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Floating Floors: Dovetailed Deck Solutions vs. Wooden Formwork
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Increasing population density and urbanisation are making the standard for low noise and vibration ever more stringent. This is increasing demand for high-quality, efficient noise and vibration isolation systems, driven by the need to build faster, lighter, and with larger spans.
Today, floating floor systems are part of state-of-the-art building technology. They are a cost-effective and efficient option to improve the acoustical performance of our buildings.
A common type of floating floor is made of poured-in-place concrete supported by resilient elements that transfer the loads from the floating slab to the subfloor. Traditional floating floors typically rely on wood-based boards as formwork; however, in recent years, new technologies and alternative formworks have emerged.
Modern building design, including floating floors, requires balancing multiple performance criteria simultaneously. Acoustic performance remains critical, but it is no longer the only parameter influencing specification decisions. Imposed loads to the structure, build-up height, installation logistics, embodied carbon and certification targets such as BREEAM (Building Research Establishment Environmental Assessment Method) or LEED (Leadership in Energy and Environmental Design) are increasingly shaping project outcomes.
In this article, we compare traditional acoustical floating floor systems, using OSB (Oriented Strand Board) as formwork, with a floating floor alternative solution using a dovetailed deck sheet, across five key dimensions:
- Global Warming Potential (GWP)
- Total build-up height
- Weight and impact on building structural design
- Logistics and installation
- Acoustic performance
Floating Floor Solutions Considered – Short Description
Solution 1: Traditional floating floor using wooden-based formwork
Isolated steel batten system incorporating elastomeric pads made of natural rubber, 50 mm thick, designed to achieve a target natural frequency of 8 Hz under the Acoustical Design Load (ADL), and using an 18 mm OSB board as formwork. Consequently, a minimum reinforced concrete slab thickness of 100 mm is recommended.
Within the CDM Stravitec portfolio, the Stravifloor Channel is a solution that meets these specifications.
Solution 2: Floating floor using a dovetailed deck sheet as formwork
Low-profile (50 mm) floating floor system using a proprietary dovetailed metal deck for thin concrete pours. This type of high-bending-stiffness formwork minimises the need for reinforcement, which can be entirely avoided at this slab thickness.
The floating slab is uniformly supported by an isolated steel batten system incorporating elastomeric pads made of natural rubber, 50 mm thick, designed to achieve a target natural frequency of 8 Hz under the Acoustical Design Load (ADL).
Within the CDM Stravitec portfolio, the Stravifloor Deck is a solution that meets these characteristics.
Global Warming Potential (GWP)
Environmental Product Declarations (EPD) provide a transparent and verified basis for comparing the environmental impact of construction solutions throughout their lifecycle.
| Floor Solution (considering cement type I) | A1-A3 GWP (kg CO₂eq/m²)* |
| Solution 1 | 25.7 |
| Solution 2 | 38.7 |
*with carbon storage
Considering the A1–A3 GWP stages - covering raw material extraction and processing (A1), transport to the manufacturing site (A2), and the manufacturing process (A3) - a traditional floating floor solution can exhibit a lower embodied carbon footprint than a thinner system using a metal deck, despite its higher concrete consumption.
One way to reduce the GWP in both approaches is by using Type III cement.
Cement type I is the default cement for most applications when type III is the same material, but tuned for rapid early strength, achieved by finer grinding and slightly different composition. Type III cement is not inherently lower in GWP than Type I, but as it develops strength faster, it can result in reduced total cement content for the same early performance target. Being cement responsible for ~85–90% of concrete GWP, this can result in lower GWP values when Type III is used.
| Floor Solution (considering cement type III) | A1-A3 GWP (kg CO₂eq/m²)* |
| Solution 1 | 20.2 |
| Solution 2 | 36 |
*with carbon storage
Returning to the observation that traditional floating floors can achieve a lower footprint, a key factor driving this result is the use of OSB as formwork. As a wood-based material, OSB contributes through biogenic carbon storage, which helps reduce the overall GWP of the floor assembly.
Total Build-Up Height
Build-up height can have a major influence on architectural flexibility, usable internal space and overall building optimisation.
| Floor Solution | Total Build-Up Height |
| Solution 1 | 168 mm |
| Solution 2 | 100 mm |
By using a high bending stiffness formwork, Solution 2 enables a floating slab as thin as 50 mm. In addition, the dovetailed metal deck sheet is only 0.5 mm thick, having a negligible impact on the overall build-up of the floor system.
By contrast, when using wood-based boards as formwork, a thicker slab is required to prevent micro-cracking, with 100 mm often recommended. Furthermore, the thickness of the sacrificial formwork cannot be neglected, as these boards are typically 18 mm thick to provide sufficient strength to support the concrete slab when being compatible with centre-to-centre (o.c.) spacing between battens of 600 mm and a bearing distance within the batten of 500 mm - an optimized configuration that delivers a cost-effective solution for traditional floating floors.
