St. Johns, Scandrett Street
A church lain derelict since being damaged by bombing during the Second World War. Utilising the full range of JNP Group engineering skills, the building was successfully converted to provide new apartments within the historic facade whilst stabilising and renovating the Clock Tower.
Old burials and coffins had to be sensitively relocated by specialists, before the land could be decontaminated and declared free of anthrax.
The excavations proved to be difficult and deeper than anticipated leading to settlement within the site and required JNP Group to design temporary restraints/supports to prevent collapse.
The existing tower was retained along with the crypt walls which retained Scandrett Street and Green Bank pavements/roads. These walls had to be temporarily propped during demolition of the crypt roof slab.
The proposed foundation design had to consider the high water table from the nearby River Thames, the possible migration of contamination from historic burials and the stability of the adjacent highways and buildings, particularly the listed clock tower. The base slab of the crypt was retained and punched through at various positions to accommodate new piles to support the new raft slab. The piling was carried out very carefully to avoid affecting the retained clock tower, crypt walls and their historic foundations.
The new basement structure, with external RC walls and internal load-bearing masonry walls was built in and around the existing structure, forming new lightwells and basement access. The walls were designed to highway standards to support parking within the site and the highway along Green Bank.
The load bearing basement walls supported a new suspended precast concrete floor system and the timber framed apartment superstructure. The external facade needed structural support in various locations, including the use of steel support members combined with reinforced masonry to combat deflections and headroom issues.
A key element of the success involved matching the existing and sourcing materials from various similar demolished buildings within the locality.
JNP Group services provided:
- Geotechnical advice regarding removal of ancient graves.
- Temporary works to prop old walls.
- Piled foundations through crypt slab.
- RC retaining walls.
- Load bearing masonry structure.
- Facade retention.