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Reinforcing steel buying guide

Updated: 23 October 2026

You are about to add a short pack of reinforcing steel to an amazon.co.uk basket, and the title, the technical table, and the grade line often name different things. A family page can offer 8 mm, 10 mm, and 12 mm, while the row you selected is one diameter and one length. This reinforcing steel buying guide is the checklist: read the variation, ask for one named grade, then check the piece count before you pay. The seven packs, in GBP, are on the [reinforcing steel comparison](/hub/diy-supplies/reinforcing-steel). Products Compared read those amazon.co.uk listings and public UK sources, and did not laboratory-test the bars. A qualifying purchase can earn a commission at no extra cost to you.

You are about to add a short pack of reinforcing steel to an amazon.co.uk basket, and the title, the technical table, and the grade line often name different things.

Our top picks

Generic Generic 8 mm bar, 5 × 1 m

Best overall

Generic Generic 8 mm bar, 5 × 1 m
9.8/10about £14.55
View offer
Just The Job Supplies Just The Job 10 mm bar, 5 × 1 m

Alternative

Just The Job Supplies Just The Job 10 mm bar, 5 × 1 m
9.0/10about £20.45
View offer
Just The Job Supplies Just The Job 6 mm bar, 10 × 1 m

Alternative

Just The Job Supplies Just The Job 6 mm bar, 10 × 1 m
9.0/10about £21.73
View offer
On this page
  1. 1.Read the variation, not the family title
  2. 2.One grade, not two classes in one phrase
  3. 3.Length, pieces, and the merchant metre
  4. 4.Surface and paperwork

Read the variation, not the family title

Start on the variation in the basket. Diameter, length, and piece count have to agree with what you meant to order. T10 and H10 both mean 10 mm high-tensile bar. One listing is titled as five lengths of 10 mm by 1,000 mm, yet the diameter field says 12 mm and the thickness field says 8 mm. Two listings print an item weight of 100 g. Published mass is about 0.617 kg per metre at 10 mm and about 0.888 kg per metre at 12 mm, so 100 g is not that bar. A 10 mm title carries part number RSB081000-10, an 8 mm-style code, and the unbranded 8 mm pack lists 20 items against a pack of five. Gauge the bar when it arrives.

One grade, not two classes in one phrase

B500 means a characteristic yield of 500 MPa. B500A, B500B, and B500C share that yield. The letter is the ductility class. The Concrete Centre shows a higher tensile-to-yield ratio, and more elongation, from A to C. Next Day Steel's usual B500B stock quotes at least 1.08 and an elongation Agt of 5.0%, and says not to substitute B500B where B500C is specified. EN 10080 on its own does not set the strength. Four listings print BS 4449:2005 Grade B500 B/C. That names two classes, not one grade and not a CARES certificate. Two packs have no BS 4449 line. The unbranded grade field says Commercial. Bar below 8 mm does not meet the Eurocode 2 ductility note. Rib direction is a clue to the class, and a UK country group is five ribs. A glance is not a certificate.
Generic Generic 8 mm bar, 5 × 1 m

Testsieger

Generic Generic 8 mm bar, 5 × 1 m
9.8/10about £14.55
View offer

Length, pieces, and the merchant metre

These packs are 450 mm or 1 m. Merchants sell 3 m and 6 m. A UK review on the shared parent sample describes one bar arriving when the buyer expected two, and count fields often disagree with the title. Two 1 m bars of 10 mm at £12.26 are about £6.13 a metre. Five 1 m bars of 8 mm at £14.55 are about £2.91, and five 450 mm bars of 12 mm at £15.32 are about £6.81. Ten 1 m bars are about £2.17 a metre for 6 mm, £2.52 for 8 mm, and £3.35 for 10 mm. The Metal Store lists 3 m of 10 mm at £9.00 including VAT. Next Day Steel lists the same length at £5.56. Jagged ends in the shared reviews are a cutting problem, on how to fix reinforcing steel.

Surface and paperwork

Self colour is uncoated carbon steel. Tight rust can be acceptable in concrete. Flaky rust, oil, mud, and lost section are not. Self colour is not stainless and it is not galvanised. One 6 mm listing shows the clash: the title and the colour field say Black, and a bullet says a self-colour finish that may have surface rust. Do not read Black as a coating. Stainless bar, where a drawing specifies it, is BS 6744. None of the seven listings prints a CARES line. For a specified pour, refuse Commercial, refuse B500 B/C as if it were one class, and refuse a pack whose diameter fields disagree, unless you have measured the bar and the drawing allows it.

Common questions

What should you read first on a short reinforcing-bar listing?
Read the selected variation: diameter, length, and how many bars are in that pack. Then read the grade line and ask whether it names one class. Only after that should you look at the technical table, because thickness, item weight, and number of items in this set often belong to a different size. A family title that lists 8 mm, 10 mm, and 12 mm is not the pack in the basket.
Is B500 B/C one grade?
No. B500 is the 500 MPa yield. B and C are two ductility classes. Printing both in one phrase does not make a single grade, and it does not replace a certificate. If the drawing names B500B or B500C, the listing needs that one letter. Commercial names neither class.
Does a 6 mm loose bar meet the same ductility note as 8 mm and above?
The Concrete Centre says bar below 8 mm does not meet Eurocode 2 ductility. BS 4449 still includes 6 mm, so a 6 mm pack can exist and still fail that note. The ten 1 m bars of 6 mm in this set are £21.73, with B500 B/C on the listing. Use that pack only where the drawing does not rely on that ductility class.
When do you need a CARES certificate rather than a VAT invoice?
Ask for the certificate when the specification or the building-control file asks for mill, batch, and a bundle tag. A VAT invoice only shows a purchase. None of these seven listings prints a CARES line. A small path repair may not need the tag. A lived-in foundation is the point where you stop and get the paperwork the drawing names.
Is a 1 m posted pack a cheap way to buy a slab?
No. These 1 m cuts sit roughly at £3 to £6 a metre, while a trade length of 10 mm can sit near £1.30 to £2 a metre including VAT. A short pack is the right buy when you need a few bars delivered, not when you are filling a slab. A slab that needs crack control is usually a mesh sheet, which is a different product.

Related pages

Best reinforcing steel

Reinforcing steel for foundations

Reinforcing steel or mesh

Reinforcing steel

How to fix reinforcing steel with chairs and cover

Sources

Public UK sources and the amazon.co.uk listings compared on this page. Updated 23 October 2026.

  1. CARES specification guide (retrieved 23 October 2026)
  2. CARES bar mark (retrieved 23 October 2026)
  3. Concrete Centre: European standards for reinforcement (retrieved 23 October 2026)
  4. LABC: reinforcement in foundations (retrieved 23 October 2026)
  5. Concrete Society: cover to concrete cast against the ground (retrieved 23 October 2026)
  6. Concrete Society: reinforcement contamination and rust (retrieved 23 October 2026)
  7. Approved Document A (retrieved 23 October 2026)
  8. Next Day Steel: 10 mm rebar (retrieved 23 October 2026)
  9. The Metal Store: reinforcing bar (retrieved 23 October 2026)
  10. HSENI via NISG: alternatives to grinding (retrieved 23 October 2026)