I’ve built or helped with four different shed installations over the past decade, each with a different flooring solution. The differences in durability, cost, and practicality were eye-opening. Here’s what I’ve learned about choosing shed floors for Australian conditions.

Concrete Slab: The Gold Standard

My workshop shed sits on a 100mm reinforced concrete slab, and after six years, it’s still perfect. Concrete is the most expensive upfront but requires almost no maintenance.

The Process

Professional slab installation for my 6m x 8m shed cost AU$3,800 in 2020:

• Site preparation and leveling
• 100mm compacted road base
• Plastic vapor barrier
• Steel reinforcing mesh (F72)
• 100mm concrete pour
• Trowel finish

The contractor used a laser level for the formwork, ensuring the slab was perfectly level. This matters enormously when you’re installing machinery or trying to get a car jack to sit flat.

Advantages I’ve Experienced

Load capacity: I can put heavy machinery anywhere without worrying about floor strength. My 200kg bandsaw sits on the slab with no concerns.

Durability: Zero maintenance in six years. No rot, no pest damage, no wear patterns even in high-traffic areas.

Cleanliness: Concrete is easy to sweep and can be mopped. Spills don’t soak in. I sealed mine with an epoxy coating after two years, which made cleaning even easier.

Moisture resistance: Properly installed with a vapor barrier, concrete blocks ground moisture. I’ve never had condensation issues.

Disadvantages

Cost: Significantly more expensive than other options. Budget $80-120 per square meter installed.

Permanence: You can’t easily move or modify a concrete slab. It’s a permanent commitment to that location.

Cold in winter: Concrete is thermally massive but provides no insulation. Standing on it in winter is noticeably cold even through shoes. Rubber anti-fatigue mats help.

Installation time: Requires excavation, formwork, reinforcement, pouring, and 7+ days curing before you can build on it.

Timber Frame Floor: Traditional and Versatile

My garden shed uses a timber floor on bearers and joists. It’s been adequate for storage but wouldn’t work for heavy equipment.

Construction

I used:

• 6 x concrete piers to support the frame
• 90mm x 45mm treated pine bearers
• 70mm x 35mm joists at 450mm centers
• 19mm structural plywood deck

Total material cost: about AU$850 for a 3m x 4m shed. I did the labor myself over a weekend.

What Works Well

Speed: Once piers were set, I had a floor built in one day.

Cost-effective: About 40% the cost of equivalent concrete slab for a small shed.

Easier to level on sloped sites: Adjusting pier heights is easier than massive site excavation.

Insulation potential: I added rigid foam insulation between joists in one section where I store temperature-sensitive items.

Easier to run services: Drilling through timber to add electrical or plumbing later is straightforward.

Limitations I’ve Found

Load limits: Calculators for joist spacing and sizes are available online, but you need to plan for concentrated loads. I can’t put a 1000kg motorcycle in this shed without reinforcing.

Maintenance: Timber requires periodic inspection for rot and pest damage, even when treated. I check bearers annually.

Lifespan: Even treated timber will eventually rot in contact with ground moisture. Concrete piers help, but timber floors don’t last as long as concrete.

Movement: Timber expands and contracts with moisture. There’s slight movement that’s fine for storage but would be problematic for precision machinery.

According to CSIRO research on timber durability in Australian conditions, treated pine in above-ground applications (like shed floors on piers) typically lasts 15-25 years before requiring replacement.

Gravel/Crusher Dust: Budget Solution

My first shed had a compacted crusher dust floor. It served its purpose for basic storage but had significant limitations.

Installation

I excavated 100mm, put down landscape fabric to suppress weeds, then filled with 100mm of compacted crusher dust. Total cost: AU$180 for materials for a 3m x 3m shed.

Pros

Cheapest option: About 10% the cost of concrete.

Easy DIY: No special skills required. Excavate, fill, compact with a plate compactor (hired for $80/day).

Drainage: Water drains through instead of pooling.

Easy to modify: Want to move the shed? Rake the gravel and start over.

Significant Cons

Dust: Crusher dust creates fine dust that gets on everything. This is unacceptable for workshop use.

Uneven surface: Even well-compacted, the surface isn’t perfectly level or stable. Things roll around.

Difficult to clean: Can’t sweep or mop effectively. Dropped small items disappear into the gravel.

Weed growth: Despite landscape fabric, weeds eventually find a way through.

Not suitable for machinery: Any significant weight creates depressions over time.

I used this shed for garden tools and general outdoor storage. For that purpose, it worked. I wouldn’t recommend it for anything else.

Composite/Plastic Shed Bases

I helped a neighbor install a plastic grid shed base system. These are interlocking plastic tiles that sit on leveled, compacted ground.

Observations

Easy installation: We leveled the area with sand, laid the tiles, and had the base done in a few hours.

Cost: About AU$12-15 per square meter for quality systems. More than gravel, far less than concrete.

Drainage: Excellent drainage through the grid system.

Lightweight equipment: Works fine for lawnmowers, bikes, general storage.

Issues Encountered

Settling: Over 18 months, we noticed settling in high-traffic areas. The grid tiles weren’t as stable as hoped on the compacted sand.

Limited load capacity: Manufacturer specs gave weight limits, but concentrated loads (like jack stands) created pressure points that deformed the tiles.

Heat sensitivity: In summer sun, the plastic became slightly soft and flexible.

For a small storage shed with light contents, these work. For anything heavier or more demanding, I’d choose a different option.

Sealed Earth/Compacted Base

Some kit sheds are designed to sit directly on compacted, level earth. I tried this with a small tool shed.

What Happened

The earth base worked for about 18 months before moisture issues developed. The floor became uneven as soil settled differently under various loads. During wet weather, moisture wicked up into the shed despite the floor having a built-in moisture barrier.

I don’t recommend this except for very temporary installations or sheds storing items that tolerate moisture and won’t be damaged by an uneven floor.

Making the Choice

Based on these experiences, here’s my decision framework:

Choose Concrete If:

• Heavy machinery or vehicles will be stored/used
• You need a perfectly level, permanent floor
• Budget allows (roughly $80-120/m² installed)
• The shed will house a workshop or workspace
• You want minimal long-term maintenance

Choose Timber If:

• Budget is moderate ($30-50/m² DIY, $60-90/m² installed)
• Storage use with moderate loads
• Site has slope that makes concrete expensive
• You may want to relocate the shed eventually
• You’re comfortable with periodic maintenance

Choose Gravel/Crusher Dust If:

• Extremely limited budget
• Simple storage of outdoor/garden equipment
• Drainage is critical
• Temporary or very basic shed

Avoid Plastic Grid Systems Unless:

• Very small shed (under 10m²)
• Light storage only
• Easy installation is priority
• Budget is tight but you want something better than gravel

Site Preparation Matters

Regardless of floor type, site preparation is critical. All my successful shed floors had:

• Proper drainage consideration (water flows away from shed)
• Level or properly graded base
• Compacted subgrade
• Appropriate moisture barriers

The one time I skipped thorough site prep (for the sealed earth attempt), I regretted it.

My Personal Recommendation

For permanent sheds where you’ll spend time or store valuable equipment, concrete is worth the investment. The upfront cost is higher, but the total cost over 20 years is probably lower than timber when you factor in maintenance and eventual replacement.

For basic storage sheds, timber on piers offers the best balance of cost, performance, and durability.

Only use gravel/crusher dust if you absolutely must minimize cost and the shed is purely for basic outdoor storage.

The floor is the foundation of everything the shed will be used for. Getting it right the first time saves money, frustration, and the hassle of retrofitting or replacing it later. I learned this lesson the expensive way, so hopefully you won’t have to.