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THE HOARDINGS HAVE NOT BEEN GRAFFITIED ONCE - IT HAS BEEN A REWARDING PROCESS

SPECIFIER'S CHOICE - THE PUBLIC

The Public is a socially engaged community arts project in West Bromwich, due to be completed by June. Despite problems which forced Alsop Architects to leave the project after the first phase, the scheme has still been a great success, project architect Max Titchmarsh tells Sutherland Lyall.

The 9,250m 2 project has been eight years in the making and has been masterminded by The Public chief executive Sylvia King.

Because this ú53 million project was a public-funding exercise, with money coming from the Arts Council, Sandwell local authority, the EU, Advantage West Midlands and Greets Green Partnership, the selection of the architect had to be carried out under OJEU rules. Alsop Architects did a 'one of us' presentation, without the drawings and models, which persuaded the client body it was the one. So it turned out until recently, when the Alsop office went briefly into administration, fortunately not until the end of the first phase: the completion of the building enclosure.

DESIGN CONSULTATION The design process was laborious but one which the practice uses for consulting potential users. A measure of the consensus achieved is, says Titchmarsh, the fact that 'the hoardings haven't been graffitied once - it has been an incredibly rewarding process'.

THE CONTRACT With so many interested funding parties, the client function has been taken on largely by King but the process is watched over by funding representatives who have a duty to ensure the money is spent correctly. The contract with the builder, Galliford Try, was a JCT 98 without quantities and with provisions for the contractor's design portion. The latter was for the cladding and Titchmarsh recalls how the successful tenderer, Richardson Roofing, took Alsop's design drawings and 'fed them back to us via a series of meetings and discussions until a consensus was reached.' Alsop selected the consultant team, which included engineer AKT, services engineer Battle McCarthy and quantity surveyor Atkins Faithful & Gould. Titchmarsh says of the team:

'We had NBS as a base template. But we used Schumann Smith to do the spec writing. They are used quite a lot by big practices and they have an excellent overview of the industry.'

TIN BOX PLUS APPLIQU+ The building is a lightweight self-supporting box with a glass curtain-walled ground floor and free-form windows in a black metal skin with a pink interior skin. The roof and the four main floors all sit on, or are hung from, a repetitive steel framework with cranked legs, rather like a row of goal posts pinched in at the crossbar. Only a few sections of the external box are braced off it, but otherwise the two structures are independent of each other.

A perimeter strip rooflight that visually isolates the ceiling from the walls further emphasises the separation of the box from its interior.

On the south-east elevation a faceted mirrored shape clings to the wall, and further along this elevation a smoothly curved groundlevel shape insinuates itself through the glass skirting wall. In the Alsop office the windows became known as 'jellybeans', the faceted wall clinger became 'the rock' and the smooth ground-hugging shape 'the pebble'. The faceted structures on the roof are plant rooms, lift and stair over-runs and workshops.

The interior is not part of this study due to the Alsop office going into administration near the end of the first phase, and some of the interiors, though following the Alsop design, are being carried out by another practice. The refinanced Alsop practice has a consultant role and advises about any proposed changes or material selection - although there have not been many.

SOFTWARE Software used for the design was primarily MicroStation, but Lightwave, Photoshop, Illustrator and the usual suspects were also used. Because of the complexity of some of the internal shapes, the practice had to deploy clash detection using TriForma.

ON THE ROOF The composite concrete floor and roof slabs have vertical supports at intervals of 8.8m. These are made up of prefabricated squaresection concrete-filled tubes, which are 750mm 2 where they crank inwards at third-floor level, tapering to 450mm 2 at ground and roof level. The 13 frames were brought on site progressively and with their own police escorts. The building is 20m wide and the frames sit about 3m in from the skin. The composite concrete roof structure is clad in a Sarnafil PVC membrane glued to Kingspan insulation, pre-cut to falls to gutters running down the middle of the roof and bonded to a torched-on felt vapour barrier above the slab. Titchmarsh says: 'Roofing systems are actually much of a muchness, but we have used Sarnafil before and they run their own on-site checks.' The perimeter strip of rooflights is framed in relatively inexpensive Lonsdale Metal Company ThermGard patent glazing frames. Pilkington Suncool double glazing with a toughened 10mm upper panel, a 16mm cavity and an 8.8mm laminated Optilam clear-float lower panel is also used. The ThermGard aluminium framing sections had the same sightlines as the rather more expensive ground-level glazing. The quite complex rooftop structures are clad in Ugine & ALZ UK's Ugibright stainless-steel standing-seam trays, which are fixed over waterproof ply sheets.

