The Difference between Interior and Exterior paints

Exterior and Interior paints in some cases share similar polymers and pigments; however they need to perform different jobs. Exterior paint needs to be hardy enough to withstand cold winds, storms, sand, hail and blazing sunshine. Interior paint isn’t faced with these conditions but does need to hold its own against scuffing, marking and regular cleaning. It’s therefore natural that each type of paint is created with specific formulations.

The Difference is in the Polymer

The type of polymer in your paint is the main differentiator between indoor and outdoor paints.  The polymer is the material in the coating that sticks to the surface.  In exterior paints, the polymer is often softer and more flexible which allows the paints to move as the substrate expands and contracts in different temperature and weather conditions.  This assists with preventing cracking, flaking and peeling in exterior paints.

Interior paints can often use a harder or less flexible polymer, which make it less prone to damage from scuffing and washing and easier to clean.

Indoor and outdoor paints

The differences in polymer and other materials means that it is mostly not advised to use exterior paints indoors and vice-versa.  Interior paints will not in many circumstances be able to withstand the outdoor environment and substrates and exterior paints may be too soft to withstand the wear and tear and marking that interior paints can.

From a health perspective, many exterior paints are not low VOC compared to interior paints.  Small amounts of solvent are added to exterior paints so that the paint does not dry to quickly and form a poor paint film when applied in warm and windy conditions. Outside these solvents will evaporate harmlessly into the air, inside they can result in a lingering odour that some people may find offensive.

Ask the Experts

If you’re in doubt about which paint to use, please get in touch with us at Pelham Painters in Hobart. We’re always available to assist and provide the information you need.

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