Total Concrete Required
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Cubic metres (m³)
Calculate concrete requirements for your shed foundation
Accurate shed slab concrete calculations for garden sheds, workshops, and storage buildings. Get instant volume, materials, and cost estimates for 2026.
Professional concrete calculations for all shed types
Calculate exact concrete volumes for shed slabs of any size. Our shed slab calculator accounts for length, width, thickness, and edge beams to ensure accurate material ordering for garden sheds, workshops, and storage buildings.
Get detailed estimates for concrete volume, cement bags, sand, aggregate quantities, and reinforcement requirements. Perfect for DIY shed builders and professional contractors planning shed foundation projects in 2026.
Understand complete shed slab costs including concrete supply, delivery charges, reinforcement mesh, and excavation requirements. Compare ready-mix concrete versus DIY mixing options for your shed project.
Enter your shed dimensions below for instant calculations
A shed slab calculator is a specialized tool designed to calculate the exact amount of concrete, reinforcement, and materials needed for constructing a concrete foundation slab for sheds, workshops, and storage buildings. This calculator determines concrete volumes based on shed dimensions, slab thickness, and edge beam requirements to ensure accurate material ordering and cost estimation.
The shed slab calculator helps DIY builders, contractors, and homeowners plan their slab projects by providing detailed breakdowns of cement bags, sand, aggregate, and reinforcement mesh needed. It accounts for Australian building standards and typical shed construction practices used in 2026.
Standard shed slab with edge beam foundation
Choosing the correct slab thickness for your shed is crucial for long-term structural integrity. The thickness depends on the shed's intended use, soil conditions, and the weight it will support. Australian building practices recommend specific thicknesses based on application.
| Shed Type | Recommended Thickness | Concrete Grade | Typical Cost Range |
|---|---|---|---|
| Light Garden Shed | 100mm | 20 MPa | $800 - $1,500 |
| Standard Garden Shed | 120mm | 25 MPa | $1,200 - $2,200 |
| Workshop/Storage | 150mm | 25-32 MPa | $1,800 - $3,500 |
| Vehicle Storage | 180mm | 32 MPa | $2,500 - $4,800 |
| Heavy Equipment | 200mm+ | 40 MPa | $3,500 - $6,000 |
Calculating concrete for a shed slab involves determining the volume of both the main slab and any edge beams or thickened edges. Understanding these calculations ensures you order the correct amount of concrete and avoid costly shortages or excess material on your shed project.
Use precise measurements for shed length and width. Mark out the slab area with string lines and check diagonal measurements are equal to ensure the slab is square. Add 50-100mm to shed dimensions for easier installation.
Edge beams (thickened edges) provide additional strength and stability, especially on reactive soils. A 300mm wide by 400mm deep edge beam is standard for most residential shed slabs and increases concrete volume by approximately 15-25%.
Beyond concrete costs, budget for excavation ($300-$800), compacted base material ($200-$500), reinforcement mesh ($150-$400), vapor barrier ($80-$200), and finishing labor. Visit Bunnings for material pricing in 2026.
Proper shed slab construction requires careful planning and execution. Following these steps ensures a level, durable foundation that will support your shed for decades. Each stage is critical to the overall quality and longevity of your shed slab.
Begin by marking out the slab area 100mm larger than your shed on all sides. Remove topsoil to a depth of 150-200mm and excavate an additional 300-400mm around the perimeter for edge beams. Ensure the base is level using a laser level or string line, checking for a fall of no more than 10mm across the entire area.
Install timber formwork using treated pine boards secured with stakes every 900mm. For a 6m x 4m shed slab, you'll need approximately 20 linear metres of formwork. Place vapor barrier (plastic sheeting) over the compacted base to prevent moisture rising through the concrete. Position reinforcement mesh (typically SL72 or SL82) on plastic chairs 50mm above the base to ensure proper concrete cover.
Order ready-mix concrete one day before pouring and confirm delivery time. For shed slabs, 25 MPa concrete with 80mm slump is standard. Pour concrete starting from the furthest corner, working backwards toward the access point. Use a screed board to level concrete flush with formwork tops, then use a bull float to smooth the surface before it begins to set.
After bull floating, wait for bleed water to evaporate (typically 30-60 minutes) before final finishing. Use a steel trowel for a smooth finish, or a broom finish for better grip under the shed. Apply curing compound or cover with plastic sheeting to retain moisture. For more advanced techniques, check our alfresco slab calculator.
