Inmos Microprocessing Factory Awarded Prestigious Grade II* Listing

The Inmos Microprocessing Factory, one of the most distinctive and innovative industrial buildings of the late 20th century, has been officially awarded Grade II* listed status, recognising its national significance as a masterpiece of British High-Tech architecture and a landmark of Wales’s technological history.

Designed by Richard Rogers, John Young and Mike Davies in partnership with engineer Anthony Hunt, the factory is now acknowledged as an important example of the British architecture in Wales, and a building of “more than special interest” for both its architectural and historic value. The Grade II* listing comes after an application by the Twentieth Century Society and highlights the building’s architectural achievement, noting its clarity of design, rigorous expression of structure and services, and its innovative approach to flexibility and construction.

The factory was conceived as a model microchip plant able to be built quickly, expanded easily, and adapted without interrupting production. Its suspended ceiling system creates wide, column-free interior spaces, while removable service boxes and exposed pipework allow for ongoing reconfiguration and technological upgrades. The square grid façade supports removable panels, enabling the building envelope to evolve alongside manufacturing needs.

The building’s structural and servicing elements form a celebrated exoskeleton. Lattice towers, suspension rods and steel trusses are visibly articulated, while roof-mounted services contribute to a bold technical aesthetic maintained through a disciplined colour scheme of blue superstructure, silver air-purification systems, and yellow for acidic gas services.

A pioneering suspended ceiling delivers both flexibility and a framework for mounting advanced services. The structure’s lightweight tubular-steel latticework exemplifies the close collaboration between architect and engineer, pushing the boundaries of industrial design during the late post-war era.

Beyond its architectural importance, the Inmos Factory is listed for its crucial role in the birth of the Welsh semiconductor industry. Developed as part of the UK government’s efforts to stimulate new forms of high-value manufacturing in Wales, the facility became the origin point of a technological sector that continues to shape the national economy.

The design also carries a subtle historic reference: the square grid of the exterior walls echoes the Inmos company logo, reinforcing the building’s identity as a symbol of technological ambition and innovation.

John McElgunn, Senior Director, RSHP says ““The Grade II* listing of the Inmos Microprocessing Factory recognises how inventive industrial architecture can be when clarity, flexibility and technical intelligence come together. Inmos was never just a factory — it was a prototype for buildings that could be assembled rapidly, adapt to new technologies, and still carry the precision and lightness of great architecture. We hope the listing will allow the building to remain flexible to its evolving needs, and reaffirming our belief that highly technical environments need not sacrifice elegance or human clarity.”

Catherine Croft, Director of Twentieth Century Society says: “Inmos is one of the most important High-Tech buildings in Britain and so we’re delighted to see it recognised with Grade II* listing. The practice's first major project to be completed in the UK following their breakthrough Pompidou Centre in Paris, it shares the same structural expressionism with its critical services proudly displayed on the exterior of the building. Impressively, it’s still serving the same purpose for which it was originally built after more than 40 years - testament to the ingenuity and excellence that remains at the heart of RSHP’s work”.