As a result, Solution 2 provides a significantly thinner build-up than Solution 1, with an overall height reduction of approximately 40%.
This reduction can create additional floor-to-ceiling height, provide more available space within ceiling voids for Mechanical Electrical Plumbing (MEP) services and contribute to reducing the overall building height envelope. In high-rise developments, the cumulative effect of these reductions can become significant across multiple floors.
For an office building, assuming a typical floor-to-ceiling height of 2.7 m to 3.0 m, this reduction could translate into the equivalent of one additional floor every 42 to 46 floors.
In residential buildings, with typical floor-to-ceiling heights ranging from 2.4 m to 2.7 m, the reduction could correspond to one additional floor every 37 to 42 floors.
Weight and Impact on Building Structural Design
Reducing floating floor surface mass can have a direct impact on structural optimisation.
| Floor Solution | Floating Slab Weight |
| Solution 1 | 250 kg/m² |
| Solution 2 | 107.5 kg/m² |
As a result of the slab thickness described in the previous section, combined with the geometry of the dovetailed deck sheet - which makes the 50 mm slab non-massive and effectively “lightened” - solution 2 provides a floating slab that is approximately 57% lighter than solution 1.
A lower floating floor weight reduces loads on slabs, columns, and foundations, creating opportunities for structural optimisation and associated cost savings.
Moreover, in projects requiring Building Base Isolation (BBI) systems - such as those located near railways or metro lines - lower overall building loads can further contribute to optimisation potential, as these systems are typically designed and priced according to total loads (kN).
From a practical perspective, in an 8-storey residential building with an average of 8 apartments per floor and 75 m² (807 ft²) per unit, this reduction corresponds to approximately 1,783.8 kN less load transferred to the structure.
Applying the same approach to a 25-storey mid-rise tower with 2,000 m² per floor, the total reduction reaches approximately 52,729 kN.
Logistics & Installation
Concrete consumption also plays an important role in transport logistics and site operations.
| Floor Solution | Concrete Consumption |
| Solution 1 | 0.1 m³/m² |
| Solution 2 | 0.043 m³/m² |
By reducing concrete consumption by approximately 57%, a low-profile floating floor with deck sheet as formwork significantly decreases transport requirements.
When considering the same residential building described in the previous section - an 8-storey apartment block with 8 units per floor and 75 m² per unit - a traditional floor solution would require approximately 480 m³ of concrete, corresponding to around 60 truckloads (assuming 8 m³ per truck). In contrast, solution 2 would require only 206.4 m³, equivalent to approximately 26 truckloads.
Applying the same comparison to the previously referenced 25-storey mid-rise tower, the number of truckloads is reduced from 625 for solution 1 to 269 for solution 2.
On the other hand, deck sheets have a surface mass of 5.9 kg/m² (vs 10.8 kg/m² for 18 mm OSB), which makes it easier for on-site handling operations. This same feature also results in transport optimisation related to the formwork type, since a deck sheet represents 76% and 37% less in volume and weight, respectively, when compared with OBS boards.
Acoustic Performance
Floating floors are mainly specified by airborne and impact sound ratings (Rw/STC and Ln,w/IIC, respectively).
| Floor Solution |
Rw |
Ln,w |
ΔLw |
| Solution 1(2) | 62 dB(4) | 39 dB | 35 dB |
| Solution 2(3) | 79 dB | 37 dB | 39 dB |
(1)Calculated according ASTM standards based on ISO measurements. Test reports and technical documentation (editable .csv files, .dwg typical cross sections, Environmental Product Declarations (EPD), etc) are available through the Stravi-dB online library.
(2)on a 150 mm concrete structural slab
(3)on a 140 mm concrete structural slab, and single figure ratings were determined not only based on ISO measurements but also on additional vibration analyses, with allowed overcoming flanking limits of the lab.
(4)Prediction by INSUL
The number of contact points within a floating floor system plays an important role in acoustic behaviour.
Thanks to its proprietary dovetailed metal deck sheet and its high bending stiffness, solution 2 type allows higher spans and approximately 40% fewer contact points compared with traditional floating floor systems.
This results of typical o.c. distances of 400-600 mm between steel battens for solutions using wooden boards (proportional to the board's length since joints should be ideally supported by the steel batten and there are standardised board sizes available in the market) and o.c. distances equal or bigger than 700 mm for solutions using steel deck sheets, which are available in all lengths (defined f.y.p.) from 800 mm.
Looking Beyond a Single Performance Metric
In practice, floating floor specification is rarely driven by a single parameter alone. While embodied carbon remains an important consideration, project decisions are typically influenced by the balance between acoustic performance, structural integrity, build-up constraints, installation logistics and much more.
By combining reduced build-up height, lower structural weight, lower concrete consumption and high acoustic performance, Stravifloor Deck offers an alternative approach for projects where space efficiency and structural optimisation are key design drivers.