Keep the slab moist for at least 7 days by spraying with water 2-3 times daily. Do not install the shed until concrete reaches 80% strength (minimum 14 days for 25 MPa, 21 days for full strength). Remove formwork after 3-7 days once edges are hard enough to resist chipping.
Understanding material costs helps you budget accurately for your shed slab project. Prices vary by location, supplier, and order volume, but the following table provides typical Australian rates for 2026. These estimates apply to metro areas with adjustments of 10-20% for regional locations.
| Material | Unit | Average Price 2026 | Notes |
|---|---|---|---|
| Ready-Mix Concrete (25 MPa) | per m³ | $320 - $380 | Includes standard delivery |
| Ready-Mix Concrete (32 MPa) | per m³ | $350 - $420 | Heavy duty applications |
| SL72 Reinforcement Mesh | per m² | $8 - $12 | Standard residential mesh |
| SL82 Reinforcement Mesh | per m² | $11 - $16 | Medium strength mesh |
| Crushed Rock Base | per tonne | $45 - $65 | 20mm or 40mm aggregate |
| Vapor Barrier (200μm) | per m² | $2 - $4 | Moisture protection |
| Excavation (Machine) | per hour | $120 - $180 | Bobcat or excavator hire |
| Concrete Pump (if required) | per hour | $200 - $350 | For difficult access |
Different shed purposes require different slab sizes. Choosing the right size ensures your shed has adequate floor space while minimizing unnecessary concrete costs. Consider future needs when sizing your shed slab, as it's much cheaper to build slightly larger initially than to extend later.
When planning shed dimensions, consider access for vehicles or equipment, internal layout for workbenches or storage, door swing clearance, and any local council setback requirements from boundaries. Most councils require sheds over 10m² to comply with building regulations and may require engineering certification for slabs over 50m².
While concrete slabs are popular for sheds, alternative foundation types exist. Each has advantages and disadvantages depending on budget, soil conditions, shed size, and intended use. Understanding these options helps you make an informed decision for your specific situation.
Advantages: Provides a flat, level floor; prevents moisture and pests; suitable for all shed sizes; allows direct shed anchoring; creates usable floor space. Disadvantages: Highest upfront cost ($800-$6,000+); requires excavation and base preparation; permanent structure; curing time before installation. Best for workshops, vehicle storage, and permanent structures. Our shed slab calculator provides accurate estimates for this foundation type.
Advantages: Lower material cost ($300-$1,200); faster installation; works on uneven ground; allows airflow under shed; relocatable. Disadvantages: Requires separate floor frame; less stable in high winds; potential pest entry points; not suitable for heavy equipment. Best for small to medium garden sheds on level ground. Typically requires 9-12 piers for a 3m x 3m shed, 16-20 piers for 6m x 4m sheds.
Advantages: Lowest cost option ($150-$500); quick installation; fully relocatable; minimal excavation. Disadvantages: Limited lifespan (5-10 years); susceptible to rot and termites; requires perfectly level ground; not suitable for heavy sheds. Best for temporary storage or relocatable small garden sheds. Not recommended for areas with termite activity or where moisture is present. For more permanent solutions, consider our balcony slab calculator for elevated structures.
Proper reinforcement prevents slab cracking and ensures long-term durability. Steel reinforcement mesh distributes loads and controls shrinkage cracking as concrete cures. The mesh type depends on slab thickness, soil conditions, and expected loads on the shed floor.
Standard mesh for light garden sheds and storage buildings. Features 7mm diameter wires at 200mm spacing. Suitable for 100-120mm slabs on stable soil. Cost approximately $8-12 per m². Provides basic crack control and light reinforcement for residential applications.
Medium-duty mesh for standard workshops and vehicle storage. Features 8mm diameter wires at 200mm spacing. Recommended for 120-150mm slabs. Cost approximately $11-16 per m². Offers better crack control and strength for heavier loads and reactive soils.
Heavy-duty mesh for equipment storage and commercial applications. Features 9mm diameter wires at 200mm spacing. Required for 150-180mm slabs or poor soil conditions. Cost approximately $15-22 per m². Provides maximum strength and crack resistance for demanding applications.
Position reinforcement mesh centrally in the slab thickness using plastic chairs spaced at 600-900mm intervals. Ensure minimum 50mm concrete cover below mesh and 30mm cover above. Overlap mesh sheets by at least 200mm and tie with wire at every second intersection. For edge beams, use additional N12 bars (12mm diameter steel reinforcing bars) at top and bottom positions for extra strength.
