Rathmore Grammar School, Convent of the Sacred Heart of Mary, Kingsway, Belfast, BT10 0LF

Rathmore House is an elegant two-storey Italianate mid-Victorian house dating from around 1870, most likely designed by the prominent Belfast architectural firm Lanyon, Lynn and Lanyon, though family records attribute the design to Sir Joseph Paxton. It is now part of the Rathmore Grammar School complex, set within its own grounds fronting onto Kingsway, to the southeast side of the M1 motorway in Dunmurry.

The house has a rectangular plan form with a single-storey entrance portico to the north, an L-shaped plan wing to the east, and a single-storey extension to the northeast. The hipped natural slate roof has a skylight to the centre, and overhanging eaves are supported on a sandstone dentilled cornice. Rainwater is carried by ogee cast iron guttering discharging to circular cast iron downpipes. Tall chimney stacks in ashlar sandstone have corbelled coping and red clay chimney pots. The walls are laid in coursed rock-faced Armagh limestone with Giffnock sandstone dressings on a projecting limestone plinth. Wraparound moulded sandstone sill courses run at ground floor and first floor level on the main building and east wing, with a moulded string course between the floors and a plain sandstone frieze below to the main building. Window openings are square-headed with plain architraves at ground floor and moulded architraves at first floor, all fitted with one-over-one timber sash windows unless otherwise noted.

The principal north elevation is five bays wide with a projecting hipped-roof bay to the east. At the centre is a two-bay projecting single-storey porch in ashlar sandstone, with paired Tuscan columns on a stylobate forming an opening to the east bay, and sandstone walling with a window and paired pilasters to the west end. The west elevation of the porch has a similar arrangement. The porch windows are round-headed with moulded arch hoods, pronounced keystones, and small flanking pilasters. The porch is topped by a plain frieze, cornice and a Renaissance-style balustraded parapet. Three stone steps lead inside the porch, which has ashlar limestone walling and a rendered ceiling. A square-headed door opening on the west face is set within a segmental-headed arch with a panelled tympanum and raised keystone, fitted with a polished timber nine-panelled door with bronze door furniture. A moulded string course runs at impost level across all three sides of the porch interior. There is a round arch window to the north face and a recessed segmental arch to the east face. Four first floor windows above the porch have segmental-headed moulded architraves, pronounced keystones and carved tympana.

The west elevation is symmetrical and five bays wide, with a single-storey semicircular bay at each end and a three-bay-wide balcony to the centre. The semicircular bays are in ashlar sandstone with three windows each and balustraded parapets above. The windows to the south bay have stained leaded glazing. A square-headed door opening at the centre, fitted with a replacement painted timber panelled door with glazing, opens onto four stone steps and is flanked by a window on each side. Four corbelled brackets support the balustraded balcony.

The south elevation is five bays wide with a two-storey semicircular bay positioned off-centre. There are paired windows to the ground floor east bay and three windows to the semicircular bay at both ground and first floor. The three ground floor windows to the west and the bay windows at ground floor have stained leaded glazing.

The east elevation is six bays wide with a window to each bay at both ground and first floor, and is abutted by the projecting east wing.

The two-storey east wing abuts the main building to the northeast and consists of two blocks: one aligned west-east and a second aligned south-north, forming an L-shaped plan. A single-storey U-shaped hipped-roof extension lies to the east of the wing, with a curved wall to the northeast corner, and a small open quadrangle is formed between the extension and the east elevation of the wing. The L-shaped plan of the east wing is visible from the north, presenting a four-bay elevation to the west-east block and a single-bay elevation to the south-north block. Ground floor windows to the first block have a stone panel to the apron and a platform enclosed by a Renaissance-style balustrade. The second block has a four-bay elevation to the east. The south elevation of the wing has three bays to the west and a single bay to the east. A square-headed door opening at the west end is fitted with a replacement painted timber panelled door and opens onto a ramp, with a balustraded platform in front of the three western bays. The first floor is recessed behind a balustraded balcony. Following the steep change in ground level, the seven-bay east elevation reads as three storeys, with the ground floor opening onto a lower level and connecting with the U-shaped extension. Square-headed window openings here are fitted with plain sash windows. The extension has uPVC rainwater goods and modern doors and windows. Entrance to the quadrangle is through a square-headed modern sheeted timber door in the east elevation of the extension, leading through a covered corridor. The four elevations overlooking the quadrangle have square-headed window openings with plain one-over-one timber sash windows. A glazed timber screen incorporating a square-headed door opening is located at the northeast corner, with a square-headed glazed timber door directly to the south. A glazed timber porch at the northwest corner forms the entrance to the east wing.

