What a first job for Irish engineer Peter Rice...working on the Sydney Opera House. Emma Cullinan traces his profound influence on modern building.

Sydney Opera House opened 30 years ago this month. It was groundbreaking architecture and engineering, from an enterprising and imaginative architect, Jorn Utzon, and the young novice engineer, Irishman Peter Rice. Rice went on to become a renowned engineer whose mathematical brain and ability to think creatively was the reason why he was sought after by the world's leading architects throughout his career.

He was born in 1935 and grew up in Dundalk, which had an indirect influence on his choice of career. A nearby town, where his grandfather lived, loomed large in his memory: "Even to an eight-year-old Iniskeen was a claustrophobic place, small fields, and tall hedges, with eyes following every move," he writes in his wonderful autobiography, An Engineer Imagines (Ellipsis, London).

"Growing up in the Ireland of 40 or more years ago there was no stimulus to think. Freedom was physical - to run, to swim with energy flowing - not intellectual. Freedom, if it existed, was in mathematics where great ideas could be explored without boundary."

Peter's natural creativity, displayed in his writing, became a coveted part of his appeal as an engineer, but an early love of numbers was crucial. As a child, "I knew I loved numbers. With numbers I could play all day in my mind. Every problem would get analysed by imagining this or that way out."His dad steered him towards engineering, at Queen's, Belfast, reasoning that, if you're good at maths then this would be the best way to make money. Soon after joining the London office of engineering firm Arups, Rice began to work on the Sydney Opera House. This was always going to be an engineering challenge, one that would break building boundaries.

The engineers spent years looking at how the building's peaked structures would stand up. The breakthrough came when they decided to "cut" the wedges from an imaginary sphere, an already calculated form.

The competition to design the building attracted 233 entries from more than 30 countries. Danish architect Jorn Utzon, then 38, won, much to his surprise.

The story still circulates that his entry was picked from a reject pile when the international assessors, who included Eero Saarinen, arrived to look through the entries. The jurors reject this notion.

The assessors hinted that the build would be a challenge. They liked the design, but realised that it hadn't been worked out in detail. "The drawings submitted for this scheme are simple to the point of being diagrammatic. Nevertheless we are convinced that they present a concept of an opera house which is capable of becoming one of the great buildings of the world . . . the white sail-like forms of the shell vaults relate as naturally to the harbour as the sails of its yachts."

Jorn's father was a naval architect, so sail shapes were imprinted on the young man's brain. Jorn had also spent a year working with Finnish architect Alvar Aalto and cited him as an influence.

"His example of the branch of a cherry blossom with each blossom different from its neighbours according to its special position on the branch, but all the blossoms composed of the same elements, was a great eye opener for me and these ideas have been the foundation of many of my own projects."

Jorn also went onto to impress Peter Rice, the young engineer assigned to the Sydney Opera House. Despite having sketched the winning entry Jorn was keen on details; the interplay between a building and its surroundings and users; and quality.

"I was sprayed by \ philosophy and genius," writes Rice. "It was a long slow apprenticeship in the art of architecture, where there was sufficient time to observe and to understand precisely the elements which contribute to making that building the masterpiece it is. The dominant memory was of the importance of detail in determining scale, in deciding the way we see buildings. Sydney Opera House was a big building. It was carefully detailed, down to the joints between the tile lids. This had been Utzon's way of making the building soft and friendly. The scale of the building works at every level, providing interest and articulation from wherever you are."

This humanising of a building, through the construction details, was referred to by Rice as a trace de la main - the trace of the human hand. He believed that a building's users should connect with a building through feeling the traces left behind by those who had worked on it. In Gothic buildings, for instance, carved details bear the mark of craftsmen. Carefully worked out details on contemporary buildings can have the same effect.

Rice also learned from his firm's founding father, another Dane, Ove Arup, who warned that in a world where building was fast becoming an industrial process, it was up to engineers to give a human scale to the expression of details. Rice's inquisitive mind and desire not to go with the easiest and most fail-safe option ensured that a new generation of architects wanted to work with him.

This was an era of lightweight structures that used materials in new ways. Some buildings resembled tents, others appeared to be mainly composed of glass and many seemed to be held together by wire, thin steel (Pompidou Centre, Paris) and a grid of slim concrete members (Lloyds of London).

If architects were to realise these structures then they needed an engineer who could make them stand on slender supports. "The most powerful way that an engineer can contribute to the work of architects is by exploring the nature of the materials and using that knowledge to produce a special quality in the way the materials are used," said Rice.

Peter came up with impressive details of his own. One key contribution to the Pompidou Centre, on which he worked with architects Renzo Piano and Richard Rogers, was the use of a beam support known as a gerberette.

Rice, keen on using non-conventional materials, pushed for the use of cast steel on the project. This had been employed in large 19th century engineering structures, such as bridges, and Rice felt that this was what gave them their special appeal.

It took a lot of work to get it right at the Pompidou, but Rice endured. The work involved copious calculations, the failure of some prototypes and opposition from various authorities, but now his imprint is on the building, both inside and out. "The gerberette at Beauberg (Pompidou) is an example of an apparently architectural decision that could only have been made by an engineer," said Rice.

He was often referred to as an architect-engineer and appreciated that the title was designed to flatter him but he would rather be known as just an engineer and have people understand that this was the way engineers should work.

But the architecture mantle stuck - in 1992 the Royal Institute of British Architects awarded him the Gold Medal for Architecture, something few engineers had achieved. Later that year Peter Rice tragically died - too young - from a brain tumour.

Architects and engineers miss him dreadfully - he played a key role in so many important buildings. As he explained: "People said to me again and again, 'Oh you've had such wonderful projects, so many interesting projects, how can you be so lucky? Why don't I get half of those projects, why doesn't anyone else get them, why do they always come to you?' But in a way that is the point: although you have commissions, you have to make what you can out of the commissions you get." And he did.

Peter Rice's buildings

Peter Rice worked with a variety of architects as this list shows - and he worked on more than one building with most of them. He also helped to develop a car for Fiat, along with Renzo Piano.

Sydney Opera House, architect Jorn Utzon; Pompidou Centre 1971, Piano and Rogers; Lloyd's of London 1978, Richard Rogers and Partners; Science City at La Villette, France, Adrien Fainsilber; Stansted Airport 1981, Norman Foster; Menil Collection Museum, Texas, Piano and Fitzgerald; Alton Towers, Staffordshire; Jet Star 2 Building, Griffin Jones Associates; Clifton Nurseries, roof, Covent Garden, London 1983, Terry Farrell; 122 St John Street, London, 1984; Eva Jiricna Ballsports Stadium, Berlin, 1984; Christoph Langhof Glass Pyramid at Louvre, Paris 1985, IM Pei; Azabu and Tomigaya Structure, Tokyo, 1987; Zaha Hadid Museum of Contemporary Art, Bordeaux, 1988; Valode et Pistre Ecology Gallery, Natural History Museum, London, 1989; Ian Ritchie Architects Museum of Moving Image tent, London 1991; Future Systems, Sainsbury's, Devon 1991, Dixon Jones; Western Morning News, Plymouth, 1992, Nicholas Grimshaw Architects.