Large Farm Sheds: Clearspan Design, Sizing and What to Expect at Scale

At spans above 18 metres, a farm shed stops being a straightforward purchase and becomes a structural engineering decision. The frame type, the span width, the door configuration, and the site conditions all interact in ways that affect both the build cost and the long-term performance of the structure.

Most farmers researching large farm sheds at this stage are trying to answer three questions: how big can it realistically be, what will it cost, and what do the regulations require. This article addresses all three.

Key Takeaways

• Clearspan sheds above 18 metres wide require heavier structural frame sections to carry the load without internal columns, which directly affects material cost and frame selection.
• Rectangular Hollow Section (RHS) frames are the appropriate structural choice for large-span farm sheds; C-section frames used in standard kit sheds are not engineered for the load demands of spans above 15 metres.
• Victorian building permit requirements apply to most farm sheds above 500m², and some structures require planning permits depending on the zone and council overlay.
• Open-front configurations at large spans are structurally achievable but require specific header beam sizing above wide door openings, which adds cost compared to a standard enclosed shed.

What Counts as a Large Farm Shed

The practical threshold for a large farm shed in Victoria sits at roughly 18 metres in width. Below that, standard portal frame designs with moderate steel sections handle the span comfortably. Above 18 metres, the structural requirements change.

Common large-shed footprints include:

• 18m x 24m for mid-scale machinery storage
• 30m x 60m or wider for hay and grain storage at significant volume
• 40 metres wide and beyond, achievable but requiring detailed engineering and site-specific wind load assessment under AS/NZS 1170.2 Wind Actions

The size you need is usually determined by your largest piece of equipment, your storage volume, or both. If you are still narrowing down which category your project falls into, the farm sheds overview covers the full range of farm shed types before you commit to a large-span design. Getting that calculation right before approaching a supplier saves time on both sides.

Clearspan Design and Why It Matters for Farm Use

A clearspan shed has no internal columns between the exterior walls, so the entire floor area is open and unobstructed. For farm use, this matters operationally: large machinery, hay equipment, and grain handling systems cannot work around columns placed mid-floor.

Achieving clearspan at wide spans requires the frame to carry the full load across the opening without intermediate support, which means heavier steel sections, more material, and a frame selection decision that becomes critical rather than incidental.

Trusteel Fabrications builds large-span sheds using RHS structural steel as the standard specification, moving to UB or OWT sections at the largest spans where that engineering is required.

Sizing Benchmarks for Common Large-Shed Applications

Real sizing decisions are easier when you have reference points. The dimensions below reflect common configurations for each use type.

Real sizing decisions are easier when you have reference points. The dimensions below reflect common configurations for each use type.

Open-Front Versus Enclosed Configurations at Large Span

Open-front farm sheds at large spans use the same clearspan frame structure as enclosed sheds, the difference is that one or more bays have no wall cladding or doors. This suits hay storage, machinery parking, and livestock shelter, where ventilation and drive-through access matter more than weatherproofing.

Wide openings put real load on the header beam above them, whether that opening is a fully open bay or a large door:

Specifying the right door configuration early avoids costly redesigns once fabrication begins.

Cost Drivers at Scale: What Makes Large Farm Sheds More Expensive

Several factors drive price variance in large farm shed construction:

• Span width: the primary cost driver. Every additional metre of width requires heavier steel sections across the full length of the shed, so a 30-metre-wide shed costs materially more per square metre than an 18-metre-wide shed, not because of a pricing formula, but because the structural steel needed to carry the span is heavier.
• Wall height: taller walls increase both wind loading on the structure and the length of cladding and structural members required, adding cost independent of span width.
• Frame section (RHS vs C-section): RHS construction costs more than C-section kit alternatives. What that difference buys is a frame engineered to perform at large spans across a 30-plus-year asset life. C-section frames aren’t specified for large-span clearspan applications for good reason, the load demands at those spans exceed what C-section profiles are designed to carry reliably.
• Wind load classification: under AS/NZS 1170.2, rural properties in exposed locations attract higher wind classifications, which require heavier sections and additional bracing.
• Door configuration: as covered earlier, wide openings and large roller doors need purpose-sized header beams, adding to both material cost and fabrication complexity.

Insulation, if specified, adds to the total as well.

