Class Q vs full planning
Costs verified against BCIS Online (May 2026 release) and ONS Construction Output Price Index, April 2026. Class Q rules current to the 21 May 2025 GPDO amendment.
Class Q is cheaper, faster and more constrained. Full planning costs roughly £14,000 more pre-build, takes 12-16 weeks longer, but unlocks new openings, dormers and material design freedom.
Side by side
Statutory fee per dwelling
£120 (Class Q) vs £578 (full)
Consultant package
£3,500-5,000 vs £8,000-22,000
Determination period
56 days vs 13 weeks
BNG (10%)
exempt vs mandatory
150 m² cap per dwelling
binding vs not binding
External design freedom
restrained vs unrestricted
Refusal risk (national, est.)
40-55% vs 8-15% on a good case
Which one for which barn
- Sound stone or steel barn, unrestricted area, under 150 m² per unit: Class Q.
- Listed, AONB, Green Belt or above 150 m² unit: Full planning (no choice).
- Borderline structural condition: Class Q likely to fail; full planning gives officer discretion.
- Multi-unit farmstead under 1,000 m² total: Class Q is the cheaper and faster route.
Sources cited on this page