Outbuilding, 20-21 Ardbeg Road, Rothesay, Bute

20-21 Ardbeg Road is a symmetrical, two-storey, three-bay flatted house built in the earlier to mid 19th century, with mid 20th century alterations. It is designed in a plain classical style and forms one of a pair of similar buildings. The house is accessed from both the front and rear. It features painted rubble sandstone with raised, painted margins and painted strip quoins. The building has a raised base course, a lintel course beneath corniced eaves, a pilastered doorpiece, and projecting cills. The rear has harl-pointed random rubble with raised, painted margins and a part-rendered exterior stair. There is also a single-storey, four-bay outbuilding at the rear, which is harl-pointed.

On the east elevation, there are steps leading to a part-glazed, two-leaf timber panelled door at the center of the ground floor, topped by an opaque-glazed fanlight. The door is framed by a corniced doorpiece with flanking pilasters, a plain frieze, a block pediment, and a raised keystone. The first floor has a single window at the center, with additional single windows in the outer bays on both floors. Above, there are three-light canted dormers.

The west elevation at the rear features a balustraded stair leading to the upper flat, offset to the left of center, with a single opening and a multi-paned fanlight. There are single windows in the remaining bays on both floors, along with piended single and tripartite dormers.

The building predominantly has replacement glazing and a graded grey slate roof with raised skews and corniced apex stacks at both the north and south ends, along with various circular cans.

The interior was not seen in 1996. The outbuilding has a three-light window in the penultimate bay to the outer right and boarded timber doors in the remaining bays. It has a grey slate roof and a harled, flat-roofed addition to the outer left.

The boundary wall along Ardbeg Road is a low coped random rubble wall with a replacement cast-iron pedestrian entry gate. There are corniced square-plan piers at the outer left and right, each topped with square caps.