What Size Rebar for a House Foundation?
Bar-diameter, spacing, mat layout, and cover guidance for reinforced concrete house foundations — DIN 488 / EN 10080 B500B rebar supplied with full export documentation worldwide.
What Size Rebar Does a House Foundation Need?
A house foundation must transfer the full structural load of the building — walls, floors, roof, live loads — safely into the bearing soil. The rebar embedded in the concrete gives the foundation the tensile strength to resist bending, differential settlement, hydrostatic pressure (for basements), and in seismic zones, lateral forces.
For most residential house foundations in Europe, 12 mm or 16 mm B500B deformed bar is the primary reinforcement, with spacings of 150–200 mm in both horizontal directions. Raft (mat) foundations for larger houses or poor soils step up to 16–20 mm. All figures below reference B500B (500 MPa min yield, Agt ≥ 5.0 %, k ≥ 1.08) per DIN 488 / EN 10080.
Rebar Size Guide by House Foundation Type
Indicative bar diameters, spacing, and cover for common residential foundation systems.
| Foundation Type | Typical Use | Main Bar Dia | Spacing c/c | Cover (min) | Bar kg/m |
|---|---|---|---|---|---|
| Strip footing (shallow) | 1–2 storey house, good soil | 12 mm | 200 mm | 50 mm | 0.888 |
| Strip footing (heavy) | 2–3 storey, heavier loads | 16 mm | 150–200 mm | 50 mm | 1.58 |
| Raft / mat foundation | Poor soil, large footprint | 16 mm | 150 mm | 50–75 mm | 1.58 |
| Basement wall | Retaining + structural | 16–20 mm | 150–200 mm | 40–50 mm | 1.58–2.47 |
| Pile cap | Piled foundation, poor soil | 20–25 mm | 150 mm | 75 mm | 2.47–3.85 |
All values indicative. Designed quantities may differ significantly. Always confirm with your structural engineer.
Strip Foundations: Standard Bar Sizes and Layout
A reinforced strip foundation for a standard two-storey house typically uses three or four 12 mm B500B bars as bottom longitudinal steel, with 10 mm transverse distribution bars at 200–300 mm c/c. The longitudinal bars resist the bending moment from the upward soil reaction; the transverse bars resist any differential bearing and tie the section together.
Key bar properties from the EN 10080 spec bank:
- 12 mm B500B: 0.888 kg/m, 113 mm² cross-section
- 16 mm B500B: 1.58 kg/m, 201 mm² cross-section
- 20 mm B500B: 2.47 kg/m, 314 mm² cross-section
Starter bars (dowels) project above the footing to lap with the ground floor wall or column cage reinforcement. Lap length is a minimum of 50d per Eurocode 2 — for 12 mm bar that is 600 mm, for 16 mm bar, 800 mm.
Raft Foundations: Two-Way Mat Reinforcement
A raft (mat) foundation distributes the house load across the entire footprint, making it the preferred choice where bearing capacity is low, ground conditions are variable, or differential settlement must be minimised. Rafts are typically reinforced with a two-way mat of 16 mm B500B at 150 mm c/c in both top and bottom layers, though heavier houses or poor soil may require 20 mm bar.
For a 10 m × 8 m raft using 16 mm bar at 150 mm c/c both ways, top and bottom:
- Each layer, one direction: (10 m ÷ 0.15 + 1) × 8 m = 68 bars × 8 m = 544 m
- Each layer, other direction: (8 m ÷ 0.15 + 1) × 10 m = 54 bars × 10 m = 540 m
- Total per layer: ~1084 m × 1.58 kg/m ≈ 1,713 kg
- Two layers (top + bottom): ~3,426 kg (≈ 3.4 t) of 16 mm B500B
Add 5–10 % for laps (min 40d = 640 mm for 16 mm bar), chairs, and waste. These are indicative quantities — confirm with your engineer’s design schedule.
Basement Walls: Retaining and Structural Reinforcement
A reinforced basement wall must act simultaneously as a retaining wall (resisting soil and hydrostatic pressure from outside) and as a structural wall supporting the floors above. This dual role typically requires vertical bars of 16–20 mm B500B at 150–200 mm c/c on both faces, with horizontal distribution bars of 12–16 mm at 200 mm c/c.
Concrete cover for basement walls in contact with soil should be 40–50 mm on the soil side (XC2/XD2 exposure class per EN 206), and 25–30 mm on the internal face. For basement slabs in contact with groundwater, 50–75 mm cover is often specified.
Steel Rebar Germany supplies the full range needed for basement construction: B500B bar 12–32 mm, cut-and-bend to shape codes, and mechanical couplers 16–40 mm for lap-free splices through thick sections. All material ships with EN 10204 3.1 Mill Test Certificates and full export documentation.
Procurement and Export of Foundation Rebar
Foundation reinforcement is typically one of the largest single steel orders for a residential project. Planning the procurement in advance — with bar schedules drawn from the engineer’s design — minimises site delays. Key considerations:
- Stock lengths: B500B is available in 6 m and 12 m standard lengths (up to 18 m on request). For strip footings and basement walls, 12 m bars reduce lap frequency.
- Cut-and-bend: Factory-bent starter bars, U-bars, and distribution links arrive pre-tagged and ready to place. See our cut-and-bend service.
- Export packaging: Seaworthy bundles of approximately 2 tonnes each; container or break-bulk to any port. Mill Test Certificates, Certificate of Origin, CE/DoP included.
- Mesh alternative: For raft slabs with uniform geometry, B500A welded mesh panels (6.0 × 2.3 m, DIN 488-4) can reduce site labour significantly.
Frequently Asked Questions
What size rebar is used for a house foundation?
How much rebar do I need for a house foundation?
What concrete cover is required in a house foundation?
Should I use a raft or strip foundation for a house?
Does Steel Rebar Germany supply rebar for residential foundation projects?
Source German-standard rebar with full export documentation
Tell us your foundation schedule, bar sizes, and destination port — we’ll respond with a detailed quotation.