A footings calculator determines concrete volumes, reinforcement, and costs for strip footings, pad footings, and trench fill foundations supporting walls, columns, and structural loads. This 2026 calculator provides accurate calculations compliant with Building Regulations Approved Document A and BS 8004:2015 foundations standards for UK construction.
Footings distribute building loads to stable ground, preventing settlement and structural failure. Typical domestic strip footings are 600mm wide × 225mm deep minimum on good ground. Depth increases for poor soil, trees, or frost conditions. All footings require Building Control approval before construction per NHBC Standards 2026.
⚒️ Footings Calculator
Calculate footing volume, materials and costs
Footing Type
Strip Footing Dimensions
Pad Footing Dimensions
Trench Fill Dimensions
Specifications
Concrete Volume Required
0 m³
Including 10% wastage allowance
Footing Specifications
Footing Area
0 m²
Concrete Tonnes
0 tonnes
Ready-Mix Loads
0 loads
Excavation Volume
0 m³
Construction Details
Footing TypeStrip Footing
Concrete GradeC25/30 (RC25)
ReinforcementNone - Plain concrete
Blinding Required0 m² @ 50mm
Building ControlApproval required
Cost Estimate 2026
Excavation & Disposal£0
Blinding Concrete£0
Concrete£0
Reinforcement£0
Labour£0
Total Project Cost£0
Footing Width & Depth Requirements 2026
Footing dimensions depend on soil bearing capacity, structural loads, building height, and ground conditions. BS 8004:2015 specifies foundation design requirements. Inadequate footings cause settlement, cracking, and structural failure. Ground investigation recommended for challenging sites.
Standard Strip Footing Sizes
Building Type
Width
Depth
Soil Condition
Single Storey (Light)
450-600mm
150-225mm
Good ground (≥100 kN/m²)
Single Storey (Standard)
600mm
225mm
Medium ground (75-100 kN/m²)
Two Storey
750mm
300mm
Good ground (≥100 kN/m²)
Two Storey (Heavy)
900mm
450mm
Moderate ground (50-75 kN/m²)
Poor Soil Conditions
900-1200mm
450-600mm
Weak ground (<50 kN/m²)
Near Trees (High water demand)
As standard
+0.75m to 1.5m extra
Clay soils with tree roots
Single Storey
Width600mm
Depth225mm
SoilGood ground
Two Storey
Width750mm
Depth300mm
SoilGood ground
Poor Soil
Width900-1200mm
Depth450-600mm
SoilWeak ground
Types of Concrete Footings
Footing type selection depends on structural loads, soil conditions, and construction method. Each type has specific applications, advantages, and cost implications.
Strip Footings
Application: Continuous support for load-bearing walls
Dimensions: 450-1200mm wide, 150-450mm deep
Advantages: Economical, simple construction, suitable for most domestic buildings
Cost 2026: £40-65 per linear metre (600mm × 225mm)
Pad Footings
Application: Isolated support for columns and posts
Dimensions: 1m × 1m to 2m × 2m, 300-750mm deep
Advantages: Efficient for column structures, reduces concrete volume
Cost 2026: £180-350 per pad (1.5m × 1.5m × 600mm)
Trench Fill Foundations
Application: Deep narrow trenches filled with concrete
Dimensions: 450-750mm wide, 900-1500mm deep
Advantages: Fast construction, less excavation width, good for trees/poor soil
Cost 2026: £65-95 per linear metre (600mm × 1000mm)
Raft Foundations
Application: Slab covering entire building footprint
Made Ground/Fill: Variable - Always requires investigation, unstable
Tree Root Proximity & Foundation Depth
Trees near buildings cause foundation movement through soil moisture changes. Clay soils particularly susceptible to shrinkage during dry periods. NHBC Chapter 4.2 specifies foundation depths near trees to prevent damage from root activity and seasonal ground movement.
⚠️ Foundation Depth Near Trees (Clay Soils):
No Trees: Standard depth 900mm minimum, 225mm strip footing adequate
Small Trees (6m mature height): Foundation depth = 0.75 × mature height (4.5m deep min)
Medium Trees (12m mature height): Foundation depth = 1.0 × mature height (12m deep typical)
Large Trees (Oak, Willow, Poplar): Foundation depth = 1.25-1.5 × mature height (18m+ possible)
Safe Distance: Minimum distance = 1.0-1.5 × mature height from building
High Water Demand: Oak, willow, poplar, elm require deepest foundations
Alternative: Trench fill or piled foundations avoid excessive excavation depth
Footing Construction Process
Proper footing construction ensures stable foundations. Building Control inspection required before concreting. Professional groundworkers recommended for quality and compliance.
1. Setting Out & Excavation
Setting Out: Mark footing positions accurately, check diagonals
Excavation: Dig to required depth, vertical sides, level bottom
Inspection: Check for soft spots, obstructions, underground services
Disposal: Remove excavated material or reuse as hardcore
2. Base Preparation
Level Check: Ensure bottom is level using laser or spirit level
Blinding: 50mm weak concrete (C10/15) for level surface
DPM Option: Polythene membrane if required for moisture protection
Inspection: Building Control checks depth and ground conditions
3. Reinforcement (if required)
Bar Placement: 16mm bars longitudinally, 50mm cover
Spacers: Plastic chairs maintain correct position
Mesh Option: A142 mesh for wider footings
Cleanliness: Remove loose material before concrete pour
4. Concrete Pour
Concrete Grade: C25/30 (RC25) minimum for domestic
Placement: Pour in layers, compact thoroughly, no voids
Levelling: Straight edge for level top surface
Curing: Protect from rain, frost, rapid drying for 7 days
Footing Costs 2026
Footing costs include excavation, concrete, reinforcement, blinding, labour, and Building Control fees. Costs increase significantly for deep foundations, poor ground, or tree-affected sites. Trench fill faster but uses more concrete.
