17 September 2025

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 is now complete.

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 existing 1970s-era 10-storey offices were demolished in 2019, clearing the site for this major urban regeneration scheme. The Henry J Lyons-designed development, for which Walls Construction was the main contractor, now delivers high-end residential units, an entertainment venue, and an impressive 540,000 sq ft of commercial ground floor space which has achieved LEED Platinum Certification. Rising 82m above street level, College Square’s residential tower has now become Ireland’s tallest. The new tower consists of 58 high end apartments spread across 22 storeys, all of which will benefit from 2,200 sq ft of internal communal amenity space, as well as external terrace areas.

 

Working in collaboration with the wider project team, we delivered civil and structural engineering expertise for this exceptional scheme. 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 limestone 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 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 limestone bedrock strata, 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 below-ground elements.

 

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, ensuring architectural precision.

Integrating the residential tower above the office floorplate introduced a series of complex challenges. To overcome these, the team developed a shared core between the tower and the offices below, providing essential stability. Complementing this, a steel frame structure transfers vertical loads from the tower directly into the core. The solution ensures the integrity of the office floorplates, and the basement car park beneath remain uncompromised.

Commenting on this landmark regeneration, Waterman Moylan’s director Richard Osborne said:

“The completion of College Square sets a new benchmark for mixed-use developments in dense urban settings, and this remarkable scheme demonstrates how a variety of building uses can be integrated successfully, even on such a constrained site. The site’s location, history, and ground conditions meant that close collaboration across the design team was absolutely vital, and this led to a series of innovative design solutions. We are proud to have played in a role in bringing to life this incredible development, creating a new icon for the Dublin skyline.”

College Square is one of the most sustainable buildings in Ireland and the largest single office letting to take place in the European office market since 2021.