Rathmoyle, 40 Craigdarragh Road, Helen's Bay, Co Down, BT19 1UB

Rathmoyle is a substantial asymmetrical split-level Arts and Crafts house with Art Nouveau detailing, built in 1901 to designs by the eminent local architect Vincent Craig, who designed it for his own occupation. It stands in extensive landscaped grounds on the east side of Craigdarragh Road and is one of the best complete surviving houses of its type from the period, retaining its original setting and representing an intact example of Craig's work.

The house is generally two storeys, rising to a third attic storey on either side of a four-stage entrance tower — the attic sits at a higher level to the right. To the rear there is a single-storey annexe joined to the main house by a curved link block. Roofs are pitched and hipped, clad in Rosemary clay tiles, with the attic storey lit by gable windows and dormers variously detailed with flat leaded or hipped tiled roofs. Chimneystacks are roughcast with flat caps and multiple clay pots. Rainwater goods are half-round cast iron on overhanging eaves with exposed rafter tails. The walling is roughcast over a rock-faced sandstone ground floor, topped by a sandstone string course. Gables are variously treated with decorative half-timbering and bargeboards. Windows are generally timber or metal framed casements (Crittall) with cement rendered reveals and projecting stone sills, unless otherwise noted. A number of feature windows have leaded and stained Art Nouveau glazing set in sandstone surrounds, as described below.

The principal elevation faces northwest and is asymmetrically arranged around a four-stage entrance tower, detailed to match the house and topped by a pyramidal roof. The tower is fronted by a projecting two-storey porch, square to the ground floor and rising to a canted first floor, with carved stone heraldic lions placed at each chamfer bearing the date 1901. A multi-panelled oak door, inset with a wicket door and fitted with ornate brass furniture, is contained within a curvilinear ashlar sandstone surround with Art Nouveau stained and leaded sidelights with wavy heads, all accessed up two curving stone steps. The first stage of the tower has a transom and mullion window with Art Nouveau detailing; the upper stages each have a three-light casement with horizontal emphasis; and the fourth-stage watch tower is set some way above, projecting slightly over a moulded stone string course. The remainder of the principal elevation has a complex arrangement of gables and fenestration. Most windows are as described, with the exception of that to the right of the entrance tower, which is a transom and mullion sandstone window. To the left, a two-storey gabled projection is lit by a full-height canted bay, fully glazed to each floor, with a catslide roof to the left over an outshot lit by an ornate Art Nouveau window.

The northeast elevation is two storeys and relatively plain in appearance, with a corner window to the first floor and a bipartite window to the ground floor right. The southeast rear elevation is divided by a half-hipped rear extension offset to the right of centre, extended further to the southeast by the single-storey annexe. To the right of this extension, the two-storey section of the main block is plainly detailed, leading to the rear yard, and is lit by a casement to the first floor and a one-over-one sash to the ground floor. There are also two segmental arched entrances: one to the coal yards and one an original timber door with an oval glazed panel leading to the kitchens.

The main section of the east elevation, to the left of the annexe, is defined by a series of variously detailed gables and irregular fenestration including a bow window to the ground floor centre. The extension is plainly detailed. The annexe has a pitched roof with an ornate timber ventilation stack to the ridge, topped by a weathervane, and a chimney to each end. To the south it is lit by a mullioned casement window, each pane diminishing beneath a single segmental arch with ashlar sandstone voussoirs. The southwest corner of the annexe has an Arts and Crafts style canted bay window with lattice lights, timber mullions and transoms, and small-paned lights above, all topped by a painted leaded dome with a tall finial. The south end of the annexe is abutted by a cast-iron conservatory. The east elevation of the annexe is lit by a substantial roughcast canted bay with Art Nouveau glazing. The annexe is connected to the main house by a curved link block lit by a series of Art Nouveau windows with segmental heads, all in a timber frame over roughcast plinth walling, with a central wide timber door of three panels beneath an Art Nouveau leaded glazed panel matching the others.

The southwest elevation is part-gabled and has a box bay over two storeys to the right with continuous glazing to each floor, and a window to three floors on the left, including a bowed bay to the ground floor.

Internally, the house is notable for the variety of period styles brought together by Craig. The entrance hall and dining room are distinguished by a medieval theme, while the heart motif — familiar to Arts and Crafts design — is employed throughout. The original fenestration, including high-quality Art Nouveau glazing, is largely intact.

The house bears a datestone of 1901 and appears on the third edition Ordnance Survey map of 1900–02. It enters valuation records at the same period, in 1902, recorded as a house, offices, gate lodge and land valued at £143 15s, occupied by Vincent Craig and leased from the Marquis of Dufferin. Valuer's notes of 1902 include a plan and dimensions for the house and gate lodge, with the cost recorded as approximately £5,000. Vincent Craig was the elder brother of Lord Craigavon. He moved to England in 1911 and sold the house to Herbert Brown, a Belfast linen merchant, who is listed as the occupier in 1913. According to Brett, Brown sold it in 1927 to the Mitchell family. In 1933 William Charles Mitchell is listed as the occupier, at which time the accommodation comprised thirteen bedrooms, three reception rooms, a kitchen, scullery, two pantries and two bathrooms. The house was then rented until 1947 to Captain Sam Duffin, and subsequently passed to new owners who used it to accommodate overseas visitors and for hospitality, training and conferences, while retaining its domestic character with many fine pieces of Edwardian furniture. The house was refurbished and in parts redecorated in 1993 under the supervision of Michael Priest of London.

The house is set well back from the road in extensive grounds of formal lawns and mature trees and shrubs. To the front is a forecourt accessed by a winding tarmac drive from an entrance to the east. To the rear are separate housekeeper's lodgings and garages, and a small group of farm buildings. The main entrance is attended by a gate lodge and comprises a pair of electronic timber gates supported on roughcast piers with stone caps topped by ball finials.