If you’re planning an upcoming DIY painting project, your first step might be to check the garage for cans of paint you already have. Using up old paint might be a good way to save money on your project, but you need to consider whether the paint you use is right for the job.
For example, can you use interior paint for an exterior project, and vice versa? Generally, no, and doing so could be both unwise and unsafe. Understanding the difference between interior vs. exterior paint can help you better determine whether swapping these paints would lead to any adverse consequences. It can also help you understand why paints are formulated the way they are and how their makeup affects their long-term durability and appearance.
So, what is the difference between interior and exterior paint? Here’s everything you need to know from professional painters in Las Cruces, NM.
Manufacturers formulate different types of paints to serve different purposes. This is why you cannot paint your house with the acrylic paint you find at the craft store, and why you shouldn’t paint your front door with watercolors.
Interior and exterior paints have very different properties that make them suitable for diverse uses.
While interior and exterior paints may appear the same at a glance, they are vastly different in their chemical formulations and properties.
Interior and exterior paints have several primary differences that make them suitable only for their intended purposes. These are the main differences between these two types of paint.
Exterior paints cover surfaces that are subject to diverse weather conditions. They need to be durable enough to withstand wind, snow, hail, rain, and debris from storms. Manufacturers formulate these paints to hold up well to different types of weather.
In contrast, interior paints are typically used in relatively controlled environments. They do not endure precipitation or strong winds. Because of this, interior paints do not need to be quite as durable and do not contain some of the same additives as exterior paints to increase weather resistance.
Interior and exterior paints need to adhere to significantly diverse surfaces. Inside, your paint generally needs to stick to either drywall or plaster, both of which are relatively smooth surfaces. Meanwhile, exterior paints are formulated to adhere to a wider range of surfaces, such as wood, stucco, vinyl, and metal.
You may wonder why it matters if you use exterior paint indoors. This paint is more durable and adhesive than interior paint; isn’t that a plus?
But interior and exterior paints have another significant difference you need to be aware of: their VOC levels. Volatile organic compounds (VOCs) are a group of chemicals commonly found in home and building products. Inhaling these chemicals can lead to adverse health effects, such as eye, nose, and throat irritation, headaches, and even organ damage.
VOCs evaporate faster in outdoor environments than indoors, where ventilation is often poor. For this reason, interior paints often contain lower levels of VOCs. In turn, their durability and adherence are often lower than exterior paints, which have a stronger chemical makeup.
Using exterior paints indoors could expose you to unsafe levels of VOCs, potentially causing negative health effects.
Another main difference between interior vs. exterior paint is each product’s temperature tolerance. Exterior paints face a wide range of temperatures, from freezing weather in winter to hot, humid temperatures in summer. When outdoor temperatures fluctuate, building materials expand and contract slightly. As a result, exterior paint needs to have the flexibility to expand and contract with the building without cracking or peeling.
In contrast, interior paint does not face the same diversity of temperatures. Most buildings with HVAC systems stay in a temperature range between 60 and 80 degrees Fahrenheit consistently. Interior paints do not require chemical additives that allow exterior paints to withstand harsh temperature changes.
You may have realized that interior and exterior paints are available in different finishes. Interior paints generally come in all of the following finishes, in order from least to most glossy:
Meanwhile, exterior paints are typically available in a more limited selection of finishes: flat, semi-gloss, or gloss.
Gloss finishes tend to be more durable and easier to clean than ones with lower sheen levels. This is why painters typically recommend using a semi-gloss paint in the kitchen, where the walls may be subject to food splatters and steam. With this principle in mind, it makes sense that exterior paints are only available in glossier finishes.
Interior and exterior paints have different drying times. Interior paint is typically dry to the touch within about one hour and ready for a second coat within four hours. Exterior paint is generally thicker and made from different chemicals than interior paint, impacting the drying time. It may not feel dry to the touch until six to eight hours after application, while it can continue drying and curing for several days.
Both types of paint benefit from good ventilation to dry faster. However, exterior paint is usually applied in a well-ventilated outdoor environment, whereas indoor paint may be challenging to ventilate on a hot or cold day, especially if you do not want to keep the window open for an extended period.
Interior paints have significantly diverse properties and chemical makeups, and the way you apply them also differs. Learn how to apply interior vs. exterior paint.
Painting walls with interior paint is a relatively straightforward process. You do not need to do much to prepare the walls unless they are overly cracked or chipped.
The steps for applying exterior paint require a bit more prep work.
One important note to consider when applying exterior paint is the weather. Keep an eye on the forecast and try to avoid rain or other precipitation during the painting process. Aim for a day when the humidity is mild, temperatures are between 50 and 90 degrees Fahrenheit, and wind speeds are low.
If you are searching through the old cans of paint in your garage and come across an exterior paint that would look great inside the house, stop and consider whether doing so would be wise. If you use exterior paint inside, you risk all of the following:
If you’re looking for ways to use up old exterior paint, continue applying it to:
While it isn’t necessarily unsafe to use interior paint outdoors, it won’t provide the necessary qualities to stand up to weather and changing temperatures. Applying interior paint outside may lead to effects like:
If you accidentally applied interior paint outside, you can simply consider it an extra coat of primer and paint over it.
Interior and exterior paint are not the only two types of paint. There are many different varieties of paint available that perform well for different materials and applications. For example, you can find paint designed specifically for exterior doors, shutters, bathrooms, kitchens, and more. Also, paints come in different price ranges depending on the quality and number of coats you would need to apply to achieve an even finish.
You need to consider several factors when determining the right type of paint to use, including:
It often helps to purchase samples of a few different colors and finishes and apply them to the surface to see how they would appear. The material, lighting, and paint finish can all impact how the paint looks on the surface.
Now that you know the difference between interior vs. exterior paint, you understand that these paint types are formulated distinctly to produce specific benefits for the type of material and environment they are targeted for. If you’re planning to paint your exterior or an interior room, you may have questions about which type of paint to use, how to apply it, and how to achieve the best results.
Engel Coatings Inc. offers comprehensive, professional painting services throughout El Paso, TX, and Las Cruces, NM, to ensure your peace of mind. Contact us today to request a free estimate.
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