Calder Stewart's new steel factory on State Highway 1 north of Milton should be finished by Christmas.
Construction of the 10,500sqm building started four months ago.
Despite being more than five times larger than its present Milton premises, it is not the biggest building the company has built - the new Fonterra factory near Darfield in Canterbury at 54,000sqm was the biggest building in the South Island.
Donald Stewart, one of company founder Bruce Stewart's four sons, said the plant would fabricate structural steel.
''We get raw steel beams from a steel mill, and we cut, drill and shot blast them - which is like cleaning them - and then we weld, fabricate and paint them, and truck them to our project sites.''
Much of the steel was intended for Calder Stewart's own projects with the company making about 30 per cent of the structural steel it uses.
The steel designs would be based on 3D models and the latest technology used in the initial cutting and processing phases.
One of the biggest changes would be a philosophy of Lean manufacturing, described by Mr Stewart as a means of high productivity and efficiency, and helped by the company's investment in advanced machinery.
Mr Stewart believed structural steel was now the predominant choice over concrete for commercial buildings in Christchurch as it has performed so well in earthquakes.
Construction was one of many industries the company was involved in and being able to make your own products was key in stopping delays further down the line, he said.
''We've got better control over finishing projects on time.''
The company was not planning to take on many new workers at the plant initially, instead intending to wait until production increased.
Mr Stewart described the company as optimistic about the future but admitted some regions were doing better than others.
Another feature of the factory is its roof, which would be covered in a solar laminate called Solar Rib, designed and marketed by Calder Stewart.
Producing 163kW of power, it would produce extra energy to run the factory during the day and at other times go straight back into the grid.
The company has had a long relationship with the local area, employing about 300 people - about 120 based in Milton.
Calder Stewart has 32ha at Revolution Hills, most of which it planned to landscape - and if you see a man mowing the lawns as you drive past, chances are it could be Donald Stewart himself.
He reckons it's not bad way of taking a break.
- © Fairfax NZ News