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Calculate concrete, reinforcement, and excavation for strip footings
Accurate material calculations for continuous strip foundations supporting walls and load-bearing structures. Get instant estimates with bearing pressure verification for 2026 standards.
Design and calculate strip footings for residential and commercial construction
Calculate precise concrete volume, reinforcement steel quantities, and excavation requirements for strip footings. Our calculator determines optimal footing dimensions based on wall loads and Australian Standards for safe foundation design.
Automatically checks bearing pressure against allowable soil capacity ensuring structural safety. This allowable bearing pressure calculator component prevents foundation failure from inadequate sizing or unsuitable soil conditions.
Get instant 2026 cost estimates including concrete supply, reinforcement steel, excavation, formwork, and labor. Compare different footing widths and depths to optimize your foundation budget while maintaining structural integrity and compliance.
Enter wall loads and soil conditions
A strip footing calculator is an essential tool for determining the correct dimensions and material quantities for continuous foundations supporting load-bearing walls. Strip footings, also called continuous footings or wall footings, distribute building loads across extended lengths beneath walls, providing stable support for residential and commercial structures. The calculator ensures adequate bearing capacity while optimizing concrete and steel usage for economical construction in 2026.
Strip footings transfer loads from walls and superstructure to underlying soil through a continuous reinforced concrete beam. Proper design requires accurate assessment of soil bearing capacity, calculation of applied loads, and verification that bearing pressure remains below allowable limits with appropriate safety factors. This basement access ramp calculator complements foundation planning for comprehensive construction projects requiring various concrete elements.
Strip footings spread concentrated wall loads over wider soil areas, reducing bearing pressure to safe levels. Footing width calculation divides total wall load by allowable soil bearing capacity, with typical residential footings ranging 450-900mm wide. Deeper footings provide greater bending resistance for heavier loads or weaker soils.
Actual bearing pressure must remain below allowable soil capacity with safety factor typically 3.0 for working stress design. Calculate bearing pressure by dividing wall load per metre by footing width. Exceeding bearing capacity causes settlement, cracking, and potential structural failure requiring immediate remediation.
Longitudinal steel bars resist bending moments and control cracking in footings. Minimum two N12 bars typically required for residential footings under 600mm wide. Transverse ties at 400-600mm spacing maintain bar position during concrete placement. Cover of 75mm protects steel from corrosion in ground contact.
Typical strip footing showing wall support, concrete dimensions, reinforcement placement, and soil bearing interface for load transfer.
Strip footing design begins with determining total wall loads including dead loads (permanent weight of structure) and live loads (occupancy and environmental loads). Structural engineers calculate these loads based on wall construction, roof spans, floor systems, and building codes. For typical single-storey residential construction, wall loads average 8-12 kN per metre for single brick, 12-18 kN/m for cavity walls, and 15-25 kN/m for double brick construction including roof loads.
| Wall Type | Typical Load | Footing Width | Footing Depth |
|---|---|---|---|
| Single Brick Wall | 8-12 kN/m | 450-600mm | 250-300mm |
| Cavity Wall | 12-18 kN/m | 600-750mm | 300-350mm |
| Double Brick Wall | 15-25 kN/m | 750-900mm | 350-450mm |
| Lightweight Wall | 5-8 kN/m | 400-500mm | 250-300mm |
| Two-Storey Load | 20-35 kN/m | 900-1200mm | 400-500mm |
Concrete N32: $180-220 per m³ delivered | Reinforcement Steel: $2.50-3.50 per kg | Excavation: $45-65 per m³ | Formwork: $35-55 per m² | Labor: $80-120 per m³ placed
Total installed strip footing costs average $350-550 per cubic metre including all materials, excavation, formwork, reinforcement placement, concrete supply, pumping, and labor for residential projects in 2026. A typical 40-metre perimeter residential house with 600mm × 300mm footings requires approximately 7.2 m³ concrete, costing $2,500-4,000 complete installed. Commercial projects with engineered designs and inspection requirements typically cost 20-30% more due to additional compliance and supervision needs. This aggregate quantity calculator assists with related material planning.
Concrete Volume: 7.2 m³ + 10% = 7.9 m³ | Concrete Supply: 7.9 × $200 = $1,580 | Reinforcement: 240 kg @ $3/kg = $720 | Excavation: 10 m³ @ $55 = $550 | Formwork: 24 m² @ $45 = $1,080 | Labor: 7.9 × $100 = $790 | Total Cost: $4,720 | Cost per metre: $118/m
Begin by clearing vegetation and topsoil from footing locations. Mark footing centerlines using string lines and profile boards positioned beyond excavation limits. Check diagonal measurements to verify square corners for building perimeters. Mark excavation width allowing 150-200mm beyond footing sides for formwork installation and working room. Level site to establish consistent excavation depths referenced to benchmark datum point or site datum established by surveyor.
