Do I Need a Heritage Impact Assessment? 2026 Decision Guide
Strictly, no UK statute uses the words 'Heritage Impact Assessment'. The legal trigger is the NPPF ¶200 obligation on the applicant to describe the significance of any affected heritage asset 'proportionate to the asset's importance'. The LPA then exercises its LBCAA 1990 s.16 or s.66 duty to have special regard. For Grade I, Grade II* and demolition cases the proportionate evidence is a full HIA; for Grade II minor works a shorter Heritage Statement suffices.
Five tests for whether you need an HIA
- Designation test. Is the asset designated (Grade I, II*, II) or curtilage-listed? If yes, you need at least a Heritage Statement.
- Conservation-area test. Is the site within a conservation area? LBCAA 1990 s.72 applies; expect to provide a short statement.
- Setting test. Will the proposal affect the setting of a designated asset, even if not on it? GPA 3 applies.
- Locally-listed test. Is the asset on the LPA's local list? NPPF ¶209 requires a balanced judgement.
- Pre-app test. Has the LPA issued pre-application advice naming the document required? That advice is the single most reliable signal.
What happens if you submit the wrong type
If you submit nothing where a statement is required, the application is returned unvalidated and the planning clock does not start. If you submit a Heritage Statement where the LPA wanted an HIA, expect a Regulation 25 request for further information, which adds three to eight weeks. If you submit an HIA where a Statement would have sufficed, the application validates but you have over-paid the consultant.
When you do not need any heritage document
If the asset is wholly undesignated, not on any local list, not in a conservation area and not affecting the setting of a designated asset, no heritage submission is required. Confirm this with the LPA's published local validation list before assuming so; some LPAs require a heritage screening note even where the answer is 'no impact'.
The four likely verdicts
- No statement needed. Wholly undesignated site, no conservation-area or setting issues.
- One-page Heritage Statement. Grade II internal-only minor works, or minor works in a conservation area.
- Full HIA. Grade I, Grade II*, demolition, major external works, or any case where pre-app advice asks for one.
- HIA plus Archaeology DBA. Demolition in a sensitive setting, ground disturbance on a known archaeological site, or where the LPA has conditioned a DBA.