Located in the vibrant heart of Dublin city centre just 140 m south of the River Liffey and immediately north of Trinity College, the major mixed-use regeneration of College Square has completely reshaped the urban landscape.
The bold mixed-use development unites two individual sites, College House and Apollo House, forming part of a regeneration programme led by Marlet Property Group. The site was neglected and unused for a generation, despite its location at the edge of three streetscapes adjacent to one of Dublin’s prominent interchanges and bookended by the cities two major infrastructure networks, the DART and LUAS. The existing 1970s College House, Apollo House, Screen Cinema and a collection of low-rise buildings of bleak concrete construction were demolished in 2019, clearing the site for this major urban regeneration development.
A prominent new feature on the city’s skyline
Originally envisioned as two distinct ten-storey office buildings, the College Square development underwent a transformative redesign under award-winning architects, Henry J Lyons. Following the amalgamation of the two plots, Marlet Property Group set their sights on a new unified commercial scheme, aiming to set a new benchmark for sustainable design. The reimagined development now delivers high-end residential units, a 500-seater entertainment venue, and an impressive 540,000 sq ft of commercial Grade A office workspace which has achieved LEED Platinum Certification.
On the northern corner of the site above the Apollo House building sits the tower section of the development, at 22 storeys it accommodates 58 residential units and 2,200 sq ft of internal communal amenity space. It also features external terrace areas above the commercial buildings and stands as one of Ireland’s tallest occupied structures – a spectacular addition to the Dublin city landscape.
Sitting above a new double-storey basement which covers the full extent of the site, is the 37,000 sq ft double-height entertainment venue, alongside car parking, bicycle spaces and ancillary areas. Punctuated by high quality soft and hard landscaping to ensure the best possible integration with its urban setting, a new public plaza and pedestrian street runs through the development’s centre, linking the Tara Street rail station with the prominent College Green in front of Trinity College.
Designing a new icon
Working in collaboration with the client and architects our team delivered civil and structural engineering services from conception to completion for this significant project. Our specialists helped to shape one of the most sustainable buildings in Ireland, which is now home to the largest single office letting to take place in the European office market
since 2021.
Considering the proximity to the River Liffey, our structural solution effectively sealed the perimeter of the site to prevent the ingress of ground water as the basement excavation proceeded via a secant pile wall, with the piles extending into the underlying mudstone bedrock. To restrain the top of the piled wall, anchor ties were used, uniquely using glass fibre instead of conventional steel rods. This innovative choice was made to prevent complications during future excavations beneath surrounding roads, where the ties extend. In addition, internal propping was deployed to stabilise the wall adjacent to neighbouring buildings, ensuring structural integrity throughout the excavation phase.
The project team faced numerous challenges during enabling works and basement excavation, including the diversion and decommissioning of major buried services and
utilities. Close collaboration with the LUAS light rail system operator was essential to agree measures to monitor and protect the on-street rail line along the western boundary of the site. The formation level for the new pads and rafts of the two-storey basement lies deep within the mudstone bedrock strata and well below the tidal groundwater table. As a result, the basement has been designed as a fully water resisting structure, incorporating reinforced concrete walls and an integral White Tank System to ensure long-term waterproofing of the entire basement box.
For the commercial floors, the design team opted for a post tensioned concrete slab system, supported by a reinforced concrete frame. This proved to be the most value-focused solution, optimising slab depths and creating a more generous column grid spacing. The upper office floors utilise steel column and high-efficiency composite cellular beams around the perimeter of the setbacks, helping to preserve the internal column grid consistent with the floors below. This system also had a lower embodied carbon figure compared to more traditional construction, adding to the buildings green credentials.
A new diagonal shortcut has been created across the site, linking College Green to the River Liffey and Tara Street Station. This new route passes beneath the buildings, and above the clear span venue, acting as a wide covered passage opening onto double-height entrance lobbies to the offices, a venue reception, and a landscaped plaza at the centre of the site. To accommodate this, column positions were aligned so they did not fall onto either the access route or within the venue space. Four major column lines were allowed to proceed from foundation up to superstructure with the more minor columns supported on a series of 20-metre transfer beams at ground level. This strategy created an impressive double height subterranean space with the active plaza and
street passing above.
To achieve the architectural vision for the plaza at Tara Street with minimal columns, a bespoke six-storey high Vierendeel truss was developed. This structural solution allows the façade to appear as a large, unsupported 21-metre clear span.
The tower section of the development, rising from levels 12 to 22 above the former Apollo House site, was introduced through a later planning amendment that expanded the projects scope. Its location, offset from site boundaries and positioned directly above the vertical cores, meant it was structurally disconnected from the lower grid, with minimal opportunity to drop vertical elements through the commercial floors and basement below. To overcome this challenge, the design team adopted a highly inventive solution. Vertical steel cantilever trusses were strategically placed along the apartment party walls, which aligned consistently from levels 12 to 21. These trusses were anchored back to the central cores, allowing the tower to be supported independently of the lower structure. This enabled the tower to effectively ‘float’ above the commercial superstructure, minimising disruption to the base build. This incredibly ambitious solution was born out of the determination of both the client and the design team to enhance the architectural and commercial impact of the scheme.
Unearthing a glimpse of the past
Given College Square’s central location, extensive archaeological investigations were undertaken as part of the enabling works at the site. This uncovered the historic ruins of a structure which once served as a covert church for Catholics living in the south inner city. Detailed research led to the discovery that the church was first built on the site in 1709, in Penal times, when the practice of Catholicism was banned. These important discoveries were preserved, recorded, and carefully removed.
Commenting on this landmark regeneration’s impact, Waterman Moylan’s Associate, Anthony Byrne, said: “We are proud to have played a role in bringing this incredible development to life, creating a new icon for the Dublin skyline. The site’s location, history, and ground conditions meant that close collaboration across the design team was vital, and this led to a series of innovative design solutions. College Square has set a new benchmark for sustainability focused, mixed-use development in central Dublin, and this remarkable scheme demonstrates how a variety of building uses can be integrated successfully, even in the most constrained urban locations.”
