BNG Biodiversity Net Gain Monitoring Survey Hillingdon, London: Uxbridge, Ruislip, Northwood
Hillingdon Council requires most new developments to deliver at least 10% biodiversity net gain (BNG), secured for 30 years under the Environment Act 2021. This guide covers BNG monitoring requirements in Hillingdon, Uxbridge, Ruislip, Northwood, and across the borough.
Hillingdon BNG Requirements
| Requirement | Detail | | --- | --- | | Minimum BNG | 10% net gain using Defra's Statutory Biodiversity Metric 4.0 | | Biodiversity Gain Plan | Baseline assessment + 30-year Habitat Management Plan submitted before planning approval | | Monitoring schedule | Reports to Hillingdon Council at years 1, 3, 5, 10, 20, and 30 post-completion | | Legal securing | Section 106 agreement or conservation covenant for 30 years | | Pre-commencement | Final HMP and Biodiversity Gain Plan approved before development starts |
Hillingdon De Minimis Exemption
Developments below this threshold are BNG-exempt:
| Condition | Requirement | | --- | --- | | Habitat type | No impact on priority habitat | | Area threshold | Impact on less than 25 m² of habitat with biodiversity value greater than zero | | Linear threshold | Impact on less than 5 m of linear habitat (hedgerows) |
If all three conditions are met, no Biodiversity Gain Plan is required.
What's Included in a BNG Monitoring Survey (Hillingdon)
| Component | Description | | --- | --- | | Baseline habitat survey | UK Hab classification of existing habitats on site | | Biodiversity Metric 4.0 calculation | Pre-development biodiversity value | | Biodiversity Gain Plan | 30-year management plan for Hillingdon submission | | Protected species survey | Preliminary ecological appraisal | | HMMP drafting | Habitat Management and Monitoring Plan for 30-year commitment |
30-Year Monitoring Schedule (Hillingdon)
| Year | Activity | | --- | --- | | Pre-development | Baseline survey + Biodiversity Gain Plan + HMMP | | Year 1 | Initial monitoring report | | Year 3 | Monitoring report + compliance check | | Year 5 | Monitoring report + metric update | | Year 10 | Full monitoring report | | Year 20 | Monitoring report | | Year 30 | Final compliance survey |
BNG Monitoring Survey Costs in Hillingdon (2025)
| Cost Component | Range (ex VAT) | | --- | --- | | BNG baseline survey | £1,200–£5,000+ (small sites) | | Biodiversity Gain Plan | £800–£2,500 | | HMMP drafting | £500–£1,500 | | Council monitoring fees | Varies — confirm with Hillingdon | | Off-site BNG units | From £19,000 per unit | | Statutory biodiversity credits | From £42,000 per credit |
Note: Hillingdon Council's specific monitoring fee schedule should be confirmed directly with the council.
Areas in Hillingdon We Cover
Ice Labz provides BNG monitoring surveys across UB1–UB10, HA4–HA5.
Frequently Asked Questions
Q: When did BNG become mandatory in Hillingdon?
BNG became compulsory for most developments from 12 February 2024 (and for small sites from 2 April 2024) under the Environment Act 2021.
Q: Does my Hillingdon development need BNG monitoring?
If your development is above the de minimis threshold (25 m² habitat impact, 5 m linear impact, no priority habitat), BNG applies. Small housing developments (1–9 homes) also require BNG.
Q: What is Hillingdon's monitoring schedule for BNG?
Reports are required at years 1, 3, 5, 10, 20, and 30 post-completion — more frequent than the national standard schedule of years 2, 5, 10, 15, 20, 25, 30.
Q: Can BNG be delivered off-site in Hillingdon?
Yes — off-site BNG units can be purchased through a conservation covenant or the Natural England statutory credit scheme. Off-site is preferred over statutory credits.
Q: What happens if I can't achieve 10% BNG on my Hillingdon site?
You can purchase off-site BNG units or use Natural England's statutory biodiversity credits as a last resort. Discuss options with your ecologist and Hillingdon planning officer.