Householder permitted development
Extensions, outbuildings, and ancillary works that fall within Class A to H of the General Permitted Development Order are not classed as development for BNG purposes and are exempt.[S4]
Self and custom build (exemption removed 6 August 2026)
Until 6 August 2026 a single-dwelling self-build on a curtilage under 0.5 ha was exempt under the Self-Build and Custom Housebuilding Act 2015. For planning applications made on or after 6 August 2026 that exemption has been removed; such schemes now rely on the 0.2 ha small-sites exemption where the site qualifies. Applications validated before 6 August 2026 continue under the previous rules.[S4]
Small sites under 0.2 ha (in force 6 August 2026)
A site below 0.2 ha containing no priority habitat is exempt regardless of dwelling count for planning applications made on or after 6 August 2026. This is the headline carve-out of the regulations laid before Parliament on 13 July 2026 and in force since 6 August 2026; the 0.2 ha boundary applies to the red-line application boundary, not the developable area.[S4]
Temporary development (in force 6 August 2026)
Development that is only permitted for a period of 5 years or less is exempt from mandatory BNG, provided the whole development is temporary and there is no impact to any onsite priority habitat as defined under the NERC Act. Where the same temporary development has had earlier grants of permission, the total period across all grants cannot exceed 5 years. A permanent development that includes a temporary phase does not qualify. Typical cases are seasonal polytunnels, touring caravan or glamping pitches, temporary construction compounds, and short-life mineral extraction accesses. If temporary works damage onsite priority habitat, BNG applies in full.[S4]
De minimis test
Below 25 sqm built footprint with no priority habitat impact, the development is exempt by the de minimis test even on a parcel above 0.2 ha. A single extension on a large agricultural holding can fall under this.
Claiming the exemption
The exemption is claimed on the planning application form (validation checklist Section X). The LPA validates the claim; mis-claim risks delayed decision or refusal. An ecologist sign-off is sensible for the priority-habitat element of the test.