The castle is a three-storey L-plan building with an attic.[5] It has circular bartizans on the second-storey level in the south east and north west angles.[3] The entrance was originally in the interior angle in the north wall, adjacent to the circular stair turret. About 1610 it was extensively remodelled with a new doorway in the western face that opened on a porch; two finialed pediments over the doorway display the monograms of Sir Archibald Stirling of Keir and his wife Dame Grizel (née Ross) Stirling. A new strait staircase that ran along the western wall was added to connect the ground and first storeys. The northern wing was extended to include a new kitchen on the ground floor and the old kitchen was partitioned.[6] A new west range of two-storey offices was also added, although this was later replaced in the late 19th century with a long single-storey wing, probably incorporating parts of the previous structure in its southern wall, with one block projecting south east.[3]
