1. The Paint Formula: Made for the Elements

The most significant difference between interior and exterior painting is the paint formula. Exterior paints are specifically designed to withstand harsh outdoor conditions. They contain additional additives like UV protection, water resistance, and mildew inhibitors to combat elements like rain, wind, and sunlight. Exterior paints must be durable enough to prevent fading, peeling, and cracking over time.

On the other hand, interior paints are formulated with durability in mind for indoor environments. These paints are designed to withstand cleaning, scuffing, and general wear without containing the harsh chemicals found in exterior paint. Interior paints also tend to have lower levels of VOCs (Volatile Organic Compounds), making them safer for indoor air quality. Choosing the right paint for the environment is critical—using interior paint outdoors will cause it to fade and fail quickly, while using exterior paint indoors may release unwanted fumes.

2. Surface Preparation: Indoor vs. Outdoor Challenges

The preparation work for interior and exterior painting also varies. For interior walls, the preparation process usually involves filling in holes, sanding, cleaning the surface, and applying primer. Since interior walls aren’t exposed to the same level of wear as exterior surfaces, the focus is on creating a smooth, clean surface to achieve a polished look.

Exterior painting requires more rigorous preparation to protect the surface from the elements. This typically includes power washing to remove dirt, mold, and loose paint, scraping away old paint, sanding rough areas, and applying primers designed to bond with outdoor surfaces. These steps are essential to ensure the new paint adheres correctly and provides long-lasting protection. Exterior walls, made from materials like wood, brick, or stucco, require careful attention to prevent moisture damage or other issues.