ProPG stage 1 risk assessment for a noisy site
Stage 1 of ProPG places a residential site in a noise risk band and sets the scope of the acoustic design work. Run it before the layout is drawn, because arrangement is the cheapest mitigation available.
A ProPG stage 1 risk assessment is a screening exercise, and its purpose is to tell you at concept stage how hard the acoustic design of a residential scheme is going to be. You establish the noise levels across the site, place the site in a risk band, and that band determines whether the application needs a short note or a full acoustic design process with layout consequences. Doing it after the layout is drawn wastes the one thing the exercise is for.
ProPG is the joint professional practice guidance on planning and noise for new residential development, published by the Institute of Acoustics with the Association of Noise Consultants and the Chartered Institute of Environmental Health. It is guidance rather than policy, and councils lean on it because national policy says little about method.
What stage 1 is for
Stage 1 answers one question: how noisy is this site, and what does that imply for the design.
It is deliberately quick. The output is a risk band, a short description of the sources, and a recommendation about the scope of work needed at stage 2. It does not attempt to predict internal noise levels or specify glazing, and an assessment that jumps to a glazing specification has skipped the part that would have informed the layout.
Four things belong in the stage 1 output:
- A site plan showing measurement or prediction positions, with the dominant sources identified.
- Daytime and night-time free-field levels across the site, including the quieter parts, not just the worst facade.
- The character of the noise, since a road, a railway with pass-by events, and an industrial source with tonal content raise different design problems.
- The risk band, with the reasoning for the band and the implications for the scheme.
Measuring or estimating the levels
Two routes, and the choice depends on the source.
Measurement is normal where the dominant source is road traffic, mixed urban noise or a nearby industrial premises. A baseline survey covering representative daytime and night-time periods, with unattended logging over several days and attended observations to identify sources, gives the levels and the character together. Avoid school holidays and unrepresentative weather, and record the reasons for discarding any period.
Prediction is appropriate where the source is well characterised and future conditions differ from current ones, such as a road due to be altered, or where a railway timetable rather than a survey week defines exposure. Calculation from traffic flow data or rail movements, validated against a short measurement, is usually the defensible approach.
The metrics to report are the daytime level over the sixteen hour period from 7am to 11pm and the night-time level over the eight hours from 11pm to 7am, both free-field, together with the maximum levels of individual night-time events. Those individual events matter, because a site with a moderate average and frequent loud pass-bys is harder to design for than the average suggests.
Risk bands and what each implies
ProPG places sites into negligible, low, medium and high risk using an indicative chart that plots the daytime and night-time levels. The band boundaries sit in that chart, and reporting the plotted position rather than a bare band name lets a reviewer check the conclusion.
| Band | What it means for the application |
|---|---|
| Negligible | No further acoustic work normally needed, with a short statement recording the levels |
| Low | Good acoustic design demonstrated, usually without extensive modelling |
| Medium | Full acoustic design process, with layout, facade and ventilation strategies evidenced |
| High | Strong presumption against permission unless a compelling case is made, with detailed justification |
The high band is where practitioners should be straight with clients. ProPG says development should be discouraged on the noisiest sites, and a scheme in that band needs more than a technical fix. It needs a demonstration that the site cannot reasonably be used for something else, that the design achieves good internal and external conditions, and that the wider benefits justify permission. Councils that refuse on noise usually do so on sites in this band where the applicant treated the assessment as a formality.
Medium risk is the common case on urban infill. It is workable, and it costs design freedom.
When the scheme needs the full stage 2 work
Anything above the low band does. Stage 2 is the good acoustic design process, and it has four elements that a noise report should address in order: good acoustic design, internal noise levels, external amenity, and other relevant considerations.
Internal targets come from BS 8233:2014, which gives guideline values of 35 dB LAeq,16h in living rooms during the day and 30 dB LAeq,8h in bedrooms at night. ProPG adds attention to individual night-time events, with 45 dB LAmax,F in bedrooms commonly used as the reference point. External amenity space guidance in BS 8233 sits in the range of 50 to 55 dB LAeq,16h, applied with judgement in urban settings where that is unachievable.
