Less-Than-Substantial Harm (NPPF Paragraph 208): How the Balance Works
On 17 August 2026 the Government published a revised National Planning Policy Framework, which is a material consideration in decisions from that date. It restructured the historic environment chapter into thematic policies (HE1 to HE9) and no longer uses the term 'less than substantial harm' explained below, which does not appear in the 2026 Framework.
Under the 2026 Framework, applicants assess the significance of the assets affected and the likely effect of the proposal under Policy HE5, on a five-point scale: positive effect, no effect, harm, substantial harm, or total loss. The two-tier ‘substantial / less than substantial harm’ test has been removed and the phrase ‘less than substantial harm’ no longer appears. Harm to a designated heritage asset is now weighed under Policy HE6, where any harm is a matter of considerable importance and weight; non-designated assets are dealt with under Policy HE7. The explanation below describes the framework that applied until 16 August 2026 and is being updated. Always check the current NPPF at gov.uk.
Where a proposal will lead to less-than-substantial harm, NPPF ¶208 requires the LPA to weigh the harm against the public benefits of the proposal, including (where appropriate) securing its optimum viable use. This is a balancing exercise, not a presumption against, but the special-regard duty under LBCAA 1990 s.66 means even minor harm carries 'considerable importance and weight' (Forge Field).
The spectrum of less-than-substantial harm
Less-than-substantial harm is not binary. The HIA should locate the harm on the spectrum: 'at the lower end', 'in the middle', 'at the higher end (approaching substantial)'. The higher up the spectrum, the more public benefit the LPA will require to justify consent.
What counts as public benefit
- Securing the optimum viable use of the asset (e.g. residential conversion that funds repair).
- Heritage enhancement (removal of unsympathetic later additions, reinstatement of lost features).
- Public access where none existed.
- Environmental benefits (PV on a non-prominent slope securing decarbonisation).
- Economic benefits where significant (employment, town-centre vitality).
What does NOT count as public benefit
The private financial benefit to the applicant. The fact that the works are needed for the applicant's preferred use of the site. These are routinely cited by applicants and routinely discounted by Inspectors.
Worked example
A rear extension to a Grade II terraced house in a conservation area causes harm at the lower end of less-than-substantial (removal of part of the rear elevation, loss of one historic window). The public benefits are: (a) securing optimum viable use as a family home, (b) reinstating a pattern of historically-correct rear glazing, (c) enabling retention of front-elevation original features through funded repair. The LPA balance lands on consent.