Rebar vs Mesh UK: When to Use Each Type | NDS 2026
Last updated:
Compare UK rebar grades, sizes T8 to T40, ductility classes B500B vs B500C, carbon vs stainless steel, weight-per-metre data, and cut-and-bent service to BS 8666.
| Size | Diameter (mm) | Area (mm²) | Weight (kg/m) | 6m Bar Weight (kg) | Typical Use |
|---|---|---|---|---|---|
| T8 | 8 | 50.3 | 0.395 | 2.37 | Links and stirrups in beams and columns |
| T10 | 10 | 78.5 | 0.617 | 3.70 | Slab distribution bars, light foundations |
| T12 | 12 | 113 | 0.888 | 5.33 | Domestic slabs, wall starters, garage foundations |
| T16 | 16 | 201 | 1.58 | 9.48 | Strip foundations, ground beams, retaining walls |
| T20 | 20 | 314 | 2.47 | 14.82 | Pad foundations, large retaining walls |
| T25 | 25 | 491 | 3.854 | 23.12 | Pile caps, transfer beams, heavy foundations |
| T32 | 32 | 804 | 6.313 | 37.88 | Deep beams, commercial columns |
| T40 | 40 | 1257 | 9.864 | 59.18 | Heavy civil engineering, bridge piers |
| Property | B500A (Class A) | B500B (Class B) | B500C (Class C) |
|---|---|---|---|
| Yield strength (Re) | 500 MPa | 500 MPa | 500 MPa |
| Min. elongation at max force (Agt) | — | 5.0% | 7.5% |
| Tensile/yield ratio (Rm/Re) | — | ≥ 1.08 | 1.15–1.35 |
| Ductility class | Class A (low) | Class B (normal) | Class C (high) |
| Weldable | Yes | Yes | Yes |
| UK availability | Rare — mostly wire/mesh | Standard stock grade | Special order |
| Typical use | Mesh fabric to BS 4483 | General construction | Seismic or >20% moment redistribution |
| NDS stock | No | Yes — T8 to T40 | No — contact for availability |
What Rebar Sizes Are Available in the UK?
The UK construction industry uses eight standard metric rebar sizes, ranging from 8mm (T8) for light shear links up to 40mm (T40) for heavy civil engineering, all supplied in standard 6-metre lengths.
Master Technical Specifications (Weight & Area)
- T8 (8mm): 50.3 mm² area, 0.395 kg/m
- T10 (10mm): 78.5 mm² area, 0.617 kg/m
- T12 (12mm): 113.0 mm² area, 0.888 kg/m
- T16 (16mm): 201.0 mm² area, 1.580 kg/m
- T20 (20mm): 314.0 mm² area, 2.470 kg/m
- T25 (25mm): 491.0 mm² area, 3.850 kg/m
- T32 (32mm): 804.0 mm² area, 6.310 kg/m
- T40 (40mm): 1257.0 mm² area, 9.860 kg/m
Application Rules
- Domestic Use (T10 - T16): Most residential foundations, slabs, and retaining walls use these three sizes.
- Commercial Use (T20 - T40): Used strictly for heavy point loads, pile caps, transfer beams, and bridge piers.
Pro Tip: T25 is the exact cut-off point for manual handling. A single 6m length of T25 weighs 23.1kg (near the HSE single-person lift limit). A 6m length of T32 weighs nearly 38kg and strictly requires a two-person lift or mechanical assistance on site.
What Is B500B Grade and Why Does It Matter?
B500B is the standard UK specification for carbon steel reinforcement. It dictates that the steel has a guaranteed minimum yield strength of 500 MPa (N/mm²) and normal "Class B" ductility, allowing it to bend without snapping.
Technical Specifications (BS 4449:2005+A3:2016)
- Yield Strength (Re): minimum 500 MPa.
- Ductility (Agt): minimum 5.0% elongation at maximum force.
- Tensile/Yield Ratio (Rm/Re): minimum 1.08.
Application Rules (Ductility Classes)
- Class A (B500A): Low ductility. Primarily used in the manufacture of factory-welded mesh fabric. Rarely used as loose loose rebar.
- Class B (B500B): Normal ductility. The default standard for 95%+ of all loose rebar used in UK construction.
- Class C (B500C): High ductility (7.5% elongation). Specified strictly for earthquake/seismic zones or structures requiring massive moment redistribution.
Pro Tip: If your structural drawing specifies B500C, you absolutely cannot substitute standard B500B stock. However, if your older drawing specifies the obsolete "Grade 460", B500B is the direct modern upgrade.
When Would You Use Stainless Steel Rebar Instead of Carbon?
Stainless steel rebar (to BS 6744) is specified only when the concrete structure will be exposed to severe chloride attack, such as coastal sea walls, road bridges subjected to de-icing salts, or marine environments, where standard carbon steel would rust and blow out the concrete.
