Fasteners play a well-known role in the stability and stiffness of mass timber structures, directly affecting their mechanical performance and long-term durability. However, their influence extends beyond structural integrity.

Fastener configurations also impact the dynamic behavior of timber floors, particularly in terms of vibration response. While optimizing screw placement can enhance connectivity and stiffness, it may not fully address occupant comfort and acoustic performance.

In this context, underfloor insulation solutions, such as resilient soundproofing profiles, could help mitigate low-frequency vibrations and airborne noise, improving both structural efficiency and user experience in mass timber applications.

Designing long-span CLT floors (typically 8 to 9 meters) presents specific challenges related to vibration and sound insulation.

Unlike denser materials, timber’s lightweight nature makes it more susceptible to footfall-induced vibrations and airborne noise, impacting occupant comfort. While international progress has been made in this field, the industry is still investing in getting extensive experimental data on how mass timber behaves over longer spans, both from a structural perspective and a soundproofing standpoint, to fill knowledge gaps.

To address these gaps, Griffith University’s School of Engineering and Built Environment (Gold Coast Campus) has launched a research project within the Advance Timber Hub (ATH), funded by the Australian Research Council.

The project focuses on improving the stability, acoustic insulation, and overall performance of band beam (BB) supported CLT floors. Rothoblaas is actively supporting the initiative with technical expertise and specialized products, helping refine design approaches for long-span mass timber applications.

The testing phase took place from November 2024 to February 2025, evaluating how fastening configurations, under floor insulation for soundproofing and floor design parameters influence the behavior of these structures.

Understanding the design considerations for long-span CLT floors

Long spans offer greater architectural flexibility in open-plan offices, commercial spaces, and residential buildings, but they also introduce structural and acoustic challenges:

Vibration Sensitivity: Longer spans can result in lower natural frequencies, increasing the risk of vibration discomfort.

Sound Transmission: The reduced mass of timber compared to concrete affects impact noise and airborne sound insulation.

Limited Industry Data: Designers and engineers need tested guidelines to optimize CLT floor performance in real-world applications.

This study aims to build a detailed dataset on fastener configurations, damping materials, and acoustic performance, providing clear insights for industry professionals.

Rothoblaas’ contribution to the study: a renewed commitment to research in acoustic comfort and under floor insulation for soundproofing.

As a partner in the study, Rothoblaas is supplying technical support and its already certified fastening and acoustic solutions to enhance the study’s impact. The research is testing:

HBS partially threaded screws: analyzed in different configurations to evaluate their effect on structural connectivity and vibration performance.

250 meters of ALADIN resilient soundproofing profile: a solution is designed to enhance damping and reduce sound transmission, improving floor comfort and acoustic performance.

By integrating these elements into controlled tests, the study aims to establish practical guidelines for optimizing long-span CLT floor systems and their acoustic performance.

Fastening configurations

Fasteners influence stability and stiffness in mass timber structures. The research team is investigating different screw arrangements for both CLT-to-CLT connections and CLT-to-band beam fastening, measuring their influence on structural integrity and vibration response.

The study evaluated three fastening configurations:

95 screws – baseline configuration.

190 screws – intermediate reinforcement.

322 screws – reinforced setup.

Results indicate a 5.2% increase in the fundamental natural frequency from the first to the third setup, suggesting that optimized screw placement enhances floor stiffness and vibration control. These findings will inform future recommendations on fastener spacing and arrangement for long-span CLT floors.

Damping performance with ALADIN resilient soundproofing profile: what happens after adding an under-floor insulation for soundproofing.

Damping—the process of dissipating vibrations—affects occupant comfort in timber structures.
This study compared a bare CLT floor configuration with one featuring Rothoblaas’ ALADIN resilient soundproofing profile as under floor insulation for soundproofing, which is designed to absorb vibrations and enhance soundproofing.

Initial findings show a 15.6% increase in damping performance when ALADIN is integrated by the designer into the floor system from the design phase. This demonstrates how ALADIN enables effective impact noise reduction, as already tested and approved according to the EN ISO 10848 standard by both Holzforschung Austria and the Industrial Research Center of the University of Bologna.

Mass Timber Construction: soundproofing profiles to enhance under floor insulation for soundproofing

While the research is ongoing, the early results indicate that a combination of optimized fastener configurations and advanced soundproofing solutions can improve the performance of long-span CLT floors.

This project is contributing valuable insights for:

Architects and engineers designing large-scale timber structures.

Developers looking to integrate mass timber into office and residential buildings.

Construction professionals seeking tested solutions for vibration and noise control.

Project Partners and Industry Collaboration

This research is being led by:

Assoc. Prof. Hassan Karampour (Griffith University, Project Leader).

Mr. Adam Faircloth (PhD Researcher, Queensland Department of Primary Industries).

Mr. Tom Watts (XLam Australia, Technical Support & Timber Supply).

Mr. Sebastian Jaimes (Rothoblaas Representative for Project 1.1).

The study is part of the Advance Timber Hub (ATH) and is funded by the Australian Research Council, with contributions from Queensland Department of Primary Industries (DPI) and XLam Australia.

For more details about the partners visit:

Advanced Timber Hub (ATH)

Griffith University

Queensland Department of Primary Industries (DPI)

XLam Australia

Interested in further test reports about our soundproofing solutions?

Check here: Rothoblaas Soundproofing Reports

Long-Span CLT Floors: the importance of under floor insulation for soundproofing.