Ribbed Deck Design Software for Eurocode 5 | Engineering Platform

Launch the free Ribbed Deck Calculator below & verify your design in seconds!

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: Design of Timber Structures) 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 European Engineering Platform for Ribbed Deck Design

Our platform performs a check for Ribbed Deck design to AS1720. The calculation module include:

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.

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Key Ribbed Deck Design Capabilities

Overview of Ribbed Deck Systems

Ribbed deck systems are timber floor systems composed of a cross-laminated timber (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 SPEC Toolbox Ribbed Deck calculator allows engineers to analyze ribbed timber floor systems under gravity loading. The calculator evaluates:

  • bending resistance

  • shear resistance

  • deflection performance

  • vibration behavior

  • connection capacity between slab and ribs

The system models the composite interaction between the CLT slab and rib beams using screw connections.

For the Eurocode region, the calculator uses the following standards:

Design Code

  • EN 1995-1-1:2004 – Eurocode 5: Design of Timber Structures

Loading Code

  • EN 1991:2002 – Eurocode 1: Actions on Structures

These standards define the structural design rules, load combinations, and safety factors used in the analysis.

Ribbed Deck Configuration

A ribbed deck system consists of two main structural components:

  • CLT slab panels

  • Timber rib beams

The CLT slab distributes loads across the floor surface, while the ribs provide the primary bending resistance between supports.

The system geometry is defined by:

  • CLT panel layup

  • rib beam dimensions

  • rib spacing

  • span length

  • connection type

These parameters determine the stiffness and load distribution of the floor system.

The ribbed deck configuration is defined using manual input. The available option is:

  • Custom Layup

This allows the user to fully define the CLT slab configuration and rib layout.

The CLT slab is defined using manual layer input, where the structural properties of each layer are specified. Input parameters include:

  • layer thickness

  • fiber orientation

  • timber grade

  • stacking configuration

This approach enables modeling of any CLT layup configuration, independent of manufacturer-specific products.

Rib beams act as the primary load-bearing elements of the ribbed deck system. Users define:

  • material type

  • supplier

  • timber grade

The rib geometry is defined using:

  • rib width (b)

  • rib depth (d)

  • rib spacing

These parameters control the bending stiffness and structural behavior of the ribbed deck.

The CLT slab and rib beams interact through mechanical fasteners. The calculator currently supports:

  • Flexible connection

This configuration models partial composite action between the slab and rib beams.

Structural Model

The ribbed deck is analyzed as a beam system subjected to distributed loads.

Users define:

  • span length

  • support conditions

  • load distribution

Loads are applied as uniformly distributed loads along the span.

The calculator can also include:

  • self-weight of structural elements

Topping

An additional topping layer may be applied above the CLT slab.

The topping load contributes to the permanent load acting on the floor system.

Vibration Methods

Floor vibration performance can be evaluated using the following methods:

  1. Hamm et al. 2010

  2. FPInnovations

  3. prEN 1995:2023

Additional parameters include:

  • vibration performance level

  • damping ratio

  • walking frequency

  • support condition

  • floating screed stiffness

These parameters influence the dynamic response of the floor.

Screw Data

The connection between the CLT slab and rib beams is achieved using screws.

Users define:

  • fastener type (screw)

  • screw orientation (vertical)

  • member configuration (timber-to-timber or steel-to-timber)

  • thread type (partially or fully threaded)

Screw properties can be defined by selecting a manufacturer or by using manual input.

Available suppliers include:

  • Schmid

  • ESSVE

  • Eurotec

  • Klimas

  • Rocket / Vynex

  • Rothoblaas

  • Sihga

  • SPAX

  • Würth

  • Manual Input

Connection geometry is defined using:

  • spacing along grain (a₁)

  • spacing across grain (a₂)

  • edge distance (a₃)

  • end distance (a₄)

  • embedment length

  • number of screws

These parameters determine the shear transfer capacity between the slab and ribs.

Analytical Methods

The ribbed deck analysis supports the following analytical methods:

  1. Extended Gamma Method

  2. Gamma Method

These methods calculate the effective bending stiffness of the composite ribbed deck system, considering the flexibility of the screw connection.

Design Checks

After analysis, the calculator provides a summary of structural performance.

The following checks are evaluated:

  • Deflection

  • Vibration

  • Shear

  • Bending

  • Connection Capacity

Each verification includes a utilization ratio and pass/fail indicator, allowing engineers to quickly evaluate the performance of the ribbed deck system.

Tutorials

CLT Floor-to-Wall Connection Design

This walkthrough covers the essential CLT Floor-to-Wall detail, critical for lateral stability. We show you how to rapidly configure the Screw Module to handle both shear forces and potential uplift, ensuring the diaphragm is securely anchored to the vertical structure.
Key Screw Benefits:
✅ Shear & Uplift Resistance: Utilizes the high tensile strength of the fasteners to prevent wall-floor separation under complex loads.
✅ Rapid Installation: Focuses on the practicality of top-down installation workflows that save crane time on-site.
CLT Floor-to-Wall Connection Design

Slab-to-Beam Connection Design

In this tutorial, we dive into the Slab-to-Beam calculator to streamline this common interface. Watch how we utilize the Screw Module to model the interaction between the floor plate and supporting beam, ensuring optimal shear transfer and composite action.
Key Screw Benefits:
✅ Inclined Installation: Demonstrates how angling screws (e.g., 45°) maximizes stiffness and utilizes the screw’s axial strength.
✅ Deep Penetration: Shows how fully threaded screws can bridge the connection effectively to handle heavy floor loads.
Slab-to-Beam Connection Design

Half-Lap Connection Design

Join us as we break down the Half-Lap joint design, focusing on maintaining structural continuity without external steel plates. Using the Screw Module, we walk through the auto-checking of edge distances and spacing requirements critical for these tight geometric joints.

