The De Minimis exemption is set out in regulation 4 of the Biodiversity Gain Requirements (Exemptions) Regulations 2024. It is narrowly defined to exclude very specific types of development - such as accessibility ramps and telecommunications masts.
If your site is larger than 25m2 you should provide a metric sheet - which you can use the Joe's Blooms BNG Tool to do - to justify the exemption. Please note that, even if you are undertaking a change of use, you should still provide a metric to justify the exemption.
KEY POINTS
Evidence should be provided to justify use of the de minimis exemption. This is set out in the Planning Guidance: "When providing reasons for the de minimis exemption, an applicant should provide sufficient evidence to support their justification. In cases where the development would be smaller than 25 square metres, the description of development, existing and proposed site plans, and the development’s area size (in square metres) may be sufficient evidence. In other cases where it cannot be clearly demonstrated through site plans and descriptions whether an onsite habitat would be lost or degraded by the development, applicants are strongly encouraged to provide a completed metric for the pre-development and post-development value for the onsite habitat and clear plans identifying the nature and size of this pre-development onsite habitat and how much of it will be impacted by the development."
The fact that land is not being built doesn't mean it won't be "impacted". The key point is whether or not the habitat will be degraded. So, for example, if grassland is being trampled all over that will lower the score.
Bare ground, or ground with little vegetation is NOT exempt. Under the BNG rules only land that is completely sealed or completely under man-made gravel is zero rated. Any other land - even if there is little or no vegetation on it - is "habitat" and should be counted towards the 25m2.
Applicants and Local Planning Authorities should note that this exemption will not apply to many types of development. The Government has been clear that the de minimis exemption is only meant to apply to very specific cases, providing the following examples:
A minor extension to a visitor centre at a public nature park to accommodate a new accessible ramp and entrance lobby on an existing hardstanding area.
A new commercial building exclusively on an existing car park where there are no other habitats (e.g. a green verge or tree) within the red line boundary
A new telecommunications mast (taking up 5 square metres of land)
How does the metric sheet demonstrate that I am exempt under the De Minimis threshold?
The metric sheet itself does not state if an exemption has been reached. Instead, the baseline values set out in tab 5 of the metric sheet can be used to determine how much "impact" there has been to non-zero rated habitats.
There are only four types of area-based habitat that have a value of zero:
Developed land; sealed surface
Artificial unvegetated, unsealed surface
Built linear features
Unvegetated garden
To prove that you are exempt, you should do the following:
Use the Joe's Blooms tool normally, up to the BNG Solution Finder
At this point, if you intend to produce a metric sheet to prove you are exempt, press "continue", and click continue past the warning boxes that appear
Complete the last stages of the Joe's Blooms tool
Press "Get Metric"
Download the De Minimis Calculator
Follow the instructions set out in the video below.
If your site is exempt, this will be clearly displayed in tab 3 of the De Minimis Checker - along with the evidence you need to prove this to the LPA.