The Pirns, Former High Tweed Mill, King Street

High Tweed Mill, also known as the Former High Tweed Mill, is a pair of rectangular-plan former mill buildings from the later 19th century, now converted into housing. The buildings are positioned at an angle to each other, aligning with King Street. The front elevations feature squared whin rubble, while the rear and sides are made of roughly-coursed rubble. Droved sandstone dressings add detail to the structure.

The former spinning mill, built around 1860, is three stories tall with an attic and has nine bays. It features projecting piend-roofed stair towers on both the front and rear elevations. The building has a single slate roof with modern rooflights and a gable-stack located on the northwest side.

The Pirns, the former weaving mill constructed around 1875, is also three stories high and has ten bays, with a gabled stair tower at the rear. It has a slate M-roof and cast iron tie plates at the floor levels.

The top-hung timber windows enhance the character of the buildings. Access to the interiors was not possible during the resurvey in 2005, but prior to conversion, the interiors included timber cross beams supported by cast iron columns.