Total Concrete Required
0.5m³
For cylindrical piers with 5% wastage
Calculate concrete volumes and pier specifications for footings
Professional concrete pier calculator for deck footings, house piers, and structural supports. Calculate volumes, spacing, and depth requirements compliant with AS 3600 standards for 2026.
Professional pier footing calculations for decks, houses, and structures
Calculate exact concrete volumes for cylindrical piers, square footings, and belled piers. Our calculator accounts for pier diameter, depth, footing dimensions, and wastage factors to ensure you order the correct concrete quantity for your project in 2026.
Determine optimal pier spacing for decks, verandahs, and elevated structures based on load requirements and beam spans. Follow Australian building standards for residential and commercial applications with proper load distribution and structural integrity.
Designed for builders, engineers, and DIY enthusiasts working on projects requiring AS 3600 compliance. Includes depth recommendations for frost lines, soil types, and bearing capacity considerations for safe, long-lasting pier foundations.
Select pier type and enter dimensions below
Concrete piers are vertical structural elements that transfer loads from elevated structures like decks, verandahs, and houses into the ground. Unlike continuous strip footings, piers create isolated points of support, making them ideal for sloping sites, areas with reactive soils, or elevated structures. Properly designed piers distribute loads over sufficient bearing area to prevent settlement while minimizing excavation and concrete volumes.
In Australian construction, concrete piers must comply with National Construction Code requirements and AS 3600 standards for concrete structures. Pier design considers soil bearing capacity, applied loads, pier spacing, and environmental factors including frost depth, reactive soils, and termite management. Typical residential deck piers range from 200-450mm diameter and extend 500-1200mm below ground depending on soil conditions.
Typical pier configuration showing shaft and footing sections
Most common pier type, formed using cardboard tubes (Sonotubes) or PVC pipes. Cylindrical piers offer excellent load distribution, easy installation, and efficient concrete usage. Standard diameters range from 200mm to 450mm. Ideal for most residential deck and verandah applications where soil conditions are stable.
Formed using timber or steel formwork, square piers provide flat surfaces for attaching post brackets and structural connections. Commonly used for house stumps and heavy structural loads. Typically 250-400mm square, these piers suit applications requiring specific connection details or higher load capacities than round piers.
Feature an enlarged base (bell) created by special augers, increasing bearing area without larger shaft diameters. Essential for reactive clay soils and high-load applications. The bell typically extends 1.5-2 times shaft diameter. Provides superior uplift resistance and bearing capacity in challenging soil conditions.
For 300mm diameter × 600mm deep: 3.14 × 0.15² × 0.6 = 0.042m³ per pier
For 300mm × 300mm × 600mm: 0.3 × 0.3 × 0.6 = 0.054m³ per pier
Calculate shaft and bell separately, then add together for total volume
Minimum pier depth depends on multiple factors including soil type, frost line, reactive soil classification, and structural loads. AS 3600 and the National Construction Code specify minimum depths to ensure adequate bearing capacity and prevent frost heave or soil movement. Most jurisdictions require piers extend at least 500mm below natural ground level, with deeper requirements for reactive soils or cold climates.
| Application | Typical Pier Size | Maximum Spacing | Minimum Depth | Reinforcement |
|---|---|---|---|---|
| Timber Deck (Residential) | 250-300mm ø | 1.8 - 2.4m | 500-600mm | 4× N12 bars |
| Verandah / Patio | 300-350mm ø | 2.0 - 2.5m | 600-900mm | 4× N16 bars |
| House Stumps | 350-450mm ø | 1.8 - 3.0m | 900-1200mm | 6× N16 bars |
| Pergola / Carport | 250-350mm ø | 2.5 - 3.5m | 500-600mm | 4× N12 bars |
| Shed Foundation | 200-300mm ø | 2.0 - 3.0m | 500mm | Optional for small sheds |
| Commercial / Heavy Load | 450-600mm ø | 1.5 - 2.0m | 1200mm+ | Engineer specified |
Excavate holes using augers or post hole diggers to specified depth. Ensure holes are vertical and clean of loose soil. Place 50-75mm crushed rock base for drainage. Install cardboard formwork tube, ensuring it's plumb and extends 100-150mm above ground. Add steel reinforcement cages before pouring. Fill with concrete in one pour, vibrating to remove air pockets. Finish top level and install post brackets while concrete is workable.
Use minimum 20 MPa concrete strength (N20 grade) for residential pier applications, with 25-32 MPa for house stumps or high-load structures. For small projects with 1-4 piers, pre-mixed concrete bags offer convenience—each 20kg bag yields approximately 0.01m³ (10 litres) of concrete. Larger projects benefit from ready-mix delivery, typically supplied in 0.2m³ increments with minimum charges applying.
Avoid these errors: Insufficient depth for soil type, holes not vertical causing misaligned posts, inadequate drainage leading to water accumulation, forgetting steel reinforcement reducing strength, poor concrete consolidation leaving voids, and installing brackets after concrete has set. Plan pier layout carefully using string lines to ensure proper alignment and spacing throughout your structure.
Steel reinforcement increases pier tensile strength and prevents cracking from loads and soil movement. Minimum reinforcement for residential piers typically consists of 4× N12 (12mm diameter) deformed bars extending the full depth of the pier. Larger piers or high-load applications may require 6× N16 bars or heavier. Maintain 40-50mm concrete cover around reinforcement for corrosion protection.
