15-17 Seymour Street, Lisburn, Co. Antrim, BT27 4

15–17 Seymour Street is a terrace of three-storey red-brick and rendered townhouses on the north side of Seymour Street, Lisburn, built around 1800 as a purpose-built County Infirmary. The building was converted into apartments in 1995. It sits on an east–west axis facing south, and its overall Georgian composition — good proportions, symmetrical arrangement, and two original decorative doorcases — remains largely intact, though extensive restoration work has diminished its authenticity. The terrace makes a significant contribution to the character of Seymour Street and holds considerable social interest for the local community.

The main central block is a five-bay, three-storey symmetrically arranged building finished in painted render, with rusticated render quoins and a red sandstone water table at ground level. To either side of this central block are two-bay, three-storey red-brick wings, each incorporating an elliptical-headed carriage arch formed in brick. The arch to the west wing has been filled in with brick and now contains a window opening, with rusticated quoins to its east jamb. The east wing retains its carriage arch with rusticated quoins to either side, an original cast-iron wheel-guard from the Portadown Foundry, and a pair of vertically-sheeted timber doors opening onto a tarmac drive. The red-brick walling to the wings is laid in Flemish bond.

Attached to the west end of the terrace is a lower three-bay, three-storey red-brick house, which served as the Nurses Home. Its top floor retains 3/3 timber sash windows and a continuous sill course runs along the first floor. Below this sill course is an inscribed stone plaque reading: "NURSES HOME, PRESENTED TO THE, COUNTY ANTRIM INFIRMARY, BY THE PEOPLE OF LISBURN, AS A MEMORIAL OF THE JUBILEES, OF QUEEN VICTORIA, 1887–1897." The off-centre square-headed door opening has a replacement timber panelled door with a two-pane overlight, flanked by a pair of panelled pilasters with oversized scrolled and foliate console brackets supporting a cornice above with lead lining. The door opens onto a paved front path set below a gravel parking area to the front. The west gable is finished in blank pebbledash render. A further three-bay, three-storey red-brick block was added to the east end of the terrace around 1995.

Roofs throughout are finished in natural slate with black clay ridge tiles, with rolled lead to the central block. The red-brick chimneystacks are covered with semi-circular caps. Rainwater goods are replacement metal and plastic.

All window openings are square-headed throughout, fitted with replacement 6/6 timber sash windows and painted sandstone sills. The central block has smooth rendered surrounds to all window openings. The central door opening of the main block has a replacement timber panelled door with a two-pane timber-framed rectangular overlight, a moulded reveal, a plain architrave surround, and two console brackets supporting a deep cornice above with lead lining. The door opens directly onto a concrete-paved footpath in front of a gravel parking area. To the rear, elevations and returns are finished in cement render, with replacement multi-pane timber casement windows fitted with concrete sills. The rear is further abutted by a pair of gable-ended, multi-bay, three-storey returns in cement render, and the east gable has a lean-to red-brick projection supported on a pair of iron posts.

The County Antrim Infirmary was originally established in 1767, pursuant to an act of parliament, in a house formerly belonging to a Mr Edward Gayer. It moved to this purpose-built Seymour Street building in the early 19th century. The building appears, uncaptioned, on the first edition Ordnance Survey map of 1833, and is identified as "Infirmary" from the third edition (around 1900) onwards.

The Townland Valuation of 1828–40 records it as a substantial complex measuring 68.6 by 19.6 by 28 feet, with a return and several outbuildings including a laundry, cow house, piggery, and cellar, valued at £38 4s 1d. The Ordnance Survey Memoirs describe it as "a fine brick building, having 24 windows in front," situated "in an airy part of the town," and record its role in providing both outpatient medicines and advice and inpatient care. On average it annually treated around 850 extern patients with medicine, 400 with advice, and 290 inpatients, and contained 42 beds. Griffith's Valuation of 1856–64 lists the Infirmary at £64 10s, with a deduction made for the gateway, and records that the buildings were leased from the Marquess of Hertford and later Sir Richard Wallace. By 1899 the valuation had risen to £84 10s, likely reflecting an extension to the building.

In the early 20th century, during what is described as Dr St George's era, the hospital was much improved with financial assistance from the Barbour family and other benefactors. An extensive internal modernisation followed in 1913 after a fundraising bazaar that raised £1,350. Improvements at that time included the installation of electric lighting, a lift, improved X-ray apparatus, and an enlarged operating theatre. The building was converted to residential apartments around 1995, at which time most of the original timber sash windows and other external fixtures were replaced and most of the internal fabric was lost.