Substantial harm to heritage assets, explained

What "substantial harm" means

Substantial harm is harm to a designated heritage asset, listed building, conservation area, scheduled monument or registered park and garden, that is so serious it drains away or vitiates the asset's significance. It is the upper end of the harm spectrum in the NPPF, sitting above "less than substantial harm" and below "total loss".

The NPPF framework

Paragraphs 206 and 207 of the NPPF apply to substantial harm or total loss. Such harm should be exceptional for Grade II buildings and conservation areas, and wholly exceptional for Grade I, Grade II* buildings, scheduled monuments and registered battlefields. Even where exceptional, consent should be refused unless the harm is necessary to achieve substantial public benefits that outweigh it, or specific tests in paragraph 207 are met.

Less than substantial harm, the more common category, is dealt with under paragraph 208. Such harm should be weighed against the public benefits of the proposal, including, where appropriate, securing the optimum viable use of the asset.

How the courts have interpreted it

The leading authority is Bedford BC v SSCLG [2013] EWHC 4344 (Admin), in which Jay J held that substantial harm "must be a high standard" and described it as harm that "vitiates" or "drains away" the significance of the asset. R (Forge Field Society) v Sevenoaks DC [2014] EWHC 1895 (Admin) and Mordue v SSCLG [2015] EWCA Civ 1243 reinforced both the high bar and the considerable importance and weight to be given to the section 66(1) statutory duty.

Practical examples

• Substantial harm: demolition of a listed building, loss of all principal historic plan form, removal of the entire historic interior
• Less than substantial harm (upper): major rear extension affecting historic fabric, removal of significant historic features
• Less than substantial harm (lower): rooflights on a rear roof slope, replacement of late-twentieth century windows, internal services routes through later fabric
• No harm or enhancement: reinstatement of historic features, removal of inappropriate later additions, sympathetic repair

Less than substantial harm

The vast majority of refused applications involve less than substantial harm. The category is broad, covering everything from negligible impact to harm that approaches the substantial threshold, and the weight given to harm within the category increases with the severity. Heritage statements should locate the impact on this internal spectrum, not just identify the category.

The public benefits balance

Where harm is identified, NPPF paragraphs 207 (substantial) and 208 (less than substantial) require the harm to be weighed against public benefits. Public benefits can include heritage benefits (repair, reinstatement, securing optimum viable use), economic benefits, social benefits and environmental benefits. The benefits must be public, private benefit to the applicant carries no weight.

Evidencing harm in practice

• Identify significance phase by phase, with reference to the listing entry
• Assess each element of the proposal against the significance it engages
• Locate the impact on the harm spectrum, and justify that location
• Identify and evidence each public benefit, with quantification where possible
• Engage explicitly with the section 66(1) statutory duty and recent appeal decisions

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