Retaining wall for Bunhill’s Sunken Tomb

The Sunken Tomb, Bunhill Cemetery - Specialist Subcontractor for SSH Conservation

The Sunken Tomb in Bunhill Cemetery, London was rumoured to show the original ground level of the cemetery before the Black Plague victims were buried in their thousands causing the ground level to rise. The retaining wall had bulged and collapsed in places and was no longer safe for public to walk around on guided tours. We were asked to safely dismantle and reuse the original bricks once we had stabilised the earth banks on each side.

The Structural Engineer specified using 7N concrete blocks laid flat, with SS Bed Joint Reinforcement in every other course. Special BJF was used and tied on the corners of the blockwork. The blocks were laid in a sharp sand: OPC mix as specified.

Following the blockwork retaining wall, reclaimed LBC were sourced and packs were separated and mixed with the original bricks we dismantled. We set up corner profiles of the original angle of the battered wall. We set our course lines using a laser level and marked these off on the profiles. We set the bed heights for 8mm to be a better match for the original brickwork. We brought the brickwork up in Flemish bond, the bricks were bedded in a well graded plastering sand: NHL 3.5.

 Every 4 course at 900mm centres we restrained the brickwork back to the retaining blockwork using a screw in wall tie, these were grade 314 stainless steel and were secured using a thick gauge Rawl plug.