Barton Willmore's riverside HQ Thames Water is an oasis of civic design in the architecture desert of Reading's city centre.
A doughnut-shaped building of pure circular geometry has appeared on the banks of the Thames in Reading. Not a petite riverside gazebo, a chapel, or even a lottery-funded cultural centre, it is a practical five-storey office block, designed by local architect Barton Willmore, to house Thames Water's 800 staff.

A segment of the doughnut facing the river has been omitted, allowing the central courtyard containing the staff restaurant to open out to the river. On the opposite side is the entrance lobby which splits the building into two symmetrical crescent wings.

Project architect Ray Curl recalls: "Thames Water's chief executive Bill Alexander had in mind a robust, permanent, stone-like building." Curl responded by using reconstituted stone blocks (supplied by Trent Concrete), deep-inset windows and a pitched roof in rolled lead. Counterpointing the massive hunk of the main building are two slender cylindrical stair towers in clear frameless glass, each containing a spiral staircase that appears to be suspended in space.

Energy efficiency was a high priority: the masonry external walls, deep-set windows, exposed concrete floor soffits (cast in situ by PC Harrington) and a low-velocity air displacement system all contributed to an "excellent" BREEAM rating. However, unlike Wessex Water's Rab Bennetts-designed headquarters, it relies on air-conditioning.

Thames Water's stone doughnut is a welcome relief from Reading's cringe-inducing collection of postmodernist office boxes tricked out with thin brick skins, dormer windows, and artificial slate roofs. Standing next to the Reading bridge and roundabout, it serves well as an enduring gateway to the city centre.

The 7600 m2 building, which includes 160 car parking spaces in the semi-basement, was built for £20m by management contractor Sir Robert McAlpine, with Ridge & Partners as project manager and quantity surveyor, Barr Gazetas as interior designer, Sinclair Knight Mertz as structural engineer and Donald Smith Seymour Rooley as services engineer.