Half-Lap Connection Design

CLT Wall Calculator

In this video, you’ll learn how to design a typical CLT wall element step by step. We’ll cover selecting a CLT supplier, using the right functionalities, dynamic images, and educational content to determine the optimal panel thickness and design. You’ll also see how to switch between Platform and Balloon framing types, apply different eccentricity methods, and add in-plane and out-of-plane loads -giving you a solid understanding of the basics of CLT wall calculations and design.

Mass timber is shaping the future of sustainable construction. With record-breaking timber buildings emerging worldwide, mastering CLT design is more relevant than ever. Check out our CLT Toolbox app for powerful design tools, automated calculations, and expert insights to help you streamline your CLT projects!

CLT Wall Calculator

CLT Diaphgram Design Calculator

A complete guide to setting up and analyzing diaphragm behavior in the X-direction using CLT Toolbox. You’ll define screw types for stiffness calculations, set panel geometry, connection types, and panel widths. We cover how to input ULS and SLS forces, and explain required in-plane shear values and lamination data. The video finishes with a breakdown of deflection results, force actions, and strength checks per Eurocode 5.

CLT Diaphgram Design Calculator

CLT Floor Fire Design

We’re excited to launch the long-awaited Fire Design module for CLT floors, now available alongside the ambient design calculator on CLT Toolbox.

This tutorial walks through how the new module works, including which standards are supported and how char depth is calculated layer by layer.

Key features include:

  • Support for multiple fire models:
    – Draft Eurocode 5 (prEN 1995-1-2:2023)
    – Austrian National Annex (ÖNORM B EN 1995-1-2:2011)
    – Standard Fire Tests (ISO 834 / EN 1363-1)
  • Flexibility to define protection layers and fire-exposed sides
  • Automatic layer-by-layer charring depth calculations over time
  • Clear logic for bond-line failure and glue-line degradation
  • Full PDF export with all intermediate steps, safety factors and inputs

Built to give engineers transparency, accuracy, and speed for CLT fire design.

CLT Floor Fire Design

CLT Shear Wall Design

Glad to announce that the Second Version Of Our CLT Shear Wall Calculator is now LIVE!

After 12 months of listening to user feedback, we’re excited to release an enhanced and more robust tool for shear wall design.

CLT Shear Walls have excellent in-plane strength and can serve as a reliable lateral load resisting system.

The second version of the calculator includes features such as five cutting-edge load transfer methods—leveraging research from Casagrande, Wallner-Novak, Tomasi, Pei, and Reynolds. We’ve also added lateral deformation checks and panel stiffness calculations following ProHolz 2014 Guide. Finally, we also include the In-plane Design of CLT as according to both Proholz 2014 & FP Innovations 2019.

We’re putting the shear wall calculator on the free version for the month of October. So go to the app to check it out🙂

CLT Shear Wall Design

CLT Floor Design Calculator

Join us as we explore everything from choosing the ideal CLT panel—whether you’re opting for a supplier’s product or manually entering your own data—to selecting the right National Annex, defining loads, and refining the finer details. This video walks you through each stage, including structural analysis, stiffness calculations, and even the integration of edge-glue lamellas into your design.

We’ll also examine how various vibration techniques affect your structure and reveal how you can optimize your design by factoring in the in-plane stiffness of the concrete screed and the influence of flexible support. Plus, you’ll be able to track results and formulas throughout the process, ensuring you’re always in the know.

Let’s get started!

CLT Floor Design Calculator

CLT Diaphgram Design Calculator

Get started with a comprehensive approach to diaphragm design by defining forces, material properties, and applying Eurocode 5 parameters. Begin by defining the input forces acting on the diaphragm in the X-direction and selecting screw types for stiffness calculations. Setting the geometry and orientation of the diaphragm in the user inputs, type of panel connections, and panel width with the technical information from CLT suppliers. Input forces for both ULS and SLS, considering force direction. Understand in-plane shear values, required lamination data, and key design parameters for Eurocode 5. Finally, analyze deflection results, the underlying theory, action forces, and strength checks to ensure a precise and efficient design.

CLT Diaphgram Design Calculator

Frequently Asked Questions

What structural advantages do ribbed timber decks provide?

Ribbed decks increase structural efficiency by separating the bending elements (ribs) from the load distribution layer (CLT slab). This configuration increases bending stiffness while reducing material usage and overall floor weight compared to solid timber panels.

How is the interaction between the CLT slab and ribs modeled?

The CLT slab and rib beams are connected using mechanical fasteners, typically screws. In the calculator this connection is modeled as a flexible connection, allowing partial composite action between the slab and ribs.

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