D.U.P. Constituency Office, 29 Castle Street, Lisburn, Co. Antrim, BT27 4SP

This five-bay two-storey building of red brick and stucco, built between 1883 and 1884, stands on Castle Street in Lisburn. It was originally constructed as an estate office for Sir Richard Wallace, Baronet, and occupies the site of a French Huguenot church dating from the early eighteenth century, which had been demolished before the building's construction.

The building is rectangular on plan, facing south, with a mid-terrace position. Its most distinctive feature is the decorative classical architectural treatment of the front elevation. The symmetrical five-bay façade is crowned with a balustraded parapet wall resting on a projecting cornice supported by scrolled modillions. A pitched natural slate roof with two tall profiled render and red brick chimneystacks rises behind the parapet, with boxed dormers set within it. The red brick walling is laid in Flemish bond with tuck pointing, and rusticated render quoins mark either end. A string course runs below the eaves cornice, with a platband forming part of the continuous sill course to both ground and first floors. Below the ground floor sill course, rustication sits upon a moulded plinth course.

The front elevation displays exceptional quality in its classical detailing. The five window openings to the first floor feature full Doric entablatures above, including a tripartite window set above a later-added carriage arch bay to the east. The central first-floor window has a full pediment supported on scrolled console brackets. Ground-floor window openings have architrave surrounds mounted on blocks to profiled sills, with square-headed openings throughout containing horizontally-glazed 2/2 timber sash windows. The first-floor windows are similarly framed. All windows retain their original timber sashes.

The central entrance comprises a square-headed door opening with double-leaf timber panelled doors beneath an overlight. The doorway is framed by an architrave surround flanked by panelled pilasters on plinth blocks, with a pair of scrolled console brackets supporting a segmental pediment above. The door opens onto a tiled step with terrazzo between the jambs. To the east, a segmental-headed carriage arch opening—added later—features scribed voussoirs, bowtel moulding, and a linenfold keystone. Above the arch sits a naturalistic relief plaque depicting a long-necked creature with serpent tongue rising from a foliate arrangement. Pair of modern timber gates close the carriage opening beneath a brick arch with a loop-hole window and metal sheeted soffit.

The rear elevation is multi-bay and three-storey in red brick, with a two-bay two-storey section built over the carriage arch and finished with a flat roof. Cast-iron rainwater goods run across this elevation with stepped brick eaves. Various square-headed window openings contain mostly 6/6 timber sash windows, with a pair of timber casement windows to the second floor. A single-storey brick accretion to the centre provides a door opening into a gravel-paved yard. The east elevation is abutted by adjoining building No. 33, whilst the west is abutted by No. 27 Castle Street, with which it has strong group value as part of Sir Richard Wallace's original estate office complex. An early rubblestone boundary wall marks the western edge of the property. To the east and north, the yard is lined with modern two and three-storey brick dwellings.

The interior retains good quality original fabric throughout. Notable features include original joinery, plaster cornicing, and an impressive stone and iron staircase. The original council chamber survives, complete with decorative timber bookcases, a coved ceiling, and various original fittings. A secret stairway once connected what became the Town Clerk's office upstairs to the surveyor's office below, allowing the chief estate agent, Mr. Capron, to avoid unwilling clients by slipping away down the hidden passage. Speaking tubes with circular name plates at the wall junction originally connected the rooms. These features have largely been lost to later alterations.

The building's history reflects changing uses and ownership. When entered into valuation records in 1883, the property was noted as "unfinished", having replaced houses taken down after 1880. By 1884, it was completed and listed as the property of Sir Richard Wallace, Baronet, valued at £75 as an estate office and yard. By 1902, it had become the property of Lisburn Urban Council, and by 1905 it was listed as the offices of the Urban District Council, serving as Lisburn Town Hall for a period. It is now in use as offices for the Democratic Unionist Party.

The building contributes significantly to the heritage of Lisburn through its interesting history as part of the development of Castle Street, its architectural quality and proportions, and its group value with the adjacent historic structures originally comprising the Wallace estate office complex. It sits within a conservation area.