Can You Use Exterior Paint Inside? – How and Why Paints Differ

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Sometimes life hands you lemons and you have to make lemonade. DIY can be fun, but if you’ve been in the game for a while, you know that you can find yourself sometimes lacking the right tool for the job. Most times, it’s a matter of simply going out and getting what you need or borrowing what you need from a friend, and others you simply have to make do with what you have. If you’ve ever found yourself looking at some unfinished wall or crunched for time when preparing your house for the holidays, you might have thought about using some exterior paint inside your home. Can you do this though? Let’s find out!




Can You Use Exterior Paint Inside?

Can you use exterior paint inside? The answer is yes! Although just because you can do something doesn’t mean that you should do something, or even that the something you’re thinking about doing is a good idea. Interior and exterior paints might look the same and might even provide the same quality of color in some instances, but they are graded for certain areas for a reason.

When to Use Interior and Exterior Paint

Overall, it’s a fairly bad idea to use exterior paint on the interior of your home, not because it won’t adhere properly and not even because the color would be off-putting, but because exterior paint is fundamentally different on a molecular level. But exterior paints are durable and will last a lot longer than interior graded paints would, no?

Interior and Exterior Paint Colors

This is true, exterior paints contain resins and other catalysts which allows the surface to dry noticeably harder in order to withstand things like wind, rain, heat, snow, and abrasion from sand. These chemicals also make the paint produce quite a bit of fumes during the curing process though, and while these would be fine outdoors where they can be dissipated, allowing these paints to cure and dry indoors poses a serious health hazard.

Exterior Paints Contain Chemicals

While most exterior paints these days are acrylic paints mixed with resin, back in the day most exterior home paints were oil-based and caused quite a lot of damage to the environment because of this. You see, oil-based paints contain solvents that are considered to be volatile organic compounds (VOCs), these cause ozone depletion and generally gunk up the immediate and greater environment.

Does this mean that you can use modern exterior paints indoors? Nope. Even though they contain fewer VOCs than their oil-based predecessors they can cause serious discomfort to those with respiratory illnesses and generally poor health, not to mention children and animals.

Toxic Fumes from Exterior Paint Indoors

So, can exterior paint be used inside? We would strongly recommend against it, and even if you were to look up “can exterior paints be used inside” you’ll find that most professionals are of the same opinion.

It can be tempting to save a few bucks and even some effort of going down to your local store to pick up some interior paint but considering the risk exterior paint poses to both you and your family’s health, it’s definitely worth the effort. In summary, here are some pros and cons associated with using exterior paint indoors:

  • You could save some money
  • Same color quality as interior paint
  • Exterior paint is more durable
  • Can be purchased in larger volumes for much cheaper
  • Contains far too many VOCs
  • Fumes are unbearable indoors when curing
  • Poses a serious hazard to those with respiratory illnesses
  • Range of colors are limited compared to interior paints
  • It will dry much slower than it would outdoors
  • Exterior paints scuff easier when applied indoors



Can You Use Interior Paints Outdoors?

Paints have come a long way since the turn of the century, and they’re improving all the time by becoming more versatile, hard wearing, easy to use, and even more vibrant in color. However, this doesn’t mean that you can simply use a paint that has been specially designed for a particular surface on something else and expect it to work in the same manner.

Exterior Paint for textured Walls

As we mentioned previously, just because you can do something doesn’t mean that you should do something, and when it comes to using interior paints outdoors it would be a bit like setting a wad of money on fire and expecting it to somehow be okay. Interior paints are nowhere near the level of toughness needed to be used outdoors.

Weather-Proof Paint on Exterior

Paint is paint, right? Wrong! Exterior paints contain chemicals and catalysts that allow them to be applied in an exterior setting without succumbing to things like moisture, torrential downpour, excessive exposure to heat, insect infestation, mold, as well as abrasion and impact resistance. Furthermore, exterior paint is designed to expand and contract with the change of seasons as your home heats up and cools down, while interior paint is not graded and does not have the elasticity of this application.

Interior Paint Will Not Last Outside

If you’re still on the fence about whether or not you should use interior paint on the exterior of your home, consider how it interacts with sunlight. While interior paint can look beautiful in the afternoon sunlight from your living room couch, it’s not graded for the constant assault of direct sunlight that it would receive if it were applied to an exterior wall.

Interior Paint is Not UV Proof

Essentially, just like it’s a bad idea to use exterior paint inside, it’s a bad idea to use interior paint on the exterior of your home. Eventually, it’s going to crack and peel, which won’t only ruin the finish, but it will expose your wall to the elements which could result in structural damage over time if the finish is not replaced as soon as possible.

This being said, let’s have a look at some of the pros and cons of using interior paints on the exterior of your home, and even though we recommend that you shouldn’t if you absolutely have to, here are a few things you should consider before doing so.

  • Readily available
  • Easy to use
  • Wide variety of colors
  • Hues are often softer than exterior paints
  • Looks better in natural light
  • Not graded for use outdoors
  • Cannot withstand excessive exposure to heat
  • Cannot withstand abrasion and impact
  • Cannot withstand constant exposure to moisture or water
  • Color will not last due to exposure to elements
  • Will crack and peel very quickly if used outdoors



Can You Mix Interior and Exterior Paint?

