Eurocode 1 Imposed Loads on Buildings (EN 1991-1-1)
Quickly estimate characteristic and design imposed loads on floors and roofs according to Eurocode 1, Part 1-1 (general actions – densities, self-weight, imposed loads for buildings).
Disclaimer: This tool is for educational and preliminary design use only. Always verify results against EN 1991-1-1, the relevant National Annex and local regulations, and have final designs checked by a qualified structural engineer.
Eurocode 1 imposed load calculator
Typical value: 1.5 (check National Annex).
Default values are indicative only.
Results
Characteristic values
qk: – kN/m²
Qk: – kN
Design & combinations
qd (ULS): – kN/m²
qd = γQ · qk
qcomb,ULS: – kN/m² ψ0
qfreq,SLS: – kN/m² ψ1
qquasi,SLS: – kN/m² ψ2
Typical Eurocode 1 imposed loads (excerpt)
The table below shows indicative characteristic imposed loads qk for common use categories based on EN 1991-1-1. National Annexes may modify these values.
| Category | Description | Typical area | qk (kN/m²) | Qk (kN) |
|---|---|---|---|---|
| A | Residential | Rooms, corridors | 2.0 | 2.0 |
| B | Offices | Office floors | 3.0 | 3.0 |
| C3 | Areas without obstacles | School corridors, assembly | 4.0 | 4.0 |
| D | Shopping | Retail floors | 4.0 | 4.5 |
| E | Storage | Light storage | 5.0–7.5 | 7.0 |
| H | Roofs | Accessible roofs | 0.4–1.5 | 1.0 |
Values are simplified and may differ from your National Annex. Always check the official tables in EN 1991-1-1.
How Eurocode 1 imposed loads work
Eurocode 1 (EN 1991-1-1) defines imposed loads on buildings as variable actions representing occupancy and use. They are used together with permanent loads (self-weight, finishes) and other variable actions (snow, wind, temperature) to design structural elements.
1. Use categories
EN 1991-1-1 groups building areas into categories:
- A – Residential, domestic areas (dwellings, hotel rooms).
- B – Office areas.
- C – Areas where people may congregate (schools, assembly halls, sports halls).
- D – Shopping areas (malls, supermarkets).
- E – Storage and industrial areas.
- F – Traffic areas for vehicles ≤ 30 kN axle load.
- G – Traffic areas for vehicles > 30 kN axle load.
- H – Roofs (accessible or inaccessible).
For each category, the standard provides characteristic uniformly distributed loads qk (kN/m²) and concentrated loads Qk (kN).
2. Characteristic vs design imposed load
The characteristic imposed load is the nominal value from the Eurocode tables. To obtain the design value for ultimate limit states (ULS), you apply a partial factor γQ from the National Annex:
Design imposed load (ULS):
qd = γQ · qk
Typical values are γQ = 1.5 for most imposed loads, but this can vary.
3. Combination factors ψ0, ψ1, ψ2
When several variable actions act together, Eurocode 1 uses combination factors ψ to reduce accompanying actions:
- ψ0 – for combination value (ULS).
- ψ1 – for frequent value (SLS, reversible effects).
- ψ2 – for quasi-permanent value (SLS, long-term effects).
Combination value (for use as accompanying action):
qcomb,ULS = ψ0 · qk
Frequent value (SLS): qfreq = ψ1 · qk
Quasi-permanent value (SLS): qquasi = ψ2 · qk
4. Example: office floor (Category B)
Assume an office floor (Category B) with:
- qk = 3.0 kN/m²
- γQ = 1.5
- ψ0 = 0.7, ψ1 = 0.5, ψ2 = 0.3
Then:
- Design imposed load: qd = 1.5 × 3.0 = 4.5 kN/m²
- Combination value: qcomb,ULS = 0.7 × 3.0 = 2.1 kN/m²
- Frequent value: qfreq = 0.5 × 3.0 = 1.5 kN/m²
- Quasi-permanent value: qquasi = 0.3 × 3.0 = 0.9 kN/m²
5. Good practice when using this calculator
- Always select the most unfavorable use category that could realistically occur over the life of the building.
- Check whether local regulations or the National Annex specify higher minimum loads.
- For storage and industrial areas (Category E), imposed loads are often governed by the actual stored material and racking layout.
- For roofs (Category H), consider snow and wind loads from other parts of Eurocode 1 in addition to imposed loads.