9th May 2022

Reducing levels for the new cathedral floor

Within the cathedral reordering masterplan, which vHH undertook in 2008-09, we proposed altering the floor levels to remove the historic steps between the nave and aisles and the spaces further east, with a new floor being installed to distribute services, provide un-stepped access, and improve the appearance of the cathedral. This is an insulated and moisture-open construction, to improve comfort and reduce energy use, and to reduce the tendency for moisture evaporation from, and salt damage to, the stonework of the walls and columns.

The first activity is therefore to remove the floor and reduce levels, under an archaeological brief. This reveals almost no archaeology, except evidence and remains of previous services routes, and their consequent disturbance to the subsoil over the entire area. The reduced levels allow us to  provide routes for new services containment, and to give enough depth for the glaspor (foamed glass pebble insulation / capillary break) and limecrete floor slab.

At the abutment of the phase 1 works, to reorder the chancel and crossing to reinter the remains of Richard III, the similar build-up of stone floor, lime mortar bedding, limecrete screed, limescrete slab and glaspor insulation is exposed.

One unwelcome surprise was the discovery that the main arcade piers had been underpinned with concrete, very close to the floor level, which precluded covering them with the limecrete slab, with a casting date already booked in for the Limecrete Company to install.

After some intense dialogue with Price and Myers, the structural engineers, and Messenger, it was agreed to link these pads together with more mass concrete, creating strips along each arcade. By setting these out to align with the floor pattern joints above, we allowed for any relative movement between the limescrete slab and concrete floor to take place at the joint.

The large brickwork services duct is to be reused as our major services run from the boiler room to the north, backfilled but with a series of ducts and chambers giving access to the smaller services runs that issue from it.

Outside the cathedral, the contiguous piled retaining wall for the HLC basements has been installed, and its capping beam cast. This will enable the deep basement void to be excavated by archaeologists without undermining the shallow foundations of the cathedral and the Deanery, both immediately beside it.