For reactive soils or areas subject to lateral loads, include horizontal ties or helical reinforcement at 200-300mm spacing. Top of reinforcement should extend 50-75mm above finished pier height for connection to timber or steel posts. Pre-fabricated reinforcement cages available from steel suppliers simplify installation and ensure AS 3600 compliance for pier foundations.
Pier spacing depends on beam span capacity, joist sizing, and applied loads. For residential decks using 190×45mm F7 hardwood beams, maximum pier spacing typically ranges from 1.8-2.4 metres. Larger beams (240×45mm or LVL beams) can span further, allowing wider pier spacing and reducing total pier count. Always verify beam capacity with span tables from Timber Queensland or engineer specifications.
Divide structure length by maximum beam span to determine number of beam supports needed. For a 6.0m deck with 2.0m pier spacing, you need 4 piers per line (6.0 ÷ 2.0 = 3 spans). Multiply by number of parallel beam lines. Add corner and edge piers as required. A 6.0m × 4.0m deck typically requires 12-16 piers depending on beam configuration and spans.
Sandy soils require larger pier diameters or belled bases to increase bearing area and compensate for lower bearing capacity (typically 100-150 kPa). Clay soils provide good bearing when firm (150-300 kPa) but reactive clays require deeper piers to reach stable soil below the zone of seasonal moisture variation. Always excavate below any fill, topsoil, or disturbed material to reach natural bearing strata.
In termite-prone areas, install physical or chemical termite barriers as part of pier construction. Physical barriers include stainless steel mesh or graded stone particles placed between pier top and timber posts. Chemical barriers involve treating soil around piers with approved termiticides. Ensure minimum 75mm clearance between ground level and timber framing for termite inspection access as required by AS 3660.
A 300mm diameter pier requires approximately 0.042m³ (42 litres) of concrete per 600mm of depth. For a typical 600mm deep pier, this equals about 4-5 × 20kg bags of pre-mixed concrete, or 0.05m³ including 5% wastage. For deeper piers at 900mm depth, you'll need approximately 0.06m³ per pier. Ready-mix concrete becomes more economical for projects requiring 8+ piers or 0.5m³ total volume in 2026.
Standard residential deck pier spacing ranges from 1.8 to 2.4 metres depending on beam size and design loads. For 190×45mm hardwood beams, use 1.8-2.0m spacing. Larger 240×45mm beams or LVL beams can span 2.4-3.0m between piers. Pier spacing must be coordinated with joist spans—typical 140×45mm joists span 1.8-2.1m between bearers. Always verify spans with engineering tables for your specific timber grade and loading conditions.
Minimum pier depth for residential decks is typically 500-600mm below natural ground level in stable soils. Sandy or loose soils require 600-900mm depth. Reactive clay soils need 900-1200mm or depth specified by geotechnical report. Sloping sites require piers extend minimum 600mm below lowest adjacent ground. Cold climate regions must extend below frost line (300-600mm depending on location). Local building regulations may specify greater depths for your specific area and soil conditions.
Yes, steel reinforcement is required for most pier applications per AS 3600. Minimum reinforcement typically consists of 4× N12 (12mm) deformed bars for residential deck piers up to 350mm diameter. Larger piers or house stumps require 4-6× N16 bars. Reinforcement prevents cracking from loads, soil pressure, and temperature changes. Steel should extend the full pier depth with 40-50mm concrete cover, and project 50-75mm above finished pier for post connections. Small garden shed piers under 200mm may not require reinforcement depending on loads.
Yes, cardboard forming tubes (Sonotubes) are the standard method for cylindrical concrete piers in Australian construction. These waxed cardboard tubes come in diameters from 200-600mm and various lengths. Place tubes in excavated holes, ensure they're plumb, and fill with concrete. Tubes remain in place permanently—no need to remove. Cardboard tubes provide smooth finish, protect fresh concrete during curing, and cost significantly less than reusable formwork. Available from hardware stores and concrete suppliers throughout Australia in 2026.
Divide your deck's length and width by maximum beam span to determine pier rows and columns. For a 6.0m × 4.0m deck with 2.0m pier spacing: length needs 4 piers (6.0÷2.0), width needs 3 piers (4.0÷2.0). Total piers = 4 × 3 = 12 piers arranged in a grid. Add extra piers at stairs, heavy features, or irregular shapes. Consider beam orientation—spanning shorter direction reduces total beam length and pier count. Always add 1-2 extra for contingencies or adjustments during construction.
Standard residential deck piers range from 250-350mm diameter for normal residential loading. Low-level decks (under 600mm high) with 2.4m² area per pier can use 250mm piers. Standard elevated decks typically use 300mm diameter piers. Large or heavily loaded decks require 350-450mm piers. For precise sizing, calculate load per pier (structure weight + live load + environmental loads) and verify against soil bearing capacity. Consult engineer for decks over 1.0m high, hot tubs, or unusual loading conditions.
Bagged concrete is practical for small projects with 1-6 piers (under 0.3m³ total). It allows flexible timing and eliminates minimum delivery charges. Ready-mix concrete is more economical and ensures consistent quality for projects requiring 8+ piers or 0.5m³+ volume. Ready-mix also saves significant labour time—one truck delivers in minutes versus hours of mixing bags. For 12× 300mm piers (0.5m³), ready-mix costs approximately $95-115 delivered versus $300+ for 50 bags plus mixing labour in 2026. Choose based on project scale and access for concrete trucks.
Australian Standard AS 3600-2018 provides comprehensive specifications for concrete pier design, reinforcement requirements, and installation procedures for residential and commercial foundation applications in 2026.
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