Site & Environment
Exposure classes · design life · cover · minimum concrete class · fire resistance · groundwater · feeds the Building designer
Inside buildings with low humidity; permanently submerged
Foundations; water-retaining tanks
Tabulated method of EN 1992-1-2: minimum member sizes and axis distance to the main bars. Typical: R60 low-rise, R90 up to about 30 m, R120 above.
Allowable bearing and ground type for earthquakes are set here and on the Building page (same data).
| Structural class | 50 years, XC1, C30 | S3 |
| cmin,dur (durability) | Table 4.4N | 10 mm |
| Beams (to links) | max(durability, fire, link Ø) | 25 mm |
| Columns (to links) | 30 mm | |
| Slabs (to bars) | 25 mm | |
| Foundations | XC2 | 50 mm |
These covers are used by the Building designer and the construction schedules. Δcdev = 10 mm assumes ordinary quality control.
| Element | Exposure | Minimum class | Max w/c | Min cement (kg/m³) | Your concrete |
|---|---|---|---|---|---|
| Frame | XC1 | C20/25 | 0.65 | 260 | C30/37 OK |
| Foundations | XC2 | C25/30 | 0.6 | 280 | C30/37 OK |
The same concrete class is used for the whole building in this tool. Where the foundation needs a higher class than the frame, use the higher one or specify two grades on site. Limits differ by country (for example BS 8500 in the UK): confirm in your National Annex.
| Member | Smallest size | Axis distance to main bars |
|---|---|---|
| Slab | 80 mm thick | 20 mm |
| Beam (simply supported) | 120 mm wide | 25 mm at 300 wide; 25 mm at 500 wide |
| Column (load level μfi ≤ 0.5) | 250 mm | 40 mm at 350; 40 mm at 450 |
The Building designer raises the smallest slab, beam and column sizes to these values and checks the axis distance of the bars it chooses. Continuous slabs and beams can be slightly better than these simply supported values; walls and flat slabs have their own tables.
- ✓ Concrete class for frame (XC1): C30 ≥ C20/25; limits w/c ≤ 0.65, cement ≥ 260 kg/m³
- ✓ Concrete class for foundations (XC2): C30 ≥ C25/30; limits w/c ≤ 0.6, cement ≥ 280 kg/m³
- ✓ Fire R60: slab: axis distance 29 mm ≥ 20 mm required for 220 mm section
- ✓ Fire R60: beams: axis distance 41 mm ≥ 25 mm required for 350 mm section
- ✓ Fire R60: columns: axis distance 48 mm ≥ 40 mm required for 350 mm section
Scope: exposure classes, covers, minimum concrete class and fire resistance use recommended/tabulated values and are indicative; they differ by country and by the type of structure. Corrosion, frost and chemical attack of the ground (sulphates) are not designed here. Results are an aid only and must be verified by a qualified, licensed engineer before use. National Annex presets are recommended values and must be checked against the official documents.