Should You Put Rebar in Concrete Footings and Why?

Concrete has a structural limitation that remains unchanged regardless of mix design or finish quality. It handles compression well, the downward force of load-bearing onto a footing. What it cannot resist on its own is tension. The pulling, flexing force generated by ground movement, uneven loading, and freeze-thaw cycles working on the structure from below. Without reinforcement, that tension finds the weakest point in the pour, and that point becomes a crack.

For anyone planning a deck, small extension, or outbuilding, understanding when rebar for footings is necessary and how to install it correctly removes the guesswork from a decision that determines whether the structure performs for decades or starts showing its weaknesses long before it should.

This guide covers when reinforcement is required under UK Building Regulations, how to achieve the right spacing and cover depth, and the installation mistakes most likely to cause problems on site.

What Rebar Actually Does Inside a Footing

Rebar spreads concentrated loads across the full width of a footing, preventing stress from accumulating at a single point. In a strip footing carrying a wall, that matters every time the load above is uneven, which, in practice, it almost always is. Reinforcement steel embedded in the pour also carries tensile loads, binding the footing together and preventing cracks from forming or widening underground movement or thermal stress.

Approved Document A sets out the Building Regulations framework for structural design in England. Section 2E covers foundations of plain concrete and defines the specific ground conditions under which they are permissible. Where those conditions are not met, whether due to poor ground, significant load, or stepped formations, the document directs designers to Eurocode 2 and the associated British Standards for reinforced concrete work. Plain concrete is not compliant in those situations [1].

The Ground Conditions That Make Reinforcement Necessary

Not every footing requires reinforcement. For very light structures on stable, well-draining ground, plain concrete to grade ST2 or GEN1, as referenced in Section 2E of Approved Document A, may be adequate, provided the ground meets specific conditions. There should be no non-engineered fill, no wide variation in ground conditions within the loaded area, and no weaker or more compressible ground at depth that could affect stability.

Where those conditions are not met, the case for reinforcement grows quickly. Stepped foundations must overlap by at least twice the height of the step or the foundation thickness, whichever is greater. On clay soils subject to shrinkage, foundation depth must reach at least 750mm on low-shrinkage clay and 1.0m on high-shrinkage clay, depths at which ground movement forces are significantly higher than a plain pour can reliably handle. Any project requiring Building Regulations approval should have the footing specification checked against these requirements before work begins.

Where ground conditions, load, or site complexity take the project outside the Section 2E provisions, reinforced design under Eurocode 2 applies. If you are working without a structural engineer, the safer default is to treat reinforcement as standard rather than optional. The cost of the steel is modest compared to the cost of a footing that fails.

Thermal movement and freeze-thaw cycles also affect how concrete performs over time. Our guide to is pouring concrete in winter for footings safe in the UK? covers the conditions most likely to compromise a slab or footing in cold weather.

Rebar Spacing & Concrete Cover Guidelines

Rebar placed incorrectly does little. Two measurements govern whether reinforcement actually works: spacing and concrete cover.

For typical domestic footing applications, horizontal bars are usually spaced at 200–300mm centres, with additional bars placed at right angles to form a grid where the footing is wide. Bunching bars together without adequate spacing prevents concrete from flowing through the cage and bonding correctly.

Concrete cover is the minimum thickness of concrete between the surface of the rebar and the outer face of the footing. It serves three purposes:

• Protecting reinforcement from frost.
• Accommodating thermal movement.
• Preventing corrosion.

According to Designing Buildings, atmospheric carbon dioxide diffuses through concrete over time, reacting with calcium hydroxide to reduce the concrete's pH. Plain cement concrete has a pH of around 12.5, at which steel is stable. When carbonation drives pH below 11.5, corrosion becomes possible. Once steel corrodes, it expands, and the surrounding concrete spalls. For commercial foundations in typical UK ground conditions, a minimum cover of 40-50mm is standard practice, increasing where soils are aggressive or sulphate-bearing. Chairs or spacers placed under and alongside the rebar cage before pouring are the only reliable way to hold cover consistently across the full footing [2].

Getting the mix right before you pour is as important as placing the steel correctly. A guide to laying concrete yourself covers preparation, mix selection, and finishing in detail.

The Installation Errors Most Likely to Cause Footing Failure

Most footing failures involving reinforcement come down to a small number of errors rather than wrong specification. Getting the preparation right matters as much as the steel itself.

These are the mistakes worth checking before you pour:

• Placing rebar directly on the ground eliminates cover and exposes steel to moisture from day one.
• Using rebar too close to the footing face leaves less than 40mm cover and creates a corrosion path.
• Omitting crossbars leaves parallel bars that distribute load in only one direction.

When combining rebar with ready mix concrete, use a mix with a maximum aggregate size of 20mm to allow concrete to flow through the cage without bridging. A slump class of S3 or S4 suits most reinforced domestic footing applications. Soil conditions are also regularly overlooked. A specification that works on firm, well-drained ground may be inadequate on clay-heavy or waterlogged sites. If ground conditions on your site are anything other than straightforward, the complete guide to concrete footings covers ground assessment in more detail, and speaking to a structural engineer before you pour is always time well spent.

Specify the Right Mix & Pour It with Confidence

Reinforcement done properly provides the structural integrity to last the life of the building above it. Position the cage correctly, hold the cover, use the right mix, and the concrete and steel work together as they should. Cut corners on any of those points, and the footing will perform below what the project demands.

Wright Readymix supplies ready mix concrete across the South West and South Wales, with mixes specified for reinforced domestic and commercial applications. With five concrete plants and a team available 24/7, the business has the capacity and experience to support projects from small self-build footings to large-scale commercial pours.

Call 0117 958 2090 or get in touch to discuss your footing mix requirements and delivery logistics.

External Sources

[1] GOV.UK, Ministry of Housing, Communities and Local Government, Ministry of Housing, Communities & Local Government (2018 to 2021), Structure: Approved Document A: https://www.gov.uk/government/publications/structure-approved-document-a

[2] Designing Buildings, The Construction Wiki, Concrete to Cover: https://www.designingbuildings.co.uk/wiki/Concrete_to_cover