C20 Concrete Supply in Birmingham
Twenty-newton concrete for the light domestic jobs: shed bases, workshop floors and unreinforced garage bases. From £105 per m³ +VAT — mixed on site, so you only pay for what you pour.
What C20 Is — and What the 20 Means
C20 is trade shorthand for concrete in the C16/20 strength class. The second number is the one that matters on site: 20 N/mm² cube strength at 28 days — "20-newton concrete" in plain English. It's the grade most garden and garage projects actually need, and nothing fancier.
If a plan or merchant's list says GEN3, that's the designated-mix name for the same C16/20 strength territory. Designated names may only be supplied as such by certified producers, so we batch an equivalent C16/20 designed mix to the strength and durability requirements of BS 8500 / BS EN 206 — the same concrete, sold under its honest name.
Where C20 earns its keep:
- Garden shed and workshop bases — around 100mm thick
- Unreinforced garage floors and bases — around 150mm thick
- Other unreinforced hardstanding for garden buildings and stores
For bases we'd normally batch it at S2 consistence — the standard workability for floors, stiff enough to level off cleanly. Standard 20mm aggregate unless the job says otherwise.
From £105 per m³, +VAT — guide price, confirmed when you book. Minimum load just 0.5m³, no part-load penalty, and you're billed on the metered volume that leaves the chute.
What C20 Is Not For
Driveways. This is the one that catches people out. A driveway doesn't just need strength — it needs to survive freezing weather. That takes an air-entrained C25/30 designed mix (PAV1-equivalent), where microscopic air bubbles give freezing water room to expand. Plain C20 laid as a drive tends to scale — the surface flakes off — after a few winters. Read our concrete for driveways page, or see C30 concrete for the strength class behind driveway mixes.
Anything reinforced. The moment there's embedded metal in the pour — mesh, rebar, any steel — the job counts as reinforced and C20 is out of its depth. Reinforced foundations want a C25/30 designed mix: that's C25 concrete territory.
It cuts both ways, mind. If you're pouring a plain shed base, don't let anyone talk you into C35 — C20 will do the job, and the difference is money in someone else's pocket. Right-sizing the grade is half the point of our concrete grades guide.
Ordering C20 Without the Waste
Volume is simple: length × width × depth in metres (100mm = 0.1m). A 4m × 3m shed base at 100mm is 1.2m³. Add 5–10% for luck and uneven sub-base — or let the concrete calculator do it for you.
Here's the volumetric difference: over-estimating costs you nothing. The truck carries the raw materials and batches your C20 on site, so we bring spare and you only pay for what's actually poured. No skip full of surplus, no returned-concrete fee, no part-load charge on a small base.
If the truck can't get next to the base — back gardens usually mean it can't — our extension chutes reach around 5m, and beyond that it's wheelbarrows: reckon on about 20 barrow loads per m³, with at least one barrow and one able adult per m³ to keep pace. Full prep detail is on our shed & garage base concrete page.
C20 Concrete FAQs
What is C20 concrete used for?
C20 — the C16/20 strength class, "20-newton" concrete — is the light-domestic workhorse: garden shed and workshop bases at around 100mm thick, and unreinforced garage floors and bases at around 150mm. Order it at S2 consistence for bases. It's for unreinforced work only.
Is C20 the same as GEN3?
They share the same strength territory. GEN3 is a designated-mix name for C16/20-strength general-purpose concrete, and designated names may only be supplied as such by producers with third-party certification. We batch an equivalent C16/20 designed mix to the strength and durability requirements of BS 8500 / BS EN 206 — the same 20-newton concrete, sold under its honest name.
Can I use C20 concrete for a driveway?
We'd advise against it. Driveways need an air-entrained C25/30 designed mix (PAV1-equivalent): microscopic air bubbles give freezing water room to expand, so the surface doesn't scale off in frost. Plain C20 driveways tend to flake and scale after a few winters. The stronger, air-entrained mix costs a little more per cubic metre and saves a re-lay later.
How much does C20 concrete cost in Birmingham?
Our C20 guide price is from £105 per m³ +VAT, confirmed when you book. Because we batch on site, you're billed on metered volume — you only pay for what's poured, from a 0.5m³ minimum, with no part-load penalty.
How thick should a C20 shed base be?
As a rule of thumb, about 100mm for paths and shed bases and about 150mm for garage floors. Volume is length × width × depth in metres (100mm = 0.1m), plus 5–10% contingency. Our concrete calculator does the sums — and with volumetric supply the contingency costs nothing unless it's poured.
Pouring a Base Soon?
Tell us the size and we'll confirm the volume, the grade and the price — C20 from £105/m³ +VAT, from just 0.5m³, with same-day slots often available.