CLT Design Software for Eurocode 5 | Engineering Platform
Launch the free CLT Floor Calculator below & verify your design in seconds!
CLT Design
The New Standard for European Mass Timber Engineering
CLT Design in Europe is transforming the skyline, yet for many structural engineers, the path to a compliant mass timber design is filled with technical roadblocks. Despite its prevalence, specialized CLT design software for Eurocode 5 is rarely taught at the university level, leaving a significant knowledge gap in the local industry.
Designing with the primary European timber code, EN 1995-1-1, presents a unique challenge: while the code provides the foundation, managing the complex layer-by-layer verification for CLT requires navigating national annexes and diverse manufacturer-specific data. This complexity forces engineers to use a verified CLT calculator to manually synthesize first principles with code-specific factors like kmod, ksys, and Ym.
The European Engineering Platform for CLT Design
This tool performs a complete structural analysis of CLT panels under gravity loads. It checks both Ultimate Limit State (ULS) and Serviceability Limit State (SLS) criteria:
Our Partner Updates
The Fastest Growing Platform for Timber Specification
Key CLT Design Capabilities
Design of CLT Floors
Supplier & Code Integration
Effective CLT floor design starts with the correct application of Eurocode material and load factors. Our platform integrates supplier data with Eurocode 5 requirements, enabling fast and reliable structural verification.
Analytical Methods for CLT Stiffness
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The Gamma Method: Best for standard, uniform CLT panels with 3, 5, or 7 layers. It accounts for the rolling shear deformation in the cross-layers by using a simplified efficiency factor.
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The Extended Gamma Method: Our recommended method for thick panels (7-ply and above) or non-uniform layups. It provides a more refined calculation of effective stiffness by accounting for the rolling shear stiffness of every individual cross-layer, preventing overly conservative designs.
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The Shear Analogy Method: The most rigorous analytical approach, suitable for highly complex or asymmetric layups. It treats the panel as a composite beam with distinct bending and shear stiffness components, providing the highest level of accuracy for all layup configurations.
High-Performance Vibration Design
Vibration is often the governing serviceability limit state for CLT floors. We have included the latest Eurocode drafts to provide a superior design outcome:
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Support Conditions: Model realistic scenarios including stiff or flexible supports to accurately predict floor behavior.
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Performance Levels: Specify target performance levels to meet specific building requirements, moving beyond simple frequency checks to holistic occupant comfort.
This calculator goes beyond simple static deflection. The tool analyzes the Fundamental Frequency (f1) and Impulsive Velocity Response, allowing you to tune the floor mass and stiffness to meet strict vibration criteria (e.g., 8Hz for offices), ensuring the “feel” of the floor matches the quality of the building.
Design of CLT Fire
Advanced CLT Fire Engineering
Structural fire design for mass timber is a critical component of any Eurocode-based structural verification and performance-based fire engineering solution.
SPEC Toolbox simplifies this complexity by offering multiple verification pathways aiding engineering judgement, ranging from the widely adopted ÖNORM B EN 1995-1-2:2011 (Austrian National Annex to Eurocode 5) to the cutting-edge prEN 1995-1-2:2023 (2nd Generation Eurocode). Whether you are utilizing a standard fire curve based on EN 1363-1 testing or project-specific fire test data, the platform calculates precise charring depths and residual load-bearing capacities, helping your CLT panels meet stringent Eurocode safety and structural integrity requirements.
Precision Charring & Bond-Line Integrity
Our engine accounts for the sophisticated physics of timber charring, moving beyond simple uniform rates. You can define the basic charring rate β₀ based on timber density and moisture content, and the platform automatically applies relevant Eurocode modification factors to determine notional charring rates βₙ. Crucially, our 2nd Generation Eurocode module explicitly models bond-line integrity and delamination effects, preventing the catastrophic loss of protection often ignored in simplified calculations for layered timber elements such as CLT.
Automated Factor Analysis for Performance Solutions
To provide total engineering transparency, SPEC Toolbox enables granular control over charring variables. The platform automates the calculation of Eurocode charring and protection factors, including parameters related to gaps, protection layers, and layer fall-off behaviour. This “No Black Box” approach allows engineers to either use code-specific default values or bypass them with manual inputs derived from manufacturer fire tests, creating a verified path from Eurocode first-principles calculations to project certification.
Design of CLT Connections
1. Moving Beyond Simplified Connection Design
While Eurocode 5 (EN 1995-1-1) is the current European standard for timber design, modern mass timber connections often require more advanced modelling and manufacturer-specific data to achieve optimal performance.
