If you are doing some home renovation and run out of paint for a few exterior surfaces, you may come across a tin of interior paint that could fit the bill.
If you wonder, can I use interior paint outside? The answer is yes, but there are many reasons you shouldn’t. While they may appear to be the same, there is a big difference between the way they work and what they comprise.
In our guide, you can learn about the different properties between the two paints and why you shouldn’t look at how to make interior paint into exterior paint.
By the end, you’ll be full of information on why interior classified products offer little weather resistance and would last a few months in an outdoor environment. (Learn How To Get Rid Of Lead Paint)
Can You Turn Interior Paint Into Exterior Paint?
Do you intend to paint some patio furniture with the remaining paint from our indoor renovation to carry out a paint job of an outside wall or door? If you think about whether you can use interior paint outside? Although the short answer is yes, it is not advised.
Rain, snow, wind, UV, mildew, or temperature extremes can take their toll on interior paint. An interior paint solution contains fewer pigments and binding resins than outdoor paints and has a porous finish. As a result, the paint will fade, powder, or chalk more quickly, crack, and flake.
Here you can find the differences between indoor paint and paint made for outdoors.
Water-based (latex paint and acrylic paint) and oil-based paints are the two most common forms of paint. Water-based latex and acrylic paints are available, whereas oil-based alkyd paints are available for interior use and exterior use.
Oil-based paint is better at resisting dirt for exterior paint, but water-based latex paint is more widely used as it is as durable as oil-based paint. These paints are better adapted to dealing with humidity, temperature changes, and other external variables, and they dry faster than alkyds. (Read Mineral Spirits Vs Paint Thinner)
Paints designed for outdoor use include ingredients to help them last longer in the weather, such as resistance to cracking and UV resistance. In addition, many come with a heavy-duty mildewcide as a component to improve weather resistance.
Indoor use of water-based paints is recommended, not just because of the fumes when you use exterior paint inside and face the fumes associated with oil-based paints.
Interior paint is now made to resist scuffs, scratches, and much more.
However, additives are only one of four essential components of paint, and the other three: pigment, binders, and liquids, change between interior and exterior paints.
Pigments and binders are combined in water as the carrier in water-based or latex paints. As the water evaporates, they dry faster, leaving the color behind.
Surfaces painted with latex are easier to clean and maintain their color longer than those painted with oil. Because it contains fewer VOCs than oil-based paints, it is more environmentally friendly.
Interior latex paints are perfect for painting ceilings and walls because they are flexible and durable once dry. Many people choose water-based paints because they are easier to clean with soap and water.
Natural oils, including linseed, tung, soybean, and synthetic alkyds, are oil-based paints. Pigment, an oil resin binder, and a solvent thinner are all included. When the thinner is applied to a surface, it evaporates, leaving the resin and pigment to form a durable hard layer. Such a layer can deal with an exterior environment to withstand rain and more on external surfaces.
Oil-based paints emit more volatile organic compounds (VOCs), making them less ecologically friendly and making cleaning surfaces more challenging if using exterior paint inside an interior environment. (Find the Best Paint Sprayer For Kitchen Cabinets)
Because of interaction with vacuums, furniture, and soiled hands, oil-based paints are specially formulated with flexible resins. They have a particular chemical makeup to resist staining and bangs on doors, trim, baseboards, and more contact surfaces.
The paint dries slower and takes longer to cure, but they produce a robust, long-lasting layer and resist peeling. Cleaning brushes, tools, and spills are more difficult and require paint thinners, turpentine, or mineral spirits.
Paint pigments can be organic or inorganic. The sort of pigment also affects how often the walls need to be repainted or spruced up. Organic pigments are translucent and come from plants or animals. Resins bind to the pigments and create a paint film, which forms the basic components of the right paint for the job.
Binders keep pigments together to form a film on a surface. The plastic-like polymers give higher surface adherence, abrasion resistance, and cleaner resistance. Binders in latex paint should be 100% acrylic, not a blend.
Differences Between Interior and Exterior Paint
When applied on outdoor surfaces, interior paints lack some environment-specific chemicals, but the distinction between interior and exterior paints doesn’t end there.
Paint’s other three major components: pigment, binders, and fluid, also show differences.