As a general anchor, large steel farm sheds at 18m to 24m width typically range from $80,000 to $210,000, with cost climbing toward the top of that range for larger, enclosed, or more heavily specified structures within the tier. These are not quotes, they are reference points to help frame the conversation before you engage a supplier.

Victorian Planning and Permit Requirements for Large Farm Sheds

Farm sheds in Victoria are classified as Class 8 buildings under the National Construction Code building classifications when used for agricultural storage or processing. This classification determines which building standards apply and what approvals are required.

A building permit is generally required for farm sheds above 500m² in rural zones, though the specific threshold varies by council and zone. Sheds in the Farming Zone (FZ) or Rural Conservation Zone (RCZ) under the Victoria Planning Provisions may also require a planning permit depending on size, siting, and any applicable overlays.

Trusteel manages the permit process in-house. Because Trusteel holds Victorian Building Authority (VBA) registration, the building permit application is handled without the property owner needing to engage a separate registered building surveyor. This removes one of the most common sources of project delay on rural builds.

Permit requirements vary across Victorian councils. Confirming the specific requirements for your property and zone before finalising a design saves rework later.

Site Access and Delivery for Large-Span Fabricated Sheds

Large fabricated steel frame sections for sheds above 24 metres wide are transported on semi-trailers. Site access needs to accommodate turning radius for a semi, overhead clearances on the access road, and ground conditions that can support delivery vehicles and crane equipment.

These are not issues that arise at delivery. They need to be assessed during the design phase. A site with narrow gates, soft ground, or low-clearance crossings changes the delivery plan and the cost.

Trusteel fabricates in-house from its Mulgrave facility and manages construction across Victoria. Factoring site logistics into the project scope from the outset is part of how the build is priced accurately.

How Trusteel Designs and Constructs Large Farm Sheds

What Trusteel Does

Large farm shed projects at Trusteel begin with a site and use assessment. Span requirements, equipment clearances, door configurations, and wind load zone are established before any design work begins. What we see most often on rural properties is that buyers underestimate eave height requirements, particularly when new equipment is purchased after a shed is built.

From that assessment, Trusteel produces a design using RHS structural steel sized for the span and load. Fabrication is completed in-house at Mulgrave. Construction is managed by Trusteel’s own crew across Victoria.

What the Customer Achieves

The customer receives a single point of contact from design through to construction. Permits, fabrication, concrete, and erection are managed without coordinating separate contractors. For a large farm shed project, that coordination saving is significant.

The result is a clearspan RHS structure built to the customer’s agricultural use case, permitted correctly for the Victorian zone, and constructed without the delays that come from managing multiple trades independently.

If you are planning a large farm shed and want to discuss sizing, frame options, and what the permit process involves for your property, talk to Trusteel about your project.

Frequently Asked Questions

Do large farm sheds in Victoria require a building permit?

Most farm sheds above 500m² in Victorian rural zones require a building permit. The threshold varies by council and zone, so confirming your specific requirements with your local council or a registered building surveyor is recommended. Trusteel manages the permit process in-house as part of the construction scope.

What is the widest clearspan farm shed Trusteel can build?

Trusteel designs and constructs clearspan farm sheds across a wide range of spans, including large-format structures at 30 metres wide and beyond. Maximum achievable span depends on wind load zone, site conditions, and engineering requirements specific to the project. Contact Trusteel to discuss the span requirements for your application.

What is the difference between RHS and C-section frames for large farm sheds?

RHS (Rectangular Hollow Section) frames are closed-section structural steel, engineered to carry greater loads across wider spans than C-section alternatives. C-section frames are lighter, cheaper, and suited to smaller, lighter-duty kit structures. At spans above 18 metres, RHS is the appropriate structural choice for long-term performance.

How long does it take to design, fabricate, and construct a large farm shed?

A large farm shed project typically runs from three to six months from initial design through to construction completion. The permit approval process and site preparation are usually the longest variables. Complex sites or council overlays can extend this timeline, which is why early engagement with the design and permit process is recommended.

Can a large farm shed be built on a Farming Zone property without a planning permit?

In Victoria’s Farming Zone, agricultural sheds used directly for farming purposes may be exempt from planning permits in some circumstances, particularly where the shed meets specific siting and size criteria under the Victoria Planning Provisions. However, a building permit is still typically required for structures above a certain size. Requirements vary by council and property, so checking with your council before finalising a design is the most reliable first step.