17 Castle Street, front railings and mounting block

17 Castle Street is a timber-framed house of the 16th century, extended to the rear probably in the 17th or 18th century and again in the 19th century. It has been in office use from the later 20th century onwards.

The building is constructed with timber framing, rendered stucco to the front elevation, and exposed red-orange brick with occasional blue brick headers at the east elevation. The roof is tiled.

The plan is double-gabled with an off-centre entrance flanked by rooms leading to a stair hall and a rear wing. The front range comprises two bays over three storeys with the third floor in the attic. The two-bay rear wing has two storeys with a part-cellar. A mid-19th century extension to the wing, believed to have been a warehouse, has three bays and three storeys.

The gable roofs are tile-covered. On the rear pitch of the front range's roof are five 16th-century diamond-profile stacks, some with repaired brickwork. The principal front of the 16th-century range has oversailing first and second floors with moulded jetties on decorated carved brackets. Windows have been restored with modern casements but frames are mainly original. At ground floor is an off-centre modern door under a restored panelled 17th-century timber porch with a moulded cornice and pediment on square posts, segmental-arched heads across openings, and panelled timber guards with an ornamental dog-gate. To each side are projecting heavily-moulded transomed and mullioned rectangular window frames of 14 lights to the west and eight to the east. Further east is a vehicular entrance with 17th-century eight-panel double yard doors with a 'porte batarde' and cobbled and paved carriage path. The entrance opening has structural bridging beams and box-framing visible on the east side. Box-framing is apparent on the east return of the front range.

At first floor are two projecting casement windows of 21 lights with lightly-moulded transomed and mullioned frames on small carved brackets. The second floor windows are small eight-light 18th-century Yorkshire sashes. The two gables have decorative cut bargeboards and central pierced finials.

The front range's rear elevation is obscured by the rear wing, built of brick in both stretcher and Flemish bond with timber framing. A modern door leads from the front range to stone steps with an early-19th-century balustrade. A 19th-century first-floor flat-roofed extension to the rear wing, with scalloped soffit, is supported on slender columns and oversails the stairs. It is of red-orange brick in Flemish bond with blue brick headers, topped by weatherboarding, with eight-light casement windows. The columns are placed either side of a mounting block.

Further south at ground floor of the rear wing is a projecting canted bay with horned two-over-two sash windows over a segmental opening into the cellar. On the first floor is exposed vestigial box-framing with a replacement corner post and mid-rail and two small sash windows. A former warehouse building is attached to the south, constructed of brick in Flemish bond with a pitched tile-covered roof and ridge stacks. All openings have segmental heads. At ground floor is a timber panelled door; flanking windows and those above are not of consistent form. At the south end a metal stair leads to a door at first floor. Metal tie rods have been inserted historically and between two windows at second floor there is a metal structure from which a sign may have been suspended.

The interior has been much obscured by lowered ceilings, modern partitions and finishes, but exposed timber members can be observed including bridging beams, wall posts, mid-rails and tie beams. Most doors are 20th century, though some 19th-century doors and one 18th-century door were observed, along with some joinery.

The main entrance leads to a large stair hall through an asymmetric screen arcade with moulded cornice. A ramped open-well stair of about 1700 with fat turned balusters, ball newels and closed moulded strings rises to all floors. Some wall panelling to the stairwell remains, along with sections of modern handrail.

At ground floor, the front west room retains an early-17th-century coffered ceiling with decorative strapwork to the main chamfered and stopped bridging beam and carved pendants at junctions of the moulded joists. The room also has exposed good-quality substantial pegged and jointed box-framing including a moulded mid-rail and possible door frame at the far west end of the front wall. Wide timber floorboards are present.

In the attic rooms of the front range, the queen post roof trusses are exposed. The wall plate, double purlins, principal rafters, tie beams and box-framed cross walls are evident. An incised carving of a 16th or 17th-century shoe is found on a front wall post in the eastern attic room.

To the front are early-19th-century railings on a dwarf wall. A four-step rendered mounting block is located beside the carriageway near the rear entrance of the front range.