There’s no shortage of options out there, but in New Zealand, two systems dominate:
- Roll-formed steel buildings
- Structural steel buildings
Both have strengths. Both have weaknesses. And depending on your situation, one will likely fit your needs better than the other.
This article will walk you through the differences, highlighting pros and cons so you can make a decision you’ll feel confident about.
What is Roll-Formed Steel?
Roll-formed steel (also called cold-rolled or lightweight steel) starts as high tensile sheet metal, usually 1–2mm thick. It’s run through a series of rollers that shape it into a profile — often a C shape or Box shape, that gives it strength.
What is Structural Steel?
Structural steel is the heavy-duty stuff you see everywhere: bridges, towers, warehouses. It comes in all shapes and sizes, universal beams (UB/I beams), H beams, square hollow sections (SHS), rectangular hollow sections (RHS), and lattice trusses.
In building systems, structural steel portals are bolted (or sometimes welded) together, creating a frame that can handle significant loads and large spans.
Roll-Formed Buildings: Pros and Cons
Advantages
- Uses less steel → usually cheaper upfront.
- Lighter members mean they can be easier to handle on-site and may not require cranes.
- Readily available. Plenty of providers across New Zealand, especially for small commercial or lifestyle sheds.
- Cost-efficient for smaller spans and light-duty applications.
Disadvantages
- Easily damaged. A single knock from a forklift can dent or weaken a leg because the steel relies on its profile for strength.
- Rust spreads quickly. At only 1–2mm thick, corrosion can turn into structural damage fast.
- Braces get in the way. Knee and apex braces save cost, but they cut into usable internal height. They’re also bird perches (and nesting spots).
- Limited capacity. Not ideal if you need gantry cranes or heavy-duty machinery inside.
A single knock from a tractor leg left a permanent bend in this rolled form building. Later, moisture got into the thin members and rust spread quickly. Within a few years the structure had visible weaknesses, forcing them to invest in a stronger system for their next build. Needless to say their next building was structural steel.
Structural Steel Buildings: Pros and Cons
Advantages
- Durable. Thicker walls mean it stands up to knocks, bumps, and long-term industrial use.
- Faster installation. Bolted connections are quicker (and stronger) than tek screws.
- Flexibility. Handles larger spans (even 50 to 80m if you need to) and can be custom-designed.
- Gantry-ready. Structural steel can be designed to safely take crane loads.
- Low lifetime cost. Requires little maintenance, offering decades of performance.
Disadvantages
- Higher upfront cost. Uses more steel, so the initial build is usually more expensive.
- Heavier members. Often requires cranes or lifting equipment to erect.
- Can be an overkill. If you’re just after a small office or retail space, structural steel may be more than you need.
One example is this Kiwi Lumber project in Gisborne. Several design-and-build options were on the table, including roll-formed systems. In the end, structural steel was chosen because it could handle the required clear spans and crane capacity. It proved the most efficient option and gave the client long-term confidence that the building would stand up to heavy industrial use.
Why Attika Uses Multiple Structural Steel Systems
At Attika, we don’t believe in one-size-fits-all. Every project is different, so we choose the structural steel system that delivers the best outcome for the client:
- RHS Portals (Rectangular Hollow Sections) → clean lines, no bulky braces, excellent for aesthetics and maximising usable space.
- Lattice Rafters → highly cost-efficient for large spans. They reduce steel usage without compromising strength, keeping big projects more affordable.
- I Beams / Universal Beams (UBs) → tried and tested for heavy-duty industrial builds where load capacity and durability are critical.
This approach means:
- We can optimise cost-efficiency for larger spans with lattice rafters.
- We can deliver high-capacity solutions for gantries and heavy loads with I beams.
- We can give clients sleek, brace-free interiors with RHS.
In this warehouse project, using RHS portals meant we could remove the bulky knee and apex braces that usually eat into interior space. That decision gave the client cleaner lines, extra storage height, and a more efficient layout for their racking system. The gain in usable volume was a clear advantage over roll-formed or braced designs.
So, Which Is Right for You?
Here’s the simple takeaway:
- Roll-formed steel buildings → Great for small, light-duty projects where cost is the main driver and durability isn’t critical.
- Structural steel buildings (whether RHS, lattice rafters, or I-beams) are the smart choice for industrial and commercial projects where strength, space, and longevity matter most.
And if you’re planning a building in the 20–80m clear span range, and you need aesthetics, bird-proofing, and gantry capacity, the RHS system we use at Attika is hard to beat.
Next Steps
If you’re in the early stages of planning, check out our other resources:
Or better yet, get in touch with our team. Tell us about your project, and we’ll walk you through which system makes sense for your needs.
