Adding the final touches to your home usually entails applying a coat of paint to the exterior walls. We have noted that many confuse different paint variants and believe them to have the same effect. Indoor and outdoor paints are usually taken to be distinct, but can you swap one for the other in a pinch?
Paint meant for indoor use lacks many qualities that would make it suitable for outdoor use. It is too runny to adhere to exterior walls, and it also doesn’t possess sufficient weatherproofing to make it resistant to rain, snow and sunshine. You might be able to use it if you add several layers, but that will add unnecessary hours to your paint job.
That’s not to say that indoor paint isn’t durable. It’s just designed to resist a different type of deterioration, such as scuffing from foot traffic. In this article, we will describe major factors that make indoor paint a lackluster performer for exterior walls. You will also learn how to extend the lifespan of indoor paint if you want to use it outside.
Does Interior Paint Work For Exterior Projects?
If you have ever tried to use interior paint outdoors, you’d immediately see why it’s not a good idea. For one thing, the thinness of the paint makes it likely that multiple coats would be required.
Paint labelled for exterior use, on the other hand, is usually thick enough that one or two coats would do the trick. The loose consistency of indoor paint also makes it patchy, giving it an unfinished or amateur look.
The weather can also do a real number on paint that was not made to endure it. You will notice indoor paint flaking or chipping off if you use it on exterior surfaces. Humidity and moisture can cause bubbling on the paint’s surface.
This can exacerbate the damage and force you to redo the paintjob. It also has the added disadvantage of not lasting as long as outdoor paint, so you’d have repaint your house more frequently if you use indoor paints.
The lack of viscosity also makes indoor paint prone to running. That can occur if it rains, but you might also have a sprinkler system that could cause some weeping in the paint coating. Washing the walls could also become excessively difficult.
Outdoor paint has a higher resistance to dirt, so cleaning it won’t be a frequent requirement anyway. Additionally, it possesses powerful mildew resistant properties, as well as resistance to color fading UV light.
All of this makes it abundantly clear that using indoor paint for outward facing surfaces just isn’t worth the trouble. Some indoor paints use latex in their formulas. They are thicker and therefore more resistant to weather related degradation. They still can’t match up to the results that outdoor paints can provide, though, so try to avoid them.
7 Reasons Why Using Interior Paint Outside is a Bad Idea
- Water damage
Perhaps the most significant disadvantage of using interior paint in exterior environments is its susceptibility to water damage. This can come in many forms. Rainfall is a prime culprit that can wash away the paint. You may also see some chipping if the pain is exposed to humidity.
That is especially common in areas with high humidity levels during summer months. Winter isn’t an exception either, since frost and snow can be even more disastrous due the added damage from the frigid temperatures.
If you take good care of your lawn, you probably leave the sprinklers on for a while. Water from the sprinklers can splash onto the paint and ruin its look. Finally, simple cleaning chores like window washing can also lead to water dripping down which can leave unsightly streaks in the paint.
- UV resistance
Exterior paint is formulated with an assortment of thickening agents and compounds which serve a wide range of purposes. Foremost among them is UV resistance. Sunlight can help to bake the paint layer in, but it can have a detrimental impact on interior paint.
Over time, this heat will create cracks in the paint and subsequently cause it to chip off. That’s because exterior paint can withstand the structural changes caused by heat, whereas interior paint will split open under similar conditions.
It’s not just the heat that will do this damage. Rather, the UV radiation from the sun’s rays can also cause a significant deterioration of the color quality. If you expose indoor paints to too much sunlight, you’d find that the colors will fade. That is not ideal for the exterior of your home. It can give it a worn out appearance that might negatively influence its price on the market.
- Mildew
Home owners can have quite a negative response to mildew growth. That’s not usually an issue for indoor paint as long as it is applied in areas it was made for. You will likely turn on heaters and dehumidifiers that can mitigate mold spread. These options aren’t available outdoors, so when the winter months roll around you might find yourself faced with a fast spreading mildew outbreak.
Mildewcides and other antibacterial compounds are common additions to exterior paint. They are noticeably absent from indoor variants. Using mold killing compounds can add more tasks to your already packed schedule, so it’s best to avoid them.
- More expensive
An oft understated factor at play with interior paint is how expensive it is. It can be up to ten to twenty percent costlier than paints optimized for external environments, and that’s if you use the same quantity as you would with the right kind of paint. Chances are that you would need to add layer after layer which can drive the price up even further.