If you’ve ever had the thought “can you mix interior and exterior paint”, you’re not the first and you’re definitely not alone. The good news is that you can and if you have interior and exterior paint, but not quite enough of each of them, you can indeed mix them together to make one usable batch, but there are a few things you should know before you give it a shot.

Leftover Paint for Mixing

Before you go ahead and mix the remaining paint you have with some other paint you have hanging around, ensure that you know what paint you have in both instances. You see, interior and exterior paints can be mixed together but only if they have the same base. For example, if you have oil-based exterior paint and oil-based interior paint they can be mixed together.

You might want to ensure that the two paint types are the same color (or at least similar) to ensure that the color you already have can be matched. Additionally, ensure that you mix these paints in a well-ventilated area. Why? Well, both interior and exterior paints contain VOCs with interior paints containing marginally less, so when they’re mixed together the fumes can become a bit overwhelming.

Also, if you’re thinking about mixing these paints by hand with a stick or similar mixing tool, you’re going to find yourself out of breath pretty quickly. Why? Well, by combining two paints you’re doubling the formula used to make them, which means there are twice as many solvents, additives, epoxies, and dyes which means the substance you’re left with is going to be really dense.

Mixing Interior and Exterior Paints

We recommend using a drill or paint mixer to avoid pulling any muscles when combining your exterior and exterior paints. During the mixing process, if you happen to see any clumps forming you might want to get something you’ll be able to use as a sift and run your paint through this to ensure its viscosity is still conducive to painting.

Once you’re happy with the consistency of your paint and you’re ready to apply it, ensure that the area you’re working in is well-ventilated and that you’re wearing a mask and some gloves graded for use with paint. Once the paint has been applied successfully, ensure that you provide as much airflow to space as possible for the next four to six months as the fumes dissipate.

Exterior Paint Used Indoors

Storing mixed paint might be a bit of a challenge considering that the interior and exterior parts will separate while they’re sitting on a shelf somewhere, with the heavier of the two settling at the bottom. The trick to maintaining your “Frankenstein” paint is to ensure that the container you choose is airtight to prevent any of those nasty fumes from leaking out.

Can You Use Exterior Paint Inside



Is It Worth Taking the Risk?

We understand that it can be tempting to use some left-over paint, whether it be interior or exterior, but it’s important to weigh up the pros and cons of using paint not graded for a certain environment, and whether it’s a viable option or not. While it might seem like a quick fix to a relatively small problem, using exterior paint indoors has pretty much the same drawbacks that using interior paint outdoors does.

How so? Well, using interior paint on exterior surfaces will result in it peeling, cracking, and eventually falling away leaving your walls exposed. On the other hand, using exterior paint indoors results in impact and abrasion damage, as well as an extremely long set and cure time for the paint, not to mention noxious fumes being trapped in a confined space.

Exterior Paint Indoors will Scuff

As you can probably tell, using paint designed to serve a specific purpose for anything other than that purpose comes with a huge margin for error, errors which have the potential to become really expensive to correct, not to mention labor-intensive and annoying.

Therefore, it’s in your best interest to simply wait it out or mix some interior and/or exterior paint together or get an additive to dilute your paint so it stretches out a bit longer. Besides the negative financial and physical implications of using these paints in settings other than where they were intended, it poses a significant risk to the environment too.

Use Specialist Paint for Exteriors

Using exterior paint indoors can lead to a build-up of VOCs for a really long time which could make the space uninhabitable and using interior paint on the outside of your home will result in it cracking and chipping, which means that small animals and birds could come into contact with and/or consume this paint chips.

This being said, it is objectively not worth the risk to use interior paint outside or exterior paint inside, so do yourself and the environment a favor and stick to using these paints for their intended purpose, or thin them out and mix them together if you find yourself running low while you’re painting.



Now that you know what interior and exterior paints are, what their strengths and weaknesses are, if you can use interior paint outside, whether you can use exterior paint inside, and what the pros and cons of each scenario are, it’s time for you to get out there and out your new-found knowledge to the test. Remember to always work in a well-ventilated area and check the base of your paints before mixing them together.



Frequently Asked Questions


Is There Really a Difference Between Interior and Exterior Paint?

Interior vs exterior paint is a very niche battle but it’s important to discuss. While interior paints dry a lot faster and are available in more colors, exterior paints typically contain more VOCs and are far more durable compared to interior paints. Who is the winner in the interior vs exterior paint battle then? Neither, as each performs perfectly in their intended environment.


What Do I Do if I Accidentally Used Exterior Paint Inside?

Have you accidentally used exterior paint inside? Well, while this can make one feel a bit silly, it’s nothing to worry about. Firstly, determine whether the exterior paint you used is water-based or oil-based. If the paint is oil-based. If your paint is oil-based, use some thinner or mineral spirits to loosen it up, if your paint is water-based, you should be able to use some rubbing alcohol and some elbow grease to remove it if the paint has already dried.


What Can You Add to Interior Paint to Make It Suitable for Exterior Use?

While there is no magical additive to allow you to make interior paint exterior paint, you can mix some interior paint and exterior paint together to make the overall substance more durable. If you do, ensure that you mix your paint well and remove any lumps before attempting to apply it.