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Stravifloor Deck on CLT: the Unexpected Match
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Mass timber buildings, including cross-laminated timber (CLT), offer an excellent and sustainable alternative to traditional building materials, with a low carbon footprint and high stiffness/mass ratio. However, this can lead to poor vibration and acoustic insulation.
Over the past year, CDM Stravitec conducted two significant test campaigns focusing primarily on dry floor solutions for CLT. While dry solutions align with CLT structures (installation speed- and sustainability-wise), it may be challenging to design them competitively to meet the most restrictive acoustic requirements. (Though not impossible. We invite you to review the solutions tested in our previous testing campaigns. Check the Technical Bulletin and its corresponding addendum at the bottom of this page for more details). Furthermore, the performance dimensions of a floating floor often extend beyond acoustics, as the flooring also serves functions related to structural protection or achieving the right balance between thermal inertia and responsiveness in a potential floor heating system. Although industry advancements now allow for all of the above to be effectively achieved with panelized solutions, it remains challenging to do so cost-effectively. So, what is the solution?
Motivated by this question, CDM Stravitec evaluated a specific solution: Stravifloor Deck - a low-profile floating floor system that uses a proprietary dovetailed metal deck for thin concrete pours. The system was tested with several configurations to understand better its performance under various scenarios, including finishing layers, void heights, electric box openings, and fiber-cement board integration.
Configurations Tested:
- Stravifloor Deck on CLT slab
- Stravifloor Deck on CLT slab with increased void height
- Stravifloor Deck on CLT slab and fiber-gypsum board (as mass added to the structure), with increased void height
- Stravifloor Deck on CLT slab and fiber-gypsum board, with increased void height and an electric box opening
- Stravifloor Deck with vinyl finishing layer
Key Findings:
- Impact of Increased Void Height:
Comparing 50 mm (2’’) and 80 mm (3-1/8’’) air voids revealed minimal differences in performance, with a slight improvement of 1–2 dB in airborne sound reduction (STC). - Influence of the Finishing Layer:
A thin [3.2 mm (1/8’’)] vinyl finishing layer, typical for office spaces, enhanced impact sound insulation by 7 dB, especially in higher frequencies, demonstrating the layer's significant contribution to performance. - Effect of Electric Box Openings:
Adding an 300 mm (12") diameter electric box opening slightly reduced both impact and airborne sound insulation by 1 dB, proving this adjustment to have a minor influence. - Role of Fiber-Cement Board Mass (added mass to the structural CLT slab):
Incorporating a 15 mm (9/16”) dense fiber-cement board [that has a surface density of 13.5 kg/m² (2.77 lbs/sq ft)] significantly improved performance, especially for impact sound insulation, which saw a 5 dB enhancement.
Explore further details about these solutions and findings on Stravi-dB, a free library where you can find the official and detailed test reports, sections of the configuration tested and even editable .csv files.
Why Stravifloor Deck?
Stravifloor Deck offers exceptional bending stiffness, allowing for concrete toppings as thin as 50 mm (2’’). This feature makes it ideal for low-profile, lightweight floating floors, particularly in sustainability-driven projects where concrete use should be minimized. The system is light yet robust, suitable for areas with high live loads.
The use of a dovetailed metal deck as formwork for the system enables a thinner floating floor compared to similar systems that use wood-based formwork. This high-bending stiffness formwork does not affect the overall build-up height of the system, and its shape further lightens the system by reducing the amount of concrete required per surface [Stravifloor Deck boasts a remarkably low dead load, starting from just 0.90 kN/m2 (1.3psi)]. By combining high-performance structure-borne and airborne noise isolation with minimal impact on floor-ceiling height, Stravifloor Deck proves to be a versatile and sustainable solution for CLT construction.
If you'd like to dive deeper into Stravifloor Deck, you can explore the product in detail.
What about Timber Frame Structures?
Stravifloor Deck is also an excellent solution for enhancing the sound insulation of both new and existing wooden joist constructions. Learn more by reading our previous article on this topic or exploring a variety of tested setups available on Stravi-db.
Technical Bulletin: Lightweight Floating Floors on CLT
The Technical Bulletin, of the first test campaign, summarizes the key findings of an extensive test campaign studying the acoustical performance (airborne sound reduction and impact noise isolation) of lightweight Stravifloor systems in combination with cross-laminated timber slabs.
Did you know we already have the results from the second round of this campaign?
We have now an addendum to the technical bulletin highlighting key findings from the second phase of this extensive study on the acoustical performance of lightweight Stravifloor and Stravilink acoustical suspended ceilings combined with CLT. Learn how you can enhance the overall acoustical behavior of the system by implementing asymmetric setups, specifically targeting the underside of the CLT slab.