Estimate concrete volume, weight, and quantities for pad footings, strip footings, and combined footings — instantly, for any project.
Types of Concrete Footings – Visual Guide
Understanding which type of footing your project requires is the first step before estimating quantities. Here are the three main types this guide covers.
Pad Footing
An isolated square or rectangular concrete pad supporting a single column or post. The most common footing type for framed structures. Volume = L × W × D × quantity.
Strip Footing
A continuous strip of concrete running beneath load-bearing walls. The standard foundation for most UK domestic buildings. Volume = Total Length × Width × Depth.
Combined Footing
A single rectangular footing supporting two or more columns. Used when columns are close together or near a property boundary. Volume = L × W × D.
Footing Concrete Volume Formulas – How the Estimates Work
Our guide uses standard civil engineering formulas. Here is the exact method for each footing type so you can verify and understand the results.
Concrete Volume Formulas for Each Footing Type
Volume (m³) = Length (m) × Width (m) × Depth (m)
Weight (kg) = Volume (m³) × 2,400 (kg/m³)
Tonnes = Weight (kg) ÷ 1,000
V = L × W × (D ÷ 1000) × N
L = length (m), W = width (m), D = depth (mm), N = number of identical pad footings. For a 1.2m × 1.2m × 300mm pad: V = 1.2 × 1.2 × 0.3 × 1 =0.432 m³
V = L_total × W × (D ÷ 1000)
L_total = total run of all strips (m), W = width (m), D = depth (mm). For 24m run × 0.6m wide × 225mm deep: V = 24 × 0.6 × 0.225 =3.24 m³
V = L × W × (D ÷ 1000)
L = overall footing length (m), W = overall width (m), D = depth (mm). For 3.6m × 1.5m × 500mm: V = 3.6 × 1.5 × 0.5 =2.7 m³
Concrete Density:Standard reinforced concrete is taken as 2,400 kg/m³ (2.4 t/m³) for weight estimates — the industry standard value perBS EN 1991-1-1 (Eurocode 1)andACI 318.
Wastage Buffer:Always add 10% to the estimated volume when ordering. Irregularities in excavation sides and base, spillage, and minor miscalculations consistently add 5–15% to theoretical volumes on real projects.
Worked Examples – Footing Concrete Estimates for Real Projects
Three complete real-world examples showing how to estimate concrete quantities for each footing type — step by step.
Example 1: Residential Steel Column Pad Footings
Example 2: Domestic House Strip Foundation
Example 3: Combined Footing for Two Columns
Minimum Footing Size Requirements – 2026 Reference Guide
Minimum footing dimensions are governed by building codes, soil bearing capacity, and load conditions. These are common reference values — always confirm with a structural engineer for your specific project.
- Footing Type: Strip — Domestic (1 storey); Application: External/internal load-bearing walls; Min Width: 450 mm; Min Depth: 150 mm; Min Concrete Grade: C16/20; Standard Reference: NHBC Standards Ch. 4.2
- Footing Type: Strip — Domestic (2 storey); Application: External/internal load-bearing walls; Min Width: 600 mm; Min Depth: 200 mm; Min Concrete Grade: C20/25; Standard Reference: NHBC / BC Approved Doc A
- Footing Type: Strip — Deep (cohesive soils); Application: Clay soils requiring deeper excavation; Min Width: 600 mm; Min Depth: 750–1,000 mm+; Min Concrete Grade: C20/25; Standard Reference: BS 8004 / NHBC
- Footing Type: Pad — Lightly loaded column; Application: Timber post, steel post, domestic; Min Width: 600 × 600 mm; Min Depth: 200–300 mm; Min Concrete Grade: C20/25; Standard Reference: ACI 318 Sec. 13.2 / EC2
- Footing Type: Pad — Structural column; Application: RC column, steel column; Min Width: 900 × 900 mm+; Min Depth: 300–500 mm; Min Concrete Grade: C25/30; Standard Reference: ACI 318 Sec. 13.3
- Footing Type: Pad — Unreinforced plain concrete; Application: Low-load applications only; Min Width: Varies; Min Depth: Min 150 mm; Min Concrete Grade: C20/25; Standard Reference: ACI 318 Sec. 14.1
- Footing Type: Combined Footing; Application: Two columns — commercial/industrial; Min Width: Designed by engineer; Min Depth: 400–700 mm typical; Min Concrete Grade: C25/30 minimum; Standard Reference: ACI 318 Ch. 13 / EC2
- Footing Type: Mat / Raft Foundation; Application: Poor bearing soil, heavy structures; Min Width: Full building footprint; Min Depth: 250–600 mm typical; Min Concrete Grade: C28/35 minimum; Standard Reference: ACI 336 / EC2 Sec. 9
Concrete Grades for Footings & Foundations – 2026 Selection Guide
Choosing the correct concrete grade for your footing type and ground conditions is critical for long-term durability. This guide covers UK, Eurocode, and ACI grade equivalents.
