The bulging order book at the firm, which started trading in 1997, is thanks to a series of framework agreements with public sector clients such as the Department for Work and Pensions, as well as supermarket chains Tesco and Sainsburys and sportswear manufacturer Nike.
John Beament, the group managing director, said the Department for Work and Pensions contract would be worth £50m over the next three years.
Longcross is one of 12 firms implementing the Jobcentre Plus programme, in which job centres and benefits agency offices in the UK will be refurbished.
This contract should mean the group, whose headquarters are in Surrey, more than doubles in size between now and next year.
Group turnover for the year to 30 September 2002 stood at £48m, with a pre-tax profit of £854,018.
Turnover is expected to rise to £60m for the year to 30 September this year and to increase to £100m for 2003-2004.
Beament, who started the firm with fellow directors Mark English and Gary Earle, said that about 90% of orders were linked to framework deals.
He said the group was well positioned to win such contracts as it offered a complete construction service.
Beament said: "We are offering the full package, from construction to fit-out and security. There are divisions within the business that are all healthy and working. It means we have a tighter control on the operation."
The group, which set out as an M&E contractor, started to advertise itself as a main contractor in 2000.
It also opened up a refrigeration installation operation this year, mainly for retail clients.
The firm, which has operations in Birmingham and Dublin, also hopes to take advantage of the glut of work that is expected in the Thames Gateway in Essex and Kent. It is negotiating to buy land to build an office in Sidcup, Kent.
Longcross also built an office in Sheffield, South Yorkshire, last month, which employs 50 staff.
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