- Decision
- allowed, 24 September 2026
- Decided by
- Planning Inspector: N Bowden
- Authority
- Three Rivers (East of England)
- Appeal reference
- 6010198
- Application reference
- 26/0236/FUL
- Procedure
- written representations
- Development
- Demolition of a mid-20th-century chalet bungalow and a larger self-build replacement dwelling in the Green Belt and Heronsgate Conservation Area
- Homes
- 1
- Site context
- green belt, conservation area, PDL
- Green Belt
- Yes (grey belt not argued)
- Framework applied
- August 2026 NPPF
- Determinative policies
- GB7(1)(e)
- Development plan policies
- Three Rivers Core Strategy CP1, CP11, CP12, Three Rivers Development Management Policies LDD DM1, DM2, DM3, Appendix 2
- Main issues
- Green Belt inappropriateness and openness; Heronsgate Conservation Area
Summary
A larger self-build replacement for a 1950s chalet bungalow in Heronsgate, a low-density Chartist settlement washed over by the Metropolitan Green Belt. The replacement was materially larger, so it failed GB7(1)(b). But the plot was previously developed land because Heronsgate is not a built-up area, and there would be no harm to openness, so it passed GB7(1)(e). The conservation area was preserved. Allowed.
Issues and findings
- Transition. "The changes to the Framework could affect the merits of this case in a material way and I, therefore, consulted the parties with regard to these changes." (DL ¶2).
- Local policy weight. DM2 "pre-dates the current Framework but is, broadly, not materially inconsistent with national decision-making policies in the Framework." (DL ¶7).
- GB7(1)(b): FAIL. "the proposal would well exceed the size of the original and/or existing building and would be materially larger than the one it replaces" (DL ¶10).
- PDL. Heronsgate lacks street lighting, footways and building lines: "I must therefore conclude that the site is not within a built-up area." (DL ¶12). "Nevertheless, the site is previously developed land." (DL ¶13).
- GB7(1)(e): PASS. "I have found that the proposed dwelling would be materially larger than the one it replaces. However, this is not the test of this element of the policy of the Framework which requires that a proposal should not cause substantial harm to the openness of the Green Belt." (DL ¶14). "I do not find it to be so significant that it would cause harm to the openness of the Green Belt in a visual or spatial dimension" (DL ¶15).
- Conclusion. "the proposal complies with the requirements of paragraph 1. e. to policy GB7 of the Framework and is therefore also in accordance with policy CP11 of the Three Rivers Core Strategy (TRCS) and policy DM2 of the TRLDD" (DL ¶16). This sits awkwardly with the DM2 conflict found at DL ¶10.
- Conservation area: no harm. "I am unable to find that it would harm the character or appearance of the CA" (DL ¶22).
- BNG. "SBCH is exempted from providing a 10% net increase in biodiversity" (DL ¶25), so self-build is secured by condition.
Planning balance
None needed: not inappropriate under GB7(1)(e), CA preserved, plan compliance (DL ¶36).
What made the difference
Reading residential curtilage in a washed-over, low-density village as previously developed land, because the Annex B exclusion covers gardens only in built-up areas. That opened GB7(1)(e), whose openness test the larger house passed, when GB7(1)(b) could not be met.
Transferable points
- A replacement dwelling that fails GB7(1)(b) as materially larger can still pass GB7(1)(e), where the plot is PDL and openness harm is not substantial (DL ¶14-16).
- Annex B's exclusion of residential gardens from PDL applies only in built-up areas; a verdant, very low-density Green Belt settlement is not built-up (DL ¶11-13).
- Caution: a local policy with a stricter original-building size test (DM2) was called broadly consistent and then treated as satisfied via GB7(1)(e) (DL ¶7, ¶10, ¶16).
Policy findings
Policy codes are those of the National Planning Policy Framework (August 2026) unless a development plan is named.
| Policy | Finding | Weight | Note |
|---|---|---|---|
| GB7(1)(b) | fail | replacement well exceeds the size of the original/existing and is materially larger (DL 10) | |
| AnnexB:PDL | pass | garden land counts as PDL because Heronsgate, though developed, is not a built-up area (verdant, very low density, no footways or street lights, lane-like roads) (DL 11-13) | |
| GB7(1)(e) | pass | no harm to openness in visual or spatial terms, so no substantial harm (DL 14-16) | |
| Transitional(2) | neutral | DM2 found broadly not materially inconsistent (DL 7), found in conflict on size (DL 10), then said to be complied with (DL 16) - internal inconsistency | |
| HE6(1) | pass | larger but muted replacement of a neutral modern building; plot layout unaltered; CA character and appearance preserved (s72, HE9(2)) (DL 19-23) | |
| HE9 | pass | HE9(2) relative significance of the element replaced (DL 21-22) |
Key facts
- Appellant's case framed on 2024 paras 154(d) and (g); inspector maps them to GB7(1)(b) and (e) (DL 8)
- Self-build secured by condition so the BNG self-build exemption applies; application made before 6 Aug 2026 (DL 25, 34)
- Permitted development rights not removed; CA is Article 2(3) land (DL 35)
Sources
This note is one of the decisions behind the NPPF 2026 Navigator, which shows how each Framework test has been applied across all the decisions in the database. Also available as Markdown.