- Grade (UK): C16/20; Grade (ACI/US): —; Strength (MPa): 16 / 20; Footing Application: Blinding layer under reinforced footings; Exposure Class: X0 / Dry interior; Max w/cm: 0.65
- Grade (UK): C20/25; Grade (ACI/US): 3,000 psi; Strength (MPa): 20 / 25; Footing Application: Unreinforced strip footings, domestic, good ground; Exposure Class: XC2 (buried); Max w/cm: 0.60
- Grade (UK): C25/30; Grade (ACI/US): 3,500 psi; Strength (MPa): 25 / 30; Footing Application: Standard reinforced pad and strip footings; Exposure Class: XC2 / XC3; Max w/cm: 0.55
- Grade (UK): C28/35; Grade (ACI/US): 4,000 psi; Strength (MPa): 28 / 35; Footing Application: Combined footings, heavy loads, normal ground; Exposure Class: XC3 / XC4; Max w/cm: 0.50
- Grade (UK): C32/40; Grade (ACI/US): 4,500–5,000 psi; Strength (MPa): 32 / 40; Footing Application: Sulfate-bearing ground (DS2–DS3), aggressive soils; Exposure Class: XA1 / XA2; Max w/cm: 0.45
- Grade (UK): C35/45 (SRPC); Grade (ACI/US): 5,000 psi; Strength (MPa): 35 / 45; Footing Application: Severe sulfate soils (DS3–DS4), made ground; Exposure Class: XA2 / XA3; Max w/cm: 0.40
- Grade (UK): C40/50+; Grade (ACI/US): 6,000 psi+; Strength (MPa): 40 / 50+; Footing Application: High-load pad footings, engineered foundations; Exposure Class: As specified; Max w/cm: 0.40
How to Pour Concrete Footings – Construction Process for 2026
The correct sequence for preparing, placing, and curing concrete footings on site — from excavation to backfilling.
Step 1 – Excavation to the Required Bearing Level
Excavate to the depth specified by the structural engineer or as required to reach firm, undisturbed ground. The base of the excavation must be level and free of loose material, water, ice, or frost. In the UK, strip footing trenches are typically excavated to 750–900mm below finished ground level to clear topsoil and achieve a bearing on firm subsoil. Have the excavation inspected and approved by the building inspector or structural engineer before placing any concrete — this is a mandatory inspection stage under the Building Regulations in the UK and most US jurisdictions. For UK building regulations, refer tothe Planning Portal guidance on foundations.
Step 2 – Blinding Layer and Formwork / Shuttering
For reinforced footings, place a 50–75mm thick blinding layer of lean mix concrete (C10/12 or C12/15) over the excavation base. This provides a clean, level platform for setting out reinforcement, protects the reinforcement from ground contamination, and prevents the formation water from soaking into the prepared base. For pad footings with straight-sided excavations in cohesive soil, formwork may not be required — the soil itself acts as the mould. For strip footings in sandy or gravelly soils, timber shuttering must be installed to retain the concrete and prevent it flowing into the surrounding ground.
