Jonathan Howell and Customer discussing plans onsite for Noise requirements

The Best Way to Discharge Noise Planning Conditions For Mixed Use Developments

Whether you are working on a conversion or a new build, if there will be a mix of residential and commercial spaces in a development, it is likely you will have to consider sound insulation between these two areas in order to meet planning requirements. Here, we explain the types of issues you may encounter and what can be done to discharge noise planning conditions.

Where To Look For The Potential For Problems

When you are submitting a planning application that will create a separating element between commercial and residential properties, you effectively have a noise source on one side of a separating floor or wall and a noise sensitive receiver on the other side. This naturally creates the potential for noise complaints and therefore noise planning conditions. As such, the design and construction of the separating elements is critical.

The Types of Noise Sources You Might Face

Example commercial noise sources include:

  • Bars
  • Pubs
  • Restaurants
  • Cafes
  • Offices
  • Doctors
  • Dentists

Each creates varying degrees of noise within their premises, which could impact on adjacent residential properties.

The below table provides examples to the different levels of noise produced by various sources:

Octave Band Centre Frequency (Hz)
631252505001k2k4kdB(A)
Quiet Restaurant6060606565555067
Busy Restaurant6070757575757080
Busy Pub/Bar8085858585807088
Music Bar/Nightclub110110100100959085101
Classroom5555556060605565

Table is taken from ‘The Little Red Book of Acoustics: A Practical Guide (Second Edition)’, published by Blue Tree Acoustics

It can be clearly seen from the above examples that the noise levels vary significantly from place to place, and therefore this would imply that the required sound insulation protection will also vary.

One important point to note is that, sometimes, it is impossible to have good enough sound insulation between a loud noise source, and a residential property, for example a nightclub and a flat which are sharing a separating wall or floor.

What You Have To Do to Achieve Planning

The criteria to be achieved by the Local Authority can vary considerably from one planning department to another. The safest route is to use Building Regulations Document E as the basis of the approach to be taken, and have your acoustic consultant decide if a higher standard is required and then select the appropriate assessment method to be used based on the noise source.

This is detailed within Building Regulations Document E as follows:
“0.8 The performance standards set out in Tables 1a and 1b are appropriate for walls floors and stairs that separate spaces used for normal domestic purposes. 

A higher standard of sound insulation may be required between spaces used for normal domestic purposes and communal and non-domestic purposes. 

In these situations the appropriate level of sound insulation will depend on the noise generated in the communal or non-domestic space. Specialist advice may be needed to establish if a higher standard of sound insulation is required and, if so, to determine the appropriate levels.

This statement implies that an acoustic consultant should be advised, to determine if higher levels of sound insulation performance are required due to noise levels generated. Noise Rating (NR) Curves are one method used by acoustic consultants and are requested by the local planning authority within Noise Planning Conditions regularly.

What are NR Curves?

Noise Rating Curves are developed by the International Organization for Standardization (ISO) and specify an indoor acoustic environment for different requirements of hearing preservation, speech communication and annoyance, in different applications.

NR Curves can be used to assess the impact of noise from one property to another that share the same separating partition by setting an NR target. The curve can then be compared to the criteria set out in BS8233:2014 and/or the NR target value.

A Summary of the Noise Rating Curves
Noise rating curveApplication
NR 25Concert halls, broadcasting and recording studios, churches
NR 30Private dwellings, hospitals, theatres, cinemas, conference rooms
NR 35Libraries, museums, court rooms, schools, hospitals operating theatres and wards, flats, hotels, executive offices
NR 40Halls, corridors, cloakrooms, restaurants, night clubs, offices, shops
NR 45Department stores, supermarkets, canteens, general offices
NR 50Typing pools, offices with business machines
NR 60Light engineering works
NR 70Foundries, heavy engineering works

A Real Example – The Micro Pub

In the following example we consider the latest trend of the “Micro-pub”. Currently many Micro-pubs are being opened across the country and they tend to be in existing retail shops which commonly have residential above and adjacent.

In this example, there was no residential dwelling directly above the micropub, but there was in the adjacent property, sharing a separating wall, which had a first floor residential.

A diagram showing the layout of the residential to micro-pub

In this case the planning authority had provided the following Noise Planning Conditions;

  1. A scheme of sound insulation to protect the existing residential dwelling to the adjacent first floor from the micro pub shall be submitted to and approved in writing by the Local Planning Authority prior to the proposed change of use taking place.
  2. The soundproofing shall be carried out in accordance with the scheme approved under (a) before the micro pub is brought into use.

Reason: To prevent unreasonable noise and disturbance to neighbouring occupants in the interests of residential amenity.

How We Handled The Noise Planning Conditions

In this case,  sound insulation tests were performed between the ground-floor proposed Micro-Pub and three rooms on the first and second floors on the adjacent residential flat. There is no direct transmission path between source and receiver rooms and so all sound insulation tests were measuring the flanking sound in the separating wall between the two properties.

Using NR Curves To Discharge Planning Conditions

As well as sound testing, we decided to use NR Curves to rate the noise in the receiver rooms.

To calculate the NR Curve rating between the ground-floor commercial and neighbouring residential, an approximation of the sound generated within the commercial premises was taken from the sound levels measured at an existing micro pub at a different location.

It is reasonable to assume that these levels will be similar, consisting mainly of 10-20 people having a drink and a chat in the early evening. The typical demographic that was present in the existing micro pub was a mature clientele, with the highest noise levels relating to the occasional laughter amongst chatting groups. There was no music. As such, we chose NR14 as a target as we expected that it would be significantly below the typical background noise of the residential above, and therefore is a target for approximate inaudability of general noise levels.

This level also provides good protection from most normally occurring levels in the Micro Pub. However, in an extreme one-off example, such as a very loud bang, this could potentially be audible in the flat. However, this is similar to the same way emergency sirens are seen as irregular and are not considered in acoustic design of the normal noise climate.

The graph below compares the estimated results with the targeted noise rating curve NR14.

A graph showing estimated results with the targeted noise rating curve NR14 for noise planning conditions

The airborne sound insulation test results and NR Curve analysis between the proposed Micro-Pub and residential shows that the current separating elements construction will provide sufficient sound insulation performance to comply with the NR14 target set.

What the Client Had To Do

As a result of involving an acoustic consultant at the planning stage, our client discovered that they did not need to carry out any remedial works. This saved considerable time and cost as it prevented the installation of unnecessary noise prevention measures, meaning that noise planning conditions were discharged early in the project.

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