Case Study - Alexandra House, Central

Project data

  • Customer
  • The Hongkong Land Property Company Limited
  • Value
  • Confidential
  • Area
  • 31,000 sq ft
  • Form of contract
  • Main contractor
  • Programme duration
  • 25 months
  • Completion date
  • May 2020
  • Architect
  • Aedas
  • Quantity Surveyor
  • Arcadis
  • Structural Engineer
  • WSP
  • M&E Engineer
  • Meinhardt


Situated at a 37-storey, grade-A commercial building in the heart of Central, Alexandra House, ISG was appointed to deliver a highly complex alteration and addition (A&A) and construction project across three phases.

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Alexandra House's rooftop before the project commencement
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Alexandra House's rooftop after completion of the new plant room

The project

Giving new life to an historic 44-year-old building and improving its operational capacity, ISG completed extensive structural and engineering works for extensions of five lift shafts and construction of a new rooftop plant room.

The plant room enabled the relocation of the mechanical and electrical floor from level 34 to the rooftop, while level 34 was converted into a new office space with new toilets and lift lobbies, expanding the leasable space for the building’s owner.


ISG was able to overcome one of the greatest challenges of the project – the vertical transportation of heavy, oversized construction materials from the ground to the highest point of the building using a derrick crane, which required a professional hoisting team, as well as a detailed calculation and work schedule. The deployment of the derrick crane not only enhanced project efficiency, but minimised the impact on the operational commercial building, and its tenants.

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Another challenge was to create openings of the external walls for installing new windows, particularly for typhoon seasons. A special dry cutting method was used to cut the concrete walls, avoiding any possible fall of the concrete from level 34 and mitigating risks of working at height.


ISG’s excellent health and safety practices on the project led us to win a silver award in the Best Refurbishment and Maintenance Contractor in Occupational Safety and Health category at the 20th Construction Safety Forum and Award Presentation Ceremony, held in June 2019.

The project was challenging and required a high level of technical expertise in structural and A&A works. The three-phased project was completed successfully after 25 months in May 2020, a testament to the ISG project team’s expertise and effective solutions.

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