The shed floor question comes up in every conversation I have with blokes planning a new shed. Concrete, timber, or gravel—each has genuine advantages and real drawbacks. The right choice depends on your specific situation, and anyone who tells you one option is always best isn’t considering the variables.

Let me break down what I’ve seen work and fail over twenty-plus years of building and working in sheds.

Concrete Slab

This is the default choice for most workshop and garage sheds, and for good reason.

Strengths. A concrete slab is solid, level, and permanent. Heavy machinery sits on it without concern. It doesn’t shift, rot, or attract termites. It’s easy to clean—sweep or hose it down. It provides thermal mass, moderating temperature extremes inside the shed. You can paint or epoxy coat it for a cleaner finish.

A well-poured slab with proper compaction underneath and adequate thickness (100mm is standard for a shed, 150mm if you’re running vehicles over it) will last essentially forever.

Weaknesses. Cost is the big one. A professional concrete slab for a standard 6x3m shed runs $3,000-5,000 in south-east Queensland, depending on site preparation and access. That’s before the shed itself.

Concrete is unforgiving to stand on all day. If you’re working long hours in the shed, your knees and back will feel it. Anti-fatigue mats at the workbench help, but they’re an extra cost.

You can’t easily modify a slab after it’s poured. Want to add drainage later? Run plumbing? Tricky and expensive. Planning ahead saves headaches.

Cracking happens, particularly in reactive clay soils where ground movement is common. Reinforcement with steel mesh (SL72 or SL82) reduces cracking but doesn’t eliminate it entirely. Proper site preparation with compacted fill is essential.

Best for: Workshops with heavy equipment, vehicle storage, any shed where you need a solid flat surface. If your budget allows it and you’re building a permanent shed, concrete is usually the right call.

Timber Floor

Timber floors are common on kit sheds and smaller garden sheds, particularly those raised above ground level.

Strengths. Timber is more comfortable to stand on than concrete—there’s inherent give in a timber floor that your joints appreciate over a long day. It’s warmer underfoot in winter. Timber floors are easier and cheaper to install as a DIY project.

A raised timber floor keeps the shed above ground level, which is useful on sloping sites or in flood-prone areas. The air gap underneath provides ventilation that reduces moisture buildup.

For a shed on stumps, the timber floor is part of the structural system. It doesn’t require the site excavation and preparation that a slab needs.

Weaknesses. Timber floors have a weight limit. A heavy lathe, milling machine, or vehicle will require specific engineering to ensure the floor can carry the load. Standard shed floor joists aren’t designed for tonnes of equipment.

Moisture is timber’s enemy. Ground moisture rising through the floor, spills, and condensation can cause rot over time. Treated timber helps, but it’s not invincible. The underside of the floor needs ventilation to prevent moisture buildup.

Termites love timber. In Queensland, termite treatment is essential for any timber floor in contact with or near the ground. Regular inspections are also important—you don’t want to discover termite damage when your foot goes through the floor.

Timber floors are less stable than concrete. They can develop squeaks, bounce, and unevenness over time as timber dries and bearers settle.

Best for: Garden sheds, storage sheds without heavy equipment, sloping sites, areas where a concrete truck can’t access. Also good for shed-to-studio conversions where comfort underfoot matters more than load capacity.

Gravel or Crushed Rock

The budget option that works better than most people expect.

Strengths. Cost. A properly prepared gravel base for a 6x3m shed costs $500-1,000, a fraction of a concrete slab. It drains well—water passes straight through rather than pooling. Installation is straightforward DIY work: excavate, compact the subgrade, lay geotextile fabric, spread and compact the gravel.

Gravel is easy to maintain and repair. A low spot develops? Add more gravel and compact it. It’s forgiving to stand on—not as comfortable as timber but better than bare concrete.

For sheds used primarily for storage rather than workspace, gravel is entirely adequate. It’s also a practical interim solution—pour gravel now, upgrade to concrete in five years when budget allows.

Weaknesses. Gravel isn’t level the way concrete is. Setting up machinery that needs precise levelling is problematic. Small items dropped on gravel can be difficult to find and recover.

It tracks into the house. If you’re walking between the shed and the house regularly, expect gravel dust everywhere. A step-off area with a brush mat helps but doesn’t solve it completely.

Moisture management is different. Gravel drains well but doesn’t prevent ground moisture from rising into the shed. In humid climates, this can contribute to condensation problems, particularly if the shed is enclosed.

Gravel shifts over time, especially near the doorway where traffic is heaviest. Periodic topping up and re-compacting is needed. Using a binding material like road base (crusher dust mixed with fine aggregate) instead of loose gravel reduces shifting.

Best for: Garden storage sheds, budget builds, temporary setups, areas with challenging access where concrete trucks can’t reach. Also works well under carport-style sheds that are open on one or more sides.

The Decision Framework

Ask yourself these questions:

What’s the heaviest thing going on this floor? Vehicles and heavy machinery need concrete. Hand tools and garden equipment are fine on any surface.

How much time will I spend in here? Long work sessions favour concrete (with mats) or timber for comfort. If you’re just grabbing the mower and leaving, gravel is fine.

What’s my budget? If the slab cost is preventing you from building the shed at all, start with gravel and upgrade later. A shed with a gravel floor is infinitely more useful than a perfect slab with no shed on it.

What’s the site like? Sloping sites are expensive to prepare for slabs. Poor drainage makes gravel problematic. Reactive clay soils require engineered slabs. Match the floor type to your site conditions.

Council requirements. Some councils require engineered slabs for sheds above certain sizes. Check your local council requirements before committing to an option that might not comply.

My Honest Take

For a proper workshop where you’ll spend real time, pour the slab. The cost difference between concrete and gravel is $2,000-4,000, and over the life of the shed that’s a rounding error.

For a garden shed or storage space, save the money. Compacted road base with a geotextile underlayer is practical, affordable, and perfectly functional.

And for the love of all that’s good, whatever floor you choose, get the drainage right. A shed with no drainage plan turns into a swimming pool in a Queensland storm.

— Dave