When to Use a Flat Finish
A flat finish minimizes imperfections in the painted surface. Light scatters evenly over it to give the illusion of smoothness, even on patched drywall and uneven textures. The finish reduces glare from various light sources, such as ceiling fixtures and large windows. These reasons make it an excellent choice for walls and ceilings in formal living areas, dining rooms, bedrooms for adults, and even closets.
Its cover-all ability makes it ideal for beginning painters, since it hides stray brush marks. Touch up is also easier with flat paint, since new patches blend in better with the existing paint. It is easier to repaint than higher gloss finishes, since it doesn't require sanding.
Things to Keep in Mind
Be aware that flat paint is not as durable as glossy ones. Stray marks and scuffs can show up quickly, and scrubbing to clean them can destroy the finish. You would do well in painting most of the house in a flat finish, and reserve gloss alternatives for high traffic areas. Flat paint colors are also not as vibrant, so if your project involves a brilliant color, you might consider a satin or semi-gloss finish instead.