Ordnance Survey Ireland

Detached five-bay two-storey former barracks, built 1886, now in use as offices. Hipped natural slate roof with clay ridge tiles, moulded cast-iron guttering and cast-iron downpipes. Roughcast rendered chimneystacks with cornices. Guttering supported on bracketed and sheeted overhanging eaves with painted frieze below. Painted roughcast rendered walls and feather-edged rock-faced granite ashlar quoins to first floor, uncoursed rock-faced calp limestone walls with tooled limestone ashlar quoins to ground floor and red brick band between floors. Square-headed window surrounds with patent rendered reveals to first floor and red brick quoined surrounds to ground floor, all having concrete sills and original six-over-six pane timber sliding sash windows with ogee horns. Door opening detailed as per window openings with replacement timber panelled door. 1960s boiler-house abutting south elevation. To southeast corner is square-plan tapered brown brick chimneystack. Forms part of Ordnance Survey complex of buildings at former Mountjoy House.

This building formed part of Mountjoy Barracks and is now part of Ordnance Survey Ireland. It is one of two distinct buildings on the same axis, the gap between them forming the main approach to the complex. The building exhibits a wealth of quality materials yet employs a conservative rhythmic fenestration pattern. Enclosing the west side of North Square, this building and that to the north retain all external materials and give the square an understated formality. It is part of a wider collection of impressive buildings on the Ordnance Survey site representing architectural styles spanning over three centuries.