In general, a 12' x 12' room can be finished in around 5 or 6 hours. A 12,000-square-foot house may have it's interior painted in less than a week on a far larger scale. This won't always be the case with every interior paint job as there are many variables to consider. For each interior painting project, the experts at Andrew Picone Painting & Paperhanging pay close attention to the smaller details and can provide you with a specific timeline for your project.