Here's how young architect Walters and Cohen transformed a squat, dingy supermarket into a chic, sleek fitness club by bouncing daylight from one end of the building to the other.
Considering that health and fitness clubs are where the beautiful people like to hang out, they tend to be dismal buildings. More often than not, fitness clubs are fitted-out basements or deep-plan buildings that are made barely habitable by artificial lighting and air-conditioning.

In the commuter town of Elstree, north of London, just such a building – an archetypal 1970s supermarket – was lined up for conversion into a fitness club by the fashionable chain Holmes Place. It was a dreary, single-storey, deep-plan building bounded by windowless, redbrick walls and surmounted by a mock domestic red-tiled roof that concealed an open municipal car park. The front portion of the building had recently been converted into the glitzy Metropole Leisure Centre, although its newly added brash neon and enamel-panelled entrance portico did little to improve the image. The rear portion was sold to Holmes Place, who called in the youthful architectural practice Walters and Cohen to convert it into a 2570 m2 fitness club containing a gymnasium, two activity studios and a small swimming pool.

As card-carrying neomodernists, Walters and Cohen's natural instinct was to open up the black box to natural daylight and clean-cut lines. The most obvious solution of cutting skylights through the roof was ruled out by the overhead car park. Instead, the company has demolished the brick external walls on either side and replaced them with floor-to-ceiling window walls – clear-glazed at the front of the building and translucent at the rear, where it backs onto another car park at ground level.

The architect has arranged the three main public spaces – the café-bar, the gym full of exercise equipment and the swimming pool – in a simple enfilade, a straight swath stretching between the two window walls at either end.

The partitions separating these three spaces have also been made out of plain glazing, clear on the top half and translucent on the bottom. The enclosing walls and ceilings are simple flat planes of plaster with recessed light fittings.

By such means, daylight, external views and a sense of space are introduced into the building, and flow right through it from one side to the other. The effect is to liberate the main gym in the heart of the building by connecting it visually to the outside world, at the same time putting the club's activities on view to passers-by.

"The gym is the focus of the building, with the pool at one end and clubroom at the other," explains partner Michál Cohen. "We have designed it to be slick, clean and elegant."

The other spaces of the centre, including the studios, changing rooms and plant rooms, are stacked out of the way on either side of the central enfilade.

The only extension beyond the existing building shell is the pool hall. The extension was limited by an existing fire-engine turning circle in the car park beyond, with the result that the pool is a compact but serviceable 12.5 × 8.7 m. The pool itself is a slick Swedish proprietary affair consisting of preformed sections of stainless steel welded together on site.

The end wall of the pool extension has been raised above the roofline to funnel in as much daylight as possible. Its design and detailing are deceptively minimalist and neat, consisting of a sheer wall of frameless double-glazing panels supported on external vertical steel T-sections.

The glazing panels butt together in front of the T-sections, and the 5 mm gap is filled with silicone sealant, effectively isolating the steel supports from the corrosive, chlorine-rich atmosphere of the pool hall. From inside, only the smallest of circular stainless steel cover plates over the fixings indicate the system of construction.

The internal layout is consistently rectilinear, with no latter-day jagged angles or gull-wing ceilings. The decor is cool and elegant, consisting of flat vertical planes of floors, ceilings and walls, the latter with recessed skirtings below shadow gaps. The counters in the reception and bar are also flat planes of brushed stainless steel. The main walls in the changing rooms and pool are finished in moisture-resistant mosaic, which covers the entire surface rather than just the well-used areas.

The atmosphere may be consistently cool, but it is anything but austere. The floor throughout is in maple strip, and occasional plain-plastered walls are picked out in vivid colours – orange in the café-bar and mauve in the pool hall – while the mosaic is a marine light-green. Dome-shaped spun-aluminium pendant lights add a touch of sculpture to the café-bar, and exercising figures glimpsed through the glazed partitions add vitality.

This is not a building that strives self-consciously after effect. But by making the introduction of space and daylight its first priority, Walters and Cohen has created a club that is attractive and exhilarating to visit.

Energetic health club market bucks leisure sector trend

Health and fitness operators are still sweating profusely to develop new centres across the country and refurbish those that already exist. This growth bucks the trend in the leisure sector as a whole, which has seen a fall-off in development over the past year. According to property consultant Strutt & Parker, based in Salisbury, 135 new centres are to be opened this year by the UK's top 20 operators alone. This is 60 more than last year, with another 117 planned next year. A typical stand-alone club is some 1850-3700 m2 in area.

Strutt & Parker reckons that UK health and fitness clubs now have some 2.6 million members, or 5.5% of the adult population – an increase of some 270% since 1992. London-based market researcher Mintel International reports that 14% of adults are current users of health and fitness clubs, and a further 20% aspire to join one. It attributes the growth to a sharp rise in obesity rates.

Both organisations believe that the saturation of the health and fitness market is still some way off – some three to five years away, in Mintel's estimation. "There are still many secondary towns that hold sufficient potential for operators to develop small- to medium-sized clubs in," it adds. Holmes Place is currently looking even further afield, expanding into France, Switzerland, Spain, Portugal and Israel.

Mintel's research also reveals that nine out of 10 clubs made changes to the club and/or its facilities in 1999. "This underlines that continuous investment is a necessity if a club is to remain competitive. Almost a quarter had undergone a complete or major refurbishment, while one third had refurbished their gym."

Mintel also notes that consumers increasingly expect more sophisticated facilities. "About eight out of 10 clubs now have air-conditioning, approaching two-thirds have a swimming pool, 60% have a beauty salon, about half have a crèche and nearly a third have a children's play area."

As for the developers of health and fitness centres, Mintel claims that the major chains will become more dominant over the next five years at the expense of independent clubs. It names Whitbread, comprising David Lloyd Clubs and Curzons, as market leader "combining an aggressive strategy of organic growth with strategic acquisitions". Other top-league players are Cannons Group, Fitness First, Holmes Place, Hilton Group, LA Fitness and Esporta (formerly First Leisure). Richard Branson has also entered the market with the launch of his Virgin Active clubs, which have no joining fee. Hotel chains such as Granada, Greenalls and Whitbread-owned Marriott/Swallow are also developing fitness centres in their hotels.