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Poetic licence

construction study

The Welsh National Opera's new home is due for completion in the autumn.Here we take a look behind the scenes at a highly contentious project Alun Pugh AM, minister for culture, Welsh language and sport in the Welsh Assembly, is reputed to be 'delighted.' On 26 November, baritone Bryn Terfel is taking time out from his global commitments to open the Wales Millennium Centre (WMC) and kick-start a 60-hour extravaganza featuring, as the WMC website says, 'world-famous Welsh stars of stage and screen.'Max Boyce will be there.

The massive new auditorium being constructed in Cardiff - famously not designed by Zaha Hadid - is certainly a big Welsh deal, enough to encourage Judith Isherwood to travel half way around the world, from her job as chief executive of the Sydney Opera House, to take charge.

Designed by local architectural firm Percy Thomas Partnership, under the guidance of its director, architect Jonathan Adams, the first phase of the building is still under construction, with the auditorium being fitted out at the moment. Adams, formerly of Alsop Architects, who moved back to south Wales to get an easier commute, picked me up in his unpretentious Fiat and showed me around.

We approached along the rear elevation, a large proportion of which will disappear from public view when the final wing of the building - housing the Academi, Urdd Gobaith Cymru and T ^yCerdd and other national organisations - is completed. Adjacent to the WMC, the new Welsh Assembly building, designed by Richard Rogers, is emerging from the ground, while a number of unprepossessing - some might say downright ugly - buildings, such as the temporary home of the Welsh Assembly, border the site.

Slate layers The goods service yard is built up of slate walls supported on a steel framework like a Hollywood set. Adams is undecided whether to leave this in the finished building. The slate is supported on angles spanning from massive steel columns. Thus, in this revealed section, it offers up the secret of how the slate seems to float across the main building and can incorporate large strips of glass. Along the main elevations, the structural concrete has been fitted with steel flats at the toe (the heads of openings) to carry the slate skin.

As a cost saving, Adams decided to source waste slate from the Pehrhyn quarry in Bethesda in north Wales, which has various shades, grains and colours, from black to purple. These have been laid in unequal and tapering layers to reflect the natural stratification of the material as found.Whether this emphasises some kind of 'Welshness' - one of the brief requirements - or whether it is just an excellent use of a spoil heap material, is open for debate, but the strength, durability and availability of a waste material, currently at £37/tonne will undoubtedly mean that Adams' idea will catch on. In some areas, the waste material lay in piles ready for site clearance.

The scale of the walls close up is certainly mountainous and very tactile. The red brick used on the rear of the building combines well with the wane-edged Sitker Spruce boarding, reminiscent of suburban fencing, which will weather to silver. Around the site are constantly referenced sample panels of brickwork, slate, concrete, etc and generally the site was well-ordered and the workmanship very good.

As we move around to the front elevation, the looming form of the roof/canopy comes into view. Adams takes over the story: 'The original recommendation of Avesta Polarit (the stainless steel manufacturer) was to use high-molybdenum grade material to avoid risk of corrosion due to the salty maritime air.

'It was after they suggested the highmolybdenum specification that we started to look at the patina treatment to get the colour, and made the choice to go for a matt finish to the sheets in order to make them less reflective and to 'introduce them' to the weathering process.

'An accelerated corrosion chemical trial was carried out by Avesta Polarit Metallurgical Development and it concluded that high molybdenum was not essential and that normal levels of molybdenum in the 316 L product grade were sufficient to deal with the marine environment. The light buffing that was needed to provide the matt appearance actually repaired the micro surface of the stainless steel.' Some early trial panels had oxidised to black almost overnight and Adams is still excited by the prospect that the cladding has an unknown quality to it, which might affect its appearance in the long term. But treating the surface with the Rimex 'Colourtex' process has added further protection.

Each panel reveals its fixings pattern and after a great deal of investigation into the issues of crevice corrosion it was resolved to leave the joints expressed between panels, relying on the weatherproofing below. The overall effect is supposed to allude to a seam ofrivets along a blast furnace - tying in with the subject of the elevational poem (see box).

The canopy itself curves around with its elevational face at an angle so that to transcribe the poem onto the wall required careful computer-generated templates that curved and distorted the letters and phrases in two dimensions so they ended up as horizontal text on the three-dimensional facade. The structure itself had to be modified to ensure no vertical support occurred within the space designated for a 'letter.' The glass for the 2m high lettering is not cut to shape, but comprises double-glazed units that have been masked out by the GRP outer skin and GRG (glass reinforced gypsum) inner skin. Gasketting at the glass/wall junction facilitates differential movement and avoids anyone suspecting that the glass is not letter-shaped. The glass inset into these letters has been tinted, in bands, from blue to copper casting even more interesting light into the mezzanine restaurant areas. Adams anticipates people looking up and being intrigued enough to come in.