The interior retains an impressive principal stairwell with a stained glass skylight, and has been carefully restored. The stained glass windows in the chapel were installed by the firm of Clokeys.

Rathmore House was built by Victor Coates around 1870. He was the son of William Coates of Glentoran and came from a long-established Belfast family of iron founders. In 1863, he married Margaret Airth Richardson, daughter of Jonathan Richardson MP of Lambeg House. They went on to have six sons and a daughter. A growing family and growing prosperity — his firm, Victor Coates and Co. Ltd, became the leading manufacturer of boilers and steam engines in Ireland — contributed to his desire for a substantial country residence. In the late 1860s he acquired a park of 120 acres on a hill at Kingsway, Dunmurry, on the site of Huntley Cottage. The house was one of the most advanced of its day. Family records describe it as "quite modern with light from the roof and central heating; the first in Ireland and considered for many years most unhealthy. The rooms were too large to be heated by fires and this central heating made the house too comfortable." The range of outbuildings was extensive, including stables, a gas works and greenhouses, as well as two gate lodges. The Valuation Revision Books record that in 1872 the buildings were valued at £180, rising to £187 in 1874. By 1884 the farm buildings were valued separately and the valuation of the house and its immediate outbuildings was reduced to £135. The 1901 census records 44 rooms in the house occupied by the family; by 1911 the household, though still large, occupied 27 rooms.

Victor Coates died on 27 July 1910, leaving an estate valued at £5,788. His obituary in the Belfast Newsletter records that he had been in ailing health for some years and had withdrawn from the family business about fifteen years before his death, with the firm itself closing in 1906. He had been active in public life, serving as a director of the Great Northern Railway Company and of the York Street Flax Spinning Company, and belonged to Drumbeg Parish Church. He was survived by his wife, daughter and five sons; a sixth son, Captain Frederick R. Coates, had been killed in the Boer War. Victor Coates' widow Margaret became the named occupier in the Valuation Revision Books from 1912 until her death on 24 December 1923.

Rathmore was then acquired by Samuel McCrudden, a linen manufacturer. In 1943 it passed from McCrudden to Harland and Wolff, who had drawing offices erected in the grounds. In 1947 the house was acquired by the Religious of the Sacred Heart of Mary, a Catholic order that had originated in France and established a presence at Lisburn in 1870. The house was used as a convent and in 1949 a preparatory school was established. By 1952 the valuation records refer to Rathmore Convent School, and in 1953 a grammar school opened at Rathmore. As numbers grew, further buildings were opened in the 1960s and 1970s. In 1997 the Sisters moved out, and the former convent was subsequently acquired by the school for refurbishment to provide additional classrooms. Plans for new school buildings were approved in 2001 and work began the following year, including the careful restoration of the original Rathmore House to house history, politics and religious education classrooms as well as the school chapel. By the summer of 2005 the building work was largely complete and the new school was ready for the start of the autumn term.

The building now occupies the north side of a large paved quadrangle surrounded by modern two and three-storey buildings to the east, west and south, with a small circular landscaped area to the north. While the modern buildings somewhat compromise the original setting, Rathmore House remains an important building and, as a school, carries considerable social importance for the local community.