Precast concrete,as cladding or structure,is a quality bespoke product;a highly crafted and precise product which is purpose-made to fit a building in a focussed collaboration between architect and manufacturer.It has all the qualities ofits main ingredient,natural stone;it weathers well,it can be produced with a wide variety ofstone-like finishes including polished marble;it adds solidity to a building and - an important energy-saving characteristic - mass.
'We're trying to change the perception of precast,to make the manufacturing environment an assembly ofcomponents rather than a building site,'says Chris O'Dea, managing director ofTechrete.It is an approach which has had great success -
Techrete has worked with John Outram on the Judge Institute,Cambridge,with Tery Farell on the Conference centre, Edinburgh,on Ludgate Hill with SOM ,Globe House with GMW and,at present,on a new building at Holborn Circus with Foster and Partners.Since its inception in 1985,the company has grown to its current turnover of£18 million.
John Conaghy,director,explains:'We decided not to offer a full range ofprecast products but focus on skills available - manufacturing and technical - giving the potential for added value.The buildings we work on are often complex;they are prestige sites and we are generally trying something new.
For example,novel jointing solutions currently being developed with SHCA (London) and architect Scott Tallon Walker (Dublin).
Senior people must be available and accountable when the need arises.Cladding is hugely demanding on time and people.'
Precast-concrete manufacturing is a skilled craft-based process.Techrete has been fortunate in acquiring the skills of precasting companies which are not now in business - Roecrete in Ireland,Empire Stone and Luda Products in the UK .In1995 the company acquired a UK -manufacturing base at Brigg in North Lincolnshire.John Stothard,production director,finds that this large 8ha site is well-placed for communications across the country and is sited near skilled labour resources;the Brigg plant allows combined production capacity for very large projects such as the three phases ofEdinburgh's Exchange Plaza for architect Cochrane McGregor.
The process ofprecast production starts at Techrete's drawing office,based in Howth,near Dublin.Design is undertaken by more than 40 engineers and draughtsmen under the guidance ofPeter Flynn, technical director.'Design is about efficiency not economy;we aim to add value to every project we do by being open in our approach to design'.A structural engineer with 10 years in multi-disciplinary architectural practices,Flynn has a keen awareness ofwhat architects want and a desire to push product design to higher levels.
A new branch drawing office has just opened in Enderby near Leicester.
Electronic transfer allows drawn information to be sent between the drawing offices and the Howth and Brigg production sites.
Techrete constantly re-examines the process ofmanufacture to bring the precast business in line with other industries.To Chris O'Dea,it is the only way forward:
'Wages have escalated a good 20 to 30 per cent from 1991-2,but we are not selling our precast products for more;in fact the price is now lower;it is the way we use equipment which has brought costs down.Over the years we have been investing in the process, from mould-making to reinforcement,handling techniques and the finishing processes.'
At Howth and Brigg,precast manufacture starts in long halls,high enough to take a 30-tonne gantry crane which lifts cast units to a finishing area.Traditionally,units are cast in timber moulds,each purposemade,a time-consuming process.Techrete has begun to mechanise this process with the use ofvibrating tables;they comprise polished steel 'tables'which form the base of the mould;the sides are oftimber or steel and are clamped tightly into position with jacks.The amount ofcarpentry work is reduced.The reinforcement laid in the mould is produced by computer-operated automated bar-bending equipment.Ifthe unit is a stone or brick-faced cladding panel, the stone/brick is laid in the mould on the base table and the concrete is cast on to it.
Finishes such as acid-etching and polishing - formerly labour-intensive processes - are now carried out by fully automated machines.A new polisher allows polished precast to be produced at a cost ofonly £15/m 2more than etched precast.
Precast units are fixed to building structures with stainless steel components - most commonly,angle brackets which are bolted to cast-in sockets.Techrete has installed a press and a multi-function machine to produce tailor-made stainless steel fixings The Howth plant also manufactures GRC (glass-reinforced cement) components.The process - a mixture ofalkaliresistant glass-fibre strands,cement and fine material - is sprayed or trowelled into single-sided moulds;it is particularly appropriate for lightweight panels eg for overcladding,and for curved or non-rectilinear shapes.Techrete is overcladding a 60s concrete facade in Dublin with GRC panels, an upgrading which did not involve disturbing the interior offices.The main tunnel to the new Heathrow Express was lined with GRC panels,chosen for ease ofhandling and lightness.
Techrete's plans for the future include developments in mould design and investigating the potential of CADCAM techniques and robotics.'It's an attitude ofmind;we are taking a low-tech industry,breaking down each process and developing it,'says O'Dea.
'It's the challenge - and also the fun - to make each activity work as efficiently as possible and then co-ordinate them.'