Class Q 10-dwelling site cap
Class Q now permits up to 10 dwellings on a single agricultural unit, capped at 1,000 m² total floor space across the planning unit. Multi-unit Class Q becomes unviable above that threshold, pushing larger farmstead schemes into full planning.
The two caps that bind together
Per dwelling: 150 m². Per planning unit: 10 dwellings totalling no more than 1,000 m². A farmstead with a stone threshing barn, a Dutch barn and a modern shed could in principle take all three down the Class Q route, provided the cumulative floor space stays inside 1,000 m².
Aggregation across the planning unit
The cap aggregates across the same established agricultural unit. Splitting ownership shortly before submission does not reset the cap. SI 2025/579 closes that loophole by tying the count to the planning unit at the date of application.
When multi-unit Class Q stops working
- Two large barns, each above 150 m² envelope.
- Three or more units pushing past 1,000 m² total.
- Highway access incapable of supporting more than one or two dwellings.
- Local plan policy that materially weighs amenity for multi-unit conversion.
In each case, full planning is the route of last resort, and the BNG, ecology and design budget grow accordingly.