Dundas Castle Keep, Dundas Castle

Dundas Castle Keep is a 4-storey L-plan tower house built around 1416. It is constructed of random rubble with long and short quoins, and some areas feature harl pointing. The castle has a corbelled and crenellated ashlar parapet from the 16th century, complete with bartizans at the external angles. A new wing was added to the northwest angle after a license was granted in 1424, which created a stepped T-plan frontage to the south and an L-plan frontage to the north. The new wing features chamfered arrises at the external angles from the second floor upwards.

On the south elevation, there are three bays. The central bay has regular fenestration at the first and second floors, while the recessed bay to the right also has regular fenestration at those levels and the recessed bay to the left has irregular fenestration at the second and third floors. A timber door with an iron yett is located at the re-entrant angle on the right. There is a later addition on the ground floor to the left, which has been used as a carriage house.

The west elevation consists of two bays, featuring a Tudor-arched window at the ground floor with ashlar sandstone dressings in the advanced bay to the left. The recessed bay to the right has irregular fenestration at the first and second floors, while the right side has a blank wall at the ground floor with a Tudor arch linking to the stable court.

The north elevation has three bays, with irregular fenestration at the first, second, and third floors of the advanced bay to the right, and irregular fenestration at the ground, first, and second floors of the bays to the left. A later addition at the northwest angle connects the keep with the mansion, which includes a single-storey lean-to building.

The keep features slit windows, some of which have been enlarged into more regular windows. There are small-pane timber windows in sash and case and casement/fixed styles. The roof is a platform style with a single lookout turret, and there is a graded grey slate roof over the water tank. Water spouts are irregularly spaced at the top of the corbel members, and Dundas shields are displayed on the outer faces of the bartizans. The building has cast-iron rainwater goods.

Inside, the keep is mainly barrel-vaulted and contains large fireplaces. The fireplace in the first-floor hall has angle supports that resist arch-thrusts. The interior was significantly altered after around 1820 when it was used as a distillery. A detached 17th-century mansion was removed, and extensive enclosing curtain walls were built, at least partly on the line of the previous walls.