Cemex (UK) Operations Ltd v Richmondshire District & Anor

In determining a retrospective planning application, the authority may assess the development as built, but must still apply the same legal and policy standards governing a prospective application. Where noise exceeds the significant observed adverse effect level, the authority must consider policy discouraging reliance on closed windows and either secure suitable mitigation or explain the balance struck. It must also consider whether a new dwelling may expose an established business to unreasonable restrictions at a future minerals-permission review. Ex post facto evidence cannot fill gaps in the recorded decision-making process.

The claimant, an operator of a quarry and asphalt plant, challenged the defendant local planning authority’s grant of retrospective permission for converting a barn into a dwelling near the plant. The challenge concerned noise mitigation, the effect of the development on the established quarry, the forthcoming review of the minerals permission, and the absence of conditions securing proposed mitigation.

Grounds 1 and 2 alleged improper constraints arising from the development being complete and occupied. Ground 3 concerned national noise policy and guidance on closed windows. Ground 4 concerned the possible effect of the future minerals-permission review. Ground 5 challenged the omission of further conditions.

1. Grounds 1 and 2. A local planning authority considering an application to regularise existing development may assess the property as built. That does not lower the threshold of acceptability or prevent the authority from requiring further mitigation or refusing permission. Grounds 1 and 2 were rejected.
2. Ground 3. The noise assessment identified significant observed adverse effect levels during day and night. Policy treated reliance on keeping windows closed as undesirable and indicated that suitable alternative ventilation was likely to be necessary. Confirmation that background ventilation complied with the Building Regulations did not address purge ventilation, the consequences of closed windows, or the noise policy. The authority therefore had either to secure mitigation designed to avoid the significant observed adverse effect level or to take the policy into account and justify a different balance. Ground 3 was made out.
3. Ground 4. The authority recognised the need to protect the quarry but did not consider whether a similar noise condition might be imposed at the 2025 review of the minerals permission, or the risk that such a condition could unreasonably restrict the established business. That possibility required consideration under paragraph 123 of the NPPF. The officer’s witness evidence could not plug the gap. Ground 4 was made out.
4. Ground 5. The authority had not shown that it considered securing the retention of the glazing and blocked trickle vents. However, condition 3 could provide a route for future control where proposed window works amounted to development. Relief was therefore refused on this ground under section 31(2A) of the Senior Courts Act 1981.
5. The court could not conclude that the outcome would inevitably have been substantially the same had the errors on Grounds 3 and 4 not occurred. The planning permission was quashed.