19B Montrose Street East, 19, 19A, Helensburgh

19B Montrose Street East, along with 19 and 19A in Helensburgh, is a villa built in the later 19th century, with an addition by architect William Leiper in 1893. The building is two stories tall and features three bays, showcasing classical details. To the left (west) is a two-story, single-bay wing that is recessed, while to the right (east) is a single-story and attic wing added in 1893, also recessed.

The structure is made of squared, stugged, and snecked sandstone with ashlar dressings. The ground level of the 1893 addition is finished in cream rubble, topped by a jettied attic storey that is hung with red tiles. The villa has a base course, chamfered arrises, and ashlar mullioned windows, along with overhanging eaves that are supported by brackets.

On the south elevation, which serves as the entrance, there is a pilastered doorway at the center with two-leaf panelled doors. Flanking this are canted windows that have a bracketted cornice and a lead half-pitched roof. Above, at the first floor, there is a central window with bipartite windows on either side. The two-story wing to the left has a window at both the ground and first floors.

The east wing, designed by William Leiper, features a south elevation with a central window at the ground level, and a canted oriel at the southeast angle that is supported by timber consoles on stone corbels and topped with a low conical roof and finial. The east elevation has a doorway on the outer left, with a window in the center and another to the right. At the first floor, there are three windows, including a squared oriel on the outer right, also supported by timber consoles and stone corbels.

The villa has plate glass sash and case windows, with small-pane casement windows in the east wing. The roof is covered in grey slate, featuring two round-headed dormers on the south elevation and end stacks, along with a tall wallhead stack at the rear of the east wing.