Horsepark, 1 Horse Park, Magheragall, Lisburn, County Antrim, BT28 2QU

Horsepark is a detached three-bay two-storey rendered former thatched house built around 1680. It is a rare survivor of late 17th-century vernacular farmhouse architecture, retaining its original composition and overall character despite the loss of its thatch and much internal detailing.

The house is rectangular on plan, facing south, with single-storey wings to either gable end and a gabled rear extension. It sits on an elevated site to the north of Horse Park, with a rear yard containing a single outbuilding. The property has east and west entrances with gravel driveways. A single-storey dwelling stands to the east drive, and a rubblestone outbuilding marks the entrance to an additional modern yard. Both entrances are marked with modern stone-faced circular piers; the eastern entrance has iron gates on cast-iron posts.

The steeply pitched roof of natural slate is fitted with black clay ridge tiles and is supported by original timber roof structures retained from the earlier thatched roof. The roof is carried on rendered eaves courses with cast-iron guttering on iron drive-through brackets and cast-iron downpipes. Three rendered chimneysstacks rise through the roof.

The exterior walls are finished in rough-cast render with a smooth rendered plinth course and rendered rusticated soldier quoins to the front elevation. Window openings are square-headed with smooth render surrounds, concrete sills and replacement horizontally-glazed timber sash windows. The front elevation displays three windows with a central square-headed door opening containing a replacement hardwood door and sidelights. The westernmost bay retains a former door opening with smooth rendered surround, now blocked up. The west gable is abutted by a single-storey wing and has a single square-headed window opening to the upper floor. The rear elevation is abutted by a single-storey gable-ended extension containing square-headed window openings of various sizes with replacement timber casement windows and a recessed square-headed door opening with sheeted timber door. The east gable is abutted by a single-storey wing matching the west gable configuration.

Horsepark originated as the horse ground for the neighbouring Brookhill estate, used by the occupant of an early 17th-century fortified Bawn to exercise his troop of horses. The Bawn, constructed during the plantation, was located within the gardens of Brookhill House, built around 1730. The house first appears on the Ordnance Survey map in 1832, depicted as an oblong building in the townland of Ballyellough, half a kilometre north-east of Brookhill. By 1832–1857 the dwelling was the westernmost of three buildings standing at Horse Park.

According to Griffith's Valuation of 1859, Richard Dawson rented the house from the Reverend James Stannus, agent to the Marquis of Hertford, at a valuation of £2. The property fell vacant between 1863 and 1866, recorded as the property of the Marquis of Hertford. Its value increased to £3 10 shillings in 1870 and then to £5, though the reason is unknown. The house was reoccupied in 1878 by James Cosgrave, a local farmer, who purchased the property from the Marquis of Hertford in 1893. Cosgrave lived there with his wife Sarah Jane and five children until his death in 1901. The 1901 census record indicates Horsepark possessed numerous outbuildings including a stable, coach house, cow house, piggery, boiling house and barn, housed in an outbuilding to the rear that still survives in dilapidated condition. Following Cosgrave's death, his widow Sarah Jane occupied the house before vacating by 1912, when Samuel Boyd came into possession and remained until the end of the Annual Revisions in 1923.

The house was listed in 1981. Around 1985 it underwent significant alteration when the thatched roof was replaced with slate, as thatching expertise was unavailable locally. The First Survey record of 1974 documents an entrance porch on the west side of the front elevation that was subsequently removed, the doorway blocked in, and the entrance relocated to the centre of the elevation as part of the 1985 works.

The house retains its original farmhouse function and rural setting, making it of considerable local historic interest and architectural significance as one of few domestic buildings surviving from this period in the county.