BS 8666:2020 vs BS 4466: What Changed in the Bar Bending Schedule Standard

If you've come across an old drawing, a legacy Excel template, or a printed shape-code chart that references BS 4466 rather than BS 8666, it's worth understanding what actually changed — because the two standards don't map onto each other cleanly, and treating a BS 4466 shape code as if it were the equivalent BS 8666 code can produce the wrong bar.

A quick timeline

• 1989

  BS 4466:1989 is published — the long-standing British Standard for scheduling, dimensioning, bending and cutting reinforcement.

• April 2000

  BS 8666:2000 replaces BS 4466:1989, which is formally withdrawn. The new standard incorporates the shape codes set out in BS EN ISO 4066:2000, so the UK's shape-code system aligns with the wider European numbering.

• 2005

  BS 8666:2005 is issued as a revision of the 2000 edition.

• 2020

  BS 8666:2020, the current edition, is published — a lighter revision that adds a small number of new shape codes and updates the formulas or dimensioning for roughly twenty others, mainly around cranked bars and obtuse-angle bends.

What actually changed from BS 4466 to BS 8666

The move from BS 4466:1989 to BS 8666:2000 wasn't just a rename — it changed several things detailers and fabricators had to adjust to at the time:

• Shape code renumbering. Shapes were redesignated with new numbers and the overall set was reorganised and reduced, aligning with the BS EN ISO 4066:2000 numbering used more widely in Europe. A BS 4466 shape code and a BS 8666 shape code with a similar-looking number are not guaranteed to be the same bar — each one needs checking against the current BS 8666 shape code chart rather than assumed.
• Steel grade notation. The way steel type and grade were designated on drawings and schedules changed, aligning with BS 4449:1997's introduction of the 460A and 460B grade designations.
• Minimum bending radii. Minimum former (bending) diameters were generally reduced under the new standard, allowing tighter bends than BS 4466 permitted for the same bar size.
• A transition period. For some time after April 2000, fabricators had to be able to process orders under both standards, since older drawings in circulation still referenced BS 4466 while new work moved to BS 8666.

What to check if you see BS 4466 on a drawing today

• Don't assume the shape code translates directly. Look up the actual bar geometry on the drawing and re-select the matching current BS 8666:2020 shape code rather than reusing the old number.
• Check the bend radius separately. If dimensions were set against BS 4466's larger minimum radii, re-verify them against the current BS 8666:2020 Table 2 values rather than carrying them over unchanged.
• Flag it for re-issue. A drawing still referencing BS 4466 is, at minimum, over two decades old for this discipline — it's worth confirming with the design team whether it should be reissued to the current standard rather than scheduled as-is.

Frequently asked questions

Is BS 4466 still valid?

No. BS 4466:1989 was formally withdrawn when BS 8666:2000 was introduced in April 2000, though older drawings and some legacy templates still reference it, which is why it's still occasionally seen on site.

What replaced BS 4466?

BS 8666 replaced BS 4466:1989, first as BS 8666:2000, then revised as BS 8666:2005, and most recently as BS 8666:2020, which is the current version.

Do BS 4466 shape codes match BS 8666 shape codes?

No. Shape codes were renumbered and the overall set was reduced and reorganised when BS 8666 replaced BS 4466, so a shape code from a BS 4466 drawing should not be assumed to mean the same bar shape under BS 8666 — it needs to be checked and re-coded.

What's new in BS 8666:2020 compared to BS 8666:2005?

BS 8666:2020 is a lighter revision than the 2000-to-2005 change — it added a small number of new shape codes and updated the formulas or dimensioning for around twenty others, mainly around cranked bars and obtuse-angle bends.

Not a substitute for a checked, engineer-approved bending schedule, or for consulting BS 8666:2020 itself (available from BSI) for the authoritative, current requirements.