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Reinforcing steel for foundations

Updated: 23 October 2026

A 1 m pack of reinforcing steel looks, in the basket, like a footing specification. It is a length of bar with a price. Reinforcing steel for foundations is a different question: whether the trench is a plain-concrete strip, or a reinforced footing that someone has designed. Approved Document A, which is England's structural guidance, does not print a domestic bar size. Wales, Scotland, and Northern Ireland have their own regimes. The [reinforcing steel comparison](/hub/diy-supplies/reinforcing-steel) holds seven short packs. This page does not score them. Products Compared read Approved Document A, LABC, and the Concrete Society. We did not design a foundation, and a purchase through our links may earn a commission at no extra cost to you.

A 1 m pack of reinforcing steel looks, in the basket, like a footing specification. It is a length of bar with a price.

Our top picks

Just The Job Supplies Just The Job 12 mm bar, 5 × 450 mm

Best overall

Just The Job Supplies Just The Job 12 mm bar, 5 × 450 mm
9.0/10about £15.32
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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
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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
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On this page
  1. 1.Plain concrete is not a bar size
  2. 2.When steel is in the footing
  3. 3.A short pack is not a schedule
  4. 4.Shed base, raft, and the phone call

Plain concrete is not a bar size

Section 2E of Approved Document A is plain-concrete foundations. The text linked from GOV.UK sets width from Table 10, a minimum thickness of 150 mm or the projection beyond the wall, and a depth commonly at least 450 mm except on rock. There is no bar schedule. That 450 mm is trench depth, not the 450 mm bar in one of these packs. Talk of T12 or T16 on a merchant page is a stockist's guide, not Approved Document A. A random bar does not turn that strip into a designed footing. An NHBC chapter summary says reinforcement, where it is used, is sized to suit the ground.

When steel is in the footing

When a drawing puts bar in the trench, cover is what a fixer can get wrong. The Concrete Society publishes at least 40 mm on blinding and at least 75 mm against soil. LABC's warranty table matches that, and adds 50 mm for external shuttered work and 25 mm internal. LABC says the table is not the enforcing body's decision. Where steel is used, an NHBC summary says support it 75 mm above the base or as the design. Chairs hold the gap. The trench bottom does not, and LABC does not want the steel trodden in. How to chair, tie, and cut is on how to fix reinforcing steel. LABC also rejects shopping-basket or trolley mesh in foundations.
Just The Job Supplies Just The Job 12 mm bar, 5 × 450 mm

Testsieger

Just The Job Supplies Just The Job 12 mm bar, 5 × 450 mm
9.0/10about £15.32
View offer

A short pack is not a schedule

These packs are straight 450 mm or 1 m bar. A strip cage is a schedule of lengths, bends, and laps. Several posted metres do not become that cage. None of the listings is CARES-certified here, and three share 4.5 from 357, so a star line is not proof the bar is fit for a wall. A short bar can suit a small non-structural pour. If the footing is under a lived-in building, call building control or an engineer before you size the trench from a title. The same stop applies to a failed wall, to B500C or stainless, and to any cut-and-bent schedule.

Shed base, raft, and the phone call

A shed base usually needs a mesh sheet and a check with the council, not a bag of offcuts. Pages disagree: one names A142 and also says a light shed is often plain concrete. Do not rely on a 15 m² or 30 m² line from a single trader. Ask the local authority. LABC says a raft usually needs a structural engineer. A 1 m pack is not that edge cage. Approved Document A is England's guidance. In Scotland, Wales, or Northern Ireland, open the national standards.

Common questions

Does Approved Document A tell you to use 12 mm bar in a strip footing?
No. Section 2E is about plain concrete. It gives rules for width, thickness, and depth. It does not print a bar diameter. Merchant talk of T12 or T16 is a selection guide, not that document. If your footing needs steel, the size comes from a design, not from a product title.
When does a foundation need reinforcement at all?
When the design, the ground, or the building-control requirement says so. A plain-concrete strip that meets the conditions in the guidance is not improved by a random bar from a short pack. Poor ground, a raft, a failed wall, or a lived-in building is the point where you ask an engineer rather than add steel to be safe.
What cover do LABC and the Concrete Society publish for steel in the ground?
Both publish 75 mm in direct contact with the ground, or cast against soil, and 40 mm on blinding. LABC also has 40 mm on a membrane, 50 mm for external shuttered work, and 25 mm internal. LABC says this is not the enforcing body's decision. An NHBC chapter summary says, where reinforcement is used, support it 75 mm above the base or as the design.
Can trolley mesh go in a footing?
LABC does not advocate shopping-basket or trolley mesh in foundations. It is not designed bar, and it is not a specified fabric sheet. If a footing needs steel, use the bar or the fabric the design names, on chairs, with the cover that design asks for.
Does a garden shed base always need building-control approval?
Not always, and not never. Some small detached outbuildings are exempt in some circumstances, and councils still say check first. A single ready-mix page's floor-area line is not your decision. Ask the local authority. A light base is often plain concrete or a mesh sheet, not a bag of reinforcing offcuts.

Related pages

Reinforcing steel buying guide

Reinforcing steel or mesh

Reinforcing steel

Best reinforcing steel bar for a short posted pack

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)