No. 1 Molesworth Street
No. 1 Molesworth Street is a five-storey, premium commercial office building located in Dublin 2. In addition to the five stories above ground level, the building has a 2-3 level basement across the full site. The basement excavation was undertaken using a secant piled retaining wall, with low movement tolerances imposed due to the adjacent Luas Cross City light rail line. The basement piling works were undertaken by Murphy Ground Engineering, with BAM Building responsible for the main works package.
The construction team appointed ByrneLooby as their design specialist for the sub-structure works. ByrneLooby prepared the design and detailing of the piled retaining walls, along with the design of the temporary propping and capping beam to restrain the pile wall at high level. The secant wall solution consisted of 1200mm diameter rotary bored piles installed to depths of up to 21m below ground level. This particular pile size was adopted to minimise the number of piles required, thus accelerating the basement construction program.
The development was being built at the same time as the new Luas Cross City Line. ByrneLooby were required to carefully assess the basement excavation to satisfy Transport Infrastructure Ireland (TII) engineers that the proposed works would not negatively impact their asset. ByrneLooby worked with the stakeholders to agree suitable construction sequences and monitoring regimes to ensure the works performed as expected.