ventilation and Safety Precautions
When painting with exterior paint indoors, proper ventilation and safety precautions are essential. Exterior paint contains volatile organic compounds (VOCs) that can irritate your eyes, nose and throat if inhaled in large amounts. Take the following steps to ensure safe and responsible use of exterior paint inside:
Open windows and use fans to ventilate the room. Run an exhaust fan to pull fumes out of the room and open windows across from each other to create cross-ventilation. Place fans in windows or use box fans to increase air flow. The more air circulation the better.
Wear a respirator mask rated for painting or organic vapors. A simple dust mask will not provide adequate protection from paint fumes. Respirator masks are available at most hardware stores. Look for a tight-fitting mask with replaceable filters designed to block paint vapors and organic chemicals.
Take frequent breaks and avoid long exposure. Even with proper ventilation, paint fumes can build up in the room over time. Take breaks every 30-60 minutes to get fresh air. Long term or repeated exposure to high concentrations of paint fumes can cause serious health issues.
Seal off the room from the rest of the house. Close doors, air vents and other openings to prevent fumes from spreading to other areas of your home. Place damp towels or weather-stripping at the base of doors to block any air leaks.
Clean up properly to avoid continued off-gassing. Once painting is complete, clean brushes and rollers thoroughly with solvent to remove excess paint residues that can continue releasing fumes as they dry. Double bag all waste and dispose of promptly outside your home.
FAQs – Using Exterior Paint for Interior Walls
A common question DIYers have is whether exterior paint can be used for interior walls. The short answer is yes, exterior paint can work inside, but there are some factors to consider.
Exterior paints typically have higher volatile organic compound (VOC) levels to withstand outdoor elements, which can produce strong fumes that linger indoors.
Look for “low-VOC” or “no-VOC” exterior paints, which have little to no chemical smell and are safer for indoor use.
Exterior paint comes in a range of sheens, from flat to high gloss. Flat or eggshell paints are best for indoor use since they hide imperfections well and are washable. Glossier paints like satin or semi-gloss can appear too shiny indoors and show more surface flaws.
Exterior paint is built to stand up to weathering, so it may be more durable than regular interior paint. This can be a pro or con for indoor use.
The paint may be more stain- and scrub-resistant, but it can also be more difficult to touch up or paint over in the future. For high-traffic or washable areas like kitchens and bathrooms, the added durability of exterior paint could be an advantage.
Exterior paint typically provides better coverage in one coat compared to interior paint. This is good if you’re painting over a dark color or want to minimize the time spent painting.
However, the higher pigment load in exterior paint may result in a slight color difference from the sample, especially for lighter shades. It’s best to test the paint on an inconspicuous area first.
So in summary, while exterior paint can technically be used inside your home, it really isn’t the best idea. The chemicals that make it durable for outdoor use can emit some pretty nasty fumes indoors and the finish often isn’t ideal for interior walls and trim.
Unless you’re in a pinch or on an extreme budget, go with paint specifically designed for indoor use. Your nose, lungs, and the overall look of your interior will thank you. Who wants their living room to smell like a freshly painted deck anyway?
Do yourself a favor and pick up a can of interior paint next time you’re at the hardware store. Your home will be happier and healthier for it.