No. 13 and Attached Railings

No. 13 is a house, now converted into flats, built around 1786 with 20th-century additions. The front is made of limestone ashlar, while the exposed left flank wall and rear are constructed from rubble. It features a double pile parapeted mansard roof covered with Welsh slate, and the coped party wall has two stacks that have been rebuilt in reconstituted Bath stone on the left.

The building has three storeys, an attic, and a basement, with a two-window range. On the first floor, there are two plate glass sash windows with splayed reveals. The second floor has two six-over-six sash windows, also with splayed reveals. The ground floor includes one plate glass horned sash window with a splayed reveal and stone sill on the left, and on the right, a six-panel door with flush, fielded, and glazed panels in a plain reveal. There is a small single-pane sash window to the right of the door, and the pennant paved crossover is flush with the pavement, featuring a cast iron footscraper. The basement has a six-over-six sash window in a plain reveal with a stone sill, and the crossover is partially infilled below with ashlar and a timber screen, along with 20th-century area steps. The roof has a triple dormer with two-over-two sash windows.

Additional architectural details include a band course over the ground floor, a weathered sill band for the first and second floors, a modillion eaves cornice, and a coped parapet that continues with No. 14 Portland Place. The rear elevation features Venetian windows with glazing bar sashes on the first and second floors, three similarly grouped windows with glazing bar sashes on the second floor's center and right, and a small 20th-century extension above the ground basement. The double dormer has 20th-century windows, and there is a lead hopperhead at the eaves on the left.

The property includes attached wrought iron railings and a gate with urn tops and an urn finial on the right, set on painted limestone bases. The history of the building is linked to the entry for 1-10 Portland Place.