Basement Construction

Specialist basement contractors for London and the South East

For over 25 years, O’Sullivan Civil Engineering has delivered complex basement structures for prime residential, commercial and heritage projects across London and the South East. We work as a trusted delivery partner to civil and structural engineers, main contractors and high end property owners who need robust, buildable solutions on constrained urban sites.

Our focus is on structural integrity, low noise methodologies and a clean, well managed site that reflects the standards expected by discerning homeowners and developers.

  • Typical applications include:
  • New single and multiple depth basements
  • Retro fit basements beneath existing properties
  • Leisure suites, pools, cinemas and car lifts
  • Extensions beneath gardens, courtyards and mews
  • Blue sky basements

Expertise in challenging ground conditions

Our teams are experienced in challenging ground conditions having worked on project with high water tables and underground rivers, where build‑sequence planning and waterproofing are critical to programme and cost. We bring practical engineering judgement to every scheme – selecting and value‑engineering the most appropriate solution.

Working with engineers and main contractors

Civil and structural engineers rely on us to turn complex designs into safe, buildable solutions on site. We engage early to review temporary works, construction sequence, access and buildability – helping de‑risk the project and protect neighbouring assets throughout.​

Our approach includes:

  • Collaborative review of engineer’s design and construction sequence​
  • Temporary works design, installation and on‑site adjustments
  • Clear reporting on progress

Proven track record

We have successfully delivered basements across The Royal Borough of Kensington and Chelsea, Belgravia, Regents Park, Hampstead, Wimbledon and the wider London and South East region, including Burkes Road, Egerton Crescent, Eaton Place, Holland Villas Road and Parkside.

Our portfolio also includes complex basements for heritage and specialist buildings such as The Crypt underneath Bevis Marks Synagogue in the City of London and St Katherines Precinct within the Crown Estate