Specifier's choice: North Tipperary civic offices, Nenagh
Sutherland Lyall talks to Robert Davys of ABK about a project that has shrunk since the original brief but is still both complex and innovative
When ABK decided to respond to an OJEC notice to design the North Tipperary civic offices in Nenagh, County Tipperary, it already had a track record. Working with a design team that included structural engineer Michael Punch & Partners and services engineer Homan O'Brien Associates, it had designed the award-winning Offaly civic centre in Tullamore and subsequently won the bid to design Galway civic centre. Now the same team was shortlisted with half a dozen others and, after an interview, was chosen to design the .21million project.
The original scheme was much larger than what is now being built, says Robert Davys, director at the Dublin office, and agglomerated accommodation for a number of civic activities. Even in a reduced form, the client list includes North Tipperary county council, Nenagh town council, the Midwestern hospital board, and Nenagh inter-agency community crèche. Davys says:
'To an extent the idea is healthy because the one building becomes the place for all the local services. But for smaller towns if you pull everything into one building, you pull too much out of the centre of the town.
Originally we had 13 different elements so you can imagine the flow diagram - with things coming in and out. Also it made for a hugely complex briefing process.' As so often happens, the vicissitudes of public funding meant that not everything could be built.
Branch and leaves The basic design consisted of a linear walkway running a little to the west of northsouth. It had branches off either side like the fronds of a fern: longish two-storey open offices on the west and more compact utilitarian activities on the east. Running down the east side of this spine was a series of shared meeting rooms, WCs, reception desks and the like. The current form is basically the same, but with the spine shortened and with only two office 'fronds' off to the west plus, at the south by the entrance to the spine, a single-storey triangular block containing the local Nenagh town council chamber and offices. Opposite, with a similar plan form, this time two storeys high and wrapped around a feature cylinder, is the North Tipperary council chamber for the whole county. On this east side there are offices for the local health board in a twostorey rectangular block, beyond that a twostorey archive store and beyond that again the plant room for the whole scheme. So the overall arrangement is to have utilitarian elements on the east, and offices on the west.
Beyond the offices is the car park, which takes its radiating plan from the direction of the offices. It is surfaced in grass and Marshalls' free-draining Grassguard paving and buff-coloured asphalt.
The construction site sloped 3m from one side to the other, and the berms are made from virtuously reused spoil. Their landscape function is to provide partial protection for a crèche at the very north of the site, which is part of the development but quite separate from the main building. It too is a reduced version of the original.
This is a scheme that can be extended (civil defence, ambulance and fire functions have been mentioned) by projecting the spine further north and adding branches on either side. The architect acknowledges, though, that the reality may be a little more complicated: it has already been through the process of doing the reverse to the original scheme.
Non-adversarial relationships The contract is a GDLA 82 form (government departments and local authorities), which incorporates quantities. Davys says:
'It is not dissimilar to the standard JCT but probably puts more strength in the hands of the supervising officer.' But, as ever, the success of a contract depends on the relationship between architect and contractor - although Davys, who has extensive experience in both the UK and Eire, argues that in the Irish construction industry there exists a less adversarial relationship than in the UK.
And, he adds, there is greater concern with producing good work. For example, one of the subcontractors was unhappy with its work, knocked a substantial part of it down and started again - without even asking the design team.
The specification was based on NBS.
Davys says that there has been a notion abroad of an Irish NBS. There are some specifically Irish standards but, until the imminent Europeanisation of standards actually occurs, Irish architects will continue to refer variously to British and Irish standards as they apply.
It wasn't a problem here, but public clients in Ireland seem to prefer generic specification rather than the handy nameor-equal provisions of the NBS. Working on the British Embassy in Moscow, Davys had issues with alternatives suggested by the builder - especially the difficult-to-bill time spent checking comparability. So at Nenagh, when he wanted a particular product, he made it reasonably obvious - for example the roof membrane was specified as Sarna from Sarnafil. Davys says: 'We made it clear that other solutions weren't acceptable.'
Printing bills In terms of CAD, Davys says: 'We run our MicroStation CAD on PCs, which is the same as the London office. We do only a tiny amount of electronic file transferring. We are happy to use email but we only accept paper as official [information transfer], although in the last couple of weeks we have started emailing drawings.' Davys points out that just the drawings associated with the elevations could number more than 100, and so emailing saves massive printing bills (especially in issuing tender documents) and couriers' bills.
