Agreement between client and members of the project team on the quality and suitability of the proposed concrete finish is now much more likely thanks to a national network of reference panels instigated by CONSTRUCT, the Concrete Structures Group. Part of the funding for the panels comes from the Department of the Environment, Transport and the Regions.
The existing definitions in BS 8100 are purely descriptive and therefore extremely subjective. The lack of any physical reference means that widely differing interpretations can be formed on what constitutes an acceptable finish. The result is often conflicting views between members of the project team.
This source of conflict should now be a thing of the past. The new network of seven sites throughout the country provides a definitive visual benchmark of structural finishes, allowing all parties to agree on an acceptable standard of finish both before and after the concrete is poured. The CONSTRUCT panels measure 3m high by 1m wide by 250mm thick and depict typical storey height construction.
The panels concentrate on the most widely used surface finishes, type A and B. The specification for Type A finish calls for untreated ply formwork, while for type B the formwork is unfinished ply. Grade C35 concrete was used with reinforcement and local aggregates to create authentic samples, with different blemish size and colour variations accounted for. Type A has an allowable blemish size of 12mm and Type B 8mm.
The panels were manufactured under the control and supervision of John Doyle Construction, a major specialist concrete contractor and member of CONSTRUCT. The location of the reference panels was determined by ease of access and range of viewing distances. At each location there are guidance notes giving an assessment of each panel, materials and manufacturing details, design criteria and specification. 'These must be read in conjunction with each viewing in order to achieve the maximum benefits,' advises Colin Cleverly, executive secretary of CONSTRUCT.
The reference panels are part of CONSTRUCT's objective to increase the efficiency of concrete construction, and feature heavily in its National Concrete Frame Specification. This is a performance-based document aimed at addressing the wide and inconsistent approach of consulting engineers to concrete frame and finish specifications.
The specification reduces the commercial risk at tendering and allows insitu frame contractors the opportunity to innovate and so meet client needs effectively. Designers no longer have to develop their own specification from scratch. Frame contractors can tender more effectively. Clients benefit from increased quality and cost savings.
The panels have proved popular and useful for numerous concrete contractors and their clients. Those that have taken advantage of the benchmarking opportunity include Matthew Greaves, of Tarmac Precast, who has used the panels in advance 'to avoid the confusion that can arise with clients when dealing with the issue of the finish on precast panels'.
The panels at the site in Manchester were used by John Simcock of Mouchel to help with advising as a third party between client and contractor. He commented: 'I wish we'd had them 15 years ago. The panels are very good at demonstrating the difference between the types of formwork used for Type A and Type B, with the types of defect clearly evident -a reference panel for Type C would also be useful. I think they will provide an excellent reference point for others in the construction industry.'
Maurice Neill of precaster Creagh Concrete Products in Northern Ireland found that the panels at Paisley University confirmed his company's views that because of subjectivity in the area of finish standards, they would produce their own panels for in-house reference to avoid confusion between designers and the manufacturing department. 'The panels are worth seeing. They are backed up with comprehensive documentation, and have given us the impetus to produce panels in-house.'
'The establishment of this network of reference panels offers a real opportunity for more realistic and positive attitudes over concrete finishes - this is a significant step forward for improving construction efficiency,' said Colin Cleverly.
The provision of the panel network allows the free inspection of real- sized physical references and provides a benchmark against which structural finishes can be judged. Any party in the construction industry is welcome to use them.
For further information contact Colin Cleverly Tel: (01344) 725744