Reinforcing bar—rebar—is the backbone of UK construction. It holds concrete in tension, forms the skeleton of every slab and column, and is regulated to the millimetre. Whether you’re buying for a merchant, a civil project, or holding stock, understanding UK rebar standards is critical to sourcing smartly and avoiding costly mistakes.
What Is Rebar?
Rebar is hot-rolled, ribbed carbon steel bar designed to reinforce concrete. Its ridged surface improves bonding with concrete, while its mechanical properties allow it to take tensile stress that concrete alone cannot handle.
In the UK, rebar must conform to BS 4449:2005 + A3:2016, the British Standard for carbon steel reinforcement in concrete
What Grade Is Standard in the UK?
The most commonly used grade in the UK is:
- B500B (to BS 4449)
- Yield strength: 500 MPa
- Good ductility
- Suitable for most structural applications
- Stocked in diameters from 8mm to 40m
There is also:
- B500C
- Higher ductility clas
- Often specified in projects requiring seismic resistance or extra deformation capacity
- Less commonly held in UK stock but available from some mill
What About Certification?
To supply rebar into major UK construction projects, the material must be CARES approved. CARES (UK Certification Authority for Reinforcing Steels) independently
certifies:
- The mill that rolled the bar
- The processing facility (if it’s been cut, bent, or prefabricated)
- The traceability of the material from melt to delivery
Projects failing to meet this standard can be rejected at site, so CARES certification is
non-negotiable.
Sizes and Weights
UK rebar is ordered by diameter (in mm) and sold by the metric tonne, though site-level discussions often use lengths and bar counts.
| Diameter (mm) | Weight per metre (kg/m) | Common Application |
| 8 | 0.395 | Links, cages, light mesh work. |
| 12 | 0.888 | Slabs, stairs, beams |
| 16 | 1.58 | Foundations, columns |
| 20 | 2.47 | Ground beams, RC frames |
| 25+ | 3.85+ | Infrastructure, civil works |
Pro tip: Rebar is typically supplied in 12m lengths unless specified otherwise.
Cut & Bent vs. Straight Bar
M7 can supply:
- Straight bar in stock lengths (typically 12m)
- Cut & bent to bespoke schedules (BS 8666-compliant)
- Prefabricated reinforcement cages via UK processors
Lead time and price vary significantly between stockholding and processed supply, so understanding project timelines is key.
Why It Matters Now
With fluctuating steel prices, tightening regulations, and emerging low-carbon requirements, buyers need more than tonnage—they need certainty.
At M7, we supply CARES-approved rebar with full traceability, quick lead times, and flexible delivery from UK ports. Whether you’re after high-volume stock or engineered solutions, our team ensures compliance and speed every step of the way.