BNG and Minor Development

I am proposing a small site or minor development, what do I need to do?

If your development proposal is not classed as 'major development', then from 2 April 2024 you are still likely to have to meet the 10% Biodiversity Net Gain (BNG) requirements unless you are exempt from doing so. If you are not exempt, then it is mandatory that you comply with the BNG rules, though some aspects are different for minor development compared with major development.

Exempt development

Certain types of development are exempt from complying with the mandatory 10% BNG requirement. These exemptions are set by government. We can not set any additional criteria for exempt development, or in any other way make an exception to the national rules for a particular proposal. 

Householder applications, such as a small home extension, will be a common example of an exempt proposal.

For a full list of exempt proposal, please see national advice at Biodiversity Net Gain: Exempt Developments (external link).

If you are exempt from mandatory BNG, you must state so on your application form, giving a valid reason why you believe your proposal is exempt.

Even if you are exempt from mandatory BNG it does not mean you are exempt from other nature related requirements set by Government or locally. These include policy requirements set out in our Local Plan and Natural Environment SPD, as well as wider national and local legislation and policy. For further details on some of these wider requirements, please see our Ecology and Biodiversity support page.

I am not exempt, what do I have to do

Full details on what you need to do to comply with your BNG obligations are set out in national guidance (external link).

This webpage only covers some of the essential requirements to get you started on what is needed, and when it needs to be done. However, this webpage is not a substitute for the full legislative requirements and national guidance which you will need to comply with.

Small Site Metric

The Biodiversity Metric is the fundamental aspect of the BNG system. If you qualify as a small site, you are likely to only need to complete a Small Sites Metric (Statutory Biodiversity Metric) (external link) rather than the fuller Statutory Biodiversity Metric. The basic principle remains, however, that your development must provide a minimum of 10% BNG. You therefore need to familiarise yourself with what the Small Site Metric is and what information is required. It is a national requirement that it is completed by a competent person.

Small Site, but full Statutory Biodiversity Metric still required

Whilst ordinarily you may qualify as only having to complete the Small Site Metric, if any one or more of the following criteria are met then you must complete the full Statutory Biodiversity Metric, and it must be completed by a competent person capable of completing the full Statutory Biodiversity Metric:

Even if you are not required to complete the full Statutory Biodiversity Metric, you can still choose to do so instead of the Small Sites Metric.

The Biodiversity Gain Plan

The Biodiversity Gain Plan is another fundamental aspect of the overall BNG system. The Biodiversity Gain Plan shows how you will achieve BNG, and must include a metric tool calculation. It will also include how you intend to manage and maintain the gains for 30 years, starting from when you complete the development.

However, it is important to note that the Biodiversity Gain Plan is something you submit to the Local Planning Authority (and thereafter gain approval for it) after you have got planning permission. You can not gain approval of your Biodiversity Gain Plan at the same time as planning permission. 

A template Biodiversity Gain Plan (external link) is available from Government.

Habitat Management and Monitoring Plan (HMMP) or a Landscape and Ecological Management Plan (LEMP)?

When you submit your Biodiversity Gain Plan, you will need to include either a HMMP or a LEMP. The latter should only be used if the scale of on-site BNG is not going to be significant. If in doubt, seek advice as to which may be the most appropriate. 

Trees and BNG on small sites

If you have existing trees on your site, or you are thinking of adding trees, it might be worth considering the advice from the Forestry Commission available via a recent Trees and BNG On Small Sites (external link) blog.

What to submit and when

There are certain things that you must submit with your planning application, and certain things you can only (but also must) submit after you have received planning permission. 

When you submit your application, of fundamental importance is the submission of a pre-development biodiversity value of the on-site habitat including the completed metric calculation. However, there are a number of other matters you must submit, including various statements about the site and its present and past biodiversity. A useful checklist (external link) can be found in national guidance. If all these matters are not included with your submitted planning application, then we will not validate your application.  

Whilst the above are compulsory matters to submit, you may also wish to submit a draft Biodiversity Gain Plan, a draft completed full metric and a draft HMMP or LEMP at the planning application stage. This might help speed up the decision making process overall. As they are only draft, you can show different options that you are considering. For a template HMMP please view the Natural England template (external link)

After you have received planning permission, you will then need to submit your final Biodiversity Net Gain Plan, including a fully complete Metric and HMMP or LEMP. Unless otherwise agreed, the Council has 8 weeks to approve or refuse the Plan.

Conditions and Legal Agreements

Significant biodiversity gains on-site and all biodiversity gains off-site will need a s106 agreement to ensure that robust and enforceable measures are in place to deliver the BNG obligations for at least 30 years. Other on-site biodiversity gains that are not significant will likely be secured via a BNG condition, though again the 30 year rule will apply.

Comprehensive step by step process for developers

For a fuller checklist and guidance of all the steps associated with meeting your BNG requirements, please refer to national steps for developers (external link) guidance.

Comprehensive step by step process for developers

For a fuller checklist and guidance of all the steps associated with meeting your BNG requirements, please refer to national steps for developers (external link) guidance.

Alternatively, a Technical Guide (external link) has been produced by CIEEM, IEMA and CIRIA which aims to provide a simple ‘how to’ guide on mandatory BNG. It is primarily for CIEEM, IEMA and CIRIA members involved in BNG but is likely to also be useful for planners, developers, architects, engineers, landscape architects and land managers. The Council may refer to it from time to time, if helpful to explain to wider stakeholders how and why we are implementing BNG procedures.