Disclosed is an apparatus and method for the uniform drying of boards, such as gypsum wallboards. The apparatus includes a dryer through which a series of boards are conveyed in a side-by-side relationship. While in the dryer, heated air is delivered over the boards via a series of separate air channels. A bypass duct delivers a portion of or a totality of unreheated air to the outermost channels where the cooler air displaces a volume of the warmer air. As a result, the air in the outermost channels is cooler than the air in the interior channels. Air from the outermost channels is then directed over the exposed longitudinal edges of the boards.