Required Footing Width
600mm
AS 3600-2026 compliant design
Professional foundation design tool for structural engineers and builders
Calculate strip footing width, depth, and reinforcement requirements per AS 3600-2026 standards. Includes bearing pressure analysis, soil capacity checks, and concrete volume estimates for Australian construction projects.
Engineering-grade calculations for residential and commercial foundation design
Calculate strip footing dimensions according to Australian Standards AS 3600-2026 for concrete structures and AS 2870-2011 for residential slabs. Our calculator ensures footings meet structural engineering requirements for bearing capacity, stability, and long-term performance under Australian soil conditions.
Automatically calculates bearing pressure and compares against allowable soil capacity. Accounts for dead loads, live loads, wall self-weight, and footing mass to ensure foundation stability. Includes safety factors and serviceability checks for 2026 building code compliance.
Provides footing width, depth, reinforcement specifications, concrete volumes, and material costs. Suitable for single-storey homes, multi-level buildings, retaining walls, and commercial structures. Results include construction details for builders and certification data for engineers.
Enter wall and load parameters for optimal footing dimensions
Strip footings are continuous concrete foundations that support load-bearing walls in residential and commercial buildings across Australia. These linear foundations distribute wall loads to the underlying soil, preventing settlement and structural damage. Proper strip footing design according to AS 3600-2026 and AS 2870-2011 standards ensures buildings remain stable throughout their design life, accommodating soil movements, seasonal variations, and applied loads from occupancy and environmental factors.
The design process involves calculating bearing pressures, determining adequate footing width to prevent exceeding soil capacity, specifying appropriate depth based on soil classification, and detailing reinforcement for crack control and durability. Australian soils range from highly reactive clays requiring deep footings with edge beams to stable sands allowing shallow, simple designs. Understanding soil bearing capacity is fundamental to economical and safe footing design for construction projects in 2026.
Footing width increases with load and decreases with better soil capacity
Professional structural engineers use established formulas based on soil mechanics and structural theory to size strip footings. These AS 3600 compliant calculations ensure footings provide adequate bearing area while maintaining structural integrity.
Basic formula ensuring bearing pressure doesn't exceed soil capacity. Example: 24 kN/m ÷ 100 kPa = 0.60m (600mm) width
Calculates wall self-weight contributing to total load. Brick veneer: 19 kN/m³ × 0.23m × 2.7m = 11.8 kN/m
Verification that designed width keeps pressure within limits. Safety factor = Allowable ÷ Actual pressure (typically 1.5-2.0)
Ensures adequate structural depth and soil confinement. Reactive soils require deeper footings (450-750mm) regardless of width
The following table summarizes typical strip footing dimensions for various building types and soil conditions according to AS 3600-2026 and AS 2870-2011 standards. These values represent common Australian residential and light commercial construction scenarios.
| Building Type | Typical Width | Typical Depth | Soil Class | Reinforcement |
|---|---|---|---|---|
| Single Storey Brick Veneer | 450-600mm | 300-450mm | S, M, H | 2×N12 + N12@450 |
| Two Storey Brick Veneer | 600-750mm | 450-600mm | S, M, H | 3×N12 + N12@300 |
| Double Brick Single Storey | 600-750mm | 300-450mm | S, M | 2×N12 + N12@400 |
| Double Brick Two Storey | 750-900mm | 450-600mm | S, M | 3×N16 + N12@300 |
| Retaining Wall (1.5m) | 900-1200mm | 600-750mm | All Classes | 4×N16 + N16@250 |
| Commercial/Heavy Load | 900-1500mm | 600-900mm | M, S | Engineer design |
| Lightweight Single Storey | 400-500mm | 300mm | S, M | 2×N12 + N12@600 |
| Three Storey Masonry | 900-1200mm | 600-750mm | S, M | 4×N16 + N16@250 |
Multiple engineering and site-specific factors influence final strip footing dimensions. Understanding these variables helps optimize designs for safety, economy, and constructability in Australian building projects during 2026.
The single most important factor determining footing width. Weak soils (50-100 kPa) require wide footings spreading loads over larger areas, while competent soils (300-500 kPa) allow narrower, economical designs. Always obtain geotechnical reports for projects exceeding single-storey residential construction to verify assumed capacities.
Total load combines wall self-weight, floor/roof dead loads, and occupancy live loads. Two-storey buildings double loads compared to single-storey, requiring proportionally wider footings. Heavy roofing materials like concrete tiles add significant dead load versus lightweight metal roofing, affecting foundation sizing by 10-20%.
AS 2870 classifies soils from Class S (stable, sand/rock) to Class P (extremely reactive clay). Reactive soils expand when wet and shrink when dry, requiring deeper footings and additional measures like edge beams and articulation joints. Class H and above typically mandate 450mm+ depth regardless of bearing capacity calculations.
Australian climate zones from tropical north to temperate south influence moisture variations in reactive soils. Darwin's wet-dry cycles cause extreme soil movement versus Melbourne's moderate climate. Depth of moisture influence (typically 1.5-3.0m) guides minimum footing depth requirements particularly for basement applications in reactive soil areas.
Accurate load determination is essential for safe footing design. Structural engineers calculate loads using AS 1170 series standards covering dead loads (permanent elements), live loads (occupancy), wind loads, and in some cases earthquake loads. Wall self-weight derives from material density multiplied by dimensions—a 230mm brick veneer wall 2.7m high contributes approximately 11.8 kN per linear metre before considering additional structural loads.