Excavate trenches to design depth using excavator for long runs or hand digging for short sections. Maintain vertical sides where soil stability permits, or batter slopes in loose materials for safety. Remove loose soil from trench bottom and compact with hand tamper or plate compactor. Check depth and level using laser level or string lines. Install 75mm sand or gravel blinding layer if required for wet conditions or soft subgrade providing clean working surface for reinforcement placement.
Install timber or steel formwork to internal and external faces of footing maintaining correct width. Brace forms securely with stakes driven into undisturbed soil beyond excavation. Check formwork is level, straight, and at correct spacing using spacers at 1.5-2.0m intervals. Apply release agent to timber forms preventing concrete adhesion. Ensure form tops are at correct height for finishing concrete surface level with top of footing. Seal form joints preventing concrete loss during placement.
Place longitudinal bars on chairs or spacers maintaining minimum 75mm cover to soil contact surface and 50mm cover to vertical faces. Tie transverse ties at specified spacing using tie wire. Ensure bars are clean, free of loose rust, oil, or contamination. Position lapping bars with minimum overlap of 40 times bar diameter or as specified by engineer. Check cover dimensions before concrete placement. Install starter bars projecting above footing for wall construction if required by design.
Place concrete in continuous operation to avoid cold joints, starting from one end and working systematically along footing length. Vibrate concrete thoroughly using poker vibrators ensuring complete filling around reinforcement and into corners. Avoid over-vibration causing segregation. Strike off excess concrete level with formwork tops using screed board. Float surface smooth for wall construction. Cure concrete by covering with plastic sheet or wet hessian for minimum 7 days, maintaining moist conditions for proper strength development. Remove formwork after 24-48 hours when concrete has sufficient strength, backfill carefully avoiding damage to footing edges.
Engineer Certification: Most jurisdictions require structural engineer design and certification for footings in commercial buildings or difficult site conditions. | Soil Testing: Always obtain geotechnical report specifying bearing capacity - do not estimate soil strength. | Building Codes: Ensure compliance with AS 2870 (residential slabs and footings) or AS 3600 (concrete structures) and local building codes. | Inspection: Arrange required inspections before concrete placement - typically pre-pour inspection of excavation, formwork, and reinforcement.
Occurs when sections of footing settle unevenly due to variable soil conditions, inadequate width, or localized bearing failure. Causes include tree roots, underground voids, poor compaction of fill materials, or water infiltration weakening subgrade. Prevention requires thorough site investigation, adequate footing width for soil type, and removal of unsuitable materials before construction.
Results from inadequate reinforcement, excessive bending moments, or bearing pressure exceeding soil capacity. Longitudinal cracks indicate insufficient steel area or incorrect placement. Transverse cracks suggest excessive footing projection or high soil pressure. Prevent through proper engineering design, adequate reinforcement with correct cover, and verification of soil bearing capacity.
Undermining of footings occurs when water concentrates around foundations, washing away supporting soil and creating voids. Common near downpipes, poor drainage areas, or sites with inadequate stormwater management. Install surface drainage directing water away from footings, provide subsurface drainage where required, and backfill with free-draining material preventing water accumulation against footings.
Integrated waffle slab or stiffened raft systems combine ground floor slab with edge beam footings in single concrete pour. Suitable for reactive clay soils subject to seasonal movement where conventional strip footings may experience differential movement. More expensive than strip footings (typically 30-50% cost premium) but provides superior performance on problem sites. Design requires specialist geotechnical and structural engineering input. Popular in areas with expansive clay soils common in parts of Australia.
Alternative to traditional bar reinforcement using prefabricated reinforcing mesh placed in excavated trenches. Faster installation than individual bars with ties, reducing labor costs. Mesh provides combined longitudinal and transverse reinforcement in single placement. Suitable for light residential loads with good soil conditions. Not appropriate for heavily loaded footings or poor soils requiring engineer-designed reinforcement layouts. Popular for small residential additions and outbuildings where engineering certification not required.
Deep foundation alternative where shallow strip footings unsuitable due to weak surface soils, high groundwater, or extremely reactive clays. Helical screw piles installed to competent bearing strata support elevated ground beams spanning between pile heads. Significantly more expensive than strip footings but necessary in specific site conditions. Common for coastal areas with poor soil, flood-prone locations, or sites with deep soft clay layers requiring bearing at depth. Requires specialist design and installation contractors.
Strip footing width depends on wall load and soil bearing capacity. Calculate minimum width by dividing wall load (kN/m) by allowable bearing capacity (kPa). Typical residential footings range 450-600mm wide for single brick walls on medium soil (200 kPa capacity), 600-750mm for cavity walls, and 750-900mm for double brick or two-storey construction. Light timber framed walls on good soil may use 400-450mm width. Always verify adequacy through bearing pressure calculation: actual pressure must remain below allowable capacity with safety margin. Consult structural engineer for unusual loads, weak soils below 150 kPa capacity, or multi-storey buildings requiring engineered foundation design.
