20 Great James Street, Londonderry, Co. Londonderry, BT48 7DA

20 Great James Street is a Georgian-style mid-terrace three-storey, three-bay red brick townhouse, built around 1847, with a modern three-storey projecting rear return. It forms part of a terrace of three similarly scaled townhouses along the north side of Great James Street, and is among the earliest examples of domestic architecture within the Clarendon Street Conservation Area. The building is rectangular on plan, with its principal elevation facing south onto Great James Street, fronting directly onto the pavement.

The pitched roof is covered in natural slate with terracotta clay ridge tiles. A red brick chimney stack with clay pots rises from the east side, and replacement PVC guttering connects to an original circular cast iron downpipe at the front. To the rear, uPVC rainwater goods have been fitted throughout.

The principal south elevation is finished in painted smooth render at ground floor level, with Flemish bond brickwork — described in 2013 as mottled brown brick — above. All window openings are square-headed and sit on painted masonry sills. The two bays to the right of the entrance doorcase have been fitted with replacement uPVC casement windows. The entrance doorway is slightly recessed beneath an elliptical arch head, flanked by engaged fluted columns of the Doric order. The door itself is a raised-and-fielded four-panel painted timber door, surmounted by a dentilled entablature and a simple fanlight with timber glazing bars. First floor windows are 6/6 timber sliding sashes; second floor windows are 6/3 timber sliding sashes.

The east and west elevations are adjoined to neighbouring properties: No. 18 Great James Street to the east and No. 22 to the west. The rear north elevation is three storeys high, with a large modern three-storey rear return built at half-landing height and covered by a slated pitched roof. Rear walls are finished in smooth unpainted render. The rear window openings are square-headed on unpainted masonry sills, with an irregular fenestration pattern featuring replacement mock-Georgian uPVC and timber casement windows throughout.

The building sits within a small rear yard enclosed by a rendered wall, alongside the large two-storey rear return.

Significant detailing and character have been lost through the rendering of the ground floor, the fitting of inappropriate uPVC windows to the front, and the replacement uPVC casement windows to the rear. Although this building is not listed — the record notes that Nos. 16 and 18 Great James Street have not retained sufficient architectural and historic interest to be considered special — No. 20 nevertheless makes a significant contribution to the Clarendon Street Conservation Area by reason of its imposing façade.

Great James Street was originally laid out around 1833, with the first buildings constructed by at least 1835–37. Its development, along with that of the adjoining Queen Street (laid out around 1847) and Clarendon Street (around 1853), was driven by significant population and economic growth in Londonderry during the mid-19th century. As John Hume has noted, the period 1825–1850 saw reconstruction within the city walls alongside the first development of housing outside them at Bogside and Edenballymore. Great James Street was the first major new street in the area.

The first edition Ordnance Survey map of 1830 for the townland of Edenballymore records that the area was originally rural hinterland. By that date, the city's built-up streets extended no further than Waterloo Place, Abbey Street and William Street. In the early 19th century, the only major construction north of the walls comprised isolated buildings such as the Londonderry Infirmary, the Lunatic Asylum and Foyle College, with almost no domestic architecture. The only building in the Clarendon Street Conservation Area predating the early Victorian development is Foyle Cottage, a Regency house constructed around 1815. Robert Simpson, writing in his Annals of Derry (1847), recorded that the entire district now covered by Great James Street and surrounding streets originally comprised meadow ground without a house. With the construction of uniform rows of neat three-storey townhouses, a new affluent area was established that became the preferred residence of the city's merchant and professional classes. The geometric street pattern of Great James Street, Clarendon Street and Queen Street was characteristic of Georgian town planning, and represented the most ambitious planning project in Londonderry since the construction of the walled city in 1613–19.

No. 20 Great James Street was constructed between 1847 and 1853. O'Hagan's 1847 plan of Londonderry records that Great James Street had been partially developed by that date but shows no buildings on the current site; by the second edition Ordnance Survey map of 1853, a small terrace had been built on the north side of the street. This terrace originally comprised four identical Georgian-style buildings — Nos. 16 to 22 Great James Street — each with a rear return and a single outbuilding. No. 22 was rebuilt in 1903 and is now significantly different from the adjoining terrace.

Griffith's Valuation of 1856 records that Nos. 16–22 Great James Street were constructed for Andrew Thompson, a local surgeon who also operated an apothecary on the Strand Road. Thompson leased No. 20, valued at £28, to a Ms. Elizabeth Browne. Andrew Thompson retained ownership of the terrace until his death around 1870, after which his widow, Margaret Thompson, took possession and took up residence at No. 20. By 1911 the house was occupied by James William Robinson, a dentist and anaesthetist; the census building return for that year described it as a first-class dwelling of ten rooms. By the 1930s ownership had passed to a Ms. Mina Hurst, and under the First General Revaluation of Property in Northern Ireland (1936–57) the value of the building had risen to £34. The house was occupied by a Ms. Rebecca Quigley between 1940 and the 1970s, with the value standing at £35 by the end of the Second Revaluation (1956–72).

In 1978 the Department of the Environment designated the mid-19th-century streets and terraces as the Clarendon Street Conservation Area, defined as an area of special architectural or historic interest, the character of which it is desirable to preserve or enhance. In 2013, Calley described Nos. 16–20 Great James Street as a fine small terrace of three mottled brown brick houses, mostly in commercial use, three-storey and three-bay with rendered reveals. Few of the Georgian-style townhouses along Great James Street now remain in residential use; the majority were converted into offices for dentists, solicitors and accountancy firms in the late 20th century. At the time of the Second Survey, No. 20 Great James Street had been divided into a number of self-contained apartments.