Global earnings by the UK’s biggest practices were up a quarter in the last year, according to research for BD’s survey of the world’s largest architects, published today.

The 18 UK-based firms in this year’s WA100 earned more than ￡725 million between them, up from ￡580 million last year.

The most successful British practice in terms of billings was Foster & Partners with net fee income of around ￡200 million — twice that of its nearest UK competitor RMJM.

Foster’s was also the highest-placed UK firm ranked by number of architects employed — the criterion by which the annual
WA100 league table is compiled.

Norman Foster’s firm employed 879 architects, a rise of 23% on last year, while RMJM’s problems in 2011, which included star name Will Alsop leaving to set up his own company, were reflected in it losing a fifth of staff, down to slightly less than 600.

Countries named as being among the best for growth next year were China, India and Brazil along with a clutch of Middle East states including Saudi Arabia and Kuwait.

This year’s top 100 sees Aedas replace US firm Aecom as the world’s biggest architect after three years as runner-up.

Keith Griffiths, global chairman of the Anglo-Chinese practice, which now has nearly 1,500 architects on its books, said its success was largely down to China.

Turnover on the mainland rose by 25% this year and Griffiths predicted it would double in 2012 as Aedas presses into the country’s second- and third-tier cities.

“Next year will be a period of very rapid growth,” he said, adding that China’s commercial market remains strong despite current worries about falling residential prices.

“Once you are out of Beijing and Shanghai it’s extraordinarily difficult to work in China but there’s a huge amount of very high quality work to be done,” he said.

“China has as many different cultures and climates as Europe and you have to understand all these things or the jobs aren’t forthcoming.”

But Griffiths warned that foreign firms would soon be facing increased competition from home-grown practices

“They are the ones to watch out for in the future,” he said. “There are not many of them yet but in the next few years we’ll find more and more local mainland architects, probably trained in the US, being very successful.”

Just 10% of practices in this year’s WA100 are based in countries tipped for most growth.