Composite Floating Floors
This represents a commonly employed solution for improving sound transmission between floors. The treatment comprises a base resilient layer that is overlaid with a suitable covering board. Depending on the type of resilient layer employed, the products are available either in a single laminated composite form or separately for a subsequent site applied built-up treatment.
Resilient layers are available in the following main generic forms:
- High-density resin bonded rockfibre slab.
- Lamella construction rockfibre (an advantageous form where the internal fibres are predominately vertically orientated - provides for improved long term mechanical characteristics).
- Thin high-performance resilient layers (normally comprising foam, rubber or rubber / cork bound granules).
Suitable covering boards include:
- Lamaphon CPB/TG19 (a high density cement bound particle board)
- Chipboard
- Plywood or OSB (Orientated strand board).
All the above boards normally incorporate an interlocking tongue & grove detail to all 4 edges. Alternatively, square edge board may be employed in constructions where multiple covering boards are to be site applied. In this case, it is important that the board joints are offset and normally the boards are site bonded.
To maximise acoustic performance, it is imperative that this treatment is applied after internal walls and partitions are constructed. This effectively creates individual floating floors within each area. It is also important to isolate the covering boards from perimeter walls and any columns by the inclusion of a continual strip of resilient material at these abutments. This also acts as a perimeter expansion strip for the floating floor.
As described in the previous section, this type of treatment is extremely efficient in improving impact sound transmission. Improvement in airborne sound transmission can also be expected. The degree of improvement is affected by a number of factors, but of primary importance are: the surface mass of the base floor construction; the surface mass of the covering boards and for some resilient layers their thickness. The factor of the depth of the resilient layer is generally only pertinent to rockfibre based products as they are available in a thickness range capable of creating an acoustically significant ‘spaced mass' system. Additionally, these resilient layers inherently provide sound absorptive qualities. The practical affect of both being an improvement in airborne sound reduction performance.
