On-site concrete is the better choice when your project involves uncertain volumes, restricted access, phased pours, or a site where the 90-minute ready mix window creates more rik than it solves. A volumetric truck carries raw materials separately and mixes at the point of pour, giving you fresh concrete in exactly the quantity needed with no minimum order and no waste.
Ready mix suits large, well-planned pours where volume is known in advance. Every other situation tends to favour on-site concrete instead.
Pro-Mix Concrete has supplied mix-on-site concrete across London for over 20 years, working on domestic and commercial projects of every scale. Call the team before ordering, and they will confirm which method suits your specific pour.
Your Volume Is Uncertain or Likely to Change
Ordering ready mix means committing to an exact volume before the lorry leaves the plant. If the pour takes less than anticipated, you pay for the unused material.
On-site concrete removes this risk entirely. The volumetric truck mixes only what is needed at the point of pour, with adjustments made in real time.
Why Volume Changes Mid-Pour
- Irregular-shaped footings where depth and width vary during excavation
- Foundation extensions were added when ground conditions shifted the original estimate
- Infill and repair work where cavities rarely match the calculated volume
When On-Site Is the Obvious Answer
Volume Under 3m³
Ready mix suppliers charge a short-load surcharge for orders below their minimum threshold. On-site concrete has no minimum and no penalty.
Volume Genuinely Unknown
If you cannot confirm the volume before the truck arrives, on-site mixing is the only format that does not penalise you for the uncertainty.
The Site Has Restricted Access for a Standard Lorry
A ready mix drum lorry needs approximately 3.5 metres of overhead clearance and full HGV turning width. Many London sites cannot accommodate this.
Volumetric mixers carry a smaller profile and reach pour points that standard lorries cannot.
Access Conditions That Rule Out Ready Mix
| Site Type | Access Problem | On-Site Solution |
| Terraced properties | No turning space, narrow street | Smaller volumetric truck profile |
| Basement pours | Low clearance prevents lorry positioning | Volumetric truck positions above and pumps |
| Town centre locations | Loading restrictions, narrow lanes | Flexible scheduling, smaller vehicle |
| Gated developments | Entry restrictions prevent HGV access | Volumetric unit fits standard gate width |
You Cannot Afford Waste on a Tight Budget
Over-ordering by even half a cubic metre on a C25 mix adds £55 to £70 of dead cost to the job. Across a multi-stage project, this accumulates quickly and comes entirely out of margin.
On-site concrete means you pay only for what is poured.
The Real Cost of Ready Mix Waste
Volumetric concrete tends to be more cost-effective for smaller projects or jobs requiring precise amounts of concrete, as there is less waste and greater control over the quantity produced.
What Waste Costs Look Like in Practice
- 0.5m³ over-ordered at C25: £55 to £70 lost per delivery
- Short-load surcharge on small pours: £100 to £200 on top of material cost
- Second delivery for a shortfall: Delivery charge repeated plus additional material cost
- Unused concrete disposal: Hardened concrete from a drum lorry requires removal at your expense
Where Waste Cuts Margin Most
- Small domestic pours where volumes are difficult to calculate precisely
- Multi-stage pours where each stage carries its own over-order risk
- Projects with design changes that alter volume requirements without warning
The Pour Is Phased Across Multiple Days
Some projects simply cannot be completed in a single continuous pour. Foundations with multiple sections, slabs poured in stages around existing structures, and ground conditions that require a phased approach all create problems for ready mix.
Ready mix must be placed within 90 minutes of leaving the plant. A phased pour needs multiple lorries, multiple delivery windows, and perfect timing between stages.
Why Phasing Breaks the Ready Mix Model
Unlike Ready Mix Concrete, there is no timeframe within which on-site concrete must be used after arriving, because the truck mixes fresh material on demand rather than delivering a pre-mixed batch.
Projects That Commonly Require Phased Pours
- Strip foundations for extensions: Ground conditions often mean that excavation progresses in stages
- Retaining walls: Sections poured sequentially to allow formwork repositioning
- Large floor slabs: Poured in bays to control shrinkage cracking
- Underpinning work: Each needle is poured and cured before the next begins
Did You Know?
A volumetric mixer is essentially a mobile batching plant. It carries sand, cement, and aggregate in separate compartments and combines them at the correct ratio on demand. The mix is adjusted between pours without any material being lost or wasted.
You Need More Than One Mix Type on the Same Job
A single project often requires different grades. Blinding uses C10. The foundation uses C25. The floor slab uses C30 with a waterproofing admixture. Three ready mix deliveries mean three lorries, three windows, and three charges.
A volumetric truck produces different grades in sequence from the same vehicle.
Common Multi-Grade Scenarios
New Build Groundworks
Blinding, foundation, and slab concrete in sequence from a single site visit.
Structural Repairs
Repair mortar, infill concrete, and capping compound, all different in grade and admixture, delivered without multiple orders.
Extensions With Basement and Ground Floor Elements
| Element | Typical Grade | Admixture |
| Blinding layer | C10 | None |
| Strip foundation | C25 | None |
| Basement floor slab | C30 | Waterproofing |
| Ground floor slab | C28/C30 | Fibre reinforcement |
The Location is Remote or Difficult to Reach
Ready mix has a practical range limit determined by the 90-minute batching-to-placement window. Sites more than an hour from a plant face a compressed working window and a higher risk of concrete arriving out of specification.
On-site concrete carries its own materials and mixes at the point of delivery, removing the distance constraint entirely.
