For the first time this week, we reveal the full extent of the pensions crisis facing the construction industry: together, the largest 20 contractors have a £1bn deficit.

In simple terms, the cost of providing final salary pensions - that is, a guaranteed income on retirement - is breaking the bank. The situation is even tougher on construction than other industrial sectors, as contractors employ a lot of people compared with their fixed assets.

Take Kier, for example: its £118m deficit is nearly one-quarter of its worth.

Although the problems with pensions have been growing worse for some time, newly introduced accounting rules have forced companies to reveal them in glorious Technicolor, and this has prompted some to take more drastic action.

Almost all the top 20 firms moved some while ago to stem their liabilities, to a certain extent, by closing the final salary schemes to new members. The only company that is still offering one to all comers is Amec, where extremely wise investment decisions mean its scheme is continuing to operate at a surplus. But many contractors are considering "doing a Rentokil" and closing final salary schemes altogether. This would leave members with the benefits they've accrued so far, but transfer them to less generous money purchase schemes. Others are insisting that staff raise their contributions.

For employees, it's an unsettling time - and a galling one for anyone who's sacrificed better pay now for the apparent security of a decent pension. But with contractors making slim pickings even when the market has enjoyed uninterrupted growth, it doesn't take an accountant to see that the sums just don't add up. Sadly, most contractors have little choice but to scale back the benefits they offer. It seems that if you want a decent pension then you have two options: work for the public sector - or work for Amec.

A cutting-edge college

Next to Terry Farrell's trio of awe-inspiring railway stations for the Far East, Wilkinson Eyre's vocational college in north London is positively minuscule - it's 11,800 m2 and has a budget of £14m. Despite that, City and Islington College projects as attractive an image as one could hope for to coax teenagers into further education. But the real surprise is that only one-quarter of the building is new; the rest is a makeover. More than that, the internal environment has been improved with natural daylighting and ventilation. The real lesson of City and Islington College, then, is that it is possible to recycle stock and use renewable energies while updating a building's appearance. For a fully developed country such as Britain in a world threatened by global warming, that is a truly sustainable development.