For a 6m x 4m shed slab with 120mm thickness, you need approximately 2.88m³ of concrete for the slab itself. Adding a standard 300mm x 400mm edge beam increases this to approximately 3.8-4.2m³ total. With 10% wastage, order 4.2-4.6m³. Use our shed slab calculator above for exact calculations including your specific edge beam dimensions. For a 150mm thick slab (heavy workshop), you'd need 3.6m³ for the slab plus edge beams, totaling 4.8-5.2m³.
The minimum recommended thickness for a shed slab is 100mm for light garden sheds storing tools and equipment weighing less than 500kg. However, 120mm is the standard minimum for most residential sheds to ensure adequate strength and crack resistance. For workshops with heavy equipment, benches, or vehicle storage, use 150mm minimum. Slabs under 100mm thickness are prone to cracking and not suitable for permanent structures. Soil conditions also affect minimum thickness - reactive clay soils may require 150mm even for light sheds.
Edge beams (thickened edges) are highly recommended for all shed slabs, especially on reactive or unstable soils. A standard 300mm wide x 400mm deep edge beam provides foundation support around the slab perimeter, prevents edge cracking, and anchors the slab against movement. In clay soils or areas prone to ground movement, edge beams are essential. You can omit edge beams only on small sheds (under 9m²) on stable rock or very stable soil, but including them adds minimal cost ($200-400 extra) while significantly improving slab durability and lifespan.
Wait minimum 14 days after pouring before installing your shed on the slab. Concrete reaches approximately 80% of its design strength after 14 days and 100% after 28 days. For light garden sheds, 14 days is sufficient. For heavy workshops or vehicle storage sheds, wait the full 28 days. During this period, keep the slab moist by spraying with water 2-3 times daily for the first 7 days, then as needed. Installing too early risks cracking the slab or causing settlement issues. Remove formwork after 3-7 days once edges are firm.
Use 25 MPa concrete for standard residential shed slabs - this is the most common grade for garden sheds, workshops, and general storage. For light applications (small garden sheds under 12m²), 20 MPa is acceptable. For heavy-duty workshops with machinery, vehicle storage, or commercial sheds, upgrade to 32 MPa concrete. If storing very heavy equipment (like tractors or industrial machinery), use 40 MPa. The price difference between grades is minimal ($30-50 per m³) but the strength improvement is significant for demanding applications.
DIY shed slab pouring is possible for small to medium sheds (up to 20m²) if you have construction experience and proper equipment. You'll need skills in excavation, formwork, leveling, and concrete finishing. For sheds over 24m² (6m x 4m), professional help is recommended as concrete volume exceeds 3m³ and requires quick, coordinated pouring and finishing. Critical factors include achieving proper levels (±5mm), correct reinforcement placement, adequate compaction of base, and proper curing. Mistakes can be costly to rectify. Budget $1,500-3,500 for professional slab installation depending on size. Check our aggregate quantity calculator for base materials.
Shed slab costs in 2026 range from $800 for a small 3m x 3m garden shed slab to $6,000+ for large 12m x 6m workshop slabs. A typical 6m x 4m shed slab costs $2,200-3,800 including materials and labor. This includes excavation ($300-600), base material ($250-450), concrete ($1,200-1,800 for 4-5m³), reinforcement mesh ($200-350), and labor ($800-1,400). DIY can save $800-1,400 in labor but requires equipment hire. Regional areas add 15-25% to metro prices. Use our shed slab calculator to estimate your specific project cost. Prices assume standard access - difficult access may require concrete pumping ($200-350 extra).
Use 75-100mm of compacted crushed rock, road base, or 20mm blue metal aggregate under your shed slab. This provides a stable, well-draining base that prevents settlement and moisture issues. Spread the base material in two 50mm layers, compacting each layer thoroughly with a plate compactor. For poor or clay soils, increase base thickness to 150mm. Install geotextile fabric under the base if soil is very soft or contains organic matter. Top the compacted base with 200-micron vapor barrier (plastic sheeting) overlapped 300mm at joints to prevent ground moisture rising through the slab. Budget $8-12 per m² for base material plus $100-200 for compactor hire.
Learn professional techniques for mixing, pouring, and finishing concrete slabs. Includes mix ratios, equipment requirements, and troubleshooting common problems.
Read Guide →AS 3600 Concrete Structures and AS 2870 Residential Slabs standards provide technical requirements for concrete construction, reinforcement placement, and foundation design.
View Standards →Complete guides for owner-builders covering site preparation, formwork construction, concrete pouring, and shed installation techniques for successful DIY projects.
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