Design Ribbed Deck Floors to Eurocode 5
Design CLT ribbed deck floor systems in Europe to Eurocode 5, combining a CLT slab with rib beams using real product and fastener data from suppliers including Schmid, ESSVE and Rothoblaas, so bending, shear, deflection and vibration checks reflect what you can actually specify and build. Define a custom layup or work from standard supplier products. Try the calculator to specify a material-efficient mass timber floor with confidence.
Start Designing for Free See Integrated Suppliers- EN 1995-1-1:2004 (Eurocode 5), EN 1991:2002 (loading), treated as a built-up/composite member per general EN 1990 principles
About Ribbed Deck · Eurocode 5
The New Standard for European Mass Timber Engineering
Ribbed Deck design is gaining increasing attention in Europe as engineers seek more material-efficient mass timber floor systems. However, achieving a compliant design under the Eurocode framework can still be complex. Despite their structural efficiency and growing use, ribbed or cassette-style timber decks are rarely covered in university engineering programs, leaving many practitioners without clear guidance on their structural behaviour and design methodology.
Designing ribbed decks within the Eurocode timber design framework (EN 1995-1-1 – Eurocode 5) presents a particular challenge: the standard does not currently include explicit prescriptive provisions for ribbed or cassette-type mass timber floor systems. As a result, engineers often need to treat these systems as built-up or composite timber members, requiring a combination of advanced structural modelling and engineering judgement.
Because ribbed decks fall outside fully standardized solutions, the design process frequently relies on first-principles analysis, validated numerical models, or testing, supported by the general requirements of EN 1990 (Basis of Structural Design) and EN 1995-1-1. This performance-based approach allows engineers to demonstrate that the system achieves the required levels of strength, stiffness, and serviceability within the Eurocode framework.
The engineer's guide
Ribbed Deck · Eurocode 5
The European Engineering Platform for Ribbed Deck Design
- Deflection Check: Deflection diagrams available for each load case.
- Vibration Check: Multiple vibration methods included (Hamm et al. 2010, FP Innovations, prEN 1995:2023).
- Shear and Bending Capacity Check: Available shear and bending diagrams for each load case.
- Connection Design Capacity Check: Head Pull Through, Tensile Failure of Screw, Characteristic Axial Capacity of Screw, Shear Capacity.
- Screw Geometry Check: Screw spacing check.
Overview of Ribbed Deck Systems
Ribbed deck systems are timber floor systems composed of a CLT slab connected to longitudinal rib beams. The ribs increase bending stiffness and load capacity while reducing material usage compared to solid CLT panels. The calculator evaluates bending resistance, shear resistance, deflection performance, vibration behavior, and connection capacity between slab and ribs, modeling composite interaction via screw connections.
For the Eurocode region: Design Code EN 1995-1-1:2004 (Eurocode 5), Loading Code EN 1991:2002 (Eurocode 1).
Ribbed Deck Configuration
Two components: CLT slab panels, Timber rib beams. Geometry: CLT panel layup, rib beam dimensions, rib spacing, span length, connection type. Configuration via manual input, option: Custom Layup (full manual definition of CLT slab configuration and rib layout).
CLT slab defined via manual layer input: layer thickness, fiber orientation, timber grade, stacking configuration — models any CLT layup independent of manufacturer-specific products.
Rib beams: material type, supplier, timber grade; geometry via rib width (b), rib depth (d), rib spacing. Slab/rib connection: Flexible connection (models partial composite action).
Structural Model
Users define: span length, support conditions, load distribution. Loads applied as uniformly distributed loads along span; can include self-weight of structural elements. Topping: additional layer above CLT slab contributes to permanent load.
- Hamm et al. 2010
- FPInnovations
- prEN1995:2023
Additional parameters: vibration performance level, damping ratio, walking frequency, support condition, floating screed stiffness.
Screw Data
Users define: fastener type (screw), screw orientation (vertical), member configuration (timber-to-timber or steel-to-timber), thread type (partially or fully threaded). Suppliers: Schmid, ESSVE, Eurotec, Klimas, Rocket/Vynex, Rothoblaas, Sihga, SPAX, Würth, or Manual Input. Connection geometry: spacing along grain (a1), spacing across grain (a2), edge distance (a3), end distance (a4), embedment length, number of screws.
Analytical Methods
- Extended Gamma Method
- Gamma Method
Calculate effective bending stiffness of composite ribbed deck system, considering screw connection flexibility.
Design Checks
Deflection, Vibration, Shear, Bending, Connection Capacity — each with utilization ratio and pass/fail indicator.
Ribbed Deck · Eurocode 5
What structural advantages do ribbed timber decks provide?
How is the interaction between the CLT slab and ribs modeled?
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