What Size Rebar for a Grade Beam?
Practical bar-size and spacing guidance for grade beams and strip footings — using B500B rebar to DIN 488 / EN 10080. Indicative figures only; always confirm with a qualified structural engineer.
What Is a Grade Beam and Why Does Rebar Size Matter?
A grade beam (also called a ground beam) is a reinforced concrete beam that sits at or just below finished grade, typically spanning between column footings, pile caps, or drilled piers to form a continuous foundation ring. Unlike an elevated beam, a grade beam transmits loads directly to the soil or to discrete foundations, and it must resist both bending and differential settlement forces.
Because grade beams are in direct contact with soil and are often partially or wholly below grade, their reinforcement must be sized to carry design loads AND to satisfy the durability requirements imposed by the aggressive exposure environment. B500B (hot-rolled, 500 MPa minimum yield, Agt ≥ 5.0%, k ≥ 1.08 per DIN 488 / EN 10080) is the standard reinforcing grade for this element in Germany and the EU.
All figures below are indicative and intended to support preliminary estimation. Final design must be performed by a licensed structural engineer using the applicable national annex to Eurocode 2 and site-specific geotechnical data.
Typical Rebar Sizes for Grade Beams
Grade beams for residential foundations commonly use 12 mm to 16 mm longitudinal bars. Commercial and industrial grade beams, or those spanning over long distances between piles, typically require 16 mm to 25 mm bars. Closed links (ties/stirrups) are generally 8 mm or 10 mm at 200–300 mm centres.
| Application | Longitudinal Bar Dia. | No. of Bars (typical) | Link / Stirrup |
|---|---|---|---|
| Residential strip foundation / grade beam | 12–16 mm | 2 top + 2 bottom | 8 mm @ 250–300 mm |
| Commercial grade beam (light column loads) | 16–20 mm | 3 top + 3 bottom | 10 mm @ 200 mm |
| Industrial / heavy grade beam | 20–25 mm | 4+ per face | 10–12 mm @ 150 mm |
| Grade beam over piles (long span) | 20–32 mm | 4–6 per face | 10 mm @ 100–150 mm |
Bar Properties Reference
Weight per metre is calculated as: kg/m = d²(mm) × 0.00617. Key diameters for grade beams:
| Diameter (mm) | Weight (kg/m) | Cross-section (mm²) |
|---|---|---|
| 12 | 0.888 | 113 |
| 16 | 1.58 | 201 |
| 20 | 2.47 | 314 |
| 25 | 3.85 | 491 |
| 32 | 6.31 | 804 |
Concrete Cover for Below-Grade Conditions
Grade beams in contact with soil or blinding concrete are subject to more severe exposure than internal beams. Eurocode 2 assigns exposure class XC2 (wet, rarely dry) or XC3/XC4 for elements in contact with soil. Typical nominal cover recommendations:
- XC2 (cast against blinding concrete): 40 mm nominal cover to links
- XC3/XC4 (cast directly against soil): 50–75 mm nominal cover
- Fire resistance R90+: may require additional cover per EN 1992-1-2
Cover is always measured to the outermost bar — the closed link or tie — not the longitudinal bar.
Indicative Material Estimate (Preliminary Only)
Consider a residential grade beam: 300 mm wide × 400 mm deep, spanning 5 m between pile caps. A simplified preliminary check (fyd = 435 MPa, factored moment ≈ 60 kN·m, lever arm z ≈ 0.85d = 290 mm):
- Required As ≈ 60×10⁶ / (435 × 290) ≈ 475 mm²
- 4 × ø12 bars = 4 × 113 = 452 mm² (borderline — likely 3 × ø16 = 603 mm² would be specified)
- Linear weight of 3 × ø16: 3 × 1.58 = 4.74 kg/m; for 5 m beam ≈ 24 kg longitudinal steel
- Closed links ø8 @ 250 mm: approximately 20 links per beam run
We supply B500B straight bars in 6–12 m stock lengths and factory-bent closed links to your bending schedule. For below-grade projects requiring spacers and tying wire, see our accessories page.
Sourcing Grade Beam Reinforcement for Export
Steel Rebar Germany supplies DIN 488-certified B500B bar in diameters from 8 mm to 40 mm. All deliveries include an EN 10204 3.1 Mill Test Certificate and, on request, a Certificate of Origin. We pack in seaworthy bundles for container or break-bulk shipment. Learn more about our export and delivery service or request a project quote.
Frequently Asked Questions — Rebar for Grade Beams
What is the difference between a grade beam and a footing?
What rebar grade should I use for a grade beam?
How much concrete cover is needed for grade beam rebar?
Can I use mesh instead of individual bars in a grade beam?
Does Steel Rebar Germany supply rebar for foundation projects internationally?
Source German-standard rebar with full export documentation
Tell us your grade beam schedule, destination port, and required standards — we’ll respond with a detailed quotation including MTC and CE documentation.