Can My Leftover Interior Paint be Used to Paint the Kids Cubby House Outside?

A bit about paint

A can of paint contains a soup of ingredients that results in a hard, protective coating for wood, metal, concrete, drywall and other surfaces. While the chemicals that form the coating are in the can, they are suspended in a solvent that evaporates after the paint has been applied. These coating chemicals include polymers, which actually form the surface; binders, which prevent it from separating and provide the ability to adhere to the painted surface, and pigments for colour. Specific paint types also usually contain additives to regulate drying time, improve weather resistance (like waterproof paint does), control mildew and keep the pigment uniformly distributed in the paint solution.

Interior paint is made to be scrubbed, resist staining, and allow cleaning. Exterior paints are made to combat against fading and mildew. When starting a painting project, it’s important to know the differences between the two and choose the right paint.

So, what’s the difference?

While there can be many subtle differences, the primary difference between interior and exterior paints is in their choice of resin, which is what binds the pigment to the surface. In an exterior paint, it is important that the paint can survive temperature changes and being exposed to moisture. Exterior paint also must be tougher and resist peeling, chipping, and fading from sunlight. For these reasons, the resins used in binding exterior paints must be softer.

For interior paint where temperature is not a problem, the binding resins are more rigid, which cuts down on scuffing and smearing.

Another big difference between interior and exterior paint is the flexibility. Interior paint does not have to deal with drastic temperature changes. If you use interior paint on the cubbyhouse odds are after a summer the interior paint (even if you put a coat over the top) will get very brittle and begin to crack which will then flake and peel as it doesn’t have the flexibly properties that exterior paint has.

What you should use for your project

While it may be tempting to use your leftover interior paint the end result will not last as long or look as good then if you were to use an exterior paint.

We recommend first using a suitable undercoat to prime the cubbyhouse like Zinsser Cover Stain to seal the wood and prepare the surface or a specialised wood stain you can easily get in any paint shop. Once dry you can then apply the top coat, exterior paint like Dulux Weathershield or Berger Solarscreen would be the best products to use as they provide exceptional coverage, tough flexible finish and will not blister, flake or peel. They also have excellent durability which allows the paint to expand and contract with climate changes.

As always, for the best advice regarding products and application we recommend you contact your nearest Inspirations Paint store.