Launch the free CLT Floor Calculator below & verify your design in seconds!
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.
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:
1. The “Gamma Method” (Flexible Bond Theory)
Unlike solid concrete slabs, CLT layers are connected by cross-layers that deform under shear. This “slip” reduces the effective stiffness of the panel.
Our calculator uses the Gamma Method (γ-method) (Annex B of Eurocode 5) or the Shear Analogy Method to accurately calculate the effective bending stiffness (EIeff). Ignoring this shear deformation can lead to dangerous under-estimation of deflection.
2. Vibration: The Design Driver
For long-span residential floors, strength is rarely the problem—comfort is.
The calculator performs a specialized Vibration Check based on Eurocode 5 recommendations. It verifies:
3. Rolling Shear Verification
The cross-layers in CLT are loaded perpendicular to the grain, where wood is weakest. This stress is called Rolling Shear.
Common in short, heavily loaded spans (or near supports), rolling shear failure can occur before bending failure. This tool automatically checks the shear stress (τroll) at the neutral axis of every cross-layer.
Effective Stiffness (EIeff)
The effective stiffness is reduced by the shear flexibility of the cross layers:
EIeff = sum (Ei • Ii + γi • Ei • Ai • ai<sup>2</sup>)
Where γi is the connection efficiency factor (dependent on the rolling shear modulus Gr).
Partial Safety Factors (γM)
Material Strength (EN 16351)
The tool uses standard strength classes typically found in the European supply chain (e.g., C24 lamellas).
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.
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).
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.
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