Typical Footing Costs (Per Linear Metre)
Footing Type
Excavation
Concrete
Labour
Total per m
Strip 600×225mm
£8-12
£15-20
£18-25
£41-57
Strip 750×300mm
£10-15
£25-32
£22-30
£57-77
Trench Fill 600×1000mm
£12-18
£68-85
£15-22
£95-125
Trench Fill 600×1500mm
£18-25
£100-125
£18-25
£136-175
Strip 600×225mm
Excavation£8-12/m
Concrete£15-20/m
Total£41-57/m
Strip 750×300mm
Excavation£10-15/m
Concrete£25-32/m
Total£57-77/m
Trench Fill 600×1000mm
Excavation£12-18/m
Concrete£68-85/m
Total£95-125/m
Building Regulations & Approval
All footings require Building Control approval under Part A (Structure). Foundation design must ensure safety, prevent excessive settlement, and comply with standards. Inspections mandatory at excavation stage before concrete pour.
📋 Building Control Requirements:
Before Starting: Submit structural calculations and foundation drawings
Excavation Inspection: Call Building Control to inspect trenches before concreting
Check Items: Depth, width, ground conditions, no soft spots or services
Approval Required: Written approval before concrete pour (legal requirement)
Poor Ground: May require deeper foundations or specialist design
Completion: Final inspection confirms compliance for completion certificate
Fees 2026: £200-400 Building Control for typical domestic extension
Footings Calculator FAQs
How much concrete do I need for strip footings?
Calculate: Length (m) × Width (m) × Depth (m) = Volume (m³). Example: 20m footing at 600mm × 225mm = 20 × 0.6 × 0.225 = 2.7 m³. Add 10% wastage = 3.0 m³. Typical detached house with 40-50m total footing length requires 5-8 m³ concrete for 600×225mm footings. Order ready-mix in cubic metres from local suppliers.
How wide and deep should footings be?
Standard domestic footings: Single storey 600mm wide × 225mm deep, Two storey 750mm wide × 300mm deep on good ground. Minimum depth 900mm below ground level (frost protection). Poor soil requires wider footings (900-1200mm). Trees nearby require deeper foundations (0.75-1.5× tree height in clay). Building Control approves final dimensions based on site conditions per BS 8004.
What is the difference between strip footings and trench fill?
Strip footings: Wide shallow trenches (600-900mm wide, 225-450mm deep) with concrete base and blockwork above. Economical concrete usage. Trench fill: Narrow deep trenches (450-600mm wide, 900-1500mm deep) completely filled with concrete. Faster construction, good for trees/poor soil, but uses 3-4× more concrete. Trench fill costs £95-125/m vs strip £41-57/m but saves labour time.
Do I need Building Control approval for footings?
Yes, legally required for all structural foundations under Building Regulations Part A. Submit plans before work starts. Building Control inspects excavated trenches before concrete pour to check depth, width, ground conditions. Non-compliance illegal, invalidates insurance, prevents sale, risks prosecution. Fees £200-400 typical domestic extension (2026). Professional structural engineer calculations required for most projects.
How much do footings cost in 2026?
Standard strip footings (600×225mm) cost £41-57 per linear metre including excavation, concrete, labour. Typical single storey extension (20m footings) costs £820-1140. Two storey (750×300mm) costs £57-77/m. Trench fill (600×1000mm) costs £95-125/m. Add £200-400 Building Control fees, £300-800 structural engineer. Poor ground or trees increase costs 50-150%. Regional price variation significant.
Can I dig footings myself?
Yes for small projects with experience but challenging. Requires: mini-digger hire (£80-150/day), ability to judge ground conditions, accurate setting out, level excavation, safety awareness (trenches collapse risk). Must still get Building Control approval and inspections. Professional groundworkers recommended (£300-600/day gang) for: accuracy, speed, experience identifying problems, insurance, equipment. Poor DIY foundations cause expensive structural failures.
What concrete grade for footings?
C25/30 (RC25) standard for domestic footings - provides 25 N/mm² compressive strength. Budget option C20/25 (GEN3) acceptable for light structures in good ground. Aggressive soil or sulfates require C25/30 minimum with sulfate resistance. Order S3 slump (125-150mm) for workability. Specify 20mm maximum aggregate for standard width trenches. Never use inferior mixes (C15, C10) for structural footings - risk foundation failure.
Do footings need reinforcement?
Most domestic strip footings don't require reinforcement on good ground with correct width. Reinforcement needed for: poor ground conditions, stepped footings on slopes, wide footings (>900mm), heavy loads, bridging soft spots. Use 16mm diameter steel bars longitudinally with 50mm concrete cover. Pad footings typically need reinforcement mesh or bars. Structural engineer specifies exact reinforcement requirements based on calculations per BS 8004.
How deep for footings near trees?
Clay soils: foundation depth = 0.75-1.5× mature tree height. Example: 10m oak requires 12-15m deep foundations. High water demand trees (willow, poplar, oak, elm) need deepest. Minimum safe distance = 1× mature height. Granular soils less affected. Remove trees if possible before building. Trench fill or piled foundations practical for tree-affected sites. Tree roots cause £400 million annual subsidence damage in UK - adequate depth essential.
What is blinding concrete for footings?
50mm layer of weak concrete (C10/15) on trench bottom before main footing concrete. Purposes: creates level working surface, protects from loose soil contamination, provides clean surface for DPM, allows accurate marking, prevents ground water washing cement. Costs £3-5/m² materials and labour. Alternative: hardcore compacted and levelled. Always required for footings with reinforcement to maintain correct bar positions and concrete cover.
