The building freeholder needed to utilise the flat roof space on top of their building and add a further 2 penthouse flats overlooking Buckingham Palace.
Croft Structural Engineers Ltd completed an extensive survey of the existing building and historic archives to determine the existing structural layout. The typical concerns the general public have with these schemes is whether the additional weight will cause the building to collapse. While this possibility is checked, it is uncommon for it to be a concern. With a high rise building of this type, the main concern is how the building will react if a gas or other explosions that would occur. Considering the location adjacent to Buckingham Palace Mews, the risk of a terrorist attack is elevated.
Croft has good experience of these types of buildings and how to increase their resistance to explosion. With a historic building it is not possible to increase the whole building without significant retrofitting of all floors. As they were occupied this was not an option.
With our extensive knowledge of historic construction we were able to propose a viable scheme to deal with the issues of terrorist explosion and access to this inner city site.
Due to its location, the large structural items would need to be craned onto the roof, and this must be kept to a minimum. Croft with its experience in modular designed proposed a modular design that allowed the primary frame units to be delivered and erected over two weekends. Due to the critical nature, Croft provided site attendance over the delivery weekends to answer any queries that may have arisen. With all the preplanning and checking procedures, all the steelwork fitted perfectly.
Around the top of the building a reinforced concrete being was cast behind the parapet directly above the existing steel frame. In an explosion, the concrete ring beam is designed to carry the loads from the new penthouses away from the affected area. The loads are transferred from the damaged columns and floors to adjacent columns.
The added advantage of the concrete ring beam was to transfer the loads from the modular frame to the columns.
Croft Structural Engineers Ltd worked closely with the Party wall surveyors, checking engineers and the local authority to ensure that the building design correctly complied with all regulations.
With Croft Structural Engineers’ knowledge base we have helped the client realise the additional potential in their property :- two penthouses in a prime central London location.
Contract Value: £1,800,000
Type: Additional storey
Client: Lawrence Smith
Architect: King Conroy