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Ultrafloor Acoustic Performance

The Ultrafloor Slab System has the flexibility to provide excellent insulation against airborne and impact sound at a low cost.

Typically no insulation is required in order to achieve the minimum airborne sound values set out by the NCC, due to the presence of the insulating air voids between the slab beam ribs and the ceiling under.

Airborne Sound

Airborne sound comes from things like people talking, television and entertainment systems etc. The laboratory measurement by which a barrier offers insulation against airborne sound is known as its “weighted sound reduction index” or (Rw) plus a spectrum adaptation term (Ctr).

The current requirement is for a floor to achieve a minimum (Rw + Ctr) value of 50 or greater. All Ultrafloor systems (with a 13mm plasterboard ceiling) achieve equal to, or better than, an (Rw + Ctr) of 50.

The higher the (Rw + Ctr) value the better the airborne sound insulation of the floor. If more stringent airborne sound insulation is required then the addition of ceiling insulation should be considered.

Impact Sound

Impact sound is due to things such as footsteps, dishwashers, clothes dryers, washing machines etc. The laboratory measurement for impact sound insulation rating is known as the “weighted normalised impact sound pressure level” or (Ln,w) plus a spectrum adaptation term (Cl).

The current requirement is for a floor to achieve a maximum (Ln,w + Cl) value of 62 or less. All Ultrafloor systems (with a 10mm plasterboard ceiling) achieve an (Ln,w + Cl) of 56.5 or less. This means that all Ultrafloor systems exceed the NCC requirements without any insulation, or the addition of carpet

The lower the (Ln,w + Cl) value the better the impact insulation of the floor. If more stringent impact insulation is required then particular attention to other elements, such as the nature of the floor surface and the ceiling system, need to be considered.

Other Considerations

Floor Surfaces and Ceiling Systems

Soft floor coverings such as carpet on a quality underlay improve the impact insulation value, however hard coverings such as tiles, polished floorboard, or parquetry can make things worse.

To achieve higher (Ln,w + Cl) and (Rw + Ctr) the following floor/ceiling elements can be added to the system:

  • A resilient layer added between the concrete surface and hard covering (such as Regupol™)
  • Insulation fabric such as glass wool or polyester fill in the ceiling void
  • Extra layers of plasterboard
  • Acoustic materials fixed to the floor soffit
  • The use of resilient-mounted fixings and ceiling hangers



For Acoustic design assistance please call 1800 858 723 or email info@ultrafloor.com.