Can You Use Interior Paint Outside?

What Stops You from Using Interior Paint Outside?

Every painting, whether interior or exterior, has a dedicated formula depending on its job. While indoor paints are made focusing on health issues and appearance and are easily manageable, outer paints focus on weather withstanding strength and durability. So, can you use interior paint outside?

In short, no! Both the paints differ in formulae, consistency, and purpose. So, even if you paint outside, whatever you have won’t hurt you. But it is going to disappoint you within a few days. Let’s get the fact clear.

Does Indoor Paint Differ from Outdoor Paint?

All acrylic and latex paints are water-based, whereas alkyds are oil-based. These are the two types of paints. Once outdoor paints used to be only oil-based paints. Now, both interior and exterior come with these two formulae.

Now which one to use depends on your intention. For example, oil-based were popular for being dirt resistant, but commonly used water-based latex is more durable.

Inside house paints are more resistant to dirt and physical damage. Outside paints are resistant to rain, wind, sun, and mildew. Moreover, it gives UV protection and safety from fungal growth and dampness over time.

Let’s see the differences on the following points:

Pigments

Pigments are responsible for the color of the paint. These colors can have multiple bases. Nowadays, these pigments have organic bases as it’s good for humans and the environment. But those organic pigments will start fading out if used outside.

Additives

Interior paints lack the additives used for withstanding the outer environment. Ask yourself what you wish from a paint used outside the house. The strong additives protecting you from adverse effects are hazardous to your health.

It’s the binder that combines the color components. Unlike interior, exterior paints need a stronger internal bond and adhesion with the wall. Cracking and chalking are a result of a weak paint bond.

Exterior wall deals with moisture control, as so the paint on it. Interiors walls deal with abrasion, which exterior walls don’t need to deal with.

Chemicals

VOCs are the volatile organic compounds used as solvents in many water-based paints. It’s responsible for many health issues like headaches, dizziness, and liver and respiratory disease. In the worst case, it can act as a catalyst for cancer.

Ever wonder why such threatening chemicals are used?

The solvent is a medium for transferring the paint from the container to the base and continuing the paint flow as well.

Outer walls need a thicker layer with better adhesion. Hence, it has a higher level of VOCs that is released into the air with time. According to the environmental protection agency, it’s suggested to look for interior paint having zero-to-no VOCs. However, outer paints do not always meet such requirements of no VOCs.

So, it’s a big “NO” if you are going to use exterior paint inside. This is a noticeable difference between the two paints.

What Happens If I Use Interior Paint Outside?

The purpose of using exterior paint won’t be met if replaced by interior paint. The internal paints aren’t supposed to be UV-resistant, dirt, and crack-resistant. More importantly, the outdoor have chemicals to withstand adverse weather.

Let’s know why indoor paint and outdoor paint can’t be interchanged:

Fade

Interior paints aren’t fade resistant as they are not exposed to sunlight, whereas outside paints need to be fade resistant. If internal paints are used outside, they will start to fade over time.

Resin

Rigid resins are used for internal cases as the indoor walls don’t have to deal with temperature fluctuations. Scuff can’t damage indoor paint easily while cleaning or brushing. Outdoor paints are prone to scratches and scuffing,

Unlike internal paints, external paints tend to be more rigid. On the other hand, the exterior walls have to deal with drastic temperature changes due to exposure to UV radiation and moisture. It goes through continuous expansion and contraction.

To resist peeling, outdoor paints have to be flexible instead of rigid like the interior.

Water-Proof

Indoor paints are washable, whereas outdoor surface demands water-proof paint.

What Happens If I Use Exterior Paint Inside?

It’s pretty easy to think that tougher outdoor paints might be more durable indoors, but that’s not the case. To your surprise, it’s more scuff and scratch, which are unnoticeable while used outside.

“Using indoor paint outside is a waste but using outdoor paint inside is a threat”- Let’s break it down.

Curing

External paints cannot cure without direct sun exposure, whereas interior paints don’t need it.

The reason is the presence of pesticides and fungicides in the external paint. That’s why you should never use exterior paint inside of your house.

Outgassing

Paints tend to outgas after application till it dries completely. Indoor paints are too delicate to outgas, so they are safe for your house. Outdoor paints have added resins for durability that result in outgassing. The gassing stops within 48-hours but continues up to years in little amount.