Technical Specifications
- Carbon B500B: Standard steel. Will rust if concrete cover is compromised.
- Stainless (BS 6744): Highly alloyed. Resists pitting corrosion even if exposed directly to seawater.
Application Rules
- When to Use Carbon: 99% of domestic builds, inland foundations, internal slabs, and standard commercial work.
- When to Use Stainless: Exposure classes XD3, XS2, or XS3 (per BS 8500), or where a 120+ year design life is mandated in harsh environments without maintenance.
Pro Tip: Stainless rebar costs 5 to 8 times more than carbon steel. A 12mm carbon bar costs under £7, while the exact same bar in stainless will cost over £35. Never order stainless steel unless explicitly detailed on the engineer's structural drawing.
How Does Cut-and-Bent Rebar Work?
Cut-and-bent rebar is steel that has been pre-cut to exact lengths and bent into specific shapes in a factory according to BS 8666:2020 shape codes, arriving on site ready to drop into the concrete formwork.
Technical Specifications (Common BS 8666 Shape Codes)
- Shape Code 00: Straight bar.
- Shape Code 11: L-Bar (90-degree bend with one long leg, one short leg).
- Shape Code 21: U-Bar (two 90-degree bends).
- Shape Code 51: Closed Link (square/rectangular hoop used in columns).
Application Rules
- Why Use It: Attempting to precisely bend 16mm or 20mm rebar on a building site is nearly impossible without hydraulic machinery. Factory bending ensures the steel physically fits inside the timber formwork with the correct concrete cover.
- Installation: Bars arrive bundled and tagged with a "Bar Mark" number that corresponds directly to the engineer's Bar Bending Schedule.
Pro Tip: Ordering cut-and-bent steel reduces site labour by up to 40% and eliminates steel waste. Do not order straight lengths and expect a groundworker to manually bend U-bars with a scaffolding pipe—it damages the ribs, weakens the steel, and violates BS 4449.
How to Calculate Rebar Weight per Metre
Mass (kg/m) = diameter (mm)² × 0.00617How to Calculate Total Bar Weight for a Given Length
Total weight (kg) = length (m) × mass per metre (kg/m)Frequently Asked Questions
Is UK rebar grade 460 or 500?
In the UK, the standard grade is now Grade 500 (specifically B500B or B500C), offering a minimum yield strength of 500 MPa. The older Grade 460 standard was phased out many years ago following updates to BS 4449. If you encounter older structural drawings specifying Grade 250 (mild steel) or Grade 460 (high yield), they must be upgraded or recalculated by a structural engineer to use modern B500B reinforcement, which is what all reputable UK suppliers strictly stock today.
What is the weight per metre of 12mm rebar?
T12 rebar weighs 0.888 kg per metre. A standard 6m bar weighs 5.33 kg. You can calculate any rebar weight using the formula: mass (kg/m) = diameter (mm) squared times 0.00617. For T12 that is 12 x 12 x 0.00617 = 0.888 kg/m.
What is the difference between B500B and B500C rebar?
Both share 500 MPa yield strength, but B500C has higher ductility. B500B requires minimum 5.0% elongation at maximum force and an Rm/Re ratio of at least 1.08. B500C requires 7.5% minimum elongation and an Rm/Re ratio between 1.15 and 1.35.
Can you weld rebar in the UK?
Yes, B500B rebar is weldable to BS EN ISO 17660. The standard requires controlled carbon equivalent values to prevent brittle welds. Welding must be carried out by certified operatives under the appropriate welding procedure specification.
What rebar size do I need for a foundation?
It depends on the foundation type and your engineer's design. Domestic strip foundations typically use T12 or T16 longitudinal bars with T8 or T10 links. Pad foundations for heavier point loads often use T16 or T20 in both directions.
What British Standard applies to rebar in the UK?
BS 4449:2005+A3:2016 is the current standard for carbon steel rebar, covering bar, coil, and decoiled product. It defines B500A, B500B, and B500C ductility grades, all at 500 MPa yield strength. Stainless steel rebar falls under BS 6744:2016. Cutting and bending follows BS 8666:2020.
What does the T mean in T12 rebar?
The "T" prefix stands for high-yield deformed (ribbed) bar. T12 means a 12mm diameter ribbed bar at 500 MPa yield strength. An "R" prefix denotes plain (smooth) mild steel bar at 250 MPa, used only for links in certain older designs.
Customer Reviews
4.8/5 from 170 Google reviews"Excellent service as always , great prices, fast delivery. What more does a customer want!? Very happy to recommend Next Day Steel"
"Good team, on time, easy communication, will recommend."
"Next day steel were recommended to me and I'd definitely use them again. Fabien was really helpful and responsive whilst making sure everything was delivered on time."