Sinking the heat Davys says of the environmental design: 'At the beginning we had wind turbines - not actually big enough to provide significant power but more as an exemplar. But the scheme was going to be surrounded with housing so?' In fact the basic approach to environmental control is to use the thermal mass of the building. So there was an early decision to have a concrete structure.
The heat-sink approach is actually a dynamic one. The common approach is to let the structure passively absorb and radiate heat at various times of the day, using conditioned air for the fine-tuning. But at Nenagh, the structure is riddled with masses of plastic water piping. This is connected to even more piping buried under the slab, and to loops of pipes buried 3-4m underground below the earth berms beyond the building to the north of the site.
Underground, they stay at around 10°C, unaffected by temperatures above, and are part of the system of stabilising and modifying the internal environment.
The long wings have solar panels in the far sections of the roofs. The WC blocks are at these ends, and conventional pipe runs from the plant room would have been too long. The offices are largely open plan.
Davys says: 'There are two cellular offices and some meeting rooms but open plan is better for ventilation.'
This is, on the whole, a naturally ventilated building. Davys says: 'What a lot of clients don't realise is that natural ventilation can mean no more than having opening windows - which isn't all that good for people sitting near the windows in winter. So what we have is a number of opening conditions, including one we have developed ourselves.
This involves a sliding sash with a stainlesssteel mesh fitted to the outside, and the inside is perforated metal.'
The exposed heavy construction is given a degree of sophistication by using coffered slabs for the roofs and first floors. Davys says: 'The design of the coffers was largely graphic, with the main thing being the need for a soft curve at the edges because there will be up- and down- lighting with a perforated metal diffuser in the coffers.'
Preparing the glass-fibre moulds involved a collaborative process. The original was made by a master joiner, Sureform Moulding Services of Norfolk, out of plywood and timber, carefully painted by specialists and turned into glass-fibre moulds by Fibre Tek, also of Norfolk. Galway subcontractor Concrete Formwork did the pours.
Constructing the slabs was an unexpectedly delicate business because they were only 135mm deep and packed with reinforcement bars and plastic water pipes (connected to the geothermal loops in the ground slab and the nearby berms). Davys says: 'The worry was about people walking over them before pouring.'
Mix and match facades There is a variety of wall surfacing materials.
They include Eglinton Facade System external insulated render from Weber for the utilitarian eastern blocks, large pieces of silver-grey granite from Wicklow by Stone Developments for the council chambers, stainless-steel mesh from Oxford-based Potter & Soar to the south-facing elevations of the offices, Moeding terracotta for their north-facing walls, and a standard Wictec 50 curtain wall from Wicona for the windows and for the two-storey spine. The special sliding ventilation system devised by the architect is made from standard Wictec 50 elements. At the time of writing, Davys was about to look at bespoke handles from William Cox intended for the windows.
Davys says the Eglinton system is one of the thicker (about 18mm) modified-polymer renders on an expanded metal mesh substrate with 100mm of insulation, coloured Monocouche Millennium white. With its little bit of mica in the surface it has, he says, 'the natural finish of a real material: an expression rather than the colour of stone'.
Davys says the terracotta rainscreen to the offices is in stack bond to indicate that it is not brick - and is on a 500mm x 250mm module, which fits in with the 1,500mm planning grid and the 6m square structural grid. He says: 'We pushed Moeding to achieve a pale ivory ceramic finish, which is not officially in production. We chose these units to an extent because of their structure and for their potential in relocating and maintaining the wall system. They are pretty robust tiles with a double skin and honeycomb connections.'
He explains the selection of metal mesh, which has only been seen relatively recently and, mostly, in European designs: 'Potter and Soar come from industrial sieves and grilles for cars and only recently have moved into construction. The mesh is made from 5mm bars, 5mm apart with vertical connections at around 100mm intervals. I know the German stuff and it's woven cable. This is entirely wire and a tad cheaper.'
The flat office roofs are in the Sarna membrane favoured by the practice, and the sloping spine roof to the two-storey spine is in Rheinzink preformed Quickstep planks. They are fixed on insulated pre-stressed birch-faced composite panels spanning 3m between the main steel roof beams. The Rheinzink, says Davys, 'is laid over lateral battens and this lapping gives a texture to the roof '.
The project started in March last year and is scheduled to complete in July 2004.