16-24 Waterloo St, and 1,3 & 4 Castle Gate, Londonderry, Co. Londonderry, BT48 6HG

16–24 Waterloo Street and 1, 3 & 4 Castle Gate is a three-storey, multi-bay red brick Edwardian commercial building constructed in 1907–08 to designs by Patrick H. Elliott, a local architect who had established his independent practice in the city in 1905. It occupies a corner site at the junction of Waterloo Street and Castle Gate, immediately outside the historic city walls in the north-west quarter of the Walled City, with the River Foyle to the north-east. The building sits within a terraced row of red brick and rendered commercial buildings in the Historic City Conservation Area.

The building has an L-shaped plan with a low solid parapet wall to a natural slate pitched roof. Two large red brick chimney stacks rise from the north-east and north-west sides, centred on the ridge. The principal elevations face north-east onto Castle Gate and north-west onto Waterloo Street, with a canted corner elevation facing north. This canted corner is the building's most distinctive feature, containing a recessed entrance doorway at ground level with curved glazed panes above a stall riser, and a curved oriel window above at first floor level. A parapet with balustrade above the oriel creates a small balcony to the second floor window. The corner is topped by a decorative rendered chimney stack with a cornice, bearing the date 1907 set inside decorative moulding with scrolled mouldings below.

The north-west elevation is divided into four bays by pilasters running from ground level to parapet level. A deep moulded rendered and painted frieze containing shop signage divides the ground floor horizontally from the first floor. Ground floor shop-front windows have square-headed openings with shouldered arched timber window frames, divided from adjacent bays by rendered and painted pilasters. To the right-hand side of this elevation are two timber entrance doorways side by side: the left-hand door has a rectangular glazed panel above two raised and fielded panels with a plain transom light over, while the right-hand door is four-panelled with raised and fielded panels and a blind transom light over. The upper floors are of red brick laid in English Garden Wall bond. At first floor level, rendered aedicules with scrolled edges, a central keystone, and a cornice above frame the windows, which are 8/2 casements with the lower section split vertically into two sections. The first floor bays are divided by rendered pilasters that are reeded up to transom level. Second floor windows align with those below; the left-hand bay windows match those at first floor but without aedicules, while the windows in the right bay are 8/2 timber sliding sashes, also without aedicules. A moulded sill-course spans between pilasters at second floor level. The elevation is topped by a salient cornice with a low parapet wall above.

The north-east elevation facing Castle Gate is of similar fenestration to the north-west elevation, with bays at first floor level divided by rendered pilasters, rendered aedicules to first floor windows, and a moulded sill-course to the second floor windows above. The right-side bay contains a coupled window aligned with the same on first floor level. The entablature above second floor level is topped by a salient cornice with a low solid parapet wall above. The ground floor shop-fronts along this elevation consist of a series of windows with square-headed openings and shouldered arched timber window frames. At the extreme left of this elevation, an iron gate between the building and the city walls at Castle Gate gives access to a shared rear courtyard. There are two timber doors to the right of the gate, similar to those on the north-west elevation, along with two further single door openings to shop units set among the shop windows. The south-west side is abutted by the neighbouring property at No. 20 Waterloo Street. The south-east gable-end elevation immediately overlooks the historic city walls; the walling is of smooth-rendered painted finish with a company printed logo at the apex. This gable end is topped by a small red brick chimney stack with a stepped cornice and two circular terracotta clay pots. Full access to the rear was not possible at the time of survey. Materials throughout are natural slate to the roof, cast-iron rainwater goods, brick with stucco dressings to the walls, and timber casements, multi-pane windows, and timber sliding sashes.

The building was commissioned by Henry McKeown, a local boot and shoemaker who had previously held business premises along Waterloo Street, and replaced a house and public house that had formerly stood at the corner of Castle Gate and Waterloo Street. It was constructed by James Gallagher, a local contractor with premises on the Strand Road. On completion, the building was divided into a number of ground floor retail units with offices and storage space in the floors above. Nos. 22–24 Waterloo Street were occupied by McKeown's shoemakers, while the adjoining units on Castle Gate were occupied by local merchants Bernard McLaughlin and Robert Flannigan. The total rateable value of the building was set at £72 and 10 shillings upon completion in 1908.

The area beneath the walls where the building now stands was originally used as a beast market in the early 17th century, later serving as a parade ground. In 1806, the city walls were breached to create Castle Gate, providing quick access to the Cow Bog on Waterloo Street. The first buildings at the junction of Castle Gate and Waterloo Street did not appear until the mid-19th century. The McKeown family retained ownership of the building until at least the 1970s. Under the First General Revaluation of Property in Northern Ireland (1936–57), the largest ground floor retail unit — comprising No. 1 Castle Gate and No. 22 Waterloo Street — remained occupied by John McKeown's shoemakers shop, with the remaining units in use as shops and offices by other tenants. The total rateable value was increased to £120 and 5 shillings by the 1950s and raised further to £177 by the end of the Second Revaluation (1956–72).

The building was included in the Historic City Conservation Area in 1977. It has since undergone extensive restoration carried out by Tracey Architects as one of the first refurbishment projects undertaken by the Walled City Partnership under a Townscape Heritage Initiative Scheme. This work involved the recreation of the ground floor shop fronts, restoration of the building's windows, removal of shutters, and repointing of the brickwork in lime mortar. Despite the survival of little or no historic detailing internally, the external detailing and the recreation of the shop fronts define this building as special within the Historic City Conservation Area adjacent to the city walls.