BNG exemptions are the list of developments the statutory biodiversity net gain requirement does not apply to, and a developer reads them before the appraisal because net gain on a small site is a cost measured in habitat units bought from a bank or delivered on land the scheme does not have: the requirement to leave habitat measurably better than before, secured for decades, applies to most planning permissions, but not to householder applications, not to development that affects less than a small area of habitat and no priority habitat, the de minimis exemption, not to self-build and custom-build schemes of a small number of dwellings on a small site, and not to certain other categories the guidance names. Permitted development is outside the requirement altogether because there is no permission to condition, which is one reason the class Q route and the householder classes are worth more than they look. This page sets out the exemptions as a developer reads them on a plot, and what net gain costs a site that is caught.
The exemptions, one by one
Householder applications are exempt; so is development that does not impact a priority habitat and impacts less than the small area or length of habitat the regulations set, the de minimis; so are self-build and custom housebuilding schemes below the dwelling count and the site area the regulations set; so are urgent Crown development, some biodiversity gain sites themselves and the development the regulations list. Each exemption has a test with figures, the guidance cited below states them, and an application that claims one has to show it in the biodiversity statement.
Permitted development and the class Q route
The requirement bites on a planning permission through a condition the law implies, so development permitted by the order itself, class Q conversions, the householder envelope, class R changes, carries no net gain requirement, and a barn converted under class Q avoids a cost a barn converted under a planning application carries. That is part of why the developer reads the permitted route first, and the class Q sheet on this site reads whether the barn fits it.
What net gain costs a small site that is caught, and what the file keeps
A caught site must deliver the gain on site, on other land it secures, or by buying units from a habitat bank or statutory credits as the last resort, and the units are priced by habitat type and distinctiveness; on a small greenfield plot the cost of units can be a material share of the land value. The developer reads the habitat on the plot, scores the baseline and the gain with the metric, and prices the units before the offer; Curtilo Pro keeps the exemption claimed or the units priced against the plot, and the guide on the valuation of development land sets out where the cost sits.
Questions people ask about bng exemptions
Are householder extensions exempt from biodiversity net gain?
Yes, householder applications are exempt, and works under the householder permitted development classes never engaged it. A larger scheme on a house, such as a new dwelling in the garden, is not householder and is read against the de minimis.
Does class Q barn conversion need biodiversity net gain?
No. The requirement attaches to planning permissions; a class Q prior approval is not one. A barn converted by planning application is caught unless another exemption applies.
What is the de minimis exemption?
Development that does not impact a priority habitat and impacts less than the area or length of habitat the regulations set. The figures are in the guidance cited below and the application has to evidence them.
Sources
- GOV.UK, Biodiversity net gain exemptions: the developments the requirement does not apply to, and the de minimis, self-build and householder exemptions
- GOV.UK, Biodiversity net gain: what it requires of a development, the metric, the habitat bank and the gain plan
- GOV.UK planning practice guidance, When is permission required: development, permitted development rights, prior approval and article 4 directions