Calculations › Timber Joist
Timber Joist
EN 1995-1-1
Checks a timber floor joist in bending, shear and deflection to EN 1995-1-1 for strength and serviceability.
Diagram
Example inputs
Span4200 mm
Joist spacing400 mm
Width b47 mm
Depth h195 mm
Ultimate load w_Ed2.55 kN/m²
Characteristic load w_k1.7 kN/m²
Timber gradeC24
Service class1
National AnnexUK
Results
Timber Joist Design
EN 1995-1-1 · C24 · SC1 · b=47×h=195mm
Results
✓ BENDING PASS
util 0.517.55EN 1995-1-1 §6.1.6
| kmod (modification factor) | 0.8 | — | EN 1995-1-1 Table 3.1 |
| Design bending strength fm,d = fm,k × kmod / γM | 14.77 | N/mm² | EN 1995-1-1 §2.4.1 |
| Load per joist wEd = w_Ed,m² × spacing | 1.02 | kN/m | |
| Design moment MEd = wEd × L² / 8 | 2.25 | kNm | EN 1995-1-1 §6.1.6 |
| Section modulus Wel = b × h² / 6 | 297863 | mm³ | |
| Design bending stress σm,d = MEd / Wel | 7.55 | N/mm² | EN 1995-1-1 §6.1.6 |
✓ SHEAR PASS
util 0.140.35EN 1995-1-1 §6.1.7
| Design shear strength fv,d = fv,k × kmod / γM | 2.46 | N/mm² | EN 1995-1-1 §2.4.1 |
| Design shear force VEd = wEd × L / 2 | 2.14 | kN | EN 1995-1-1 §6.1.7 |
| Design shear stress τd = 1.5 × VEd / (b × h) | 0.35 | N/mm² | EN 1995-1-1 §6.1.7 |
✓ DEFLECTION PASS
util 0.628.60EN 1995-1-1 §7.2
| Second moment of area I = b × h³ / 12 | 29041594 | mm⁴ | |
| Characteristic load per joist wk = w_k,m² × spacing | 0.68 | kN/m | |
| Instantaneous deflection wInst = 5wkL⁴ / (384 × E × I) | 8.6 | mm | EN 1995-1-1 §7.2 |
| Deflection limit = L / 300 | 14 | mm | EN 1995-1-1 Table 7.2 |
WARNINGS
Vibration check recommended — EN 1995-1-1 §7.3. Slender floor; dynamic response may govern.
Try it yourself
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