Walden Manor, Waldens Road, Orpington (rear extension, LBC - substantial harm)

Decision

dismissed, 11 September 2026

Decided by

Planning Inspector: R Sabu

Authority

Bromley (London)

Appeal reference

6006506

Application reference

24/01895/LBC

Procedure

written representations

Development

Listed building consent for demolition of a conservatory and bay window, a flat-roofed single-storey rear extension with lantern across most of the 17th-century rear elevation, and a basement extension

Site context

listed building setting

Green Belt

No

Framework applied

August 2026 NPPF

Determinative policies

HE6(1), HE6(5)

Development plan policies

London Plan 2021 HC1, Bromley Local Plan 2019 Policy 38

Main issues

listed building

Summary

Listed building consent was refused for a single-storey, flat-roofed rear extension across most of the 17th-century rear elevation of Walden Manor, a Grade II house in Orpington. Unusually for a single-storey domestic extension, the inspector found substantial harm, because it would "seriously affect a key element of the asset's significance". The inspector therefore applied the HE6(5) refusal test and not just an HE6(4) balance.

Issues and findings

• Effect. "the height, width and massing of the extension would unacceptably obscure views of large parts of the historic rear elevation … diminish the legibility of the 17th century elevation" (DL ¶11). Full-height glazed doors would "egregiously detract from the legibility and character of the rear elevation" (DL ¶12). Conditions on materials could not overcome that (DL ¶13).
• Degree: SUBSTANTIAL. "The harm would be substantial as the proposal would seriously affect a key element of the asset's significance. In this case, the proposal would unacceptably erode the legibility and character of the 17th century rear elevation" (DL ¶16).
• HE6(1). Quoted in full, including the new "irrespective of whether any potential effect amounts to a positive effect, harm, substantial harm, or total loss" (DL ¶17).
• HE6(5): FAIL. "The Framework states that in this circumstance, consent should be refused unless it can be demonstrated that the harm is necessary to achieve substantial public benefits that outweigh the harm or loss, or if a number of factors apply. The listed factors are not applicable in this case, and the scheme would not give rise to substantial public benefits" (DL ¶20).

Planning balance

The HE6(5) substantial-harm test: refuse unless substantial public benefits necessitate the harm. None were offered. "Public benefits such as enabling energy efficiency are not before me" (DL ¶19), and continued residential use did not depend on the scheme.

What made the difference

The extension would cover most of the width of the 17th-century rear wing, the part of the building whose legibility carries its significance. Treating that as substantial harm set a much higher bar than the usual low or moderate finding for rear extensions. The finding sits at the stringent end of practice. Note that the "seriously affects a key element" test comes from case law (Bedford), and most inspectors reserve it for far greater interventions.

Transferable points

• A single-storey rear extension can be substantial harm where it obscures the elevation that holds the key significance (DL ¶11, ¶16). Use this with care: it is an outlier finding.
• Once substantial harm is found, HE6(5) requires substantial public benefits or all four listed factors; a domestic extension will not meet it (DL ¶20).
• Removing later, non-contributing additions (conservatory, bay) causes no harm (DL ¶10).

Policy findings

Policy codes are those of the National Planning Policy Framework (August 2026) unless a development plan is named.

Key facts

• Grade II house, early 17th-century core refronted in the late 17th or early 18th century; significance in the legibility of the two phases and plan form (DL 6-9)
• Removing the 19th/20th-century conservatory and bay would not harm significance; basement preserves special interest (DL 10, 14)
• Parties consulted on the August 2026 Framework (DL 2)

Sources

• Appeal on the Planning Inspectorate appeals service
• Decision letter (Planning Inspectorate)

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.