Let’s start with pigment, which gives a paint that can change its color. Interior paints may contain organic pigments, which may fade if used on an exterior surface; exterior paint formulae omit these pigments, extending the duration between outdoor paint projects.
Similarly, binders are employed in paint formulations to bind the pigment together and offer adhesion to the painted surface. (Read Can Paint Go Bad)
Binders used in outdoor-friendly paint formulas give the paint resistance to integrity issues like cracking and chalking and improved moisture control. Instead, interior paint binders may offer superior abrasion resistance, which isn’t always needed in exterior paint.
Interior and exterior paints also use different liquids. Interior paints, specifically water-based paints, including latex, have the lowest VOC levels (volatile organic compounds).
VOCs are employed as solvents in paints and vaporize at room temperature. Besides headaches and dizziness, VOCs are connected to respiratory disease and liver damage (long term). They may also be linked to cancer.
The EPA notes indoor VOC levels can be two to five times higher than outside levels and that levels can rise dramatically after painting. Look for low- or no-VOC interior paints.
Because exterior paints (especially oil-based paints) do not all fulfill the same low-to-no VOC regulations as interior paints, it is crucial not to use outside paint inside your home as certain environment-specific additives to resist mildew, and the weather is wasted when used for interior use.
Luckily, there is now another option; paint formulated to be used indoors or out. There is hybrid interior and exterior paint formulations.
Can You Use Interior Paint Outside?
Outside use of interior paint has several benefits. Just a few reasons are it’s cheaper, you can use up leftover paint, or you enjoy the color. You can apply interior paint outside, but you shouldn’t.
Interior paints are not made like outside paints. As a result, they will swiftly fade and chalk because of the lack of moisture resistance. Interior paints are porous and don’t offer the better adhesion to exterior surfaces exterior paint offers.
If you must use interior paint outdoors, protect it with one or two layers of external clear coat sealer. It may increase the time it adheres, but it won’t prevent fading, and the sealer may yellow on exterior surfaces.
You’ll also find you need several coats, and even then, it can appear patchy and chalk quickly from the sun.
Using interior paint with a sealant adds work and makes pricey exterior paints look cheap.
Painting the inside of a front door is fine because it is protected from the elements. Preparation is still required, especially if the door is metal, as you need to improve adhesion. The same paint can be used on the exterior if it has protection from a storm or glass door; otherwise, it will fade, crack, and chip.
Using interior paint on inner concrete walls or slabs requires a lot of prep work – fixing gaps, cleaning with TSP, sealing, priming, and painting. For exterior concrete, a quality exterior sealer must be applied over the interior paint. Interior paints will fade and wear faster than exterior paints because of the sun and other factors.
What Happens If You Accidentally Used Interior Paint Outside?
Accidents happen, whether you grabbed the wrong can of leftover interior paint or didn’t realize there was a difference between exterior paint until it was too late. It’s not the end of the world if you use interior paint outside. It simply implies that instead of ten to fifteen years, you’ll be repainting the surface in two to five years.
Interior paints maintain the protected surfaces of a building, not to survive the ravages of nature. It will fade faster and lack the ingredients that protect against temperature extremes, UV rays, and mildew. You can either paint it over now with exterior paint or wait a year or two.
You might as well finish the job if you’re almost done. If it’s only just started, you can use exterior paint to cover it.
Some people recommend sealing the interior paint with an expensive sealant and chalking it up to a lesson learned. Instead of spending additional money on a sealer, buy quality exterior paint in the same color and base and apply another layer.
There is a difference between interior and exterior paint. The items for indoor and outdoor use have been improved by modern technology and chemistry. If you want to put interior paint over exterior paint, the short answer is yes; the long answer is, why would you want to use interior paint as exterior paint?
When applying interior paint over outside paint, you’ll need to do some prep work and use a primer if you’re using water-based paint over oil-based paint.
It is vital to note that if the paint is exposed to the outdoors, it will not tolerate temperature changes, humidity, UV, mildew, or weather variables and exterior paints.
Using inside paint instead of outside paint can initially save money. However, because it won’t stay as long, you’ll have to apply another coat sooner, negating any savings. It also raises the labor component.
If an external wall has been converted to an inside wall because of a repair or addition, you can confidently paint over exterior paint with interior paint. Interior paint is not recommended for outdoor usage and frequently violates warranties.