No 8 The Square is hailed as the UK's first purpose-designed serviced office building, even though it is the fourth in a new generation of office buildings designed by Arup Associates at Stockley Park, the self-styled “leading business park in Europe”.

As in the earlier three buildings, Arup Associates has given the offices the novel configuration of a cruciform plan that sits diagonally within a large glazed box. The four triangular voids between the arms of the offices and the outer envelope serve as conservatories – in effect, perimeter atria. The big difference between No 8 and its precursors is that the office space in the four arms of the St Andrew’s cross is only 13.5 m deep.

“Building depth is absolutely critical,” explains James Burland, former director of Arup Associates. “A depth of 13.5 m gives a layout of 6 m office, 1.5 m corridor and 6 m office. This is perfect for serviced offices, which are largely cellular and do not need back-up space for secretaries and equipment such as photocopiers and fax machines, as these are provided centrally. The usual depth of a Stockley Park building is 18 m, which suits single tenants as it combines open plan and cellularised offices.”

For Peter Kershaw, managing director of the UK subsidiary of the building’s operator, HQ Global Workplaces, the narrow floor plates also have a unique selling point for multinational corporations. “The Germans are driving EC building codes, and insist on narrow buildings where nobody sits more than 6 m from an openable window. This gives users control of their working environments and reduces operating costs.”

The raison d’être of the building is to provide serviced cellular offices furnished with desks and telephones that can be let singly or in suites for periods of three months or longer. Conference rooms are shared between tenants. In addition, there is a cybercafé with five PCs for the use of any of HQ’s established customers that might want a touch-down base near Heathrow Airport. There is also an executive club and a kitchenette on each floor.

The building’s nerve centre is the business centre on the first floor, from where HQ’s 12 staff dispense such services as telephone reception, post handling and secretarial tasks, as well as managing general building security, cleaning and maintenance.

Unlike its main competitor, Regus, HQ’s policy is to provide discreet, high-profile premises. “Our buildings are never branded as HQ business centres, and our trading is invisible,” says Kershaw. “The majority of our customers want a fine building in a prime location, where they can say: ‘This is our building.’”

Burland is delighted to have squeezed the depth of the office wings, as this has given the conservatories between them a greater depth and a more clearly defined triangular shape than was the case with Arup Associates’ three earlier buildings. Like traditional conservatories, these serve as indoor gardens and environmental buffer zones. As well as cutting heat loss from the building, the unheated buffer zones offer tenants the option of opening the windows of their air-conditioned offices for boosts of fresh air.

The glazed perimeter screens to the conservatories are made up of large unframed panes of glass that overlap to leave continuous 100 mm ventilation gaps – an arrangement that Arup Associates describes as “shiplap glazing”.

Service risers, toilets, lifts and some stairs have been efficiently concentrated into a large central core, with plant rooms sitting directly overhead within a hipped metal roof. The only service functions left out of this central core are the escape stairs, and these are located at the end of each arm of offices.

The St Andrew’s cross shape has produced novel architectural effects. In contrast with the very first buildings at Stockley Park, which took the form of ring doughnuts with central internal atria, the cruciform buildings face outwards towards the landscaping of Stockley Park. And although the new building’s outer box faces the approach square head on, the diagonal office wings are oriented so as to give long sight lines between surrounding buildings.

The other advantage of the cruciform arrangement is that the cladding of the offices does not require weatherproof materials and detailing. At No 8, this internal cladding takes the form of particleboard panels finished in an attractive Douglas fir veneer.

The visual effect is particularly striking when viewed from the outside, as you look straight through the shiplap glazing to the Douglas fir-clad walls. This produces the slightly surreal effect of looking at a free-standing building clad in delicate cabinetwork.

The downside of the cruciform design is that the wings’ interiors are highly disorientating – all the more so as the corridors end in escape staircases rather than windows through which occupants could recognise landmarks in the surrounding parkland.

The ground floor does not conform to the cruciform design. Instead, it stretches out to the full length and width of the building’s envelope. The result is a deep-plan office space punctuated by four small internal courtyards sunk into the floors of the conservatories. This deep-plan space is not intended to be divided into short-lease cellular offices, as in the upper floors, but is entirely let to one single company for one year or longer.

The offices are fitted out as for permanent offices with drylined partitions and cherry-framed doors. Kershaw is particularly proud of the 600 modern screenprints and works of art that he comissioned for the building.

Since completion last October, office space in the building has been nearly entirely let to several international corporations attracted by the business park’s proximity to Heathrow Airport.

Purpose-designed serviced office building

Serviced office operator HQ Global Workplaces Serviced office design features Narrow 13.5 m floor plates to suit self-contained cellular offices Location Stockley Park, an upmarket business park near Heathrow Airport Base building developer Stockley Park Consortium Building owner Mercury Asset Management/HQ Global Workplaces joint venture Base building team Arup Associates (architect, structural and services engineer), Davis Langdon & Everest (quantity surveyor), Schal (construction manager) Fit-out team Amalgam (architect), Second London Wall (project manager), Hilson Moran (services engineer) Interior (contractor)