Hay Shed Design: How to Size, Position and Ventilate a Hay Storage Shed

Most farmers underestimate how much a hay shed design decision affects what happens inside it. Get the size wrong and you run short in a dry season. Get the position wrong and moisture creeps in from the prevailing weather. Ignore ventilation and you risk spoilage, or worse.

This article covers all three decisions together, because they are not independent. Each one constrains the others, and getting them right before you talk to a builder saves time, money, and frustration.

Key Takeaways

• A 90-day dry period for 50 breeding cows needs about 36,000 kg of hay in reserve, or roughly 60 to 72 large square bales at 500 to 600 kg each.
• Face the shed opening away from the prevailing weather (typically south or south-west in Victoria), and leave at least 10 to 12 m of clear apron for loader turning.
• Hay stored above 20 to 25% moisture heats internally through microbial activity and can spontaneously combust if ventilation is inadequate.
• In Victoria, hay sheds in rural zones may be exempt from a planning permit within set thresholds; sheds in bushfire overlays or over the exempt floor area will need one.

Why Hay Shed Design Decisions Matter Before You Build

Size, position, and ventilation are interdependent when you’re building your farm shed. A shed that is the right size but faces the weather loses hay to moisture. A well-ventilated shed that is undersized creates operational failure the first time you need full reserves.

Fixing these problems after construction is expensive. Getting them right at the design stage costs nothing extra.

How to Size a Hay Shed for Your Property

Start with feed demand, not floor area. Using Agriculture Victoria’s feed budgeting guidance as a basis, work through it in this order:

• Feed demand: 50 breeding cows through a 90-day dry period, at roughly 8 kg dry matter per animal per day, needs approximately 36,000 kg of hay in storage.
• Bale count: at 500–600 kg per large square bale, that’s 60 to 72 bales. At 20–25 kg per small square bale, the same reserve needs 1,440 to 1,800 bales.
• Floor area anchor: a shed measuring 32 m x 18 m holds approximately 1,000 large square bales, so you can work backwards from your bale count to estimate footprint.
• Clearance height: double-stacking large round bales needs a minimum of 6 to 7 m of internal clearance.
• Loader access: a standard front-end loader needs at least 6 m of clear opening width to operate safely, which sets your minimum bay opening.

If you want to work through sizing for your specific stocking rate, try Trusteel’s Shed Designer.

Hay Shed Types: Open-Sided, Enclosed, and Barn Designs

The main structural types each suit a different operation. Here is how to self-select.

Design Type	Structure	Best Suited For
Open-sided steel frame	Three or four columns per bay, open on one or more sides, no wall cladding	Maximum airflow, lowest cost per m², standard baled hay storage where orientation manages weather exposure
Three-sided enclosed	Closed rear and side walls, open front	Sites with variable prevailing weather or where ideal orientation isn’t possible
Fully enclosed	All four walls clad, roller or sliding doors	Mixed storage (hay plus machinery or feed); ventilation must be designed in deliberately
Barn-style	Raised roof, multiple bays, sometimes a loft	Stud properties or operations needing weather separation between bays (Aussie barn configuration)

• Open-sided steel frame: The most common hay storage design in Victoria. Three or four columns per bay, open on one or more sides, no wall cladding. Maximum airflow, straightforward loader access, lowest cost per square metre. Best for standard baled hay storage where weather exposure is managed through orientation.
• Three-sided enclosed: Closed rear and side walls, open front. Reduces wind-driven rain ingress. Suits properties where prevailing weather is variable or where the site cannot be oriented ideally.
• Fully enclosed: All four walls clad, with roller doors or sliding doors. Better suited to mixed storage, such as hay combined with machinery or feed supplements. Ventilation must be designed in deliberately.
• Barn-style: Raised roof, multiple bays, sometimes with a loft. An Aussie barn configuration suits stud properties or operations needing weather separation between bays.

For open-sided designs, structural steel framing matters more than it does in enclosed sheds. An open-sided shed has no wall bracing to help carry lateral wind loads and the outward pressure from stacked bales. 

Rectangular Hollow Section (RHS) steel frames carry these loads more effectively than C-section alternatives. C-section frames are lighter and cheaper upfront. For a hay shed expected to hold large bale stacks over 30+ years, RHS is the right choice. The cost difference is real and worth it.

Positioning a Hay Shed: Orientation, Access, and Separation Distances

Three variables determine where your shed should sit on the property.

1. Orientation: Face the opening away from the prevailing weather, which in Victoria is typically south or south-west. This reduces rain ingress and supports cross-ventilation through the shed.
2. Access: Allow a minimum 10 to 12 m of clear apron in front of the opening, so a front-end loader has enough room to turn and approach without reversing into stacks.
3. Separation distances: Hay is a flammable material, so separation from other structures and ignition sources is both a fire safety consideration and, in bushfire-prone areas, a planning requirement. In designated bushfire-prone areas across Victoria, a Bushfire Attack Level (BAL) assessment under AS 3959-2018 may impose minimum setback distances and construction material requirements. 