Standard residential strip footings typically 300mm deep for normal loading and soil conditions. Minimum depth 250mm may suit light loads on very good soils. Increase to 350-450mm depth for heavier loads, weaker soils, or wider footings requiring additional bending capacity. Depth must extend below frost line in cold climates (600mm+ in severe areas) and below zone of soil moisture variation for reactive clays (400-500mm typical). Footing bottom must reach undisturbed natural soil or engineered fill compacted to specification - never found on loose fill, topsoil, or organic material. Deeper footings also resist frost heave and provide greater embedment preventing lateral movement or erosion undermining.
Strip footing costs average $100-140 per linear metre for standard residential 600mm × 300mm footings fully installed in 2026. This includes excavation, concrete N32, reinforcement (2 × N12 bars with ties), formwork, placement, and basic finishing. Smaller footings 450mm × 250mm cost $80-100/m, while larger 900mm × 400mm footings cost $160-220/m. Regional variations significant - metropolitan areas typically 20-30% higher than regional locations. Add $15-25/m for difficult access, $10-20/m for removal and disposal of excavated material, $20-35/m for deeper footings in reactive soils. Engineered designs requiring site-specific reinforcement, special concrete mixes, or certification add 15-25% to base costs. Always obtain multiple quotes for projects exceeding 50 linear metres.
Minimum reinforcement for residential strip footings typically comprises two N12 (12mm diameter) longitudinal bars with N12 transverse ties at 600mm spacing maximum. Footings wider than 600mm often require three N12 bars, while very wide footings (900mm+) need four bars. Increase bar size to N16 for heavily loaded footings or longer unsupported spans. Maintain 75mm minimum cover to bars contacting soil, 50mm cover to vertical faces, and 25mm cover to top if protected by floor slab. Ties prevent bar movement during concrete placement and control crack distribution. Bar laps minimum 40 times diameter (480mm for N12 bars). Engineer-designed footings may specify different reinforcement based on structural analysis - always follow approved drawings for commercial work or unusual residential conditions.
Calculate bearing pressure by dividing wall load per metre by footing width in metres: Bearing Pressure (kPa) = Wall Load (kN/m) ÷ Footing Width (m). Example: 15 kN/m wall load on 600mm (0.6m) wide footing produces 15 ÷ 0.6 = 25 kPa bearing pressure. This actual pressure must remain below allowable soil bearing capacity specified in geotechnical report. Working stress design typically requires actual pressure less than 50% of ultimate bearing capacity, providing safety factor of 2.0 or greater. For multiple load cases (dead load only, dead plus live load, wind loading combinations), check worst case governs design. If calculated pressure exceeds allowable capacity, increase footing width, improve soil conditions, or reduce building loads through structural modifications.
Yes, strip footings suit sloping sites using stepped footing design. Steps occur at intervals along footing length maintaining minimum 300mm overlap between adjacent levels and maximum 500mm vertical step height. Each step must have minimum 600mm horizontal length at consistent depth before next step. Bottom of footing must be level within each step section. Increase reinforcement through step locations and provide additional transverse bars across step preventing cracking. For steep slopes exceeding 1:4 gradient, consider alternative foundations including stepped pads, screw piles, or piled ground beams depending on site conditions and structural loads. Engineer certification typically required for stepped footings in most jurisdictions due to additional complexity and potential failure modes at step locations.
Strip footings are continuous linear foundations supporting walls, transferring loads along extended lengths to underlying soil. Pad footings are isolated square or rectangular footings supporting individual columns or posts, spreading concentrated point loads over limited areas. Strip footings suit load-bearing wall construction in residential buildings, boundary walls, and commercial structures with closely spaced columns. Pad footings appropriate for post-and-beam construction, steel frame buildings, and structures with widely spaced point loads. Strip footings more economical for continuous support requirements, while pad footings better suit flexible layouts and buildings requiring large column spacing. Design calculations differ - strip footings analyzed per linear metre, pad footings analyzed as individual elements supporting specific column loads with checks for punching shear and flexural capacity.
Strip footings typically require proper drainage to prevent water accumulation causing soil weakening, erosion, or frost damage. Install surface drainage directing runoff away from footings using minimum 5% grade for 3m distance from building perimeter. Consider subsurface drainage using slotted agricultural pipe in gravel backfill where groundwater high, soil poorly draining, or site prone to water infiltration. Place geotextile fabric preventing soil migration into drainage aggregate. Connect to stormwater system or suitable discharge point maintaining positive flow. Critical in reactive clay soils where moisture variation causes shrink-swell movement damaging footings and superstructure. For basements and below-grade construction, waterproofing membranes plus drainage systems mandatory preventing water entry and hydrostatic pressure against foundation walls.
Access AS 2870 (Residential Slabs and Footings) and AS 3600 (Concrete Structures) for design requirements, material specifications, and construction standards applicable in 2026.
Visit Standards →Technical resources covering concrete specification, placement, quality control, and troubleshooting for foundation construction. Industry best practices and design guidelines.
Learn More →Soil investigation guidelines, bearing capacity determination, and site classification procedures. Essential for proper foundation design and site assessment.
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