BAA to trial off site building of T5 roof

Part of BAA's T5 core terminal is being built off site in a trial run aimed at streamlining its final construction.

The trial run is part of BAA's wider policy of maximising off-site assembly and pre-fabrication techniques on the T5 programme.

An integrated team of suppliers are pre-assembling the façades and roof cassettes of the core terminal at a test site at Severfield Rowan's yard near Thirsk, Yorkshire.

T5 construction director Andrew Wolstenholme told CJ: "A critical element of achieving and delivering the T5 programme is in maximising off-site assembly and prefabrication and in taking some key elements off the critical path on site to ensure a smoother, safer construction process with no surprises." He added: "This is live, off-programme risk management."

The study involves building one full-scale end roof abutment section, which is 30m long by 30m high. The trial run is expected to be completed by September. The components will then be transported to the T5 project ready to be rebuilt on site. The study aims to resolve any unknown problems prior to assembly on site, test the engineering principles, refine the temporary works and improve safety.

The integrated team members are: Ove Arup; HOK; Rowan Structures; Hathaway Roofing; Schmidlin UK; Laing O'Rourke; and Mace.

Wolstenholme said the additional cost of a trial run was more than compensated by the learning curve. "There is a clear business case for a trial run of the structure. The only elements we will lose are the concrete piles, the overslabs and the man hours of the erection team, but the lessons learnt are hugely valuable in order to guarantee a clear production run."

Off-site manufacturing will feature large in the 3.7bn project in a bid to keep down costs, reduce risks and limit the numbers of workers on site at any one time. The bulk of materials will be delivered by rail to the site's Coln Brook logistics centre, where it will then be prefabricated or distributed to site using just-in-time methods.

All concrete reinforcements will arrive by train and for the first two years of the contract be prefabricated at the factory. Lead in times for reinforced cages will be reduced from 10 days to two to three days using this method. More than 70% of M&E components will also be manufactured off-site.

Wolstenholme commented: "We expect to increase productive working on site by 10% to 20% above the average 50% to 60% on a typical site."