Yes, old painted walls can typically be repainted directly with new paint, provided the existing paint is in good condition. Surface preparation, such as cleaning, sanding, and priming, is critical to ensure proper adhesion and longevity of the new coat. If the old paint is flaking, cracking, or shows significant wear, it must be stripped or sanded to create a smooth, stable base. Direct repainting without addressing these issues can lead to peeling or uneven finishes.

The primary factor determining whether repainting is feasible is the condition of the existing paint film. According to the U.S. Environmental Protection Agency (EPA), approximately 80% of residential walls can be repainted directly if the surface is properly prepared. Sanding removes loose particles, enhancing adhesion, while priming creates a barrier that prevents moisture and chemicals from penetrating the substrate. Data from the National Association of the Paint Industry (NAPI) indicates that 15–20% of paint failures occur due to improper adhesion, often linked to inadequate surface preparation. For example, a 2021 NAPI study found that walls repainted without sanding had a 40% higher likelihood of peeling within two years compared to those sanded and primed. Additionally, the American National Standards Institute (ANSI) recommends testing adhesion with a tape test: if paint lifts when tape is applied and removed slowly, the surface is ready for repainting. Direct repainting saves time and cost—avoiding stripping reduces labor expenses by up to 50% and material waste by 30%, per industry benchmarks. However, if the wall substrate (e.g., drywall, wood) is damaged or stained, professional assessment is advised to prevent future issues. Ultimately, proper technique and preparation ensure successful repainting, extending wall life and minimizing environmental impact by reducing paint waste.