23 Ballyskeagh Road, Ballyskeagh, Lisburn, Co Antrim, BT27 5SZ

This mid-18th century two-storey former lock keeper's house stands on the summit of a wooded hillock at Ballyskeagh Bridge, a short distance south-east of lock number 8 on the Lagan Navigation, which it served. It is accessible only on foot via a narrow path from the east end of the bridge.

The house was constructed around 1760 as part of the Lagan Navigation scheme, built between Belfast and Lisburn under the direction of the canal engineer Thomas Omer. Work on the Navigation commenced in 1756 and the waterway opened in 1763. This is one of only three lock houses designed by Omer to survive in Ulster—all located on the Lagan Navigation—and one of only two still inhabited. The house appears on the 1834 Ordnance Survey six-inch map. It ceased functioning as a lock keeper's house when the Navigation was officially abandoned for commercial traffic in 1956, subsequently falling into disrepair. The building was sympathetically restored by HEARTH in 1992-93 using traditional materials and techniques, and has been occupied since.

The house is aligned north-east to south-west, with its principal elevation facing north-west towards the lock. It features a pitched natural slate roof with small rebuilt brick chimneys on both gables, and half-round cast-iron gutters and downpipes. The walls are of limewashed random rubble with distinctive curved-headed recesses and striking contrasting sandstone dressings. There is a finely dressed sandstone string course between ground and first floor levels and a sandstone eaves course under an ogee-profile sandstone cornice, with plain string courses continuing along the base of the gable apexes.

The principal north-west elevation is symmetrical, with a six-panel timber door at centre, approached up three concrete steps. The door has replacement stepped ashlar sandstone jambs and a voussoired head with projecting keystone, set within a semicircular-headed recess at first floor level above the string course. The doorway is flanked by two 6/6 timber sliding sash windows at ground floor, with 3/6 sash windows of diminished height directly above at first floor level. All windows retain original sandstone cills. The north-east gable features an identical semicircular-headed recess to the façade, with an 8/8 sash window at ground floor with replacement sandstone cill.

The south-east (rear) elevation is not symmetrical. It has a keystoned semicircular-headed recess to centre with a 6/6 sash window, and a smaller 6/6 sash to its left in what is probably a new opening. A 4/4 sash and 6/6 sash are positioned at left and right respectively to the first floor, of diminished height, with a mix of original and replacement sandstone cills. There is no door to this elevation, and the base of the wall projects outwards. The south-west elevation is identical to the north-east in every respect. All openings have flat heads with replacement frames. Windows are timber sliding sash replacements, the door is panelled timber replacement, and rainwater goods are cast-iron half-round replacements.

Despite its isolated hilltop setting, the house retains group value with the other listed structures on the Lagan Navigation. It is of particular architectural interest for its distinctive design by Thomas Omer and for its scarcity value as a surviving example of this engineer's work, as well as being of national importance in the context of Ireland's waterways heritage.