1A Castle Hill

1A Castle Hill is a late 18th-century house that has been converted into offices. It is constructed from sandstone ashlar with ashlar dressings and features a slate roof and gable chimney stacks. The building has a double-depth plan, with the entrance located in the right-hand bay. It stands three storeys tall above a basement, which is expressed as a plinth, and has three bays with raised quoins and an eaves cornice.

The entrance doorway is adorned with a moulded architrave and a frieze inscribed 'GILLOW & Co', topped with a simple cornice on fluted consoles. The door itself is approached by three recessed steps and consists of five panels, with all but the upper panel being raised and fielded. The windows throughout the house have plain raised surrounds and are sashed with glazing bars, featuring 12 panes on the ground and first floors and 9 panes on the second floor. The basement plinth is painted and has two openings that were likely originally shuttered but now contain glass bricks.

Historically, this building served as the office for Gillow & Co during much of the 19th century, until 1887, and is located next to its warehouse at No. 1 Castle Hill.