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-build under the statutory definition
A single dwelling self-build on a curtilage under 0.5 ha is exempt; the definition is the Self-Build and Custom Housebuilding Act 2015 plus the BNG regulations. Multi-plot custom-build over 0.5 ha falls back to the SBM.
Small sites under 0.2 ha (confirmed 31 July 2026)
A site below 0.2 ha containing no priority habitat is exempt regardless of dwelling count. This was the headline carve-out of the 31 July 2026 regulatory update; the 0.2 ha boundary applies to the red-line application boundary, not the developable area.[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.