Class Q vs full planning, £-delta
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.
For a 200 m² barn, Class Q lands at £7,690 to £14,640 in pre-build cost, against £8,106 to £28,956 for the equivalent full planning route. The headline gap is £16,000 but refusal risk on a borderline Class Q can wipe the saving.
Same barn, both routes
Worked example: 200 m² stone threshing barn, sub-divided into two 100 m² units. Fee schedule from gov.uk planning fees.
Class Q fee (2 x £120)
£240
Class Q consultant
£3,500 - £5,000
Class Q drawings
£2,750 - £7,000
Structural appraisal
£1,200 - £2,400
Class Q sub-total
£7,690 - £14,640
Full planning fee (2 x £578)
£1,156
Pre-app
£450 - £1,800
Design and access statement
£2,000 - £6,000
Ecology and arboriculture
£2,500 - £8,000
BNG metric and unit plan
£2,000 - £12,000
Full planning sub-total
£8,106 - £28,956
The refusal-risk premium
A failed Class Q costs the consultant fee, drawings, structural appraisal and the £120 fee. A re-submission as a fresh prior-approval is permitted, but a borderline barn will typically lose twice. Modelling a 30% refusal probability turns a £14,000 Class Q into an expected £18,000 to £23,000 once re-submission cost is added, narrowing the gap to full planning.
The non-monetary trade-offs
- Class Q gives 56 days; full planning gives 13 weeks plus pre-app.
- Class Q caps design freedom; full planning unlocks new openings, dormer roofs, single-storey extensions.
- Class Q escapes BNG today; full planning must address the 10% mandatory gain.
Sources cited on this page