50-54 West Princes Street, Helensburgh

20-22 Colquhoun Square in Helensburgh is a three-storey, symmetrical L-plan tenement building, possibly designed by William Tait in the later 19th century. The building features classical detailing and includes shops on the ground floor that face Colquhoun Square and Prince's Street East. The exterior is rendered and painted at the ground level, with ashlar dressings. A continuous dentilled cornice runs between the ground and first floors, supported by consoles at the advanced bays on the Colquhoun Square elevation. The first-floor windows are corniced, and there is a moulded cill course, eaves course, and a cornice above. The advanced bays on the Colquhoun Square side have a corbelled dentilled and modillioned cornice, with pilaster-mullioned windows at the first floor.

On the east elevation facing Colquhoun Square, there is a 19-bay semi-circular-headed arcade at the ground level, with 13 bays above. The central section has seven slightly advanced and taller bays, featuring a pend with an iron gate in the centre, while three bays to the right are blocked as windows. There is a doorway flanked by windows to the left. The first, third, and fourth bays on the right have doorways, with windows in the remaining bays, although the fourth bay on the left is blinded. The advanced centerpiece has five closely spaced windows on the first and second floors, with the centre bays blinded. Full-height canted oriels flank this centerpiece, and there are two windows on either side of it on the first and second floors, with full-height canted windows in the outer bays.

The south elevation facing Prince's Street West features five shops at the ground level, including the original shop front for No. 46 (General Hairdresser), which has two-leaf panelled doors on the left and a large plate glass window on the right, along with a deep fascia. The centre has three slightly advanced bays, each with a window on the first and second floors. There are five closely spaced windows flanking the centre bays on both the first and second floors, with windows in the two end bays as well. Most of the windows are four-pane sash and case windows, and the building has a grey slate roof with coped and rendered stacks.

Inside, at No. 48 Prince's Street West (Central Pharmacy), the interior retains original furnishings, including timber counters and shelving.