13-14 Hanover Square

In 2020, O’Keefe were employed to carry out the controlled demolition of 13-14 Hanover Street in Mayfair, with the works paving the way for the extension of the new building to be constructed; a double storey basement & seven storey buildings, offering prime office retail and restaurant space.

O’Keefe used two controlled methods of demolition on Hanover Street, using both hand and a top-down methodology. Works also included façade retention and protection, temporary works to support part of the existing Hanover Street façade with three party walls, substructure and superstructure including formation of a ground floor slab.

With an extra basement level, the O’Keefe team were tasked with underpinning up to 7m along all three party walls. With one party wall, originally specified as a sheet-piled structure, the team noticed that the original design of using contiguous bored concrete piles, would have caused severe interference with a mains electric supply. All existing cables would have had to be lifted and moved temporarily to the other side of the street. O’Keefe designed a solution to install contiguous piles in front of the existing retaining wall.

Due to the location and size of the project, another challenge O’Keefe faced on this project was logistically coordinating works to simultaneously carry out underpinning and piling works whilst demolishing the upper storeys of the building and taking into consideration neighbours located closely to the works.

With all three neighbouring properties fully occupied, one by a Michelin-starred restaurant, works had to be very carefully planned and all noisy works scheduled to cause minimal disruption to the occupiers within the buildings.

This required O’Keefe to adopt a more pragmatic approach, utilising hand demolition techniques to mitigate any impact caused to the walls and abutting structures.

Due to the project’s sensitive & busy urban location and proximity of nearby structures, access and egress from site also presented challenges. These were mitigated by O’Keefe’s creation and implementation of a robust logistics regime which ensured the impact on neighbouring parties was minimal and the safety of all stakeholders and public maintained.

Dedicated traffic marshals were employed to manage access and egress controlling traffic and pedestrian movements to ensure full site-safety.

In a further effort to reduce the impact on neighbouring parties, demolition works were carried out with suitable dust suppression systems installed with a water supply gained from a metered supply source. Other environmental pollutants such as noise and vibration were carefully monitored, and constant communication and interface was maintained between O’Keefe and third parties, with weekly site visits, monthly meetings with the environmental agency and via a real-time monitoring system.

As the project was located in such an exclusive area of London, O’Keefe considered it of the utmost importance to foster good relations with surrounding businesses and residents. This was achieved by maintaining consistent liaison with all stakeholders, publishing newsletters, ensuring the tight side road (Pollen Street) remained open throughout the works and ensuring working hours and breaking times were in-line with the voluntary section 61 notice applied for by O’Keefe prior to the commencement of any noisy works.

With all arisings from the demolition phase of works removed from site and recycled, along with other initiatives, this project earned a BREEAM rating of excellent.

• Contract: 13-14 Hanover Street
• Client: Frank Capital
• Location: Mayfair, W1S 1YH
• Value: £4.5m
• Duration: 49 weeks
• BREEAM RATING: Excellent
• Scope: Hand & Top Down Demolition, Façade Retention, 7m Underpinning, 3 Party Walls, 2F Basement Formation