So, avoid using external paints inside the house.

VOCs

As discussed above, it’s the volatile compounds that can cause several health issues, even cancer. It’s strongly suggested to use indoor paints with low to zero VOCs. Outdoor paints have a high level of VOCs.

Can You Use Interior Paint on an Exterior Door?

Any front doors with interior grade paint can be painted again as they are sealed from elements. While using the same paint on the exterior, ensure the door has protection from the storm door or glass door. Or else, the color may chip, fade or crack.

In case your outdoor has lousy old paint, sand the door’s wood.

What to Do If You Accidentally Used Interior Paint Outside?

Now that we have talked about what can be done and what’s not let’s talk about the accident. Let’s say you have accidentally used indoor paint outside. Now, how can you redo it?

At first, stop panicking. It won’t damage anything. You only need to bear in mind that it won’t last long. Soon, it will start to flake, fade and peel.

Solution

Sanding

Walls previously painted with high-gloss or glossy paint need smoothening before repainting. If the previous use of paint is water-based, fine-grit sandpaper is suitable for the job. As for oil-based paint, choose medium-grit sandpaper having 100 to 150-grit.

When the color starts wearing, give a hand sanding over the paint. After a proper sanding, all the lousy paint will fall apart.

Re-Prime

The surface is not ready for paint right after it is sanded. Re-priming the surface will give a base to the paint and will enhance adhesion.

Repaint

Repainting the surface is your final job. This time you don’t want to make the same mistake again. Use good outdoor paint for a long-lasting paint job.

Do you want to avoid such a hassle job?

Well, there is another way but quite irritating. If you are not late, quickly brush a layer of outdoor paint over the indoor paint. While applying, take off any peeled paint by sanding and re-prime before painting.

However, it’s better not to commit such a costly mistake.

What to Do If You Accidentally Used Exterior Paint Inside?

Accidental use of outdoor paint inside is more of a threat than a problem. It concerns about health issues of the family members. The possible solutions could be:

Ventilation

Outdoor paints out-gasses the most while drying. So, ensuring a well-ventilated room with proper airflow is a must.

Stay Away

Stay out of the room for a day and avoid entering the room as much as possible for weeks. If you live in a cold region or it’s cold season, the paint might take a few months to dry.

Sanding

In case you have used oil-based paint and want to repaint, sand the wall properly. Then you can reapply layers of interior paint.

How to Make Interior Paint into Exterior Paint?

You must have encountered the question – can adding any chemical to indoor paint turn it into outdoor paint? Well, you can seal indoor paints to make them last longer, but the paint won’t have all properties of the exterior paint. Though there are some possible solutions, you might want to know.

Hybrid Paints

Ever heard of hybrid paints? It’s a blend of acrylic resins and alkyd that can be used both indoors and outdoor. You can get hybrid paints easily in the market without calculating all the pros and cons of indoor-outdoor paints.

Feeling relieved? Wait, hybrid paints have their disadvantages.

Hybrid paints are convenient and fun to use if the project is smaller and inside rather than outside the house. You can’t expect the hybrid paint to give similar cracking, moisture, and mildew prevention as the conventional outdoor paints.

DIY Mixing

Many times, we are left with extra indoor paints that we want to utilize. In such cases, you might want to use it outdoor. Mixing both of them can be an experimental job. Now, you must be thinking – can we mix indoor and outdoor paints?

Paints differ in 4 components- binder, additive, solvent, and pigment. It’s necessary to match at least half of the components. If you are mixing paints of different brands, there is a 50-50 possibility of success. Perform a trial test before mixing the color.

Mixing colors having the same finish would be a hassle-free job. So, try to match them.

You probably don’t want to have lung diseases by painting outdoor paints inside. So, DIY mixing is for exterior surfaces.

Termination

Now, you know- can you use interior paint outside? Even if you are left out with extra indoor paints, you need to agree on the peculiarities of the result before using it outside.

Interchanging indoor and outdoor paints aren’t worth the hassle. You will be fixing it again after a short time. And if you have used outdoor paint inside, then it strongly concerns your health.

At last, it can be said that interchanging or mixing them isn’t a wise plan. However, if you have accidentally made such a huge mistake, there are ways to redo them. But that will also cause you time, energy, and money.

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