Oxford Street

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Location

London

Architects

Campbell Architects and Sterling Services

Products

Terracotta Faience

An unconventional facade in the bustling Hanover Square

Hanover Square is a famous square in Mayfair in London and it's situated to the south west of Oxford Circus, the major junction where Oxford Street meets Regent Street. This square was redeveloped around 1713 as a fashionable residential address by Richard Lumley. Nowadays, it is almost entirely occupied by offices. Oxford Street is a major road in the City of Westminster and Europe's busiest shopping street with around half a million visitors a day. This new build, retail scheme houses the New Balance flagship UK Store.

The unusual north elevation consists of precast panels faced with our bespoke faience tiles.

The project

We used a combination of poured and pressed tiles to achieve the 14 different tile types. It took a significant period of R&D to create the large tiles to the required tolerance. Throughout the multi-stage drying and firing, the tiles expanded and contracted and we had to adjust durations and temperatures to achieve the required dimensions.

The manufacturing process

This would have been a simple process for smaller and more uniform tiles of a flat profile, but due to the volume and shape of the tiles it represented a noteworthy challenge. Once the drying and initial firing had taken place, the first glaze and then the coloured 'mottle' was sprayed on, before being fired again. The start-to-finish manufacturing process for a single tile was approximately 14 days.

To manufacture a tile covered precast unit the mould is lined with face-down tiles prior to casting. However, the mounting of the tiles to the surface of the concrete panel did not fall into any British Standard. Therefore,S.Anselmo and Sterling Services developed a method that followed the principles where possible. A mechanical connection was required between each tile and the concrete, but they had to be de-bonded to allow differential thermal expansion between the tiles and the concrete.

As part of the tile manufacture process, large cross-shaped recesses were pressed into the rear face of each tile. It was essential to ensure that this did not provide a positive key for the concrete. To prevent the concrete flowing into the recesses, they were firstly filled with polystyrene strips and, eventually, the whole assembly of aligned tiles was covered in a layer of plastic sheeting to ensure the concrete did not directly bond with the tiles. The mechanical fixing was then achieved using a standard methodology of 4 Nº 60 degree pins per tile (orientated in opposing vertical planes) punched through the plastic sheeting.

Manufacture Sequence

Step One - Lay Tiles

Tiles are laid in timber moulds by using timber coursing guides for alignment and joint spacing. All tiles are laid with dowel holes pointing up or down in the vertical plane.

Step Two - Fill Recesses

The recesses were filled with polystyrene strips to support the plastic membrane and to prevent the weight of the concrete causing it to sag into the recesses. The joints were also filled with sand.

Step Three - Lay de-bonding sheeting

A Single polythene sheet was laid over all tiles to act as the debonding membrane. This assured that the tiles were not bonded to the concrete.

Step Four - Insert reinforcement cage and pins

The reinforcement cage was placed into position using 40mm plastic chair spacers to ensure the correct concrete cover and to prevent contact with the stainless steel pins. All stainless steel dowel pins were inserted through debonding membrane into pre-drilled holes in the rear of the natural stone and resined epoxy in place. Rubber grommets were placed on the pins where they entered the stone.

Step Five - Inset fixings and Pour Concrete

Stainless steel fixings and lifting sockets were positioned and tied into the reinforcement cage. The concrete was poured and vibrated, with exposed upper faces trowelled to achieve a smooth finish.

Installation

Installation on this confined site meant that on-site storage of panels was not an option, and that delivery sequencing and timing was critical. The main installation period was 8 weeks for the panels themselves, with a remaining 4 weeks for the hand fixed bricks, tiles, mastic works and natural stone elements.

Mansard Roof

The Oxford Street units were the first to be installed, and culminated in the challenging installation of the sloping mansard roof units. Elements of the parapet rear wall ere installed first for the main units to bear upon, with the infill units above the balconies and remainder of the parapet rear wall to follow. Due to the units forming part of the external envelope the joints had to be fitted with an EPDM before the tiles on each side of the joint were hand fixed over the top.