Exterior
Symmetrical 2-storey 5-window range, containing a wide 3-window gabled bay, slightly advanced to centre. Extension with similar detail added to the R. Constructed of roughly coursed stone with yellow sandstone dressings under a hipped slate roof; detail includes moulded sandstone eaves cornice, continuing to central advanced bay as string course to triangular pediment; leaded copings to gable. Windows are 4-pane horned sashes in square sandstone surrounds, but that to lower L is a 2-light wooden casement. Central entrance in a tall recessed round-arch of stone voussoirs. It includes a shallow stone doorcase with moulded cornice containing a central 6-panel door, the panels at mid-level glazed, flanked by 4-pane sidelights, with recessed panels beneath. Above, a 4-pane sash, as elsewhere. To pediment, a roundel in sandstone surround with inscription: 'The Magistrates sensible to the miserable state of the antient prison, in compassion to the unfortunate, caused this building to be erected in the year MDCCLXXV, Joseph Turner, Architect'. West end has alterations to openings: 4-pane sashes to L and R, the former moved slightly; at mid-level to R is a blocked window; upper storey has 3-light horned sash to L and 2-light casement to L of centre. Rear is of rougher coursed masonry with wide boarded eaves; to L end, a full-height canted bay with hipped swept roof, possibly added later. It has pairs of 12-pane hornless sashes to each storey, and single sashes to each canted face. To R, irregular openings: Boarded door in rendered surround, immediately R of which is a tall 12-pane horned sash at mid-level, probably a stair-light. Two windows to L of doorway, paired horned sashes except for 6-pane sash to upper R. To R of stair-light, 2 small windows, a boarded door and a blocked opening to each storey.
Addition to W end has2-gable to road, that to L narrower and slightly set back; continuous sandstone string course to pediments. Former doorway to far L, infilled with a 9-pane fixed window, with a small 16-pane horned sash immediately to its R; 4-pane sash to upper storey. Wider gabled bay has 2 x 4-pane sashes to each storey, symmetrically-placed. To pediment, a semi-circular opening with radial glazing bars, possibly a ventilator. E gable end has a catslide lean-to with no openings. Rear is 3-window, with tall 2-light casements to ground floor. Upper storey has 2-light casement to L, 16-pane horned sash to centre, and inserted double boarded doors to R, reached by a fire-escape staircase.
Chapel and Machine House Range: A long 2-storey range facing S constructed of large blocks of ashlar under a shallow hipped slate roof, with wide boarded eaves and plain sandstone eaves cornice. Upper storey has 4 x 2-light wooden casement windows, and a narrow iron-glazed window to R end. Against L end, and in angle with Female Wing, is a 1st floor walkway of c2000, a curved steel structure on a steel post, with full-height glazing. Ground floor has 2 narrow boarded and studded doors to R end, with plain overlights and large stone lintels. Small wooden casement to L of these, beyond which are 4 irregular iron-glazed windows. The rear elevation has rough irregular masonry to the base, possibly constructed by prisoners. Ground floor has boarded door R of centre, 2 iron-glazed windows to R, and a shallow round-arched light of stone voussoirs to L of centre. Upper storey is 4-widow with alternating tall iron windows and 2-light wooden casements. Adjoined by later Pentonville wing to far L. Canted NW angle with narrow boarded and studded door. The W end has a similar door with small-pane overlight reached by stone steps. Abuts Female Wing to R.
Female Wing: Narrow rectangular 3-storey range facing E into yard, constructed of large blocks of ashlar with a shallow hipped slate roof, with wide boarded eaves and dressed sandstone eaves cornice: brick stack to S end. East side has boarded door to L, shallow window to L of centre with cambered stone head and small-pane iron glazing, and similar blocked window to R. The upper storeys have very small windows with single wooden casements; 1st floor has 3 windows offset to L; 2nd floor has 6 windows. A curved steel and glass walkway, from the Machine House and Chapel Range, joins the R end at 1st floor level. North end has external full-height projection, possibly for a staircase, with a small-pane horned sash to its R at 1st floor level. West side is irregular 4-window: raised doorway to L with double panelled doors, L of which is a tall 4-pane horned sash to each storey, probably lighting stairs. Elsewhere, small iron-glazed windows, paired to L of centre at ground and 1st floor levels. Similar window to S end at 2nd floor level, above an adjoining 2-storey bay constructed of the same materials. Its W side has a wide infilled opening under a segmental brick arch; E side has opposing infilled opening with stone lintel. Evidence for alterations to S end.
Pentonville Wing: A large 4-storey 12-window range to NE of complex, constructed of snecked dressed stone under a slate roof with wide bracketed eaves, surmounted by a brick ventilation tower. Small square windows in stone surrounds, with chamfered heads and stone sills, containing small-pane iron glazing. The E side has larger windows to far L of 1st and 2nd floors, possibly stair-lights. Corresponding taller windows to R end of W side. The L pairs of windows to W side are closely-spaced; ground floor has boarded doors to L and L of centre. Skylights to roof pitch. The N gable end faced the prisoners' yard, with a tall central canted bay with flat moulded roof; tall lights with small-pane iron glazing spanning 1st to 3rd floors. At 1st floor level, to R canted face, a boarded door with stone steps bound by plain iron railings leading down to former exercise yard. To ground floor, to front of canted bay, double boarded doors with small-pane overlight under a stone lintel. To L of canted bay, a lintel marks the blocked doorway which led to the hanging scaffold, at 1st floor level. The S gable end is cut back to the L, having been constructed around the 1820s block. To centre of gable end, at 2nd and 3rd floor levels, are tall tripartite windows with small-pane iron glazing. Linking ranges to the infirmary adjoin beneath, probably obscuring the original entrance. Square brick ventilation tower with sandstone dressings, on a battered base. Pyramidal swept slate roof surmounted by a large square finial of decorative iron openwork, recently restored to its original position. Each face of the tower has a 5-light stone mullioned opening; deep sandstone eaves cornice with recessed quatrefoils; arcaded stone band to base.
The Infirmary: Attached to the S end of the Pentonville Wing via a short linking range. A tall 2-storey range with irregular fenestration, constructed of snecked stone, under a hipped slate roof, with truncated brick ridge stack and brick corner stack to SW; detail includes dressed quoins, boarded eaves and square sandstone surrounds to windows. The E side has 4-pane horned sashes, those to upper storey taller with overlights; the upper storey is 4-window, the ground floor 6-window with a small light to L end. The S end has a narrow boarded and studded door offset to R, inset under a stone lintel. Small square Pentonville-style window to upper storey with small-pane iron glazing. Angle buttress to SW, stub wall to SE, forming part of entrance to rear yard. West side of range has 2 former doorways to L and R, now infilled with 4-pane sashes; further 4-pane sash above the latter. Tall window to centre of upper storey with small-pane glazing. Remaining windows are irregular and at different levels, mainly Pentonville-style.
The short 2-storey linking range between the Penonville Wing and Infirmary provided a new main entrance. It is L-shaped, wrapping around the NW angle of the Infirmary; entrance facing S leading directly into Pentonville Wing, and abutting the Chapel and Machine House Range to L. Constructed of snecked stone under a slate roof, hipped to L end, with an angled buttress beneath, said to be on the alignment of an earlier building. Tall round-arched entrance of stone voussoirs, over a flight of stone steps leading up to an inset doorway with boarded door to R and tall small-pane iron window to L. Above entrance, a pair of narrow 8-pane sashes in sandstone surround. East side of linking range is set back from infirmary, with altered openings including an infilled doorway and window; upper storey has 2 small windows, iron-glazed to L and a 4-pane sash to R.