Check your property’s bushfire-prone area status and BAL rating through VicPlan or your local council before finalising a site.

Ventilating a Hay Shed: Preventing Moisture Build-Up and Spontaneous Combustion

Poor ventilation creates two problems, not one. First, moisture accumulates and causes mould and spoilage. Second, hay stored above approximately 20 to 25% moisture content generates internal heat through microbial activity. In severe cases, this leads to spontaneous combustion’ which the CFA identifies as the leading cause of haystack fires in Victoria.

The design response involves four practical measures:

• Open eaves or a ventilated ridge to allow convective airflow through the shed
• Avoiding solid rear walls where cross-flow ventilation is needed
• Raising stacks off the ground on pallets or timber bearers
• Maintaining row spacing to allow air movement between stacks

Roof pitch also affects ventilation outcomes. A pitch of 15 degrees or greater reduces condensation pooling on roof sheeting and improves water discharge away from stored bales. A flat or low-pitch roof holds condensation longer and increases the moisture load inside the shed.

Planning Permits for Hay Sheds in Victoria

In Victoria, hay sheds may be exempt from a planning permit if they meet criteria under the applicable zone in the Victoria Planning Provisions. In rural zones, including the Farming Zone and Rural Activity Zone, exempt status typically applies to structures ancillary to the agricultural use of the land that fall within certain floor area and height thresholds. These thresholds vary by council and zone.

A shed that exceeds the exempt threshold, sits in a bushfire overlay, or falls within a heritage or environmental overlay will require a planning permit before a building permit can be issued. A building permit is a separate requirement, assessed against the National Construction Code.

Confirm your planning permit obligation through your local council or planning.vic.gov.au before committing to a site or design.

What to Confirm Before Talking to a Builder

Having this information ready shortens the design conversation and avoids delays.

• Estimated bale count: Based on your stocking rate and feed reserve target, as worked through in the sizing section above.
• Shed type preference: Open-sided, three-sided, fully enclosed, or barn configuration.
• Site dimensions and access: Available footprint and the entry path for your loader or tractor.
• BAL classification: Required if your property is in a bushfire-prone area.
• Council zone and overlays: Farming Zone, Rural Activity Zone, or any known heritage or environmental overlay.
• Loading equipment: Whether a front-end loader or tractor with forks will operate inside the shed regularly, which affects bay width and internal clearance requirements.

How Trusteel Designs and Builds Hay Sheds Across Victoria

What Trusteel Does

Trusteel Fabrications designs, fabricates, and constructs steel sheds entirely in-house. For agricultural sheds like hay sheds, that means the sizing conversation, structural design, permit management, fabrication, and construction are handled by one team. Customers do not coordinate separate builders, concreters, or permit agents.

What we see most often on rural properties is that undersized hay sheds create problems within the first season. Farmers underestimate how quickly accessible storage fills once a dry stretch sets in. Getting the sizing right at the start is the most important thing we can do for a customer.

As a registered Victorian Building Authority (VBA) builder, Trusteel manages the building permit process for structures it constructs in Victoria. This removes the need to engage a separate registered builder and keeps the project moving without gaps between design and approval.

What You Get

A Trusteel hay shed is built on RHS structural steel frames, sized to your bale count and loader access requirements, oriented and ventilated to your site conditions, and permitted through your council. Construction is available Victoria-wide.

Talk to Trusteel about your hay shed design.

Frequently Asked Questions

How big should a hay shed be?

The right size depends on your stocking rate and how many days of feed reserve you need to hold. A property running 50 breeding cows through a 90-day dry period needs roughly 36,000 kg of hay. At 600 kg per large square bale, that is approximately 60 bales. A 32 m x 18 m shed holds approximately 1,000 large square bales, which gives a useful floor area anchor to scale from.

What are the different types of hay shed designs?

The main types are open-sided steel frame, three-sided enclosed, fully enclosed, and barn-style. Open-sided is the most common design for standard hay storage in Victoria. Enclosed designs suit mixed storage. Barn configurations suit stud properties or operations needing weather separation between bays.

Does a hay shed in Victoria need a planning permit?

It depends on your council zone, the shed’s floor area, and whether any overlays apply. In rural zones, sheds ancillary to agricultural use may be exempt within certain thresholds. A shed in a bushfire overlay or above the exempt floor area limit will require a planning permit. Check with your local council or planning.vic.gov.au to confirm your obligation before committing to a site.

How do I ventilate a hay shed to prevent mould and fire risk?

Open eaves or a ventilated ridge allow convective airflow through the shed. Avoid solid rear walls where cross-flow ventilation is needed. Raise stacks off the ground on pallets and maintain row spacing to allow air movement. A roof pitch of 15 degrees or greater also reduces condensation pooling on sheeting.

What is the minimum opening width for loader access in a hay shed?

A standard front-end loader requires at least 6 m of clear opening width to operate safely inside the shed. The apron in front of the opening should allow 10 to 12 m of clear space for turning radius. These dimensions should be confirmed against the specific equipment used on your property before finalising the design.