Biodiversity Net Gain cost
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.
Mandatory 10% BNG applies to most full planning applications since February 2024. Cost ranges from £2,000 (on-site, low-baseline site) to £12,000+ (off-site units). Class Q permitted development is not currently caught by BNG.
When BNG applies
Full planning applications validated after 12 February 2024 must demonstrate 10% biodiversity net gain measured by the statutory metric. Class Q prior approval is not on the BNG hook today; that may change in a future legislative round.
Cost stack
Baseline metric (ecologist day rate)
£700 - £1,800
Habitat enhancement plan
£800 - £2,400
On-site delivery (planting, ponds, wildflower)
£500 - £5,000
Off-site BNG units (if needed)
£8,000 - £42,000 each
30-year monitoring contribution
£1,500 - £4,500
How to keep BNG cheap
Convert from a hardstanding or arable baseline (low score, easier to beat) rather than from a meadow or hedgerow (high score, harder). Provide on-site delivery rather than buying units. Hold a hedgerow rather than replacing it.
Sources cited on this page