Volex Labs / Calculations / Timber rafter and joist design to Eurocode 5.

Timber rafter and joist design to Eurocode 5.

Enter the timber grade, section and span, and Volex Anvil designs the rafter or joist: the design bending strength fm,d (with the load-duration factor kmod, the size factor kh and the material factor γM), the bending and shear stresses under the roof/floor loads, and the instantaneous and final deflection including creep (kdef).

The strength modification factors follow EC5 §2.4 and §3, so the design bending strength and utilisation match the code for solid and glulam timber.

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What Volex Anvil checks

Design bending strength fm,d (kmod, kh, γM) — EC5 §2.4 / §3.2
Bending stress σm,d and utilisation — EC5 §6.1.6
Shear stress τd — EC5 §6.1.7
Deflection incl. creep (kdef) — EC5 §2.2.3 / §7.2
Load-duration and service class — EC5 §2.3

Validated against the published example

Timber rafter — design bending strength and stress EC5 §2.4.1 + Table 3.1 (kmod / material factors)

Quantity	Published	Volex Anvil	Error
Design bending strength fm,d	14.77 MPa	14.77 MPa	0.00%
Applied bending stress σm,d	9.42 MPa	9.42 MPa	0.00%

This case is one of 359 published checks the platform passes — the full table, with every source and every error, is public at volexlabs.com/verification.

Frequently asked

Solid timber or glulam?

Both — solid, glulam and LVL are supported, with the strength class and size factor kh applied to the section.

Does it include creep?

Yes — the final deflection uses the kdef creep factor for the service class and load-duration mix, per EC5 §2.2.3.

Is it validated?

The design strength and stress are checked against EC5 — within 0.00%.

Free to use?

Yes — 10 calculations a month free; Pro (£29/month) adds unlimited runs and PDF calc sheets.

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