Summary of Key Statutory Amendments in SI 2024/579
The Town and Country Planning (General Permitted Development) (England) (Amendment) Order 2024 (Statutory Instrument 2024 No. 579) came into force on 21 May 2024, representing the most extensive reform of agricultural permitted development since 2018.
The changes aimed to accelerate rural housing delivery by encouraging smaller, more affordable family dwellings rather than a handful of sprawling luxury barn conversions. To achieve this, the government restructured the internal dwelling allowances and introduced new design flexibilities.
Historically, Class Q strictly prohibited any expansion beyond the external envelope. Under SI 2024/579, developers can construct a single-storey rear extension protruding up to 4 metres, provided it is sited on existing hardstanding built before 24 July 2023.
Old Class Q vs. New Class Q: Detailed Comparison
Prior to May 2024, Class Q permitted a complex two-tier system: up to 3 'larger homes' (capped at 465 sq m each) or up to 5 'smaller homes' (capped at 100 sq m each), with an aggregate maximum of 5 dwellings and 865 sq m.
The 2024 amendment simplified this structure into a single unified formula: up to 10 dwellings with a maximum aggregate floorspace of 1,000 sq m, subject to an absolute ceiling of 150 sq m for any single residential unit.
| Parameter | Pre-May 2024 Rules | Post-May 2024 Rules (SI 2024/579) |
|---|---|---|
| Maximum Dwellings | 5 dwellings | 10 dwellings |
| Cumulative Floorspace Cap | 865 sq m | 1,000 sq m |
| Maximum Individual Unit Size | 465 sq m (Larger dwelling) | 150 sq m (All dwellings) |
| Extensions Permitted | Strictly 0m (Must stay in envelope) | Up to 4m rear single-storey on existing hardstanding |
| Qualifying Baseline Date | 20 March 2013 | 24 July 2023 |
| Non-Agricultural Buildings | Strictly excluded | Included if formerly part of agricultural unit |
Transitional Provisions and Strategic Planning Implications
To avoid disadvantaging schemes already designed under the previous rules, Regulation 4 of SI 2024/579 introduced transitional arrangements running until 20 May 2025. During this period, landowners could submit prior approval applications under either the old or new rules.
For developers seeking to build 1 or 2 large luxury homes up to 465 sq m, the old rules were superior. For landowners seeking maximum density and capital return (e.g. creating 6 to 8 starter homes or holiday cottages), the new 2024 framework provides unprecedented commercial scope.