Suppliers quote against what you tell them, so an accurate order starts with five things: volume, strength, address and access, date and time, and any additives. Get those right and the rest of the process is straightforward.
Most problems with ready-mix are not the concrete. They are ordering the wrong quantity, not being ready when the truck arrives, or discovering on the day that it cannot reach the pour.
What the supplier needs from you
| Information | Why it matters |
|---|---|
| Volume in m³ or yd³ | Sets the price and whether a part-load fee applies |
| Strength or grade | C25, GEN3, 3,500 psi — determines the mix |
| What it is for | Lets them advise if your grade is wrong |
| Slump / workability | How wet the mix arrives |
| Full address and postcode | Distance banding and surcharges |
| Access constraints | Narrow lane, low branches, soft ground, weight limits |
| Date and time window | Scheduling, weekend premiums |
| Additives | Fibres, air entrainment, retarder |
| Whether you need a pump | Often booked through the same supplier |
Describing the job is as useful as quoting a grade. “A base for a double garage, 150mm thick, with mesh in it” tells an experienced order desk everything they need, and they will correct you if the grade you have in mind is wrong.
Specifying strength
In the UK, order by C grade or by designated mix — GEN3 for a shed base, ST3 or C25 for a driveway, C30 for a garage floor. In the US, order by psi. Across the EU, EN 206 dual notation such as C25/30.
If building control is involved, order the designated grade on the drawing rather than an approximate equivalent, and keep the delivery ticket as evidence.
Our guide to concrete grades covers how the naming systems map onto each other.
Slump
Slump describes how wet and workable the mix is. It is measured by filling a cone, lifting it, and recording how far the concrete slumps.
| Slump | Consistency | Use |
|---|---|---|
| 50mm | Stiff | Roads, machine-placed work |
| 75mm | Medium | Standard slabs, general use |
| 100mm | Workable | Slabs by hand, light reinforcement |
| 125mm | Wet | Trench fill, congested rebar |
| 150mm+ | Very wet | Pumped work, deep narrow sections |
Higher slump is easier to place and slightly weaker, since the extra workability usually comes from water. Modern plants achieve high slump with plasticisers instead, which gives flow without the strength penalty — worth asking for if you need a wet mix.
How much to over-order
Under-ordering is far worse than over-ordering. Running short mid-pour means a cold joint through your slab and a second part-load charge.
Add 5% on a well-formed slab with a level sub-base, 10% where the ground is uneven or you are pouring against soil. Trenches and footings warrant 10 to 15%, because trenches always over-dig.
Then round up to the supplier’s increment, usually 0.25m³ in the UK or 0.5yd³ in the US. Work your figure out with the cost calculator before you ring, so you are giving them a number rather than a guess.
Booking the delivery
Book several days ahead in spring and summer, which are the busiest months. Ask for a time window rather than an exact time — plants dispatch in sequence and a first-thing slot is the most reliable.
Confirm three things when booking: the free unload allowance, the part-load threshold, and whether the price includes VAT. All three vary between suppliers and all three change which quote is genuinely cheapest.
Get a phone number for the driver or the dispatch desk. Being able to ring and check progress saves standing around.
Preparing the site
Do this the day before, not the morning of. The list is short and every item on it has caused someone a waiting-time charge:
- Formwork complete, braced and checked
- Reinforcement tied and on chairs
- Membrane laid and taped
- Truck route agreed and cleared, cars moved
- Boards down over anything the truck or barrows will cross
- Crew confirmed, arriving 30 minutes before the truck
- Barrows, screed, floats and jointing tools on site
- Water available for washing tools and the chute
- A washout area that is not a drain
- Plastic sheeting for curing or unexpected rain
- A plan for spare concrete
Paying
Most suppliers take card payment over the phone at the time of booking, or on delivery. Trade accounts are available if you order regularly, though they usually need a credit check and a minimum spend.
Confirm whether the quoted price includes VAT before you commit — trade quotes are typically ex-VAT and consumer quotes inclusive, and 20% on a £700 order is enough to change which supplier is cheapest.
What to check when it arrives
Look at the delivery ticket before discharge starts. It records the grade, batch time, volume and any admixtures. If it does not match your order, say so before the concrete comes out.
Check the batch time. Concrete has roughly 90 minutes of working life from batching, and a truck that has been stuck in traffic may have used most of it.
Look at the mix as it discharges. It should be uniform in colour with no segregation — stones separating from paste means it has been over-mixed or is too wet.
Multiple loads
Any pour over about 6m³ needs more than one truck, and the timing between them decides whether you get one slab or two.
Order the second load to arrive as the first finishes discharging. A gap of more than 30 to 45 minutes lets the placed concrete begin setting, and where the two meet you get a cold joint — a permanent plane of weakness.
Tell the supplier it is a multi-load pour when booking. They will space the dispatches rather than sending both at once or leaving an hour between them. On a large pour ask for the loads to be “on call”, so the second waits at the plant until you ring.
Discharge and water on site
The driver discharges down the chute, which typically reaches three to four metres from the back of the truck. Beyond that it is barrows or a pump.
If the mix looks too stiff to place, ask for a plasticiser rather than water. Water added on site raises the water-cement ratio, lowers the strength and gets recorded on the ticket — which matters if the slab is ever tested.
Keep the ticket. It is the only record of what was actually delivered.
Common questions
How far in advance should I order concrete?
Two to five days in normal conditions, longer in spring and summer or for a Saturday. Same-day is occasionally possible but you take whatever slot is left.
What slump should I ask for?
75mm for a standard slab, 100mm if you are placing by hand or working around reinforcement, 125mm for trench fill. Ask for extra workability via plasticiser rather than water.
Can I cancel a concrete order?
Free the day before. On the morning, once the load is batched, you generally pay for it whether you take it or not — it cannot be stored or resold.
What if the concrete arrives too stiff?
Ask the driver for plasticiser, which most trucks carry. Adding water reduces strength and is recorded on the ticket. If it has genuinely gone off in transit, reject the load and speak to the supplier.
Should I be there when it is delivered?
Yes. Somebody has to direct the truck, check the ticket, sign for it and manage the discharge. Leaving it to a driver who does not know the site is how driveways get cracked.