For most hay shed slabs, 32 MPa concrete is the practical best choice, giving the strength and durability to handle the machinery that works a hay shed, and stepping up to 40 MPa where heavy telehandlers, loaded trucks, or constant traffic are involved. A plain residential mix of 20 to 25 MPa is not enough, because a hay shed floor is really a machinery floor that happens to store hay. Just as importantly, the mix is only part of it. A good hay shed slab also needs enough thickness, proper reinforcement, a vapour barrier to help keep the bottom bales dry, and falls so water runs off rather than pooling. Get those together and the slab carries the gear and protects the hay for decades. The sections below set out how to spec it.
A Hay Shed Slab Is Really a Machinery Slab
The first thing to understand is where the load actually comes from, because it is not mainly the hay. That changes how you think about the mix.
Hay bales are heavy, but their weight is spread across the floor, and concrete handles distributed weight well. The punishing loads in a hay shed come from the machinery moving the hay: tractors, telehandlers, forklifts, and trucks, with their weight concentrated on a few wheels or legs. Those point loads are what bend and crack a slab, so a hay shed floor has to be specced like a vehicle and machinery slab, not like a storage pad. This is why the mix steps up from residential strength and why thickness and reinforcement matter as much as the grade, which is the same principle behind any slab that carries machinery. Picture the heaviest machine that will use the shed, loaded, and spec the slab for that, not for the hay.
The Mix: 32 MPa, or 40 MPa for Heavy Gear
With the loads in mind, the mix choice is straightforward. 32 MPa is the sensible default for a hay shed slab, and 40 MPa is the upgrade for heavy use.
A 32 MPa mix gives noticeably more strength and durability than a house floor, enough for the tractors and telehandlers most hay sheds see, and it stands up to the knocks, abrasion, and general wear of an agricultural floor. Where the shed will take genuinely heavy telehandlers, fully loaded trucks driving in, or near-constant traffic, 40 MPa is worth the step up for the extra strength and surface toughness. The higher grades also wear better under the grit, fuel, and scraping a working shed floor copes with. Choosing the right concrete grade in MPa for the heaviest machine is the core of the decision, and a consistent pre-mix concrete batched to that grade gives you a reliable floor.
Thickness and Reinforcement for Farm Traffic
The mix works alongside thickness and steel, and on a hay shed slab both are heavier than a house floor because of the machinery. This is where the slab really earns its strength.
Where a residential slab sits at 100mm, a hay shed slab usually wants 125 to 150mm, and more where heavy telehandlers or trucks run on it, sometimes with thickened sections at the entrance where machinery turns and brakes. Thickness is what spreads a heavy wheel load over the ground and stops the slab bending and cracking, so it does much of the hard work. Reinforcement goes up too, from the light mesh of a house slab to heavier mesh, often with reinforcing bar through the high-traffic zones, held up on bar chairs so the steel sits in the slab rather than on the ground. For a large or heavily used shed, having the thickness and steel specified by an engineer for the actual machinery is money well spent, since a cracked hay shed floor is a major job to replace.
Keeping the Hay Dry: Vapour Barrier and Falls
Here is the part that sets a hay shed slab apart from a plain machinery slab, because the floor also has to protect the hay. Moisture is hay’s enemy, and the slab can help.
Ground moisture can rise up through a bare concrete slab and dampen the bottom layer of bales, which is exactly what you do not want in stored hay. Laying a vapour barrier, a plastic membrane, under the slab before the pour blocks that rising moisture and helps keep the bottom bales dry. On top of that, the slab should be built with a slight fall so any water that gets in, whether rain blown through the sides or wash-down, runs off and away rather than pooling on the floor under the hay. Good drainage around the shed matters too, keeping surface water from running in. These moisture details are small to build in at pour time and expensive to fix later, so they are worth planning from the start.
The Base on Rural Ground
As with any slab, a hay shed floor is only as good as the ground it sits on, and rural sites bring their own challenges. The base deserves proper attention.
Farm and rural blocks often have variable or reactive soils, uneven ground, or soft spots, and a hay shed is frequently large, so the base has to be properly excavated, levelled, and compacted, with a solid layer of compacted crushed rock to spread the machinery loads. Skimp on the base and even a strong, thick, well-reinforced slab will settle and crack under the traffic. On reactive clay that moves with the seasons, common across parts of Central Victoria, the design may need to allow for that movement. Getting the base right is part of the same picture as the mix, thickness, and steel, and our owner-builder concrete guide covers preparing it on a rural site.
Do You Need to Concrete the Whole Shed?
Before pouring the entire footprint, it is worth asking whether you need a full slab, because a hay shed is a big area and concrete is a real cost. There is often a smart middle ground.
Some hay sheds use a full concrete floor throughout for a clean, dry, hard-wearing surface, which is ideal if machinery works across the whole shed and you want maximum protection for the hay. Others concrete only where it earns its keep, such as a hardstand or apron at the entrance and the main traffic lanes where the machinery runs and turns, while leaving compacted gravel under the stored bales. That approach puts the strong concrete where the heavy point loads are and saves on the areas that only hold hay. Which makes sense depends on how you use the shed and your budget, and working out the volume for either option is easy with our concrete calculator. It is worth deciding this before you order, since it changes the quantity considerably.
A Finish That Grips
Finally, the surface finish matters on a working floor, and the aim is grip rather than a smooth, slick surface. Machinery and footing both need traction.
A broom or lightly textured float finish gives the floor grip for tyres and boots, which matters where loaded machinery is braking, turning, and lifting, and where the floor can get dusty or occasionally wet. A smooth, trowelled finish looks tidy but can be slippery under those conditions, so it is not the best choice for a hay shed. The textured finish costs no more and makes the floor safer to work on. Matching the right concrete to the project, and ordering it from a local supplier who can deliver the volume a large shed needs, rounds out a hay shed slab built to last.
Frequently Asked Questions
What concrete mix is best for a hay shed slab?
For most hay sheds, 32 MPa is the best practical choice, since the floor has to carry the machinery that moves the hay. Step up to 40 MPa for heavy telehandlers, loaded trucks, or constant traffic. A residential 20 to 25 MPa mix is not strong enough.
How thick should a hay shed slab be?
Usually 125 to 150mm, and more where heavy telehandlers or trucks use the floor, often with thickened sections at the entrance. Thickness spreads the concentrated machinery loads and does much of the work in stopping the slab cracking, so it should suit the heaviest gear.
Does a hay shed slab need a vapour barrier?
It is strongly recommended. A vapour barrier under the slab blocks ground moisture from rising through the concrete and dampening the bottom bales. Combined with a slight fall so water runs off, it helps keep stored hay dry, which is a key job of the floor.
