24 Clarendon Street, Londonderry, County Londonderry, BT48 7ET

24 Clarendon Street is a mid-terrace, two-bay, three-storey with attic, red brick Georgian-style townhouse built in 1863 as part of a continuous terrace of eleven similar houses lining the north side of Clarendon Street, between Queen Street and Princes Street, in the Edenballymore townland. It was built at the same time as numbers 6–10 and 22 and 26 Clarendon Street, completing the terrace. The house shares group value with numbers 6–22 and 26–48 Clarendon Street, the full terrace having been constructed over an eight-year period. It sits within the Clarendon Street Conservation Area, and its well-preserved setting adds to its significance. The building retains much of its original character and detailing.

The plan is rectangular with a projecting rear return. The principal elevation faces south onto Clarendon Street, set behind a low rendered plinth wall surmounted by replacement cast iron railings enclosing a small hard-surfaced area.

The roof is pitched natural slate with black clay ridge tiles and two rooflights to the front. A slender rebuilt red brick chimney stack rises from the east side, centred on the ridge and fitted with terracotta pots. Cast iron half-round guttering and a circular downpipe serve the front elevation.

The principal south-facing front elevation is laid in Flemish bond brick. The window openings have cut brick flat arches with six-over-six timber sliding sash windows set within painted cement-rendered reveals and painted sills. The entrance doorway is to the left and has a three-centred arched opening with a moulded surround, a moulded entablature supported by a pair of Doric columns, a simple glazed fanlight, and a four-panelled timber door. To the right of the door are two diminished windows at ground floor level, with two windows each at first and second floor — note that the upper-floor openings are not aligned with those at ground floor. The east and west sides of the building are abutted by the adjoining properties, numbers 22 and 26 Clarendon Street respectively.

The rear north elevation is three storeys with an attic dormer to the left. A three-storey pitched roof rear return abuts to the right — the right half of which forms the return of number 26 — and this in turn is further abutted by a single-storey extension. The fenestration at the rear is irregular, combining timber sliding sash and casement windows. The exposed section to the left has a single window at ground, first, and second floor levels, with a single dormer above. The north face of the three-storey rear return is abutted at ground level by a single-storey extension and has a single window at first and second floor; the east face is obscured; the west face is abutted by the return of number 26. An exposed section above the return has a single window.

To the rear, the property has an enclosed yard. At the north end of the site stands a two-storey pitched roof mews building. A laneway runs along the rear of the mews building providing access to the rest of the terrace.

The Clarendon Street area was originally rural hinterland on the townland of Edenballymore, recorded as such on the first edition Ordnance Survey map of 1830. At that time, urban development extended no further than Waterloo Place, Abbey Street and William Street. The only significant buildings north of the city walls in the early 19th century were isolated institutional structures — the Londonderry Infirmary, the Lunatic Asylum, and Foyle College — with little domestic architecture in the vicinity. The sole surviving building in the area predating the early Victorian development is Foyle Cottage, a Regency house of around 1815. As Robert Simpson noted in his Annals of Derry, published in 1847, the entire district later covered by Great James Street, William Street, Little James Street and the surrounding lanes had originally comprised meadow ground without a house.

The laying out of Clarendon Street, Great James Street, and Queen Street followed a geometric street pattern characteristic of Georgian urban development, and represented the most ambitious town planning project undertaken in Londonderry since the construction of the walled city between 1613 and 1619. The street was originally named Ponsonby Street, after the Right Reverend Richard Ponsonby (1772–1853), Bishop of Derry and Raphoe. By the 1850s it had been renamed Clarendon Street in honour of George Villiers (1800–1870), the Fourth Earl of Clarendon, who served as Lord Lieutenant of Ireland between 1847 and 1852. The second edition Ordnance Survey map confirms the new name was in use by at least 1853.

Although a plan of Londonderry dated 1847 depicted Clarendon Street extending from the quay up to Francis Street, only the lower section between the Strand Road and Queen Street had been laid out by 1853. Development progressed slowly through the 1850s. In 1851 Skipton and Miller advertised building ground on Clarendon Street, Queen Street and Patrick Street to be let in perpetuity. Griffith's Valuation, recorded in 1856, noted only nine dwellings along the entire length of the street. Additional leases for building ground on the north side of the street were advertised in 1856.

Number 24 was one of the last houses to be built on the north terrace. It was constructed in 1863 for John Allen, a wine merchant and property owner who also held business premises in Linenhall Street. The house was originally valued at £28 and was first occupied by a Mr William Mackey in 1863. By 1901 it was occupied by Mr John MacDevette, a local magistrate, Justice of the Peace, and consul for Italy, the Netherlands, Austria and Portugal. The 1901 census described it as a first-class dwelling consisting of ten main rooms.

Number 24 remained in the ownership of the Allen family until at least the end of the Annual Revisions in 1931, by which time it was occupied by a Ms Sarah A. Hanna and had been reduced in assessed value to £24. Between 1931 and 1935 the entire row of numbers 6–26 Clarendon Street was purchased by a Ms Jennie Steen, and the First Revaluation of 1935 records that the value of number 24 was consequently increased to £42. The Second Revaluation, covering the period 1956 to 1972, records that a Ms Mary Stevenson took ownership in 1967. At the close of that revaluation the property's value stood at £38, and it continued in use as a private dwelling.

In 1978 the Department of the Environment designated Clarendon Street and the surrounding streets a Conservation Area, defined as an area of special architectural or historic interest whose character it is desirable to preserve or enhance. Number 24 was subsequently listed in 1979. At the time of the second survey the building was in use as office premises for a firm of solicitors — a use shared by the majority of the mid-Victorian townhouses along Clarendon Street, most of which were converted into offices for dentists, solicitors and accountancy firms during the late 20th century and are no longer occupied as residential dwellings.

Writing in 2013, architectural historian D. Calley described numbers 6–48 Clarendon Street as a "delightfully long red brick terrace of the mid-19th century," noting that the buildings are nearly all the same — three-and-a-half storeys, two bays — with most ground floors "rather inelegantly squeezing in a doorway with two reduced scale window bays," and characterised by "depressed arched recessed timber-framed doorways with simple segmented fanlights and thin Doric columns supporting entablatures."