How Far Apart Should Rebar Be?

Why Rebar Spacing Matters

Reinforcement spacing is not just a structural calculation — it is also a construction practicality. If bars are placed too close together, fresh concrete cannot flow around the reinforcement cage, creating voids and honeycombing that drastically reduce durability. If bars are too far apart, crack widths will exceed the limits set by Eurocode 2, allowing water and chlorides to reach the steel.

The governing European standard is EN 1992-1-1 (Eurocode 2), clause 8.2, which sets both minimum and maximum spacing requirements. DIN 488 defines the bar dimensions; the layout itself is a structural design decision governed by the design standard and local national annexes.

Minimum Spacing Rules (Eurocode 2 cl. 8.2)

The clear distance between parallel bars (in the same layer) must be at least the greatest of:

• The bar diameter (or the diameter of the larger bar if different sizes are used)
• The maximum aggregate size (d_g) plus 5 mm
• 20 mm

For a Ø16 mm bar with 20 mm aggregate, the minimum clear distance is therefore max(16, 25, 20) = 25 mm. This ensures concrete can be properly compacted around every bar.

In bundled bars (where two or more bars are grouped), the equivalent diameter d_n = d × √n governs, where n is the number of bars in a bundle (maximum 4 for vertical bars in compression zones).

Maximum Spacing Rules

Maximum spacing is set to control crack widths and ensure that the reinforcement adequately distributes stress across the element:

• Slabs (principal reinforcement): The lesser of 3h (where h = overall slab depth) or 400 mm in areas of maximum moment; 3.5h or 450 mm elsewhere.
• Slabs (secondary / distribution reinforcement): The lesser of 3.5h or 450 mm.
• Beams (longitudinal bars): Eurocode 2 does not impose a specific maximum spacing for main beam reinforcement, but crack width rules (cl. 7.3.3) impose maximum bar spacings based on steel stress and crack width class.
• Walls: Vertical and horizontal bars should not exceed 400 mm c/c (centre to centre) to control thermal and shrinkage cracking.

Typical Spacing Values for Common Elements

Crack Width Control and Bar Spacing

Eurocode 2 clause 7.3.3 provides direct limits on bar spacing as an alternative to explicit crack width calculations. For a design crack width of wk = 0.3 mm (the standard limit for reinforced concrete in exposure class XC1) and a steel stress after cracking of approximately 280 MPa, the maximum bar spacing is 200 mm for Ø16 mm bars, or 300 mm for Ø8 mm bars. Finer bars at closer spacing are always more effective at crack control than larger bars at wider spacing with equivalent steel area.

Spacing in Prefabricated Mesh and Cut-and-Bent Cages

For projects using prefabricated reinforcing mesh panels (e.g. A142, A193, A252, A393 or equivalent DIN 488-4 types), spacing is already fixed in the manufacturing process — typically 100–200 mm in both directions. Cut-and-bent cages are fabricated to the structural drawing spacing, allowing precise and consistent bar positioning on-site.

For international projects requiring B500B bars shipped from Germany, Steel Rebar Germany provides export documentation including Mill Test Certificate (EN 10204 3.1), packing lists, and Certificate of Origin — suitable for all major port destinations.