What Type of Concrete Do I Need? (C20 vs C25 vs C35 Explained)

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Which Concrete Grade Do You Need?

Project Type Needed Grade Notes
Garden patio or path C20 Plenty strong for foot traffic, furniture, and light use
Shed or garden office base C25 Suitable for small buildings or insulated timber structures
Driveway (cars) C25–C30 Handles standard vehicles and regular domestic use
Driveway (vans, trailers, heavy loads) C35 Stronger mix that resists surface wear and point loading
Concrete footings or foundations C30–C35+ Needed for structural integrity and long-term load bearing

What C20, C25, and C35 Concrete Grades Actually Mean

  • ✔ C20 – Light-use general concrete

    C20 is a standard mix used for paths, patios, and unreinforced bases. It offers a compressive strength of 20 newtons after 28 days and is perfectly suitable for most domestic surfaces that won’t take heavy loads.
  • ✔ C25 – Ideal for bases and small buildings

    C25 is a strong all-round mix used for shed bases, garden offices, and light structural work. It’s stronger than C20 and gives a solid foundation for timber frames and low-rise builds.
  • ✔ C30 – Mid-strength for heavier surfaces

    C30 concrete is often used in domestic driveways or footings where the structure needs extra durability. It’s capable of supporting repeated loads like cars or wheelie bins over time.
  • ✔ C35 – High-strength concrete

    C35 is typically used for structural bases, reinforced slabs, or commercial surfaces. It resists cracking and pressure from vans, trailers, or dense structures and is great for high-load areas.
  • ✔ The ‘C’ stands for compressive strength

    The number in the grade represents the concrete’s strength in newtons per mm² after 28 days. So C25 = 25N/mm² — a higher number means a stronger, denser mix.

Using a Stronger Grade (e.g. C30/C35)

  • Handles heavier loads without cracking or deformation.
  • More resistant to frost, wear, and long-term settling.
  • Ideal for driveways, foundations, and structural work.

Using a Stronger Grade (e.g. C30/C35)

  • More expensive per cubic metre — especially with additives or fibres.
  • Harder to work with — faster setting, stiffer mix, heavier handling.
  • Overkill for patios, garden paths, or decorative slabs.

Using a Lower Grade (e.g. C20/C25)

  • Cheaper and easier to mix or order from ready-mix suppliers.
  • Ideal for domestic landscaping, garden bases, and general DIY use.
  • Easier to float, level, and finish for smaller pours.

Using a Lower Grade (e.g. C20/C25)

  • Less durable under heavy loads or long-term wear.
  • Higher chance of cracking if poured too thin or on poor sub-base.
  • Not suitable for structural or load-bearing builds.
🔹 Can I use C20 concrete for a driveway?
C20 is generally not recommended for driveways. While it can technically hold light loads, it may not resist cracking under regular vehicle use — especially over time. For most domestic driveways, C25 is the safer starting point. If you’ll be parking vans, trailers, or anything heavy, go for C30 or C35 instead.
🔹 What’s the difference between C25 and C30?
C25 and C30 are both strong mixes, but C30 offers higher compressive strength and is better for heavier loads or longer spans. If your slab will see regular vehicle use or needs extra durability, C30 is the upgrade. For garden bases and light foot traffic, C25 is usually more than enough.
🔹 Is stronger concrete always better?
Not necessarily. Stronger mixes like C35 are harder to work with, more expensive, and may be overkill for smaller jobs. The best concrete is the one that suits the job’s load, use, and conditions. Going stronger than needed just adds cost — going weaker can lead to early cracking or failure.
🔹 Can I add fibres or mesh to any concrete grade?
Yes — fibres or mesh can be added to almost any concrete mix to improve crack resistance and durability. Fibres are mixed in before the pour, while mesh sits within the slab. These reinforcements are especially useful on thinner slabs or where ground movement is likely.
🔹 How do I know which grade to order?
Match the concrete grade to your use: C20 for light-use patios or paths, C25 for garden rooms and general bases, C30+ for driveways and footings. If in doubt, C25 is a safe all-rounder for most domestic jobs. Speak to your supplier or builder if the structure is load-bearing.