The Facts and Ruling of Hibbitt v SSCLG [2016]
The leading case governing the structural viability of Class Q applications is Hibbitt and another v Secretary of State for Communities and Local Government [2016] EWHC 2853 (Admin). The case concerned an agricultural building consisting of a steel portal frame and corrugated roof, but which was largely open to the elements on three sides.
The High Court held that enclosing an open barn by constructing four entirely new external walls and installing extensive structural supports went far beyond what could reasonably be described as 'conversion'. Mr Justice Green established that where the works amount to rebuilding or the creation of a new building in substance, the development is ultra vires Class Q and requires full planning permission.
Planning inspectors routinely cite Hibbitt to refuse schemes where new walls are built across open bays. If you are building walls through 'fresh air' where no substantial agricultural cladding existed, the scheme will be treated as an unlawful rebuild.
Planning Practice Guidance (PPG) Paragraph 105 Criteria
Following the Hibbitt ruling, the government updated Planning Practice Guidance (PPG) Paragraph 105 (Reference ID: 13-105-20180615). The guidance explicitly confirms that it is not the intention of permitted development to allow new buildings to be constructed in the countryside.
LPAs must evaluate whether the existing building is structurally strong enough to take the loading which comes with the external works to provide the walls and roof. While works such as installing insulation, weatherproofing, windows, and doors are permitted, adding new primary foundations or heavy structural steel framing to prop up a dilapidated shell will trigger a refusal.
| Building Element | Permitted Under Class Q (Conversion) | Prohibited Under Hibbitt (Rebuild) |
|---|---|---|
| External Walls | Re-cladding existing framework; adding insulation and membranes | Erecting full perimeter blockwork where no walls existed |
| Roof Structure | Replacing corrugated sheets with lightweight standing seam metal | Replacing rotted primary trusses or sagging main ridge beams |
| Foundations & Slab | Underpinning for damp proofing; leveling screeds | Pouring completely new primary load-bearing foundation grid |
| Internal Structure | Inserting independent timber-frame studwork and mezzanine floors | Internal frame designed to prop up collapsing external walls |
Commissioning an Unassailable Class Q Structural Survey
To satisfy the LPA's planning officers and avoid a Hibbitt challenge, applicants must instruct a Chartered Structural Engineer (MIStructE) to produce a comprehensive condition report before submitting prior approval.
The engineer must inspect foundations, calculate existing steel or timber section capacities, evaluate wind loadings, and explicitly conclude that the building is structurally sound, stable, and capable of residential conversion without requiring secondary load-bearing structural works.