Dead loads include roof structure and cladding (1.0-2.5 kN/m²), ceiling and insulation (0.3-0.5 kN/m²), suspended floors (2.0-3.5 kN/m² for timber, 3.5-5.0 kN/m² for concrete), and partition walls (1.0-1.5 kN/m²). For a 6-metre wide single-storey house, one external wall footing might carry 8-12 kN/m from roof plus 4-6 kN/m from internal floor loads, totaling 12-18 kN/m before wall self-weight.
AS 3600-2026 mandates minimum reinforcement in strip footings for crack control and distribution of concentrated loads. Standard practice specifies at least two longitudinal N12 bars (12mm diameter deformed bars) along footing length, positioned in bottom third of footing depth with 50-75mm cover to bottom surface. Transverse reinforcement (typically N12 at 300-600mm centres) controls longitudinal cracking and ties longitudinal bars together.
For wider footings exceeding 750mm or heavily loaded applications, three or four longitudinal bars provide additional capacity. High-strength installations may specify N16 or N20 bars instead of N12. All reinforcement must achieve specified cover requirements (50mm minimum in non-aggressive soils, 65mm+ in aggressive conditions) and maintain proper development lengths at lap splices and terminations per AS 3600 detailing rules.
Always engage a qualified structural engineer for footing design on projects requiring council approval. This calculator provides preliminary estimates for planning purposes. Actual designs must account for specific site conditions, unusual loads, sloping sites, poor soil zones, tree influences, and local authority requirements. Engineers provide sealed drawings necessary for building permits and construction insurance coverage. DIY footing designs risk structural failure, property damage, and legal liability.
Strip footing construction costs in 2026 Australia range from $180-350 per linear metre depending on dimensions, site access, reinforcement complexity, and regional pricing variations. A typical single-storey home with 80 linear metres of strip footings costs $14,400-28,000 for materials and installation, representing approximately 8-12% of total construction budget for houses in the $300,000-400,000 range.
Concrete costs $150-220 per cubic metre delivered for N25 grade suitable for most residential footings. A standard 600mm × 450mm footing consumes 0.27m³ per metre, costing $40-60/m for concrete alone. N12 reinforcing steel costs $1.80-2.50 per kilogram; typical footing requires 6-10 kg/m totaling $11-25/m. Formwork (if required) adds $15-35/m for materials and labour, though many Australian footings are cast directly into trenches without formwork.
Capital city pricing typically exceeds regional costs by 15-25%. Sydney and Melbourne command highest rates at $250-350/m for standard footings, while regional Queensland and South Australia average $180-240/m. Remote locations incur additional delivery surcharges ($200-500+) for concrete and materials, potentially doubling unit costs. Concrete Institute of Australia publishes quarterly cost indices tracking national trends useful for budget planning in 2026 construction markets.
Specify wider shallow footings instead of narrower deep footings where soil conditions permit—less excavation and concrete reduces costs 15-20% with equivalent performance. Coordinate concrete deliveries with other pours (slab, piers) to share delivery fees. Use standard reinforcement spacings (300mm, 450mm, 600mm) allowing pre-cut steel bundles. Negotiate fixed-price contracts including all footing works to avoid variations. Well-planned designs meeting first-time approval save engineering fee revisions and construction delays worth thousands of dollars.
Several recurring errors compromise strip footing performance and lead to costly remediation or structural failures. Understanding these pitfalls helps ensure robust designs complying with Australian standards and delivering long-term building performance.
Under-sizing footing width causes excessive bearing pressures exceeding soil capacity, resulting in settlement, wall cracking, and structural distress. Always verify actual bearing capacity through soil testing rather than assuming conservative values. A 10% width reduction might save $500 on a small house but risks $50,000+ in underpinning and repairs if settlement occurs. Include safety factors (typically 1.5-2.0) ensuring adequate capacity margin for uncertainties.
Shallow footings in reactive clay soils experience seasonal heave and settlement cycles causing extensive cracking and structural damage. AS 2870 mandates minimum depths based on soil classification—ignoring these requirements voids insurance and approval. Class H soils require 450mm minimum, Class H2 need 600mm+, regardless of bearing capacity calculations. Geotechnical reports provide classifications avoiding guesswork on footing depth specifications.
Inadequate cover to reinforcement causes corrosion and spalling within 10-20 years. AS 3600 specifies 50mm minimum cover in non-aggressive soils, 65mm+ in coastal or aggressive conditions. Insufficient lap lengths at bar splices create weak points risking footing failure. Chair spacers or bar supports must maintain specified cover during concrete placement—reinforcement sitting on trench bottom provides zero effective reinforcement. Professional detailing ensures compliance with code requirements for durability and structural performance.
Tree roots extract soil moisture creating voids under footings in reactive soils. AS 2870 mandates increased depths or structural isolation within tree influence zones—typically 1.5× mature tree height. Large eucalyptus might influence soil 15-20 metres from trunk, requiring footing depths to 1.5-2.5 metres or expensive articulation joints isolating foundation sections. Tree removal is insufficient—roots continue extracting moisture for years after felling, maintaining risk. Professional geotechnical assessment identifies tree-related design modifications.
Official source for AS 3600-2026 concrete structures and AS 2870-2011 residential slabs and footings standards. Essential reference for compliant foundation design in Australian construction projects.
Visit Standards Australia →Professional engineering body providing technical resources, continuing education, and practitioner directories. Find qualified structural engineers for foundation design and certification services.
Engineers Australia Resources →Technical publications, research findings, and best practice guidelines for concrete construction including foundations, reinforcement detailing, and durability specifications for Australian conditions.
Concrete Institute Australia →