The skin of the big box is quite simple. The main cladding is a Corus 80mm-thick insulated steel Trisomet panel spanning the 8.8m between the U columns of the skin-support structure. Its carrier is a 0.9mm Corus profiled structural decking sheet, laid vertically and faced with Gasell GA-1825 0.9mm sinusoidal profile aluminium cladding with a bespoke duotone dark-blue finish. On the inside, the 0.7mm perforated-steel sinusoidal profiled cladding from Corus is carried by a 500mmwide, 90mm-deep Haironville TAC Tactray liner tray holding 60mm of Rockwool quilt sound insulation and 30mm of semi-rigid thermal insulation.

'JELLYBEAN' WINDOWS The design idea behind the windows is that every time you puncture the almost black skin of the box, it bleeds pink. So the inner side of the pink reveal to each window has a 100mm x 100mm trench containing cold cathode lighting with a pink translucent perspex cover, flush with the reveal.

The inside section of the reveal to each 'jellybean' is made from 18mm-thick flexi-MDF on a curved ply backing, cut around the mullions, fixed and then adjusted and painted pink. The front section of the reveal is a prefabricated 2mm-thick aluminium profile which was butt welded. The mullions and transoms are from a standard Sch³co FW6 structural silicone glazing system with 2.2m glass panels, supported by the skin's inner support system.

UP TO THE ELBOWS IN PAINT The architect wanted a duotone colour on the exterior. Gasell, manufacturer of the external cladding, introduced it to colourcoating company Euramax. The Euramax technicians at Corby gave the architect some training and, Titchmarsh says: 'We spent a day up to our elbows in paint getting the right colour. It is black with red and blue mica in a clear lacquer over a black undercoat.

So the flip is a very subtle thing and there is a lot of richness.

'The pink for the interior and the jellybean reveals, actually a magenta, took a long time to find. There were difficulties with warranties because magentas are the volatile end of the spectrum, but we were eventually able to get a 25-year guarantee from DuPont - and a BBA certificate for the Corus cladding it coated.'

'THE PEBBLE' The CAD profiles were drawn as B-splines and modified by the fabricators. The secondary ribs were fixed and shimmed up to produce fair curves. Then timber battens were fixed diagonally with another layer in the opposite direction - all very like boat building. So they built up a perfect curve with the last layer of timber and the final ply base. Then Ugine & ALZ operatives laid 0.6mm mirror finish Ugibright AME stainless-steel standing-seam cladding.

'THE ROCK' 'The rock' was much more difficult, even though it is made up of facets rather than curves. Titchmarsh says: 'Everything had to be right or you would go incrementally out of tolerance'.

Prefabricated timber trusses were fixed to steel cleats on the outer face of the cladding sub-structure. They were clad from the inside in ply and then all the gaps were filled with insulation.

Bespoke triangular windows from The Rooflight Company were fitted. The same Ugibright cladding was used and a lot of thought was given to positioning the seams in the constantly changing hips and valleys. Titchmarsh says: 'We had to make sure the water could run off at sensible places and we sometimes had to use flattened seams so that each facet is articulated.'

Credits Architect Alsop Architects: Will Alsop, Max Titchmarsh, Ed Norman Main contractor Galliford Try Cladding contractor Richardson Roofing Quantity surveyor Atkins Faithful & Gould Structural engineer AKT Services engineer Battle McCarthy Building control MLM Building Control Consultant Interior Design Ben Kelly Design Lighting Design Kevan Shaw Lighting Design Form of contract JCT 98 (with amendments) Standard Form of Building Contract: Private Without Quantities (with integrated provisions for Contractor's Designed Portion) Gross external floor area 9,250m 2Total cost ú53 million (including fit-out and gallery design) Start on site June 2003 Completion Autumn 2006 CAD package used Microstation J, Triforma (Clash detection), Lightwave

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