20, Castle Street

No. 20 Castle Street is a house that has been converted into offices. It features a mid to late 18th century front, which is attached to a slightly older structure, and has undergone some alterations in the late 20th century. The building is constructed of red brick in Flemish bond, with some overburnt headers, and has orange-red dressings. The sides and rear are plastered over timber-frame, and it has a three-quarter hipped roof covered with old tiles.

The front of the building has a central entry plan with three bays. On the first floor, there are two triple 4:12:4-pane sash windows and a central 12-pane sash window, all recessed beneath rubbed brick arches. A plat band runs along the first floor. The ground floor features two triple 4:12:4-pane sash windows as well. The central entrance is a recessed six-panel door with panelled reveals, an architrave surround, and a doorcase that includes Tuscan Doric pilasters, an entablature with a triglyph frieze, panelled metopes, and a flat modillioned moulded cornice. The threshold is made of Portland stone.

The roof includes three box casement dormers, with the outer ones having three lights and the central one having two lights, along with square red brick chimneystacks. At the rear, there is a two-storey outshut with a weatherboarded upper floor, which is connected to a large modern rear outshut that is not of special interest.

Inside, the building has been significantly altered, but some 18th century cornices remain. The staircase features Tuscan column newels, stick balusters, and moulded handrails. The roof has riven and sawn rafters with a thin ridge board.