The trap is achieving internal levels only with windows closed. Where that is the case, the ventilation strategy has to provide adequate airflow without opening windows, and the overheating assessment has to work on the same basis. An Overheating Risk Assessment that assumes openable windows while the acoustic report assumes closed ones is the contradiction environmental health officers look for first.
Layout responses at concept stage
This is the value of doing stage 1 early. The least expensive acoustic mitigation is arrangement.
- Use the buildings as the barrier. A perimeter block with the noisy facade forming the edge protects the courtyard behind it, and the courtyard then provides the external amenity space.
- Avoid single-aspect dwellings facing the source. Dual-aspect units give a quiet facade for bedrooms, which resolves the night-time criterion without mechanical ventilation.
- Put non-residential or circulation uses on the exposed elevation where the scheme can absorb it.
- Set back upper floors from a raised source where the geometry helps.
- Use winter gardens or enclosed balconies on the exposed side rather than open balconies that cannot meet amenity guidance.
- Locate private amenity space and play space in the acoustic shadow, and show the calculation rather than asserting the shadow exists.
Barriers are the last resort rather than the first, because a barrier tall enough to protect upper floors is rarely acceptable visually, and our note on what an acoustic barrier actually achieves covers the limits.
Reporting the outcome
A stage 1 report should be short and complete. Site description and sources, survey or prediction method with dates and equipment, results tabulated by position, the risk band with the plotted position shown, and a recommendation on the scope of stage 2 work.
Include the limitations. Where the survey period was shortened, where a source was not operating, or where future conditions were assumed, say so. Councils and their consultants read the limitations section first, and a candid one buys credibility for the rest.
Where the scheme progresses, the stage 1 work becomes the first chapter of a full Noise Impact Assessment rather than a separate document, and the levels in it carry through to the facade calculations.
How councils use the result
Environmental health officers use the band to decide how much scrutiny the application gets, and then use the stage 2 evidence to frame conditions. Expect conditions requiring the mitigation to be installed as assessed, a verification report after construction, and in some cases a limit on internal levels achieved rather than on the products specified.
Two practical points. A performance-based condition is harder to discharge than a specification-based one, so offer the specification if you can evidence it. And where the noise source is a commercial neighbour, the officer will also be thinking about complaints from future residents, which is the reasoning behind the agent of change approach in national policy, and our note on servicing and night deliveries covers that interaction from the operator's side.
PlanScope drafts noise-related planning documents structured to UK planning policy and flags missing site data rather than inventing it. Reports should be reviewed before submission, and we do not guarantee planning approval. Councils usually expect a suitably qualified acoustician, and professional review is strongly advised.
This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.
Frequently asked questions
What does a ProPG stage 1 assessment produce?
A risk band for the site, supported by daytime and night-time free-field noise levels at representative positions, a description of the dominant sources and their character, and a recommendation on the scope of stage 2 work. It does not specify glazing or predict internal levels, which belong to the later stage.
Which noise metrics should be reported?
The daytime level over the sixteen hours from 7am to 11pm and the night-time level over the eight hours from 11pm to 7am, both free-field, plus the maximum levels of individual night-time events. Those events matter because a site with a moderate average and frequent loud pass-bys is harder to design for than the average implies.
What happens if a site falls in the high risk band?
ProPG discourages residential development there, so permission needs a case rather than a technical fix. That means showing good internal and external conditions are achievable, explaining why the site cannot reasonably serve another use, and setting out the wider benefits. Refusals on noise grounds cluster on sites in this band.
Are the internal noise targets in ProPG or in BS 8233?
The guideline internal values come from BS 8233:2014, namely 35 dB LAeq,16h in living rooms by day and 30 dB LAeq,8h in bedrooms at night. ProPG adds emphasis on individual night-time events, with 45 dB LAmax,F in bedrooms commonly used, and on external amenity space in the range given by BS 8233.
Can internal targets be met with windows closed?
Only if the ventilation strategy provides adequate airflow without opening them, and the overheating assessment is run on the same assumption. An acoustic report assuming closed windows alongside an overheating assessment assuming open ones is the first contradiction an environmental health officer will look for.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.