Every concrete job starts with the same question: Do you mix it yourself or order it from a plant? The answer seems simple until you start adding up the real costs. Bags of cement look cheap at the builders’ merchant. A ready-mix truck looks expensive when pulling onto your site. But the final bill tells a different story once you factor in labour, time, waste, and quality. Choosing concrete mixed on site over ready mix, or the other way around, depends on the size of your pour, your crew costs, and how much rework you can afford. Here is how the numbers actually break down.
What “Mixed on Site” and “Ready Mix” Actually Mean
These two methods deliver the same end product through very different processes. Understanding the basics helps you compare costs accurately.
On-Site Mixed Concrete
On-site mixing means combining cement, aggregates, sand, and water directly at the job location using portable mixers or small batching setups. You buy the raw materials separately, transport them to the site, and proportion each batch manually. This method gives you full control over timing and volume.
Ready Mix Concrete
Ready mix is plant-batched concrete delivered to your site by truck. The supplier controls the mix design, proportions, and quality to meet a specified strength and slump. You order the volume you need, and it arrives ready to pour.
Typical Use Cases
On-site mixing suits small residential jobs like fence posts, small slabs, and patch repairs. Ready mix is the standard choice for foundations, driveways, floor slabs, and any pour above roughly one cubic metre.
Direct Cost Breakdown: On-Site Mixed vs. Ready Mix
The price gap between these two methods shifts depending on what you include in the calculation. Raw materials alone do not tell the full story.
Material Costs
Bagged cement and loose aggregates cost roughly £80 to £120 per cubic metre when purchased from a builders’ merchant, depending on region and supplier. Ready mix concrete typically runs £65 to £130 per cubic metre delivered, varying by mix specification and order size.
Labour And Equipment
On-site mixing demands more crew hours per cubic metre. You need workers to measure, load, mix, and transport each batch to the pour area. A portable mixer rental adds £30 to £80 per day. Ready mix eliminates mixing labour entirely, and pumping services handle placement for an additional fee if access is tight.
Extra Fees
Ready mix suppliers charge delivery fees (typically £15 to £40 per load) and may add short-load surcharges on orders under four to six cubic metres. On-site mixing avoids those fees but carries its own transport costs for bagging and delivering raw materials to the job.
When On-Site Mixed Concrete Usually Saves More Money
For certain projects, mixing your own concrete genuinely costs less. The savings are clearest in these situations:
- Small pours under one cubic metre, where buying a few bags of cement avoids minimum order charges and delivery fees from a ready mix plant.
- Remote or hard-to-access sites where ready mix trucks cannot reach the pour location without expensive pumping or manual wheelbarrowing, making the delivery surcharges steep.
- Flexible timelines where you can mix small batches as needed over several days, producing only what you use and eliminating leftover concrete waste.
When Ready Mix Concrete Tends to Be More Cost-Effective
Once a project crosses a certain size threshold, concrete mixed on-site starts losing the cost battle against plant-batched delivery. Ready mix pulls ahead in these scenarios:
Medium to Large Pours
Anything above two to three cubic metres gets expensive to mix by hand. A ready mix truck delivers five or six cubic metres in one visit, placed by a smaller crew in a fraction of the time. The labour savings alone offset the delivery cost on most jobs this size.
Quality Sensitive Projects
Structural foundations, reinforced slabs, and commercial floors need consistent strength across the entire pour. Plant-controlled batching delivers that consistency. On-site mixing introduces variability from batch to batch, which can lead to weak spots, cracking, and costly rework.
Tight Schedules
When day rates for crews, scaffolding, or crane hire are running, every extra hour on the pour costs real money. Ready mix cuts pour time dramatically compared to manual batch mixing. On a project with £400 per day crew costs, finishing a pour in one day instead of three saves £800 before you even compare material prices.
Hidden & Long-Term Costs People Forget
The invoice total on our day is never the full picture. Several hidden costs tilt the real comparison further than most people expect.
Waste And Rework
On-site mixing produces inconsistent batches. Over-watered concrete, incorrect proportions, and cold joints between batches lead to cracking and structural weakness. Rework on a failed slab or foundation can cost two to five times the original pour.
Life Cycle Costs
Poorly proportioned concrete mixed on site may develop cracks, scaling, or reduced durability within a few years. Plant-batched ready mix, designed to meet BS 8500 specifications, delivers predictable long-term performance and lower maintenance costs over the life of the structure.
Opportunity Costs
Slow pours delay follow-on trades. If bricklayers, plumbers, or framers are waiting for concrete to cure before they can start, every day of delay adds cost to the overall project budget.
Simple Rules of Thumb to Decide
When you need a quick answer without running a full cost comparison, these guidelines cover most situations:
- Under 1 cubic metre: On-site mixing is usually cheaper. Buy bags, mix by hand or with a small mixer, and save on delivery fees.
- 1 to 3 cubic metres: Either method can work. Compare ready mix quotes (including delivery and short-load fees) against your labour and material costs for mixing on site.
- Over 3 cubic metres: Ready mix almost always wins on total cost once you account for labour, time, waste, and quality consistency.
- High crew day rates: If your labour costs exceed £250 per day, the time savings from ready mix pay for themselves on nearly any pour above one cubic metre.
Other Factors Beyond Price
Cost is king, but a few additional factors still affect your bottom line indirectly.
Sustainability And Waste
Ready mix suppliers can optimise mix designs to reduce cement content and carbon output. On-site mixing tends to generate more waste from over-ordering, spillage, and unusable leftover batches.
Safety And Site Disruption
Continuous on-site mixing creates ongoing noise, dust, and congestion. A single ready mix pour is faster, quieter, and reduces the window of disruption for neighbours and other trades working on site.
When to Get a Professional Quote
If you are unsure which method saves more on your specific project, ask a ready mix supplier and a contractor to run a side-by-side cost comparison. A project-specific quote removes the guesswork and accounts for access, volume, schedule, and local pricing that general rules cannot capture.
Conclusion
The cheapest concrete method depends entirely on your project’s size, schedule, and quality requirements. Small jobs favour on-site mixing. Anything larger tips the maths toward ready mix once you include labour, waste, consistency, and long-term durability in the calculation.
That is where concrete suppliers like Pro-Mix Concrete come in. They deliver plant-batched, specification-grade ready mix across the UK with transparent pricing, reliable scheduling, and no hidden surcharges. If you are pouring a single driveway or supplying a multi-unit development, they match the right mix design to your project and get it to your site on time.