When you order concrete, you’ll usually see it listed as something like C10, C20, or C30. Those numbers tell you how strong the concrete will be once it has set. If you’re planning a driveway, patio, or shed base, knowing which grade to choose can make all the difference between a surface that lasts and one that cracks too soon.
This guide explains what the grades mean, what they’re used for, and how to choose the right one for your project.
What does the ‘C’ mean in concrete grades?
The ‘C’ stands for concrete, and the number that follows (for example, C20) refers to the strength of the mix. In simple terms, this is how much pressure the concrete can handle once it has cured, measured in Newtons per square millimetre (N/mm²).
So, C10 concrete can withstand about 10 N/mm², while C30 can take roughly 30 N/mm². The higher the number, the stronger the concrete.
How to choose the right grade
Driveways and parking areas
For a standard domestic driveway, you’ll usually want C25 or C30 concrete. These grades are strong enough to handle vehicles and resist cracking from repeated use. If you’re expecting heavier vehicles such as vans or motorhomes, C30 is the safer choice.
Patios and paths
A C20 mix is normally ideal for patios and garden paths. It’s durable enough for foot traffic and outdoor furniture but not over-engineered for the job.
Shed bases and garage floors
For a shed base, C20 will usually do the job. If it’s a garage floor or something that might bear vehicle weight, go with a stronger C25 or C30.
Foundations and footings
For domestic foundations, C20 or C25 is most common. The exact grade depends on soil type and the structure being built. It’s always best to check with your builder or engineer if you’re unsure.
Typical concrete grades and what they’re used for
Here’s a quick guide to the most common concrete grades used around the home. This should help you choose the right one for your next project.
| Grade | Approx Strength (N/mm²) | Typical Uses |
|---|---|---|
| C10 | 10 | Blinding layers, fill and non-structural work |
| C15 | 15 | Paths, kerbs and light foundations |
| C20 | 20 | Domestic floors, driveways, garages and foundations |
| C25 | 25 | Reinforced bases and general building work |
| C30 | 30 | Heavy-duty floors, external paving and high-traffic driveways |
| C35 / C40 | 35–40 | Structural work, commercial floors and industrial use |
PAV grades
While most domestic projects use the standard C-grade mixes, you may also see concrete sold under PAV grades. These are designed specifically for external paving and driveways, where the surface is exposed to frost, rain and de-icing salts.
Here’s a quick look at what PAV grades mean and when to choose them.
| Grade | Approx Strength (N/mm²) | Typical Uses |
|---|---|---|
| C10 | 10 | Blinding layers, fill and non-structural work |
| C15 | 15 | Paths, kerbs and light foundations |
| C20 | 20 | Domestic floors, driveways, garages and foundations |
| C25 | 25 | Reinforced bases and general building work |
| C30 | 30 | Heavy-duty floors, external paving and high-traffic driveways |
| C35 / C40 | 35-40 | Structural work, commercial floors and industrial use |
These mixes are similar to standard concrete grades but include an air-entraining agent that makes the concrete more resistant to frost, freeze–thaw damage, and de-icing salts.
In most cases, PAV concretes are used for external paving and heavy-use areas. They provide an extra layer of protection in cold or wet conditions, making them ideal for British weather.
What affects concrete strength and cost?
The strength of concrete depends on the mix proportions of cement, water, and aggregates.
- More cement generally means higher strength, but also higher cost.
- More water makes the concrete easier to work with, but too much can weaken it.
- The type of aggregate also matters. Coarser aggregates add strength, while finer ones give a smoother finish.
In short, higher-grade concrete costs more but is also more durable and less likely to crack or wear down.
What about additives and specialist mixes?
For outdoor projects exposed to frost, you can ask for air-entrained concrete. This has tiny air bubbles that help it withstand freeze-thaw cycles, which can otherwise cause cracking.
You can also add fibres to help reinforce the concrete and prevent expansion and cracking, or plasticisers to improve flexibility or make the concrete easier to pour. These don’t change the grade, but they improve performance for certain applications.
How grades relate to professional standards
Concrete grades in the UK are defined under British Standard BS 8500, which works alongside European Standard EN 206. These standards ensure mixes are tested to meet the right strength and durability levels.
You don’t need to understand the detailed code if you’re a homeowner, but it’s good to know that every C-grade mix follows a standardised strength test.
Checking your concrete order
When ordering from a ready-mix supplier, you can usually specify the grade directly. To give you some examples, you can say:
- ‘C20 for a patio base’
- ‘C25 for garage foundations’
- ‘C30 for a driveway’
Reputable suppliers will know exactly what you mean and can confirm the right mix for your job.
Key takeaways
- The number in a concrete grade (C10, C20, etc.) shows its compressive strength in N/mm²
- C20–C30 are the most common for domestic work
- Always match the grade to the job
- Consider additives like air-entrainment for outdoor or frost-prone areas
Final thoughts
Choosing the right concrete grade isn’t complicated once you understand what the numbers mean. Whether you’re building a patio, driveway, or foundation, the key is balancing strength, durability, and cost.
But even if you are still unsure, if you explain what you’re using the concrete for when you order, the concrete sales team should be able to advise you of what type you need.
Industrial projects sometimes require specialists grades of concrete. You can read a guide on that here.
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