Answer: There is a major safety hazard here, even if your old cans of paint are still good, you will not be saving money trying to use exterior paint inside. You’ll likely get sick or at least collect toxins in your body. Plus exterior paints are softer to expand and contract outside: not the best for interior painting.
Add to any paint: If you are looking for a way to keep mildew from growing in a high moisture area, add a mildew-scide to your interior paint. It’s not expensive at all.
Mold-proof paint: Need paint for high moisture areas: Use Zinsser Mold and Mildew-Proof Interior Paint.
Our tool page for every basic professional painter’s tools at the best prices we can find
Can You Use Old Paint? Yes, If Your Paint Passes a 3-Question Test
What’s the difference?
The difference between interior and exterior paint is that exterior paint contains a lot more toxic chemicals. Additives that make exterior paint softer, so it can flex in the extremes of outdoor existence. That is why it is not always a good idea to use exterior paint inside.
Exterior paint contains fungicides, mildewcides, and UV blockers that are toxic anywhere. Using exterior paints indoors will expose you and your family to harmful chemicals—if you use exterior paint inside, that is forever.
If you can’t use it, what can you do?
There are lots of great community recycling programs, (find yours here)…but if the old paint is beyond help…
If you cannot save all that leftover exterior paint for the next time you need it, there is a product to quickly turn old paint into a solid for safe disposal. Paint in landfills leaks and pollutes our drinking water. These powder packets treat 12 gallons.
Tempted to be using exterior paint inside? You will be hurting your real bottom line: your lifespan!
Once in a blue moon: “Can you use exterior paints indoors?”—Yes if…
One time we can say that you can use exterior paints inside is if the area is a storage shed or other outdoor building (pool cabana or detached garage) where nobody sleeps. In that case, using exterior paint indoors would be a great way to use up the old paint.
Just stay away from the area until the paint cures (off-gases), which takes some weeks in the summer, or months when it’s cool out. Doing this, if you don’t have good ventilation, use a respirator. We simplified the complex filters/masks of those products.
There are alternatives to using exterior paint inside. Reduced-cost, high-quality paint is available at most paint shops in the form of ‘mis-tints’. These are gallons of paint that came out slightly wrong. You just have to accept the colors available on the store shelf at the time. Look for bathroom paints, especially Zinsser Mold and Mildew-Proof is very reasonably priced.
Bottom line regarding the question ‘can you use exterior paint inside’?
Using exterior paint indoors is a bad idea, but only in outdoor sheds or a pool house etc, can you use exterior paint inside. So to my reader who emailed us asking, “can I use exterior paint indoors?”, please don’t try to save on paint this way.
Related: be sure to read our complete list of every painting tool you could ever need.
Did we leave anything out? Let us know in the comments below.