Structural works to London vaults

The existing vaults of many London properties, which typically extend beneath the pavement, offer an opportunity to provide additional space for storage or M&E plant. Typically these are low headroom, small spaces and difficult to use effectively.

As such Abbey Pynford Geo Structures are frequently asked to consider structural alterations of vaults; to lower the existing ground floor level, provide openings between adjoining vaults or both.

These works often involve some specific challenges such as;

  • Shallow existing foundations
  • Vaulted ceilings
  • Restricted space and access
  • The strength and structural adequacy of the existing structure may be unknown
  • Lateral thrust at spring points and a reliance upon adjoining vaults
  • Rear walls of vaults retaining highways and subject to surcharge and cyclical loading
  • Internal walls acting as shear walls retaining the rear walls.

Vaults are often adjacent to public highways and therefore are subject to Technical Approval of Highway Structures from the Local Authority

Abbey Pynford Geo Structures can call upon the extensive experience of our in-house Chartered Structural and Civil Engineers along with our extensive Geotechnical knowledge to provide bespoke solutions for these situations.

A recent project within London’s West End that Abbey Pynford Geo Structures were involved with required two vaults to be lowered and the internal supporting masonry wall between the vaults to be removed. The solution proposed by the client team was to underpin the perimeter and install a structural steel box frame in place of the internal wall.

The temporary works required to remove the internal wall and install the steel frame, while retaining the vaulted ceiling over and the soil it supported were detailed and drafted using a 3D BIM model in Revit.

A key requirement of the temporary works was not to significantly inhibit the ability to undertake the demolition of the internal wall and subsequent construction of the steel frame. Within small vaults this is particularly difficult and therefore a cantilever frame within each vault was proposed to enable access to the working area by our operatives.

The innovative design chosen incorporated elements of bespoke structural steelwork with bolted connections which could be manhandled and assembled within the vault and timber beams cut and bolted to follow the ceiling profile. Timber spreaders were used to support the vault between beams.

Following sign off of the design from the Local Highways Authority, the structures were constructed and installed by Abbey Pynford Geo Structure’s skilled labour force.

Abbey Pynford Geo Structures are the recognised market leader in the foundation and complex geostructural engineering sector. We specialise is retro-fit basements, all forms of underpinning, structural opening up (Pynford beams) and lifting and moving of buildings. Projects are undertaken on a D&B or build only basis.

If you have a project that you would like us to look at or just discuss options, please contact us.