For a true 30 m clear span, a steel truss is the cheaper structure — and the gap is backed by engineering data, not opinion. 

A peer-reviewed study from the University of Technology Sydney, which modeled 24 optimized configurations from 30 to 60 m, found that portal trusses are lighter and roughly 40% cheaper to fabricate than pitched portal frames at these spans, and remain the cheaper option once erection is priced in. A 30 m portal frame is fully viable — our own system takes clear spans from 18 m to 36 m and beyond — but past 30 m the frame's sections grow sharply and its cost curve steepens. And if your building can host an interior column line, a multi-span layout beats both clear-span options on price.

Every figure in this article comes from a published source, listed at the end. Your final price still depends on wind, snow, and code at your site — but the ranking of the options is stable.

What Is the Difference, Exactly?

A portal frame (the standard PEB system) is one continuous rigid frame: columns and tapered rafters joined by moment-resisting knee and ridge connections. It is the world's most widely used single-story industrial system, and it is economical right up to its practical limit.

A steel truss replaces the deep bent rafter with a triangulated roof of top chords, bottom chords, verticals, and diagonals that work in straight tension and compression. The truss chords create a larger lever arm, which cuts bending dramatically — and smaller members carry the same load.

Why 30m Is the Crossover Point

This is where the research gets specific. In the UTS study (24 configurations, spans of 30/40/50/60 m, column heights of 5/7.5/10 m, second-order optimized in SAP2000):

• At 30 m, the optimized portal frame already needs a 310UC137 rafter and 310UC118 column — a 137 kg/m rafter section.
• At 40 m, the same frame jumps to a 500WC267 rafter and 800WB146 column. The rafter more than doubles in section weight (137 → 267 kg/m).
• At 60 m, standard rolled-section frames fail the capacity check — only high-strength fabricated sections (600HCC386 class or larger) work, and they cost more per ton.
• The truss, by contrast, is carried by "much smaller" sections across every one of the 12 configurations, because the chord lever arm does the job that a deep rafter would have to do.

This is why the steel design literature (Woolcock, Kitipornchai & Bradford, 2011) advises that as span increases, a roof truss should replace the rafter — the weight saving "becomes more pronounced" exactly where your budget is most exposed: past 30 m.

What the Data Says About Cost at 30 m

From the same study, with prices benchmarked against One Steel member pricing and a quantity surveyor's per-tonne range for fabrication, detailing and erection (A3,000–A3,000–A4,200/t, Rider Levett Bucknall, 2011):

1. Fabrication: the truss is approximately 40% cheaper than the portal frame for the same spans, even though it has more members. The frame's larger sections simply cost more per meter.
2. All-in: the truss is still the cheaper option. Because steel building contractors price per tonne, the tonnage saving flows straight into the construction bill — and the study's conclusion is that "the portal truss provides the lighter weight and lower-cost alternative, whereas the portal frame results in a heavier and more expensive structure."
3. The trend widens with span. Averaged over column heights, portal frame construction cost "increases at a higher rate in comparison with the portal truss system" for spans over 30 m.
4. Two caveats the study flags, and we agree with:
   • The truss takes longer to erect — more members and connections versus the frame's four primary pieces. If your site window is the binding constraint, that time has a price.
   • Cost vs. weight is parabolic, not linear (Brohn et al., 1995). The minimum-weight frame is not always the minimum-cost frame; optimization matters, which is why the comparison should be run on your actual geometry, not a generic table.

Because the 40% gap is driven by section size — a structural fact, not a commodity price swing — it holds across steel price cycles. That is why we stand behind it in the 2025 price environment, not just the study's 2011 pricing.

When the Portal Frame Is Still the Cheaper Choice

A truss verdict at 30 m does not mean a truss verdict everywhere. The frame wins when:

• Your true clear span is under 30 m. Much of the "30 m building" is actually a 26–28 m clear requirement once walls, racking, and door lines are overlaid. Below the crossover, the frame uses less steel and erects faster — and our portal frame system is designed for clear spans from 18 m to 36 m, and up to 60+ m with specialized design.
• The schedule is the budget. Fewer members, fewer connections, one clean lift per rafter. The UTS study's own recommendation: frame where construction time is limited, truss where time is available.
• The eaves are low. A 30 m truss needs real depth to work. At 6 m eaves, the truss depth eats headroom; a tapered rafter keeps the underside cleaner.
• You will add a lean-to or second bay later. The modular, repetitive frame bays expand longitudinally with minimal disruption.

The Option Most Buyers Forget: Interior Columns

The single biggest lever in the entire question is whether the floor must stay clear. A clear span forces the roof to carry the full 30 m with nothing underneath; the same 30 m built as two 15 m bays with a column line in the middle needs far lighter steel — and our 2025 Warehouse Cost Guide makes the same point in buyer terms: "A clear span requires heavier steel beams to support the roof, increasing the price per square foot. If your operation allows for interior columns (Multi-Span), you can significantly lower your steel building prices."