Step 3 – Steel Reinforcement Fixing
Place and fix the reinforcing steel per the structural engineer’s drawings. All rebar must be held at the correct cover using approved concrete spacer chairs — the minimum cover for foundations is 75mm (cast against earth) or 50mm (cast against blinding) perACI 318 Table 20.6.1.3.1and Eurocode 2 Table 4.4N. Ensure all bars are tied securely, laps are of the correct length, and no bars are displaced. The reinforcement cage must be stable enough not to shift during concrete placing and vibration. A pre-pour inspection by the engineer or building control is required before any concrete is placed.
Step 4 – Ready-Mix Delivery and Placement
Order ready-mix concrete specifying the correct grade, slump class (typically S3 for footing pours with reinforcement), and cement type. On delivery, check the delivery ticket — verify the mix design reference, water-cement ratio, and time since batching. Concrete must be placed within 90 minutes of water addition or 300 drum revolutions. Place concrete directly from the chute into the footing if possible — avoid long-distance raking or moving with a shovel which causes segregation. For deep or narrow trenches, use a concrete pump or tremmie pipe to place concrete at the base without dropping from height. Target a continuous pour without construction joints.
Step 5 – Compaction and Finishing
Compact the concrete using an electric poker vibrator — insert at 300–450mm centres, push to within 100mm of the footing base, and withdraw slowly. For strip footings, ensure the vibrator reaches the full depth of the concrete at every insertion point. Compact in 300mm maximum layers for deep footings. After compaction, screed the top surface of the footing flat and level — the top surface will be the bearing surface for the first course of masonry or the column base plate. For reinforced pad footings, leave starter bars (column kickers) protruding at the specified height and position, tied to the footing cage.
Step 6 – Curing, Protection, and Backfilling
Cover all exposed footing surfaces immediately after placing with polythene sheeting and maintain for a minimum of 7 days. In hot or windy conditions, use wet hessian under polythene. Never allow footing concrete to freeze — insulate with blankets in cold weather until the concrete reaches a minimum of 3.5 MPa. After 7 days of curing, backfill carefully around the sides of the footing in 150–200mm compacted layers. Do not allow construction plant or vehicles to drive over footing concrete until it has reached 28-day strength — typically 4 weeks from the pour date. Remove formwork only after the minimum formwork striking period has elapsed (typically 18–48 hours for footing sides; never remove while concrete is still green).
Pro Tips for Concrete Footing Projects – 2026 Best Practice
Expert advice from structural engineers and site professionals for getting footings right first time.
Always Get a Ground Investigation First
Never design footings without knowing the soil bearing capacity. A basic trial pit or hand-dug inspection is the minimum — a proper soil investigation including CBR or shear vane tests is required for any building above a single storey. Unexpected soil conditions are the most common cause of project overruns and costly redesigns.
Check for Buried Services Before Excavating
Before any excavation, use a CAT scanner to locate buried utilities — gas, water, electricity, and telecoms. Contact your utility providers and obtain drawings. In the UK, register withLSBUDand dial 811 in the US before digging. Striking a buried service is potentially fatal and always the contractor’s liability.
Never Place Concrete on Frozen Ground or in Standing Water
If the base of the excavation is frozen, wait until it has thawed and dried before pouring — concrete placed on frozen ground will crack and heave as the ground thaws. If standing water is present, pump dry and compact the base before placing the blinding layer. Concrete placed in water is immediately weakened as the water dilutes the cement paste at the base.
Order 10% More Than Estimated — Every Time
Excavation bases and sides are never perfectly flat or plumb. The actual concrete volume needed in a real trench or excavation is almost always 5–15% more than the theoretical estimate. Order 10% extra as a standard practice. Running short mid-pour and having to stop creates a construction joint — a permanent cold joint in the footing that must be reported and may require engineering review.
