Can You Use Exterior Paint Inside (or Interior Outside?)

Exterior paints are known to be very durable and weather-resistant. But can you use exterior paint inside?

It’s generally not advised to use exterior paints indoors. This is because exterior paints are usually formulated with resins and chemicals that can prove toxic indoors especially if used in an enclosed or poorly ventilated room.

Also, exterior paints are designed with weather-resistant additives like UV blockers that will be of no use indoors. Since it’s not advised to use exterior paints indoors, can you use interior paint outside? Let’s find out.

Can You Use Interior Paint Outside?

Can You Use Interior Paint Outside?

You can use interior paints outside but only on an exterior surface that will be shielded from the elements. This means interior paints can only be used on outdoor surfaces that will not be exposed to UV rays, sunlight, rainfall, wind, or frost.

This is because interior paints are not formulated with weather-resistant additives. And, as such will fall off if exposed to such conditions. Interior paints are designed with two major features; beauty and strength.

Since the paint is commonly used indoors, the paint is formulated with more colorants to make the finish beautiful. The paint is also formulated to have improved strength to hold up to heavy foot traffic, weight, bumps, stains, and scratches. Both features make indoor paint great indoors but not outdoors.

If indoor paint is used outdoors, the paint will fail. You can only use indoor paint outdoors if the exterior surface to be painted will be shielded from the elements. For instance, if you want to paint a table to be used under a shed outdoors. Indoor paint can go on such a table because the table will be under a shed which will offer protection from the elements.

However, if you expose indoor paint to the elements, the finish can develop bubbles and lumps when exposed to heat. The finish can also become waterlogged and peel off if exposed to rainfall. The UV rays of the sun can cause discoloration and color fading. All of this will happen because the indoor paint is not designed with weather-resistant additives like exterior paints.

So to be on the safer side, never use indoor paint outside. Even items that will be shielded should be painted with exterior paint for maximum protection. Let’s have a comparison between exterior and interior paints to figure out their differences.

Interior Vs Exterior Paint

Here is a table to help you understand the differences between both types of paint:

 Interior PaintExterior Paint
Beauty and DesignVery GoodGood
Strength and DurabilityGoodGreat
Paint ChemicalsLowHigh
Weather ResistancePoorVery Good
Paint ApplicationEasyModerate

From the table above, you can see that interior paints are designed to beautify while exterior paints are designed to protect. Interior paints are formulated to reveal bright sheens and colorful finishes. While exterior paints are designed to be weather and moisture-resistant.

The attention to beauty and appearance is why interior paints have more colors and designs than exterior paints. Exterior paints however have more resins and paint chemicals.

Interior paints are also easier to apply than exterior paints since interior paints dry slower. So now that we know the differences between both types of paint, can we mix them? Let’s find out.

Can You Mix Exterior Paint With Interior Paint?

You can mix exterior and interior paints together but the paints must be of the same base. This means you can only mix interior water-based paint with exterior water-based paint. This is because if the paints have varying bases, it will ruin the viscosity (or thickness) and flow of the paints.

For instance, if you mix an oil-based enamel paint with water-based latex paint, the oils in the enamel will be separated from the water in the latex. This will lead to weak paint adhesion and peeling.

Also, if you mix interior and exterior paints, don’t use the mixture indoors regardless of the paint type. This is because the chemicals in the exterior paint will produce strong odor or fumes when used in enclosed areas.

It’s generally advised to allow a higher ratio of interior paints than exterior paints in the mixture to limit the possibility of toxic paint fumes.

Another thing to know is if you can use exterior paint over interior paint. Can you and what happens when you do? Let’s take a closer look.

Can You Use Exterior Paint Over Interior Paint?

Can You Use Exterior Paint Over Interior Paint?

Yes, you can use exterior paint over interior paints. Many paint professionals and manufacturing brands even advise it, especially for improved durability and weather resistance.

However, if you are to use exterior paint over interior paint, ensure the type of interior paint that is on the surface isn’t oil-based. This is because oil-based interior paints have a naturally glossy finish that will prevent good paint adhesion. So you’ll have to sand before painting over such interior paints.

Water-based interior paints however can be painted over with any type of exterior paint because the paint doesn’t have a natural gloss that can repel the exterior paint.

You should apply a paint primer on the interior paint before painting over it. Though exterior paints usually go over interior paints well, a few coats of paint primer will prevent bleed-through and improve paint adhesion.

It’s also not advised to put exterior paint over interior paint that is indoors. This is because the fumes and chemical odor that will be produced from the fresh exterior paint can prove very toxic in an enclosed environment.

So in simple terms, you can put exterior over interior paint but ensure both paints are compatible and this should only be done outdoors.

Can You Use Interior Paint Over Exterior Paint?

You can use interior paint over exterior paint. But, you shouldn’t because exterior paints usually have a top coat that will prevent paint bonding. Most exterior paints including the water-based versions are usually designed or coated with additives to produce a moisture-resistant top coat.

This top coat is to help the exterior paint thrive outdoors. But, this coat also prevents good paint adhesion because it is moisture-resistant. Since it is moisture-resistant, the interior paint will not adhere very well to the exterior coating.

The weak adhesion will make it easier for the paint coating to be easily affected by moisture, heat, and dust. Eventually, the interior paint will crack, peel, or blister off the surface.

However, you can use interior paint over exterior paint if you do enough prep work. You’ll need to scrape, sand, clean, and prime the exterior paint before you can apply interior paint over it. This way, you’ll scrape and sand off the exterior top coat. Since the top coat is off, the interior paint can now adhere properly to produce a strong finish.

Do you think it’s possible to turn interior paint into exterior paint? Let’s find out.

Can You Turn Interior Paint Into Exterior Paint?

You can’t turn interior paint into exterior paint but you can make interior paint have similar features to exterior paint. No matter how hard you try or what method you use, you can’t change interior paint to exterior paint. The paint formula will always be different.

Interior paint’s formula makes it more porous and less resistant to the elements. Exterior paint is the opposite. No matter what you do, you’ll always have some of the features of interior paint present.

However, you can make interior paint have similar features to exterior paint if you mix both paints in the correct ratio. This process is called thinning. You’ll need a higher ratio of exterior paint in the mixture.

Here are some questions commonly asked by DIYers like yourself about interior and exterior paints.

Will Interior Paint Last Outdoors?

Interior paints will not last outdoors except the paint is sealed with a top coat.

Can I Put Oil-Based Exterior Paint Over Water-Based Indoor Paint?

Yes, you can because indoor water-based paints can be painted over with both oil-based and water-based exterior paints.

Related Read: Can You Use Wall Paint on Ceiling?

Final Words

Overall, interior paint is suited for indoor and decorative uses. While exterior paint is suited to outdoor and protective needs.

As long as you remember this, you won’t have any issues with applying both paints. Also, you can mix both paints but it’s not a good idea to do so for indoor uses.

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