Number 22 Stukeley Street is a six storey Edwardian building occupying a corner site in a quiet side street, close to the business district of High Holborn and Covent Garden, known for the Opera House and the more recent shops and cafes developed in the former flower market.
Number 22 spent most of its life as a furniture store for the Savoy Hotel, and the building has a very deep plan consisting of two rectangular blocks divided by a narrow light well.
In its new guise the building is used as offices, and so the refurbishment required new lifts, improved access to each of the floors, upgraded natural lighting and a new entrance and reception area. The project also aimed to develop a new street presence and a new image. Architects Jestico + Whiles already had an established “green” approach to design.
Their buildings include the Policy Studies lnstitute’s headquarters building in London which featured in a recent Department of Energy Good Practice Guide on energy efficient buildings. So when Jestico + Whiles took the commission at Stukeley Street they set out to bring the benefits of natural light and ventilation to all occupants of the building while giving each of them a high degree of control over their environment.
Innovative ideas in the design include special light fittings, a perforated solar reflector and electromagnetic fail-safe door closure mechanisms.
Externally, the building needed a facelift, achieved by grit blasting and cleaning the original brickwork, and carefully restoring and cleaning the glazed bricks at street level.
The original window openings were used to accept new, double glazed steel frames.
At street level each window is protected by a galvanized steel balustrade surmounted by a stainless steel top rail. Only the installation of a new main en-trance has changed the external appearance.
22 Stukeley Street – a Winner for Galvanizing
An existing masonry has been removed to create a larger opening, signalled in the street by an undulating window. And inside the en-trance lobby comes the first surprise.
The doorman’s reception desk has a wooden top surface, but the desk front is fabricated from galvanized steel. Some floor panels are of steel and, looking up, visitors see galvanized steel walkways immediately above. The architects’ main concern was to develop a building in which users had the maximum control over the conditions in which they worked.
This meant adapting the existing building to get most advantage from natural light and natural ventilation. Of course, all the other needs of the modern office environment are provided together with basics such as new plumbing and electrical systems, fire protection and emergency escapes.
Atrium is focal point
The focal point of the building is the atrium. The existing light well has been capped by a composite curved roof light. The old building was dark and oppressive, so materials used in the new design are exclusively glass and metal, chosen for their qualities of strength, durability and low maintenance requirements.
New, glazed lifts run within a partially enclosed steel-framed shaft. The lifts serve each floor via cantilevered landings and bridges of translucent glass blocks supported on steel. Existing openings onto the light well have been enlarged until they are floor to ceiling height, and then enclosed by sliding of frameless glass doors. In the entrance lobby the ceiling consists of planar glass, allowing a view upwards to the top of the atrium and the source of natural light.
The interior is a surprise, the silver grey of galvanized steel and the lightness of the glass in contrast with the red brick exterior. The surprise continues with a close look at materials of construction. The steel structure is exposed everywhere, and the silver colour is due to the zinc coating of hot dip galvanizing. Around the lift lobbies galvanized steel forms the main structural members of the bridges, the structures of the stairways, the handrail standards and the exposed structure of the lift shaft.
Exposed steel is used in the lift cages, where the galvanized finish matches the appearance of the steel in the lift lobby. And the play of light from above accentuates small differences in appearance of the spangle in the zinc, adding extra interest. And here and there, where safety requires a barrier to curious hands, galvanized perforated steel plate has been used.
The atrium also acts as the air extraction system for the building. A combination of tight budgets and the architect’s commitment to energy efficiency meant that conventional heating, ventilation and air conditioning systems were rejected at an early stage. In-stead, solar gain through the glazing above the atrium is used to create a chimney effect, exhausting stale air at roof level. The bigger the difference in temperature between the top of the atrium and the bottom, the greater is the circulating effect. Occupants can con-trol the flow by opening or closing the sliding glass panels between their rooms and the atrium. The stack effect is enhanced by the shape of the roof light. The S-shape, aligned across the prevailing wind, acts like an aerofoil section, creating reduced pressure just at the point where stale air leaves the building. The reduced pressure close to the exhaust encourages an upward flow.
These are ideal conditions for galvanized steel. The enclosed but well ventilated atmosphere means that there will be no need to maintain the internal steelwork – ever. And the zinc coating will be completely undamaged by strong sunlight at the atrium’s upper levels. In fact, sunlight is directed downwards into the light well by a perforated reflector, creating sparkle from the spangled surface of the metal and increasing awareness of light and weather conditions outside.
Galvanizing award winner
But when London architect Julia Barfield was judging the entries for the 1994 Award for Best Use of Galvanizing in Architecture, she chose the Stukeley Street design because “it really celebrates the use of galvanizing not just for its corrosion protection and low maintenance performance, but for its appearance as well.”
Galvanizers Association Chairman Alan Morrell, presenting the award at a reception held in London in the early summer, also mentioned the potential for innovative use of galvanizing. Speaking to about it to galvanizers, journalists and members of the engineering and architectural professions at a reception held at the Royal Aeronautical Society, he said that entries had covered a wide range of applications, all of them interesting and many of them exceptional. But Jestico + Whiles’ design for Stukeley Street had been chosen for the award because it realised all the benefits of hot dip galvanizing – economy, long life, low maintenance and appearance.
And the idea seems to work. In a market characterised by too many offices and many unoccupied buildings, the strategy of using small scale, energy conscious design to create a user friendly, easily controlled work space has paid off. The building is now fully let. The qualities of hot dip galvanizing – the strength of steel combined with the benefits of the pure zinc coating -have combined to make Number 22 Stukeley Street a winner in more ways than one.
Tips for Specifying Steel for Internal use
Most hot dip galvanized steel is used in rugged external environments where the corrosion protection performance is everything. The coatings are much thicker than the coating applied to continuous steel strip in the steel mill, where a very smooth surface can be achieved. The surface of the post-lab. hot dipped product is always a little bit rougher than the continuously galvanized strip pro-duct, but if your galvanizer knows that your steel is intended for use indoors, painted or unpainted, and in places where sensitive hands may rub the surface, he can add a special degree of post-galvanizing care to make sure that burrs and rough edges have been removed.
So, the tips are:
- Talk to your galvanizer or to a Galvanizers Association specialist if you think you have a special requirement for using galvanizing indoors where smoothness is important.
- Make sure your steel fabrication people communicate every detail of the spec. to the galvanizer.
- If in doubt check with the Galvanizers Association specialist or with your galvanizer to ensure that your design has not created metal traps or other features which make it difficult for him to galvanize your steel to the quality which you want, and to the high quality which the galvanizer would like to give you. If you follow these tips you will have one of the lowest installation cost, long lasting, low maintenance finishes available.
Images © Jo Reid & John Peck
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