The National Theatre – London

The National Theatre – London

Situated on the south bank of the river Thames in London the National Theatre is an iconic long standing London landmark, constructed from reinforced insitu cast concrete.

The task was to provide a new stair access to the upper gallery level and to construct a new spine fin wall to match the existing structure in terms of colour, finish and board marking, along with a ‘flying’ parapet panel to junction with a newly reinstated balcony.

Left – The existing insitu R.C. stair was cut back and removed, with the balcony wall edge shown to be cut back to allow the new stair to land.

The remainder of the existing balcony parapet was to be made good or to be replaced with new panels to match the existing board marked pattern.

Due to the undercroft car parking, a weight limit was imposed upon the existing floor slab and the fin wall was produced ‘hollowed out’ to remove mass.

Each of the existing board marked walls were site surveyed to ascertain both the top of board levels and the height of each board. This information was then transferred on to the exposed faces of the new panels to ensure that the new works would align with the existing.

Birds mouth joints between the panels at the external corners give the impression that the spine wall is produced as one solid instu cast component, where as actually it is a front, rear and top panel cladding a secondary steelwork frame.

View from upper gallery.
Board marked finish.

The right hand side of the ‘flying’ parapet panel is secretly housed into the left hand side of the fin panel with a projecting R.C. tenon, which seats onto an inverted supporting angle fixed to the secondary steel U.C. within. The front fin wall panel has a rebated mortice to the left hand side to allow the tenon to pass through. The left hand end of the parapet panel takes a bearing directly onto the existing balcony slab edge.

Below is a picture of the finished arrangement. If the fin wall had have been produced from solid cast R.C. it would have weighed in excess of twenty tonnes, but by producing the elements as precast board marked panels, the fin wall weighed half that amount.