Eurocode 5 Timber Beam Calculator (EN 1995-1-1)

Design a simply supported timber beam to Eurocode 5. Check bending, shear and deflection for solid timber and glulam using EN 1995-1-1 design rules.

For preliminary design and educational use. Always have final designs checked and signed off by a qualified engineer.

Timber Beam Design – Input

1. Geometry & Loading

From service class & load duration (EN 1995-1-1, 3.2).

Partial factor for material (Table 2.3).

2. Timber Strength Class

Default values are typical for the selected strength class (EN 338). You can override them for manufacturer-specific data.

Results – Eurocode 5 Checks

Enter span, section, loads and timber class, then click “Calculate design checks” to see utilisation ratios for bending, shear and deflection.

How this Eurocode 5 timber beam calculator works

This tool follows the main design rules of EN 1995-1-1 (Eurocode 5) for a simply supported rectangular timber beam under uniformly distributed load. It performs ultimate limit state (ULS) checks for bending and shear, and serviceability limit state (SLS) checks for deflection.

1. Design actions (ULS)

For a single load combination with one permanent and one variable action, the design line load is:

Design UDL

\( q_d = \gamma_G \, G_k + \gamma_Q \, Q_k \)

with typical partial factors: \(\gamma_G = 1.35\), \(\gamma_Q = 1.50\) (EN 1990, NA may differ).

For a simply supported beam with span \(L\):

\( M_{Ed} = \dfrac{q_d L^2}{8} \)

\( V_{Ed} = \dfrac{q_d L}{2} \)

2. Design material properties

The calculator converts characteristic strengths to design strengths using the modification factor \(k_{mod}\) and the material partial factor \(\gamma_M\) (EN 1995-1-1, 2.3.2 and 3.2):

Design strengths

\( f_{m,d} = \dfrac{k_{mod} \, f_{m,k}}{\gamma_M} \)

\( f_{v,d} = \dfrac{k_{mod} \, f_{v,k}}{\gamma_M} \)

You can either use the default values for common strength classes (C16, C24, GL24h, etc.) or override them manually.

3. Section properties

For a rectangular section of width \(b\) and depth \(h\) (depth in the direction of bending):

Section properties

\( W = \dfrac{b h^2}{6} \)   (section modulus)

\( I = \dfrac{b h^3}{12} \)   (second moment of area)

4. Bending and shear checks (ULS)

The design bending and shear stresses are:

Bending stress

\( \sigma_{m,d} = \dfrac{M_{Ed}}{W} \)

Shear stress

\( \tau_{v,d} = \dfrac{1.5 \, V_{Ed}}{b h} \)

The utilisation ratios are then:

\( \eta_m = \dfrac{\sigma_{m,d}}{f_{m,d}} \)

\( \eta_v = \dfrac{\tau_{v,d}}{f_{v,d}} \)

If \(\eta \le 1.0\), the corresponding check is satisfied.

5. Deflection checks (SLS)

Instantaneous deflection is calculated using the mean modulus of elasticity \(E_{0,mean}\) and the service load combination (usually \(G_k + Q_k\) without partial factors):

Instantaneous deflection (UDL, simply supported)

\( w_{inst} = \dfrac{5 \, q_{ser} \, L^4}{384 \, E_{0,mean} \, I} \)

To approximate final deflection including creep, the calculator multiplies the instantaneous deflection by a creep factor \(k_{def}\) (user input, default 2.0 for softwood in service class 2):

\( w_{fin} = (1 + k_{def}) \, w_{inst} \)

Typical deflection limits are \(L/300\) to \(L/400\) for total deflection and \(L/250\) for variable load only, but you should follow your National Annex and project specification.

6. Interpreting utilisation ratios

The summary card shows the governing utilisation ratio (maximum of bending, shear and deflection). Values below 1.0 indicate that the beam satisfies the corresponding Eurocode 5 requirement. If one utilisation is much higher than the others, that criterion governs the design.

Limitations and good practice

  • The beam is assumed to be simply supported with a single span and uniformly distributed load.
  • Lateral stability (lateral–torsional buckling), notches, holes, and connections are not checked.
  • Service class, load duration class and kmod/kdef must be chosen by the designer.
  • Always verify results against the full text of EN 1995-1-1 and your National Annex.

For more complex structures (continuous beams, frames, composite action, fire design, vibration), use dedicated structural analysis software and detailed Eurocode 5 guidance.

Eurocode 5 timber beam – FAQ

What checks does this Eurocode 5 timber beam calculator perform?
It performs:
  • ULS bending check \(\sigma_{m,d} \le f_{m,d}\)
  • ULS shear check \(\tau_{v,d} \le f_{v,d}\)
  • SLS instantaneous deflection under service loads
  • SLS final deflection including creep using a user-defined kdef
Which timber strength classes are supported?
The calculator includes common softwood classes C14, C16, C18, C24, C30 and glulam classes GL24h and GL28h. You can also select “Custom values” and enter your own fm,k, fv,k, E0,mean and density.
Can I use this for cantilevers or continuous beams?
The internal formulas assume a simply supported beam with uniform load. For other cases you can:
  1. Obtain MEd, VEd and deflection from your own structural analysis.
  2. Override the calculated values by matching them via equivalent loads or by checking stresses manually.
For safety-critical projects, use full structural analysis software.
How should I choose kmod and kdef?
kmod depends on service class (1–3) and load duration (permanent, medium, short, etc.) as defined in EN 1995-1-1 Table 3.1. kdef depends on service class and product type (solid timber, glulam, LVL, etc.) per Table 3.2. Always follow your National Annex values where they differ from the main Eurocode.