According to architect John Mitchell, the average office desk is occupied for only 40 per cent of the time - which is one of the many challenges that faces companies when it comes to figuring out exactly how much space they really need, and designers when it comes to designing that new space.

His firm, Duffy Mitchell, specialises in office fit-outs and it recently had firsthand experience of the business of moving office when it transferred from a Georgian building on Fitzwilliam Square to a more purpose-designed premises in Ranelagh. The move prompted the company to publish a booklet with advice and guidelines for prospective re-locators. "The first thing we would say is that your premises should reflect your processes," says John Mitchell. This may seem an abstract notion but is in reality a very sound rule of thumb when looking at how design works in the workplace.

He cites the example of a life assurance company which moved office and, in the process of the move, dramatically changed their work environment. In the old premises each salesperson had an enclosed office with the traditional hierarchical structure being reflected in the amount of space allotted, so the higher up on the corporate rung an employee was, the bigger the office.

However, following a review of how the office actually worked on a day-today basis, the real needs of the employees became clearer. The sales staff were out on the road most of the time with their laptops, so Duffy Mitchell designed team desks large enough to accommodate four people at a time and equipped with the necessary IT ports and phones so that the sales people could simply dock their computer and log in to the phone system on the infrequent occasions they actually were in the office.

Peripheral to this were enclosed combi-offices which could be booked by the sales staff if they needed privacy or a space to work on a specific project. These mini-offices were designed so that they could be inter-linked to make one large office suitable for team meetings or presentations. In the booklet, the architects advise re-locators to really look at the cost of the proposed premises. "The cost factors in relocation are obviously to the fore in everybody's mind," says John Mitchell "and the best way to analyse them is to break them down into two areas - once-off costs, such as capital and disposal costs, and ongoing costs, such as running costs and service charges. "When people are assessing potential new office space, they must be clear that they are comparing like with like," he says.

For example, square footage costs have to be broken down into net and gross areas. Business parks tend to quote gross area, which include areas such as the stairways and the lavatories, while city lets tend to be quoted in net terms. "It is important to be very clear what space you actually are going to get to work in," he says.

It's also important to be very clear on the ongoing costs of a move. An office which, for example, has air conditioning is much more expensive to run than one that doesn't. Not only should the move be in keeping with the day-to-day process of the company's work practices, it should, according to John Mitchell, be intrinsically linked to a business plan. "You may only need double the space now but if your business plan suggests that you might need, say, three times the area in five years' time, then that's the sort of move you need to make, anything else is a waste of time and money."

The booklet is available from Duffy Mitchell Architects, 12 Northbrook Road, D6. Telephone: 4911700.