Coresteel Buildings

Tapered Box Beam


Cost-effective system without compromising structural integrity

  • Buildings not confined to set sizing - fully bespoke
  • No obtrusive knee or apex braces
  • Fully bolted primary and secondary sections i.e. not TEK screwed
  • Bird-resistant purlins and vermin resistant girts
  • Coresteel is your designer, engineer, manufacturer and builder all in one, which considerably reduces costs
  • 50-year design life
  • Coresteel is 100% New Zealand owned and operated


The Tapered Box Beam is manufactured by folding two halves of flat steel plate and welding them together to form a box. It is tapered through its length, utilising only the amount of steel required for any given design, yet without affecting structural integrity.

This design offers several exciting features, including bird and vermin-resistant properties, a reduced overall surface area (resulting in less steel and paint being required), plus a simple, quick construction process which reduces labour costs.

Tapered Beam Box Structure


“It was a large build with heaps of precast, which turned out really well. The way in which the Tapered Box Beams and supports were constructed was impressive. We will certainly consider Coresteel for our next project, which could be even larger.”

Robert Bartley, Bartley Group Holdings Ltd
Ali Arc Logistics, Palmerston North

Cost Benefits

Because the amount of steel needed in the structure is less than industry standard, the cost is subsequently reduced. Using tapered, hollow sections with internal flanges reduces the weight and square face meterage for paint area. Paint coverage is typically 28% less compared to I-beams, which creates further cost-savings, especially where high-level paint systems are specified.

All of Coresteel Buildings’ projects are manufactured in New Zealand by Donovan Group NZ Ltd (Coresteel Buildings’ parent company). When the steel frame is complete it is packaged up together with all fastenings and sent to the building site as a complete structural kitset. 

Because each building is prefabricated, it is quick and simple to construct on site. Within a few days the entire frame can be erected, without the need for onsite welding .Due to the speed in which the building can be erected, significant labour cost-savings can be made. Ultimately, less staff are needed for a shorter amount of time.

Once the portal frame is complete, cladding and joinery is installed. Following this, the internal fit out begins. A project that is completed on time and within the budget, results in a happy customer - the ultimate goal.

Wider spans than ever before

When space is an issue, Tapered Box Beam allows for simply supported spans larger than many thought possible. To date, our largest span is 75m. The bracketless, streamlined design also means customers can utilise more of the available space within their building’s floor and ceiling area.

The innovative design of Tapered Box Beam allows Coresteel’s inhouse design team to incorporate virtually any architectural or practical element into the design of your building.

Architectural features such as branded store fronts, attractive showrooms and modern reception areas are easily paired with practical aspects like racking, gantry cranes, mezzanine floors and cantilevered canopies.

The Tapered Box Beam design has been independently checked and verified by the Heavy Engineering Research Association (HERA). HERA is recognised in both New Zealand and overseas as a leading authority in the design of steel structures.