Concrete grades tell you how strong the concrete will be once cured. In the UK, grades are expressed as C-values — for example C10, C25, C35 — where the number is the concrete’s compressive strength at 28 days, measured in megapascals (MPa or N/mm²).
Getting the right grade matters. Too weak, and your project fails building regulations. Too strong, and you pay more than you need to.
Standard structural concrete grades (C10–C40)
C10 concrete
Very low-strength concrete used mostly for kerb bedding, drainage, non-load-bearing bases. Rarely specified for structural work.
C15 concrete
Light-duty applications: blinding, drainage surrounds, pipe bedding. Not suitable for reinforced work.
C20 concrete
Good general-purpose grade. Suitable for garden foundations, mass fill, non-structural slabs, footpath work.
C25 concrete
The workhorse of domestic construction. Perfect for domestic foundations, extension bases, patios and garden slabs. Most commonly specified for house extensions.
C30 concrete
Standard domestic driveway grade. Also used for garage floors, pathways and light commercial slabs. Meets most residential building regulations.
C35 concrete
One of the most versatile structural mixes. Ideal for reinforced foundations, external paved surfaces, agricultural yards and light commercial slabs. See our full C35 concrete guide.
C40 concrete
Heavy-duty grade for commercial and industrial floors, warehouse slabs, heavy load bearing structures.
C45 & C50 concrete
Specialist high-strength grades for bridge decks, multi-storey structures, precast panels, marine works.
GEN concrete grades (GEN0–GEN3)
GEN (General) grades are designated mixes intended for non-structural, general-purpose use. They’re nominally cheaper than structural C-grades because they don’t need to hit precise strength targets.
- GEN0: Kerb bedding, drainage works
- GEN1: Blinding, mass fill
- GEN2: Unreinforced strip foundations, house floor slabs
- GEN3: Reinforced house foundations, garage floors
PAV concrete grades (PAV1 & PAV2)
PAV (Paving) grades are designed specifically for external paved surfaces. They’re highly durable, weather-resistant and air-entrained to survive freeze-thaw cycles.
- PAV1: Domestic driveways, garden slabs, hardstanding
- PAV2: Heavy-duty external paving, external agricultural slabs, commercial yards
RC concrete grades (Reinforced Concrete)
RC grades (RC25 to RC50) are designated mixes for reinforced concrete structural work. They correspond broadly to their C-value equivalents but are tested against durability requirements for specific exposure classes (e.g. XC exposure to carbonation, XD chloride, XF freeze).
Which grade do I need?
| Project | Typical Grade |
|---|---|
| Kerb bedding / drainage | C10 or GEN0 |
| Shed base / garden slab | C20 or GEN2 |
| Domestic foundations | C25 or GEN3 |
| House extension | C25–C30 |
| Domestic driveway | C30 or PAV1 |
| Garage floor | C30–C35 |
| Reinforced foundations | C35 or RC30 |
| Commercial slab | C35–C40 |
| Warehouse / industrial floor | C40 or PAV2 |
Not sure which grade you need? Our team will recommend the right specification for your project. Get an instant online quote or read our guide to concrete for foundations.
FAQs
What does C35 mean in concrete?+
C35 refers to concrete with a compressive strength of 35 megapascals (MPa or N/mm²) at 28 days. The "C" stands for compressive strength. It is one of the most common grades used for structural work and driveways.
What is the difference between C25 and C30 concrete?+
C25 has a 28-day compressive strength of 25 MPa — suitable for domestic foundations and general use. C30 is 30 MPa — stronger, used where slightly heavier loads are expected such as garage floors and commercial slabs.
What grade of concrete for foundations?+
For most domestic foundations, C25 or C30 is standard. For heavier loads or commercial structures, use C30, C35 or C40. Always check with your structural engineer or building control officer.
What is GEN concrete?+
GEN grades (GEN0–GEN3) are general-purpose designated mixes typically used for non-structural work like blinding, mass concrete and unreinforced domestic foundations.