Protect Starter Bars During and After the Pour
Column starter bars protruding from pad footings must be held at the exact specified position during pouring and vibration. Use a steel template fixed across the top of the formwork to locate starter bars precisely — even 10mm displacement can mean column base plates don’t align. After the pour, cover protruding bars with pipe lagging or foam to protect workers from impalement injuries.
Get Building Control Approval Before Pouring
In the UK, all foundation concrete must be inspected and approved by the Local Authority Building Control (LABC) or Approved Inspector before it is covered. In the US, a similar foundation inspection is required by the Authority Having Jurisdiction (AHJ). Pouring without approval means you may be required to excavate and remove the concrete at your own cost — an expensive and avoidable mistake.
Footing & Foundation Glossary – Key Terms Explained
Essential vocabulary for understanding footing design, construction, and concrete specification.
Pad Footing (Isolated Footing)
A discrete square or rectangular concrete pad supporting a single column or post. Load is transferred from the column through the pad into the soil below over a larger bearing area. Designed to spread the point load of the column to within the soil’s safe bearing capacity.
Strip Footing (Continuous Footing)
A continuous concrete strip running beneath load-bearing walls. Distributes wall loads uniformly along its length into the supporting soil. The standard foundation for masonry houses in the UK. Width and depth governed by wall load and soil bearing capacity. For related background, see Foundation Guide.
Combined Footing
A single rectangular or trapezoidal footing supporting two or more columns. Used when columns are too close together for separate pad footings, or when one column is at a property boundary and an eccentric pad would be unsafe. Requires specific engineering design for the bending moments induced.
Raft / Mat Foundation
A large concrete slab covering the entire building footprint, distributing loads from all columns and walls uniformly to the ground. Used on weak or variable soils where individual footings would cause unacceptable differential settlement.
Bearing Capacity
The maximum load per unit area that the ground can safely support without shearing or excessive settlement. Expressed in kN/m² or kPa. Stiff clay: ~75–150 kN/m². Dense gravel: ~200–600 kN/m². Bedrock: 1,000+ kN/m². Always determined from a site investigation — never assumed.
Blinding Layer
A thin (50–75mm) layer of lean-mix concrete (C10/12 or C12/15) placed over the excavation base before the structural footing. Provides a clean, level surface for reinforcement fixing and setting out, and prevents ground contamination of the reinforcement cover.
Cover (Reinforcement Cover)
The clear distance from the outer face of reinforcing bar to the nearest concrete surface. For footings cast directly against earth: 75mm minimum (ACI 318 / EC2). For footings cast against blinding: 50mm minimum. Cover protects steel from corrosion and provides fire resistance.
Starter Bars
Reinforcing bars projecting vertically from a footing or slab to provide a lapped connection with the column reinforcement above. Must be positioned precisely (typically within ±5–10mm) to ensure column base plates and formwork align correctly. A template should be used during the pour.
Safe Bearing Pressure (SBP)
The load per unit area that can be applied to a soil without risk of shear failure or excessive settlement, incorporating an appropriate factor of safety (typically 2.5–3.0). The SBP governs the required footing area — divide the column load (kN) by SBP (kN/m²) to get the minimum pad area.
Settlement
Downward movement of the ground — and therefore the structure — due to compression of soil under load. Differential settlement (unequal movement at different points) is more damaging than uniform settlement. Footings must be sized and positioned to minimise differential settlement across the structure.
Punching Shear
A shear failure mechanism in a reinforced concrete footing or flat slab around the perimeter of a column, occurring on a cone-shaped failure surface. Critical design check for pad footings under concentrated column loads. Governed by ACI 318 Section 13.5 and EC2 Section 6.4.