There’s also the ever present risk of accelerated degradation with interior paints if used improperly. They rarely last beyond a couple years, with wind erosion and excess heat further muddying up the waters.
That will ramp up your repainting timeline and force you to buy a whole new set of paint cans which can lead to serious cost overruns in due course. The confluence of these expenses can make your paintjob far more expensive than it needs to be, and you don’t get much value for the money you spend either.
- Time consuming
If you want to soldier on and finish off that can of interior paint by touching up outside walls, you’ll have a long and hard road ahead of you. Not only will you need to paint over the layers at least four to five times, you’d also have wait for each layer to dry. Sanding the paint down before adding a new layer is also important, otherwise the coating may end up lumpy or uneven.
Using clear coat sealant is another necessity for indoor paints. They can boost the durability of the paint by shielding it from the harsh elements, but drying and curing yet again delay completion.
A three hour job may end up taking days to finish if the wrong type of paint is used. Save yourself some time by skipping the indoor paint and getting something better suited to what the outward facing parts of your home need.
Another factor that may cause delays is the extended drying time. Interior paints are made to dry in internal environments with all of their climate control settings. Using them in outdoor areas will not be conducive to speedy drying. These delays may seem insignificant individually, but they can add up to a lot when viewed in aggregate.
- Loose texture
This is a relatively lowkey disadvantage, but it is pertinent nonetheless. Since it is meant for bedrooms, living rooms and other spaces that don’t require thick coats, interior paint is generally quite loose. The lack of viscosity can be a real nightmare when you apply it to the granular surface of your exterior walls.
The softness of the paint also diminishes its adhesive qualities. Extremely careful application may give you a smooth finish, but the slightest deviation can create prominent brush strokes. Dripping is another inevitability caused by the texture. Thickening the paint up can help somewhat, but why would you do that when there are readymade paints that are already thick enough?
- Dirt resistance
Though interior paints are designed for easy cleaning, that only applies to indoor spaces. When used outdoors, they can be a veritable nuisance from a cleaning perspective. Firstly, a lot of the dust particles in the surrounding air would cling to the interior paint before it gets the chance to dry.
They can also be challenging to clean once dried and cured. You can clean the coating with a bit of soapy water, but the amount of dirt it collects outdoors is so great that scrubbing may be necessary. Unfortunately, scrubbing could strip the paint off and reveal the bare wall beneath.
- Weathering
We have mentioned sunlight and the rain, but did you know that wind erosion is also a weather related factor that can degrade interior paint? You won’t get much wind inside your home, but it’s a constant presence in the great outdoors. Abrasive particulate matter in the wind can brush up against the paint.
Exterior paint can hold its own without getting worn away, but interior paint simply isn’t up the task. Use it with caution outdoors. A particularly windy day may dim the brightness of the paint colors and render them uneven to boot.
Can You Make Interior Paint Used Outside Last Longer?
The disadvantages of using inside paint outdoors are undeniable, but you may still want to use it. If you have a can of indoor paint, you might want to try applying it to the outer walls. This would save you a trip to the store and help you avoid blowing cash on a new can of paint.
Alternatively, you may have not been aware of the incompatibility of indoor paint for outdoor areas before using it. Don’t worry if you made this mistake, though. There are a few ways to make interior paint last longer if used outside.
One thing that you can do is to add a layer of mildewcide. This can compensate for the lack of mildew resistance in indoor paint types. It’s not a perfect fix, but it can make up for your lack of judgement by making the paint less prone to mold build up which can spread rapidly.
Alternatively, consider using primer or sealant to lock the paint in. This creates an added layer of protection from moisture and UV radiation. Again, having to apply sealant to your finished paint coat will add a few hours to your project timeline. That’s a worthy exchange because it can save you a lot of grief down the line when your paint begins to fade or crumble.
There’s also nothing wrong with applying a final coating of water based acrylic paint to finish the job. That will compensate for the fragility of the underlying indoor paint layer. It’s also easier to apply than primer, and it takes far less time to cure.
Consider thickening the indoor paint if you want to be conservative about spending money. Adding clay or a bonding agent can increase its longevity somewhat.
Verdict
Interior paint is more expensive than its exterior counterpart. This leads many to assume that it is superior. Unfortunately, almost everyone comes to regret using interior paint for walls that are exposed to the weather. Color fading, chipping and bubbling are all common complaints. Try to buy both paint types when sprucing up your home. That will help you cover all your bases.