The castle is a fortified house (fortalice) designed on a Z-plan running east-west, with square towers at the north-west and south-east corners, each containing a circular staircase. "Externally, Fordell remains pretty much as it was when first built, a simply treated, dignified dwelling, on which corbelled turetts and projections, happily grouped, relieve the plane wall-surfaces below." Fordell Castle is the only example of a tower house with two main stairs, each with its own door to the outside. The entrance is at the foot of the north stair tower and is through a studded door with a metal grate (yett) behind. It gives access to a vestibule. Stairs lead down to three vaulted basement chambers. The western chamber included stocks and branks, but the room has since been converted to a wine cellar. A rogue's collar or jougs hangs near the front entrance to the castle.