Getting the concrete mix right is the foundation of any lasting DIY project. Add too much water and the mix turns weak and crumbly. Add too little and it will not set properly. For small jobs like a fence post or a driveway repair, dry mix from 20kg bags is almost always cheaper than a lorry delivery, since most ready-mix suppliers charge for a minimum load regardless of how little concrete is actually needed. This guide covers how to mix dry concrete by hand to the right consistency, when a delivered pour makes more sense instead, and the safety precautions wet concrete requires.

Quick Reference Tool List:
What is dry mix concrete? (And when you actually need it)
Dry mix vs ready mix (Which is best for your project?)
Concrete burn risk and safety gear
Essential tools and protective gear (Don't skip the PPE)
Step-by-step: How to mix dry concrete by hand
Pouring, levelling, and curing your concrete
Common concrete mistakes to avoid (and how to fix them)
Concrete Bag Calculator

Quick Reference Tool List:

Standard 20kg bags of pre-mixed concrete
Clean water (approx 2 to 2.5 litres per bag)
Square-mouthed shovel
Spot board or wheelbarrow
Waterproof gloves and trousers
Safety goggles and dust mask

What is dry mix concrete? (And when you actually need it)

Mixing dry concrete yourself is the most cost-effective solution for small DIY projects like setting fence posts or repairing a driveway. Dry mix concrete is a pre-mixed bag containing the correct ratios of cement, sand and aggregate already combined, so there is no need to calculate ballast-to-cement ratios yourself. One mix-up worth clearing up: “dry mix” does not mean the bag is missing water, it means the dry ingredients are pre-combined and ready for you to add water on site. You simply buy a 20kg bag, add water and mix it up. This is ideal for small jobs where hiring a cement mixer or paying for a delivery lorry is overkill.

Dry mix vs ready mix (Which is best for your project?)

The difference is exactly what it sounds like. Ready mix concrete arrives at your property wet and ready to pour straight from a lorry, while dry mix comes in bags for you to mix on site. For anything under a cubic metre of concrete, you are almost always better off buying 20kg bags and mixing it yourself. When planning your garden layout, check out our Outside Your Home hub for more on when to use which method.

Standard truck minimums and short-load surcharges

A standard ready-mix delivery truck carries around 8m³ per load, according to Hanson (Heidelberg Materials). You do not need to order a full truckload to get a delivery though. Tarmac’s own guidance on minimum concrete mixes states minimum orders as low as 0.5 to 1m³ depending on the region and plant, rising to 2m³ for waterproof or lightweight aggregate mixes. Order below the stated minimum and most suppliers add a surcharge to cover sending a full truck out for a partial load, so it is worth checking the exact threshold for your postcode before assuming a small order is not viable.

Mini-mix and volumetric alternatives for smaller jobs

For pours too small to justify a full truck, mini-mix (also called volumetric) services fill the gap. Hanson’s Supamix delivers 1 to 4m³ loads within 15 miles of a participating plant, aimed at driveways, garage floors and footpaths. Tarmac runs a similar small-load network under the Minimix brand, with regional operators supplying anywhere from 0.5m³ up to 6m³. For a single fence post or a small patch repair, bagged dry mix is still usually the cheaper and faster option. Once a job reaches driveway or slab scale, though, these smaller delivered loads are worth pricing against a stack of 20kg bags. Our guide to concrete driveway costs has typical UK project sizes to help with that comparison.

Concrete burn risk and safety gear

Wet concrete is highly alkaline and can cause chemical burns to skin, particularly with prolonged contact through clothing that is not waterproof, such as denim. The Health and Safety Executive’s guidance on cement dermatitis confirms this is a genuine and common risk on building sites, not a rare reaction. Always wear waterproof trousers and thick gloves before kneeling near wet mix.

Make sure you have the right gear by reviewing our essential Tools and Trades guide.

Essential tools and protective gear (Don’t skip the PPE)

You only need a few basic tools to mix concrete by hand. Skip the standard gardening spade. It will not handle the weight of wet concrete and will slow the job down rather than speed it up. A square-mouthed shovel is what you need to properly fold and chop the heavy mixture. You will also need a solid mixing surface. A large plastic spot board is perfect, but a clean wheelbarrow works well for very small amounts. Finally, grab heavy-duty waterproof gloves, a dust mask for pouring the dry powder, and safety goggles.

Step-by-step: How to mix dry concrete by hand

Start by pouring your 20kg bag of dry mix onto a clean mixing board or into a wheelbarrow. Create a crater in the centre of the pile so it looks like a small volcano.
Slowly pour roughly half a litre of clean water into the crater. Using your square-mouthed shovel, fold the dry mix from the outside edges into the water.
Keep folding and chopping the mixture repeatedly. Add small splashes of water as you go until the concrete looks thoroughly wet but still holds its shape.
You will typically need between 2 and 2.5 litres of water for a standard 20kg bag. Resist the urge to add it all at once. It is far easier to loosen a stiff mix with a splash more water than to rescue one that has gone to soup.

If your project involves brickwork instead of a poured base, the rules change entirely. Check out our complete guide to mortar mixing ratios.

Pouring, levelling, and curing your concrete

To test the consistency, drag your shovel through the mix. The concrete should hold the groove without collapsing or leaking a puddle of water. Once mixed, shovel the concrete into your prepared hole or formwork.

Use a piece of straight timber to tamp and level the surface. This removes trapped air bubbles and creates a smooth finish.

Concrete does not “dry” like paint. It cures through a chemical reaction that requires moisture. In freezing UK winter temperatures, cover fresh concrete with a plastic sheet or old carpet to protect it from frost. In hot summer weather, lightly spray the surface with a hose daily to stop it drying out too fast and cracking. Rushing the cure is the most common way a good pour goes bad, so resist the temptation to check on it every hour.

Common concrete mistakes to avoid (and how to fix them)

The most common mistake is creating a mix that is far too wet. Soupy concrete will bleed water and lose its structural strength. If your mix is running off the shovel like soup, add a handful of dry cement and sand, or a small scoop from another dry mix bag, and fold it in until the consistency thickens up.

Another mistake is underestimating how much concrete is actually needed. As a rough guide, you need roughly one and a half 20kg bags to secure a standard 2.4m fence post in a 300mm hole. Always buy one bag more than you think you need to avoid abandoning a project halfway through.

If you are building a solid base for a new patio, our step-by-step guide on how to lay paving slabs covers how to make sure the groundwork is completely level and secure.