12 Princes Street West, Helensburgh

10 Princes Street West in Helensburgh is a three-storey, five-bay tenement building designed in the Jacobean style by W Hunter McNab in 1911. The south elevation features cream sandstone ashlar and includes a cornice between the ground and first floors, as well as cill and eaves courses. The building has chamfered and moulded arrises, transomed windows, and mullioned and transomed canted windows on the first floor, with roll-moulded surrounds for the second-floor windows.

The south elevation, facing Princes Street, has a central pilastered entrance with a round-arched doorway that includes a keystone and twin round-arched lights in a panel above. This entrance is flanked by modern shops. Above the entrance, there is an ashlar balcony. The flanking windows are pilastered, with a decorative pediment on the central window set in a tall wallhead stack that breaks the eaves. There are also pilastered windows breaking the eaves on both the right and left sides. The outer left bay is gabled and finialled, featuring full-height canted oriel windows set in a panel with an ashlar half-pitched roof and a crenellated parapet. A mirror image of this bay is found on the outer right, which has banded colonnettes flanking the second-floor window, topped by a round-headed open pediment that cradles a niche surmounted by an ornate finial. An octagonal corniced wallhead stack is located at the southeast angle.

The building exhibits a variety of glazing patterns in its sash and case windows, with plate glass in the lower sashes, four-pane upper sashes on the first floor, and six-pane lower sashes with four-pane upper sashes on the second floor. The roof is covered with grey slate, and the original rainwater goods are still in place.