High Tech architecture emerged as a strand of late Modernism.

It represented a bridge between more traditional Modernist architecture and the more ostentatious styling of Post-Modernism, the latter emerging as a response to the perceived standardisation and monotony of the former.
Expressed construction
Much like its predecessor Brutalism, the structure and frame of a High Tech building often remain exposed.

So do its services, like the installed systems for making a building functional and comfortable, including heating and air conditioning, lifts and drainage.
Exposed pipes, nuts, and bolts become decorative and give buildings a ‘technological look’ while serving a practical purpose.
The Lloyd’s building in London exemplifies the High Tech style in Britain: toilet pods, staircases, external lifts, pipes and ducts are dramatically expressed externally.

The steel frame at the Sainsbury’s supermarket in Camden, London, is proudly left on display and clad in glass and aluminium panels.

The architects innovatively used a coating developed for military applications to fireproof the structural frame.
Lightweight materials
Steel frames are a common feature in High Tech buildings.

No. 22 Parkside in Wimbledon, London, was built as a private house and separate studio between 1968 and 70 by Richard and Su Rogers for Richard’s parents, Nino and Dada.
The bright yellow steel frame and uninterrupted glazing are an early example of High Tech.
Across the river, Michael and Patty Hopkins’ House in Hampstead is a similarly elegant and economically lightweight steel frame and glass building.

Experimental and influential, it informed the practice’s subsequent commercial work.
Flexibility
The interiors in High Tech buildings, both private and public, are often flexible to allow a quick change of use.

At 22 Parkside, sliding interior walls allow internal space to be reconfigured, and Venetian blinds are used throughout the Hopkins House for a similar effect.
On a larger scale, Norman Foster’s Sainsbury’s Centre in Norwich was designed to meet the changing needs of its use as a museum gallery and education centre.
This has allowed regular, sympathetic changes to work, but means the essential elements of the building survived intact.

In London, the Lloyd’s Building was innovative for the in-built flexibility of its design that would respond to changing needs in the market.

When design work began, personal computer technology was only emerging. The design had to be altered following the realisation that desktop terminals would become a major part of working life.
Use of colour
Colour is often used to illuminate a building’s services

Norman Foster used bright yellow masts and stays as an integral part of the concept in the designs for The Spectrum, in keeping with Renault’s branding. At 22 Parkside, the yellow steel frame is accompanied by green sliding walls.

The Hopkins House, designed by Michael and Patty Hopkins, in Hampstead, employs a vibrant blue for the steel frame and steel spiral staircase.

Innovation
High Tech architects used various innovative new techniques for their buildings, often giving greater credence to engineering over architectural style.
The Schlumberger Gould Research Centre in Cambridge has a Teflon-coated fibreglass membrane: the first for a major roof covering in the United Kingdom.

Meanwhile Pillwood House was the first modern domestic property to use Glass Reinforced Plastic (often better known as Fiberglas).

The Hopkins House is notable for its energy efficiency, and in Ipswich, the Willis Building in Ipswich, Suffolk, was the first office building in England to use escalators.

Further reading:
1980s Sainsbury’s in Camden Becomes First Listed Supermarket
Channel 4’s London Headquarters Listed at Grade II
Very interesting information