In Welsh, Cerrig means stone. It is also the name of the Welsh company who won the contract to put the Welsh slate cladding on to the new Welsh Assembly Government building in north Wales at Llandudno Junction. It is the Assembly’s most energy efficient building, achieving an ‘Excellent’ rating under BREEAM with a score of 75.8. And it has already won a BREEAM Wales Award in the Bespoke Category.

The first of the 650 Welsh Assembly Government staff who will be housed in the new, 9,000m² north Wales regional offices in Llandudno Junction, with their 2,500m² of slate rainscreen cladding, have started moving into the building, one of the greenest in Wales with a BREEAM rating of ‘Excellent’.

In 2006 the Assembly made a significant statement with its Richard Rogers building in Cardiff Bay, the Welsh equivalent of the Houses of Parliament. There, 9,000m² of Welsh slate flooring, paving and walling were used to contrast with the glass perimeter walls of the building. The new Llandudno building makes no less of a statement, although it is slightly more modest, once again using the essential Welshness of slate for impact.

This time the slate, again from Welsh Slate’s Penrhyn Quarry, is arguably even more appropriate as the building is even closer to the quarry.

Pochin Construction were appointed in 2008 as the main contractors to carry out the brown field development on the site of a former Hotpoint factory. The new offices were built under a £21million JCT Design & Build contract.

The stone contractors appointed for the £1.5million stone cladding contract were Welsh company Cerrig (which is Welsh for ‘stone’) based in Pwllheli.

The Heather Grey slate cladding has been used 20mm thick, 90% of it with a honed finish and 10% in a flamed finish to create contrasting bands that represent the benches in the quarry. The slate is fixed on to a Fischer ACT aluminium support (undercut anchor) system with Kingspan K15 black foil insulation, so it does not show, and a Tyveck vapour barrier.

Using the stone in such thin sections meant most of the cladding panels could be lifted into place by hand. Scaffolding was kept to a minimum and most of the cladding was attached from mobile lifting work platforms, mostly scissor lifts and cherry pickers.

Not only Welsh slate, but also folded copper has been used for cladding, because copper is another historically important product extracted from Snowdonia. Its use increases the significance of the building to its location.

Using local materials and services was important to the Welsh Assembly and Pochin have calculated that 64% of the cost of construction went to local suppliers and labour.

The architects appointed by Pochin were Austin-Smith:Lord, with Brian MacEntee, from their Liverpool office, who has now left to established his own practice, designing the building.

He told NSS: “The choice of slate was heavily influenced by the history of the site: the purpose of the railway junction at Llandudno was to transport slate directly on to the main North Wales railway line from the quarries in Snowdonia. Llandudno junction came into being because of the transportation of local slate by rail to the rest of the UK. The most obvious statement of this connection was to clad the building in locally sourced slate. This slate was intended as a celebration of the relationship between the quarries and the railway.  

“The slate was set into a rainscreen façade with a degree of variance in the panel dimension designed to break any significant repetition. Combined with selective placement of flamed and honed finish panels, the overall effect was to suggest the stratification of the natural material as it occurred in the quarry.

“The panel sizes were appropriately large in keeping with the scale of the building but governed by the ability to transport and practically mount into the façade. The overall effect demonstrates a subtlety of texture variation and colour that displays the inherent qualities of the Welsh Slate and the precision that can be achieved with the material.

“The building is A rated, which was significantly contributed to by the efficiency of the façade system that incorporated the natural Welsh Slate, locally sourced.”

Security and bomb blast requirements had to be incorporated into the design, as well as active and passive systems to minimise energy consumption – the building would meet the expected requirements of the new Part L of the Building Regulations due to come into force in October as well as having achieved the BREEAM ‘Excellent’ rating and an A-rated Energy Performance Certificate.

In construction, 25% recycled material was used in the building materials and 80% of waste was recyclable.

In use, passive energy saving measures include: natural ventilation, high thermal mass, passive solar gain, night cooling and fixed solar shading. Active measures: automated solar shading, a biomass boiler plant, rainwater harvesting, pond water cooling, ammonia chiller plant, daylight dimming, DC fan coil motors and inverter drives on those measures that need motors to drive them.

The project is participating in the Demonstration Programme for Wales, which promotes best practice and innovation in construction through a wide ranging programme of projects and initiatives.

Cerrig Managing Director Ian Williams, the sixth generation of his family in the stone industry, says: “It was a good, flagship project for us here in north Wales. It’s nice to sit back and say: we did that.

“We were delighted to win this contract since not only is it valuable to us from a financial point of view, but also from a prestige and credibility point of view. We faced stiff competition from other companies based in the UK and, naturally, it makes us very proud, as a local Welsh company, to be working on such an important building for the people of North Wales.”

Recent high profile rain screen cladding contracts undertaken by Cerrig, such as the Menai Centre at Bangor and Birmingham’s Snow Hill Station, no doubt helped them secure the contract as it demonstrated they clearly had the ability to fulfil large scale projects within pre-set budget and time constraints.

When Carwyn Jones, the First Minister of Wales, picked up the keys to the building on 20 May (with it yet to be fitted out), he said: “This is a building both the Welsh Assembly Government and North Wales can be proud of. Its design reflects the heritage of the area, while making as little impact on the environment as possible. It is a striking landmark building which will be open to the public. I hope as many people as possible come to see it.”

Jon Pochin, the Managing Director of Pochin Construction, speaking at the handing over of the keys, said: “Not only does the building incorporate state of the art sustainable design, the ‘one-team’ approach to getting the job done has been exemplary. This excellent working practice I know will shape the way Pochins conduct all our construction projects in the future. We have enjoyed working with the Welsh Assembly Government and I thank all involved.”