Before you rule it out, check the column line against the real operation:

• Warehouse: if the line can ride a rack row or a service aisle, take the discount; if it lands mid-aisle, you have paid for clear span you never used.
• Production: place the line at the conveyor gap or machine bay.
• Hangar or aviation: no. Wings and taxi paths need clear span — that is exactly where the truss earns its place (see our Aviation Hangar solutions).

A hybrid — truss over the crane bay, portal bays at the ends — is frequently the best total price, and it is a design call our engineering team makes with you before fabrication, not after.

What a 30 m Building Actually Costs (2025–2026 Pricing)

For planning, use the ranges from our own Steel Structure Warehouse Cost Guide (global average, USD):

• Rigid frame steel package (materials only): $12–22 per sq ft — primary steel, secondary framing, roof and wall sheeting, fasteners.
• Turnkey (finished building): $45–85+ per sq ft — adds foundation, erection labor, insulation, doors.

Worked example: a 30 m × 60 m warehouse (1,800 m² / 19,375 sq ft):

Now apply the structural decision. With a clear-span portal frame roof at 30 m, the primary steel line is priced by the heavier bent sections the study documents. Switch the same roof to a truss and the fabrication line for the primary structure comes down by roughly 40% — before a single square foot of cladding is priced. On a turnkey bill of this size, that is the difference between the low and high end of the steel package, while the cladding, foundation, and labor lines stay fixed.

Because erection is priced per tonne (the study's A3,000–A3,000–A4,200/t covers fabrication, detailing, and erection), lighter primary steel also trims the installation bill — even though the truss needs more connections to bolt up. Net effect at 30 m: the truss roof is the cheaper all-in structure for the same clear span, and the multi-span frame is the cheaper structure for the same footprint if your layout allows columns.

Five Questions That Decide Your Answer

Answer these before you request a quote — they move the number more than the frame type does:

1. Is your clear span really 30 m, or is 30 m the building width? Overlay the racks, doors, and equipment first. A 26 m clear requirement is a cheaper frame.
2. Where would the mid-column line fall? Rack row or aisle → take the multi-span discount. Mid-storage → clear span is mandatory.
3. What are the eave height and roof pitch? Truss depth is set by span; low eaves punish it, high eaves don't.
4. What are the wind, snow, and seismic loads at the actual site? The study's Sydney wind loading is not your project's — load tables are the biggest silent cost driver (a Canadian warehouse roof is structurally heavier than one in Dubai).
5. What is your erection window? Short season or occupied site → the frame's erection speed has a real price tag. Long window → let the truss's steel savings do the work.

One-Stop Procurement: The Frame and the Envelope From Two Liaoning Bases

The roof system is only half the bill — steel is priced per tonne, and the envelope (roof and wall panels, color-coated sheeting, insulation) is the other large line. When structure and cladding come from two suppliers, neither is responsible for the interface, and the gap between them gets discovered on site, where it is expensive.

Loong's Arc Steel Building removes that risk by building both sides in-house, from two production bases in Liaoning:

• Liaoning Longshida Steel Structure Co., Ltd. — our steel structure manufacturing base, part of Longshida Holding Group and manufacturing steel structures since 1994. EN 1090 (EXC3) certified fabrication, ISO 9001 quality control, CNC precision for pre-punched, bolt-on-site members, and the engineering bench that runs the frame-versus-truss comparison for your geometry.
• Liaoning Lonte Building Materials Technology Co., Ltd. — our building materials base: color-coated steel, roof and wall panels, and insulated sandwich panels.

Designing to AISC, AWS, and CWB for North America, Eurocode and EN 1090 for Europe, and GB for domestic work, we price both structures the same way:

• One design team owns the interface. Frame reactions, purlin gauges, and panel profiles are matched before cutting — no field modifications, no "the panels arrived before the drawings."
• One point of accountability. The gap between steel and cladding is someone's problem to fix — and it is fixed at the factory, where it is cheap.
• One consolidated shipment from Dalian Port. Steel and panels load together, planned around container geometry from day one, under the Incoterm that fits your import experience — FOB, CIF, DAP, or DDP (see our Shipping Guide).

For this specific decision, that means you can request both schemes priced identically — 30 m truss roof and 30 m frame roof, same steel scope, same cladding, same Incoterm — and choose the cheaper structure from two real numbers instead of a guess.

FAQ

Is a 30 m portal frame economical? It is fully viable but not the cheapest clear-span option. A peer-reviewed UTS study (Haydar, Far & Saleh, 2018, Steel Construction) found portal frames at 30 m and above require sharply larger sections — a 137 kg/m rafter at 30 m jumping to 267 kg/m at 40 m — and that portal trusses are lighter and roughly 40% cheaper to fabricate. Choose the frame when erection time, low eaves, or future expansion matter more than steel cost.