Remote Project Types Where On-Site Wins
- Rural barn conversions and agricultural buildings are often far from any ready-mix plant
- Country house groundworks where long private drives push ready mix beyond its practical range
- Coastal and island sites where logistics make pre-batched delivery impractical
- Areas without a local batching plant, where travel time consumes most of the working window
Pro-Mix Concrete delivers volumetric mix-on-site concrete across London and the surrounding area, with same-day and next-day availability for projects where distance or access would make ready mix impractical.
Time Pressure Makes the 90-Minute Window Risky
Ready mix starts its clock the moment it leaves the batching plant. A lorry held up in London traffic, delayed at the gate, or waiting for formwork to be checked is burning through that window before a single cubic metre is poured.
On-site concrete mix fresh material as required and pauses between pours without any waste.
Where the 90-Minute Window Fails
- Central London sites with traffic unpredictability: Journey time from plant to site can vary by 30 to 45 minutes on a bad day
- Complex formwork setups: Any delay before the pour reduces the working window significantly
- Structural pours needing careful placement: Slow, precise positioning consumes time that ready mix cannot spare
- Hot weather pours: High temperatures accelerate setting, reducing the effective window further still
The Project Is Small but Still Needs Quality Concrete
Most ready mix suppliers set a minimum order of three to six cubic metres. A foundation needing one cubic metre attracts a short-load surcharge of £100 to £200 on top of the base price.
On-site concrete has no minimum order restriction.
Small Pour Volumes and What Ready Mix Charges
| Volume Required | Ready Mix Cost Issue | On Site Advantage |
| Under 0.5m³ | Not supplied by most ready mix companies | Volumetric supplies from 0.5m³ |
| 0.5m³ to 2m³ | Short-load surcharge of £100 to £200 | No surcharge, standard per-m³ rate |
| 2m³ to 3m³ | Surcharge still applies below the minimum | No minimum threshold |
| 3m³ and above | Ready mix becomes cost-competitive | Both options are viable; choose based on access |
Small Domestic Projects That Benefit From On-Site Mixing
Garden and Landscaping Work
- Garden wall foundations: 0.5 to 1m³ typical volume
- Fence post bases and step foundations: Often under 0.5m³
Light Structural Work
- Single garage slab: Typically 3 to 5m³, often just below the ready mix efficiency threshold
- Extension footing for a single bay: Small enough that the minimum ready mix charge inflates unit cost significantly
On-Site vs Ready Mix: At a Glance
| Factor | On-Site Concrete | Ready Mix Concrete |
| Minimum order | From 0.5m³, no surcharge | Typically 3 to 6m³ |
| Waste | Zero, pay only for what is poured | Over-ordering risk on every delivery |
| Time constraint | No 90-minute window | 90 minutes from batching to placement |
| Mix adjustability | Adjustable on-site between pours | Fixed at the plant before delivery |
| Multiple grades | Single truck, multiple mixes | A separate lorry per grade is required |
| Access | Smaller vehicle profile | Full HGV clearance required |
| Best for | Small, phased, uncertain, or restricted pours | Large, planned, high-volume pours |
| Cost at low volume | More efficient | Short-load surcharges apply |
What is the difference between on-site concrete and ready mix?
Ready mix is batched at a plant and delivered in a drum lorry ready to pour. On Site Mix Concrete is produced using a volumetric truck that carries raw materials separately and mixes them at the point of delivery. On Site Mix Concrete has no 90-minute window and no minimum order, while ready mix is better suited for large, planned pours where the required volume is fixed in advance.
Is on-site concrete more expensive than ready mix?
On-site concrete is priced slightly higher per cubic metre, but this premium is often offset by the elimination of waste, short-load surcharges, and multiple delivery charges. For smaller volumes or phased pours, on-site concrete frequently costs less in total.
Can on-site concrete be used for structural work?
Yes. On-site concrete is mixed to the same grade specifications as ready mix and is suitable for foundations, floor slabs, retaining walls, and structural columns across the full range of grades.
What volume can a volumetric truck supply?
A standard volumetric truck carries approximately 10m³ of raw materials and supplies multiple pours from a single visit. For larger volumes, trucks are scheduled in sequence without the time pressure of ready mix deliveries.
How quickly can Pro-Mix Concrete deliver on-site concrete?
Pro-Mix Concrete offers same-day and next-day delivery for on-site concrete across London and surrounding areas. Booking secures availability for specific pour dates and times.
Does on-site concrete meet the same quality standards as ready mix?
Yes, Pro-Mix Concrete’s on-site concrete is produced to the same mix specifications and quality standards, with mix design controlled on the volumetric truck to the same ratios used at a batching plant.
Final Note
On-site concrete suits any project where volume is uncertain, access is restricted, pours are phased, budgets are tight, or the 90-minute ready mix window creates operational risk. For small domestic pours, multi-grade jobs, and remote locations in particular, the flexibility and zero-waste pricing of on-site concrete consistently outperform ready mix on total project cost.
Pro-Mix Concrete supplies mix-on-site concrete across London with same-day and next-day delivery, using volumetric trucks suited to both restricted urban access and open site conditions. Call 0800 772 3808 to discuss your project and confirm whether on-site concrete is the right choice for your specific pour.
- Dennis Broderick is the founder and owner of Pro-Mix Concrete Company, a trusted name in ready-mix concrete solutions across the UK. With over 20 years of hands-on experience in the construction and concrete industry, Dennis brings unmatched expertise, practical insights, and a commitment to quality on every project - from residential driveways to large-scale commercial developments.
