Project Description

Abbey Pynford were appointed to design and construct a scheme to provide the maximum possible area for a one-storey retro-fit basement below an existing three-storey brick property in Marylebone, London.

The site had restricted access via a cobbled mews and the presence of an adjacent existing basement required the use of a number of Abbey Pynford’s innovative construction methods;

  • Restricted access piling with fully PUWER compliant caged rigs
  • PynWall underpinning
  • Temporary propping of superstructure with PynColumns & Pynford Stooling
  • Stainless steel masonry support system
  • Cavity drainage system

Construction Phase Highlights


A fully caged mini piling rig was used to install a bored contiguous pile retaining wall to the front of the property and temporary piles within the footprint of the property.


The existing superstructure was temporarily supported on steel props whilst a reinforced concrete underpinning slab was constructed at ground level. This slab transfers the load of the existing structure to the PynWall underpinning bases.


Abbey Pynford’s in-house designed PynWall system was installed beneath the 3-storey structure & listed garden wall, enabling a top down construction method.


In order to provide a Grade 3 performing structure to BS 8102, a cavity drainage system was specified and installed by Abbey Pynford. The system comprises of a waterproof membrane applied to the walls & basement slab which channels water to a sump tank to be pumped out of the basement.