Other novel glass panels have been created, and subsequently patented, at Swansea Institute's Architectural Glass department. This 150mm thick sculptural glass is formed of glass bricks each made by fusing blown glass layers together to create translucent veins, which provide an eerie striated light through the building to the external environment at night.When I pointed out that the contractors had been careless in dribbling of paint or whitewash along the glass, Adams reassured me that it was 'artistic'manifestation.

Grand entrance The soffit of the entrance canopy is shaped into what senior technologist Mike Dacey calls a 'smile on the outside, turning into a frown on the inside'. There is no symbolic meaning intended, it is just that the project team found this the most useful way of conveying the geometry to the fabricators. The soffit is convex on the outside, flattening out to a horizontal at the glass entrance wall - the interface between inside and out - and gradually opening out as a concave internal soffit.

This complexity, added to by the fact that the soffit is on a rake, has been framed out from the relatively straightforward cantilevering steelwork. Adams has been quoted as saying, 'the reason some architects cleave to the obvious fallacy that less is more is because it is usually easier not to do something than it is to think of a meaningful way to do it.'

At the external wall, three pits currently demarcate the vertical means of escape stairs which rise up into the building envelope.

Because of the openness of the foyer area, escape from the auditorium and function rooms, etc has to be by means of protected shafts across this space. So, since the site was being partially excavated it was decided that the internal escape stairs would be carried down to a 'basement' level, run under the main foyer concourse and rise up within the curtilage of the building behind 60-minute firewalled lobbies, for final egress through emergency escape doors at the front elevation. This has been worked out as part of an overall fire strategy which will include an on-site Fire Marshall, a full detection, monitoring, voice alarm and smoke control system combined with a main building sprinkler system (the concourse is in excess of the 4,000m 2recommended in Part B3 for sprinklers), although as a result of a fire risk strategy review, the compartment size has not been limited to the extent required by the Approved Documents. Disabled visitors have been provided with landing refuges and all wheelchair positions in the auditorium are within single means of escape travel distance to external conditions.

The rear delivery yard has been marked out in a series of angular paths which, it turns out, is the demarcated fire assembly route should the yard be filled with lorries. If vacant, the fleeing occupants would do well to shortcut to the boundary wall, rather than stick to this directional bureaucracy.

Work in progress The works are being carried out under a standard Design Build Contract (JCT with Contractors' Design [amended]) with Percy Thomas Partnership novated to provide detailed information. Currently, a team of about six are housed in cabins, which will have to be moved to allow a start on phase two.

Internally, the place was an ordered hive of activity, with the ceilings being fitted, electricians taking them down again, plasterers touching up and painters listening to the radio. The sweeping balustrades being clad in horizontal hardwood planks - more striated layers - display great variety in colour and texture. As the contractor moves on, unfortunately the workforce has been dropping scaffold poles from a great height directly onto the terrazzo flooring, making great pitted holes which will be difficult to patch up.

The huge public atria spaces lead into the 1,900-seat horseshoe auditorium that has been engineered to give the best operatic acoustic possible while at the same time catering for amplified music (see box). The walls are fitted with applied GRG stone-pattern tiles, in a not-very-appealing throughcolour red, I have to say, that are angled to maximise or minimise resonant frequencies.

Backstage, the fly tower is huge - apparently the entire New Theatre Cardiff can be fitted onto the stage area - and the service yard and internal street rises to 15m, serving the auditorium and all rehearsal rooms.

Around the building, there were certainly a few problems. For example, the standardisation of laminate doors in the office areas had led to some uncomfortably inadequate overdoor panel details; the naff external light fittings to the rear yard; and the timber seemed a bit overdone internally (cherry, walnut and American oak), but these are minor niggles.My biggest problem with the building was its setting, looking out over a desolate reclaimed dock that had been landscaped in the most anodyne way possible as enabling works to some future scheme - any future scheme. It is kitted out with the obligatory water feature, stepped 'seating area' for public performances/sandwich eating; monstrous lighting columns and a sea of paviors. Hopefully, the promise of outdoor concerts might liven this depressing regenerative desert.

However, after my visit, I found the building had grown on me. The built-in maintenance-free ethos was well handled - Adams is certainly an astute designer with an eye for economy as well as a desire for quality, able to explain his design in no-nonsense prose. Now, the project team is awaiting funding for the completion of the final wing that will be the symmetrical closure to the rear yard. If you want to help, for £500 you can sponsor a main auditorium chair, designed and built near Parma, Italy. if you are not that flush, why not adopt a slate for £75? On the other hand, for a few quid less, you can get to see Max Boyce!

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