Advanced Yield Modeling: SPEC Toolbox utilizes the Eurocode Johansen Yield Models to provide accurate and reliable design outcomes for dowel-type fasteners in timber connections.
ETA Integration: We integrate supplier-specific European Technical Assessments (ETAs), ensuring your designs utilize ultimate performance data unique to specific product families.
2. Simplified Screw & Joint Design
Our platform transforms complex connection math into a streamlined, high-speed workflow:
Preconfigured Joint Types: Rapidly design and verify Half Laps, Splines, and Butt Joints with automated geometry checks.
Steel-to-CLT: Specialized modules for timber-to-steel connections, handling the complex stress distributions at the interface.
3. The “Global-Local” Connection Library
SPEC Toolbox is the only platform that allows you to pair your choice of CLT Supplier with the world’s leading Connection Manufacturers:
Universal Fastener Selection: Choose from top-tier brands including ESSVE, Eurotec, Klimas, Rocket/Vynex, Rothoblaas, Schmid Schrauben, Sihga, SPAX, Würth, or Pitzl.
Verified Compatibility: Seamlessly verify these fasteners against European CLT panels such as KLH, Kalvasta Timber, Binderholz, Södrа, MTT, Theurl, or Xlam Dolomiti.
Design of CLT Shear Walls
In-plane CLT Design
ProHolz vol 1 Clause 5.8
ProHolz identifies three failure mechanisms for CLT shear walls:
- Mechanism 1: Shearing of failure of the boards along a joint
- Mechanism 2: Shearing failure of the glued surface at the intersection of joints.
- Mechanism 3: Shearing failure of the entire plate.
FP innovation Clause 3.8
By considering the shear stresses in the lamellas and the crossing areas, three different failure modes exist in CLT beams subjected to shear stresses such as
- Failure Mode I: Shear failure parallel to the grain in the gross cross-section
- Failure Mode II: Shear failure perpendicular to the grain in the net cross-section
- Failure Mode III: Shear failure in crossing area of orthogonal lamination
Wall Connection Models
In summary of the methods that are used to determine the capacity of the CLT shear wall at the connection points include:
| Methods | Summary | |
| Method I, Casagrande et al. 2016 | Analyzes shear walls using rigid body rotation and static equilibrium, with the rotation point at the panel edge, focusing on internal force balance. |  |
| Method II, Wallner-Novak et al. 2014 | Uses a simplified rectangular stress block and accounts for frictional resistance, providing a more detailed approach to sliding resistance.
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| Method III, Tomasi, 2014 | Similar to Wallner-Novak but with different compression zone length and assumes an extremely stiff foundation with a refined neutral axis calculation.
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| Method IV, Pei et al. 2012 | Treats the CLT panel as a rigid body rotating around a corner with connectors modeled as elastic springs, relying on back-calibrated connection resistance and excluding sliding resistance from the analysis.
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| Method V, Reynolds et al. 2017 | Enhances the triangular tensile distribution method by including a compression zone and factoring in friction to improve sliding resistance evaluation.
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The Ultimate CLT Design Platform for Australian Structural Engineers
If you’re looking to design CLT on your next project, then SPEC Toolbox has you covered!
Tutorials
CLT Floor-to-Wall Connection Design
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 Calculator
Learn how to use the CLT Toolbox Half-lap calculator to model a floor-to-floor diaphragm connection. We start with selecting the CLT layup, supplier, and lap width, and then walk through the difference between discrete and continuous calculation modes. Explore screw supplier options, screw families, and ETA-based optimization.
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 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 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 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.
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 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.
Frequently Asked Questions
Does this calculator handle Fire Design?
For this specific module, we focus on “Cold” (Ambient) design. However, CLT generally performs well in fire due to the “Charring Rate” (β0 approx 0.65 mm/min). We recommend checking our standalone CLT Floor Fire Calculator for fire limit states.
Can I define custom layups?
Yes. You can select standard layups (e.g., 100mm 3-ply, 140mm 5-ply) or define a custom buildup layer-by-layer to match a specific manufacturer (e.g., Sodra, KLH, Binderholz).
What about Point Loads?
The current version analyzes Uniformly Distributed Loads (UDL) typical for floor joist design. For concentrated point loads, local punching shear checks may be required separately.
CLT
Dowels
Screws
GLT
Brackets
Light-frame
Ribbed Deck
TCC