Understand the two main kinds of transmission
Airborne sound includes sound transmitted through the air and building construction. Impact sound arises from impacts such as footsteps on a floor. Approved Document E uses different measures for these: a higher airborne insulation result is better, while a lower measured impact level is better. Do not compare the numbers as though they were the same rating. [2]
The separating-construction benchmarks
For the relevant separating walls and floors in new-build dwelling-houses and flats, Table 0.1 gives a minimum airborne performance of 45 dB, expressed as DnT,w + Ctr. For separating floors and stairs, the maximum impact level is 62 dB, expressed as L'nT,w. [2]
For dwellings formed by material change of use, the corresponding values in that table are 43 dB minimum airborne insulation and 64 dB maximum impact level. These are the stated on-site performance measures, not a guarantee obtained merely by purchasing a product with a similar number on its packaging. [2]
Requirements for relevant internal construction are different. A laboratory rating for an internal partition should not be substituted for the required on-site performance between separate homes. [2]
Design the complete construction
Ask the acoustic designer to specify the floor or wall system, junctions and treatment of services. Sound can pass through connected construction as well as directly through the separating element, so isolated upgrades may not solve the whole problem. The guidance addresses these flanking paths and construction details. [2]
Coordinate the acoustic design with structure and fire safety. A change made to one layer or a service penetration may affect more than the sound performance, and needs review by the relevant designers. [3] [4] [5]
Agree the test or alternative route
The normal pre-completion testing arrangements must be planned where applicable. Qualifying new-build work can use the recognised Robust Details alternative where the relevant registration and construction conditions are met; it is not a blanket exemption from testing for conversions. [2]
Agree the evidence route before selecting the system. Plan the programme so testing and any necessary remedial work can be completed before the final certification stage.
Keep the final evidence
Retain the acoustic specification, relevant construction records and test or accepted alternative evidence. Provide them to building control with the rest of the completion information. A floor finish chosen after handover should not be assumed to preserve a tested construction without checking the specification. [2] [6]
The objective is a coordinated system that achieves the required performance, rather than a promise that one insulation product makes a converted flat “soundproof”.