Request quotes from a handful of concrete suppliers across London, Kent or Essex and you'll notice they all sound remarkably similar: volumetric trucks, on-site mixing, pay only for what you use. It's become the industry's favourite line. What's harder to find is a straight answer to the question that actually matters, which method suits your specific project, and why.

Both ready-mix and on-site volumetric concrete will get a strong, workable pour to your site. The difference lies in how that concrete is made, how it's priced, and how much flexibility you have once the truck arrives. Here's a clear breakdown of both, so you can choose with confidence rather than guesswork.

What Is Ready-Mix (Drum Mix) Concrete?

Ready-mix, sometimes called drum mix, is batched at a plant to an exact specification, then loaded into a rotating drum and driven to your site. The rotation keeps the mix workable during transport, so it arrives ready to pour rather than beginning to set en route.

Because it's measured and combined under controlled plant conditions, ready-mix offers strong consistency from load to load, and batches can be cube-tested to confirm they meet the specified strength. That matters most when a project calls for a certified grade with no room for variation, such as C20 for domestic footings, C30 for driveways and floor slabs, or C40 and above for structural and load-bearing work. You order a fixed volume, and that's what turns up.

What Is On-Site (Volumetric) Concrete?

On-site, or volumetric, concrete works differently. Rather than mixing the batch in advance, the raw materials, cement, aggregate and water, travel to site in separate compartments inside a mobile mixer. They're only combined once the truck is parked and ready to pour, in the exact quantity the job needs at that moment.

This setup means the mix can be adjusted on the spot. Need a slightly different grade halfway through the pour? The operator can change it without sending the truck away and starting a new order. It also means you're only charged for the volume that actually leaves the mixer rather than a pre-agreed load, which is the main reason this method gets marketed so heavily on cost grounds.

Comparing the Two

 Ready-Mix (Drum)On-Site (Volumetric)Where it's mixedAt the batching plantOn site, at the point of pourPricingFixed volume orderedPay only for what's usedMix flexibilitySet before deliveryAdjustable during the visitBest suited toLarge, continuous poursSmaller or uncertain volumesSite access neededReasonable room for a loaded truckCopes well with tighter or awkward spots

Cost predictability is the other piece worth weighing up. A fixed ready-mix load is easy to budget for on larger commercial jobs with a known specification. Volumetric pricing is harder to pin down in advance, but it removes the risk of paying for concrete that ends up wasted, which matters more on smaller or less predictable domestic jobs.

When Ready-Mix Makes More Sense

Ready-mix tends to be the better fit for larger, continuous pours, new-build foundations, big slabs, or any job where a high volume needs to go down quickly in one pass. If your engineer has specified a particular grade for structural work, the plant-controlled consistency of drum mix gives a verifiable, repeatable result with less room for on-site variation. It also suits sites with good access, where a fully loaded truck can get close enough to pour directly or feed a pump without difficulty.

When On-Site Volumetric Wins

Volumetric comes into its own when the exact volume is hard to predict, think garden bases, driveways, extensions, or repair work, where over-ordering ready-mix means paying for concrete you'll never use. It's also the practical choice for restricted access, a common reality on tighter urban plots across London, where a standard mixer simply can't get close enough. And on jobs needing more than one grade in a single visit, footings followed by a floor slab, for example, on-site mixing avoids the cost and hassle of arranging two separate deliveries.

Don't Let Access Decide the Mix Method for You

Sometimes the real obstacle isn't the concrete at all, it's getting it to the pour point. A boom pump can place ready-mix concrete over walls, fences or multiple storeys, while a line pump threads it through tight residential plots or basement conversions. Pumping can be paired with either ready-mix or volumetric supply, so a restricted site doesn't automatically mean volumetric is your only option, it just means the delivery method needs more thought than the mix itself.

Quick Questions

Can I mix different grades within one volumetric order? Yes, that's one of its main advantages. The operator can adjust the mix design between pours during the same visit.

Is ready-mix always cheaper for big jobs? Usually. For large, predictable volumes, the fixed batching cost of ready-mix is hard to beat. Volumetric narrows that gap as volumes become harder to predict.

Does either option affect curing time? No. Curing time depends on the grade, weather and site conditions, not on how the concrete was mixed.

Choosing the Right Option for Your Site

In practice, the right choice comes down to volume certainty, access, and how much flexibility the job needs, not whichever method a supplier happens to push hardest. At RMS Concrete, we supply both ready-mix and on-site volumetric concrete across London, Kent and Essex, alongside boom and line pumping for sites where access is the real constraint.

If you're not sure which fits your project, that's exactly the kind of question our team is set up to answer before you order, not after the truck has already left the yard. Use our concrete calculator to get a feel for the volume you'll need, or give us a call and we'll talk through the best approach for your site.