How much cheaper is a steel truss at 30 m span? The UTS study measured portal truss fabrication at approximately 40% below portal frame fabrication for the same spans (30–60 m), benchmarked against One Steel pricing. Because contractors price erection per tonne (A3,000–A3,000–A4,200/t fabrication, detailing and erection, Rider Levett Bucknall 2011), the all-in structure cost still favors the truss, while acknowledging the truss takes longer to erect.

What span should I use a portal frame for? Portal frames are the default for spans up to roughly 30 m, where the study and the steel design literature (Woolcock et al., 2011) both place the crossover to trusses. Loong's Arc's portal frame system covers clear spans from 18 m to 36 m as standard, and up to 60+ m with specialized fabricated or high-strength sections — a cost that grows quickly, which is why we run the comparison before you commit.

Which is faster to erect, a portal frame or a truss? The portal frame. A frame is two columns and two rafters — four primary members and a small number of connections — while a truss is many lighter members and pin joints. The UTS study and the literature it builds on (Van Rensburg & De Vos, 1996) both note the truss takes longer to construct. If your erection window is tight, that time has a price.

What is the cheapest way to cover a 30 m building? A multi-span layout with an interior column line, provided it does not collide with racking, conveyors, or vehicle paths. Our 2025 Cost Guide states it plainly: clear span requires heavier steel; allowing interior columns significantly lowers the price per square foot. If the floor must stay clear, the steel truss is the cheapest clear-span option.

Can one supplier deliver the steel frame and the roof and wall panels? Yes — when one group owns both production sides. Loong's Arc Steel Building manufactures structure at Liaoning Longshida Steel Structure Co., Ltd. (since 1994, EN 1090 EXC3) and building materials at Liaoning Lonte Building Materials Technology Co., Ltd., so the frame and the envelope are engineered, fabricated, and shipped as one package from Dalian Port.

Bottom Line

At a true 30 m clear span, specify the steel truss — peer-reviewed data puts its fabrication roughly 40% below the portal frame's, and the all-in cost advantage survives erection. If your layout can host a column line, multi-span bays are the cheapest structure of all. And because steel is priced per tonne while the envelope is its own large line, price both schemes, and both scopes, from one source that builds both. Send us your plot, span, and layout — our engineering team will return two real numbers under the same Incoterm, so you can buy the cheaper structure instead of guessing which one it is.

Sources & Data Notes

1. Haydar, H., Far, H., & Saleh, A. (2018). "Portal steel trusses vs. portal steel frames for long-span industrial buildings." Steel Construction, 11(4). DOI: 10.1002/stco.201700011 — University of Technology Sydney. 24 configurations (spans 30/40/50/60 m; heights 5/7.5/10 m), second-order optimized in SAP2000 to AS 4100 / AS 1170. Source of: truss fabrication ≈40% cheaper; all-in cost advantage of the truss; frame section sizes (310UC137 rafter at 30 m; 500WC267 rafter + 800WB146 column at 40 m; rolled-section failure at 60 m); steeper frame cost trend past 30 m; truss erection taking longer.
2. Woolcock, S., Kitipornchai, S., & Bradford, M. (2011). Design of Portal Frame Buildings. Australian Institute of Steel Construction — as cited in [1]: as span increases, a roof truss should replace rafters; weight saving becomes more pronounced beyond ~30 m.
3. Brohn, D., Brown, D., Henderson, R., & Rathbone, A. (1995). Modelling of Steel Structures for Computer Analysis. SCI Publication 148 — as cited in [1]: cost–weight relationship is parabolic; minimum weight ≠ minimum cost.
4. Rider Levett Bucknall (2011). Review of steel costs (Australian Steel Institute) — as cited in [1]: fabrication, detailing, and erection in the range of A3,000–A3,000–A4,200 per tonne (2011 AUD, reference value for the per-tonne pricing logic).
5. Loong's Arc (2025). "Steel Structure Warehouse Cost Guide 2025." https://www.loongsarc.com/newsinfo/1106180.html — source of: rigid frame steel package 12–22/sqft;turnkey12–22/sqft;turnkey45–85+/sq ft (global average USD); clear span requires heavier steel, multi-span lowers price/sq ft; 60–100 ft width as the efficiency range.
6. Loong's Arc product pages (2026). Portal Frame Steel Structures, https://www.loongsarc.com/productinfo/1605048.html — source of: clear spans 18–36+ m, up to 60+ m with specialized design; tapered variable-section members; 100% bolted site assembly. Steel Truss Structures, https://www.loongsarc.com/productinfo/1606443.html.
7. Worked example (30 m × 60 m = 1,800 m² / 19,375 sq ft; 233k–233k–426k package; 870k–870k–1.65M turnkey) is calculated from the ranges in [5]. The ≈40% structural fabrication reduction in the example is applied from [1]. All other project figures (loads, sections, final price) must come from engineering on the actual site data.