Frost Depth
The depth to which the ground freezes in winter at a given location. Footings must extend below the frost depth to prevent frost heave — the upward movement of saturated soil as it freezes — lifting and cracking the structure above. Typically 450mm in southern UK; 1,200–1,800mm in northern US/Canada.
Frequently Asked Questions – Footing Guide & Concrete Foundations
Answers to the most common questions about estimating concrete for footings and foundation construction.
How do I estimate concrete for a pad footing?
What concrete grade should I use for house foundations in the UK?
For most standard domestic strip foundations in the UK, C20/25 (formerly GEN 3) is the minimum grade for unreinforced strips and C25/30 (formerly RC25) for reinforced footings, per NHBC Standards and Approved Document A. If the ground investigation identifies sulfate-bearing soils (DS2 or above per BRE Special Digest 1), a higher grade with sulfate-resisting cement is required. Always confirm the specification with your structural engineer and building control officer — they have the final say on the required concrete grade for your specific ground conditions.
How deep should a concrete strip footing be?
Strip footing depth is determined by several factors: the minimum depth to reach firm, undisturbed ground capable of supporting the loads (confirmed by a building inspector at excavation stage); the frost depth for your location (typically 450mm minimum in the UK); and the NHBC / Approved Document A minimum of 750mm below ground level for most UK domestic buildings on clay soils. On non-clay soils or with a competent soil profile, shallower depths may be accepted by building control. Never assume depth — always have the excavation inspected before pouring.
How do I estimate concrete for strip footings with corners?
Measure the total centreline length of all strips — that is, the length measured along the centre of each strip, not the outer or inner face. This automatically accounts for corners correctly without double-counting the overlap at each corner junction. Multiply this total centreline length by the strip width and depth. This method is used by quantity surveyors and is significantly more accurate than measuring outer perimeters, which overcounts corner areas, or inner perimeters, which undercounts.
Can I pour concrete footings in cold or freezing weather?
Concrete can be poured in cold weather with proper precautions, but must never be placed on frozen ground or when temperatures are forecast to fall below 0°C before the concrete reaches at least 3.5 MPa strength. Key measures for cold weather footing pours include: using heated mix water (most effective measure), heating aggregates, using an accelerating admixture, insulating the top surface immediately after placing, and monitoring concrete temperature. Follow ACI 306R-16 (Cold Weather Concreting) guidance for full protocol. See ourACI Standards Guidefor detail on ACI 306.
Do I need building control approval before pouring foundation concrete?
Yes — in the UK, a foundation concrete inspection by LABC or an Approved Inspector is a mandatory staged inspection under the Building Regulations. You must notify building control when the excavations are ready and wait for their approval before placing any concrete. Pouring without approval means the inspector may require you to excavate and expose the footing for inspection, or in the worst case, require it to be removed and replaced entirely. In the US, a similar foundation inspection (footing inspection) is required by the local Authority Having Jurisdiction (AHJ) before concrete is placed.
What is the difference between a raft foundation and a strip footing?
A strip footing runs only beneath load-bearing walls as a continuous strip — there is no concrete under the floor area between walls. A raft (mat) foundation covers the entire building footprint as a single reinforced concrete slab. Rafts are used when the soil is weak or variable and individual strips would cause unacceptable differential settlement, or when the total plan area of strips would exceed 50% of the building footprint (at which point a raft is more economical). Rafts are also used on ground subject to tree root movement or heave. For raft volume estimates, use ourConcrete Volume Guidewith the full slab dimensions.
How long should I leave before building on top of a new concrete footing?
This depends on the structural loads being applied. For domestic masonry construction above strip footings: a minimum of 3–4 days is commonly acceptable for first courses of blockwork (which applies very low loads). For structural columns bearing on pad footings: wait until the concrete achieves at least 75% of its 28-day strength — typically 7–10 days under normal curing conditions for C25/30 concrete. For heavily loaded columns: wait for the full 28-day strength before applying significant loads. Never apply vehicle traffic or heavy plant loads over new footings for at least 28 days.