"Hatbanding" describes a coating with an excessively heavy textured look.
What Causes It?
When you use a brush, it can occur with excessive cutting in of walls, corners, trim, and ceiling areas.
It can also occur when you use a nap roller cover that
is too long, which will produce a heavily textured look compared to brush-applied cut-in areas.
Hatbanding also can occur when you apply a wet finish coat over areas that are already dry.
How to Solve It
To prevent hatbanding, use a technique called feather-edge brushing, which will leave a coat of paint of about the same thickness as the coat you apply later with a roller.
With feather-edge brushing, your brush should leave a thin, feathered edge of paint that will merge into a smooth layer of new paint.
When you use a roller on smooth surfaces such as drywall, use roller covers ranging from ¼-inch to ½-inch nap, depending on the sheen of your finish coat.
When using a roller on surfaces that have already been cut in with a brush, turn your roller sideways - about 90 degrees - and apply a thin coat of finish on the previously cut-in areas.
Make sure to roll your finished coat back into the drying paint. Remember also that properly priming drywall will help prevent hatbanding from occurring.
Note: Images provided by The Rohm & Hass Paint Quality Institute.