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
RESTRICTED ACCESS PILING
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.
TRANSITION RAFT SLAB
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.