Housebuilders have pulled back from the market faster than many expected, and the numbers released this week prove it. On 6 November 2026, Rightmove confirmed that new-home developments on site were 6% lower at the end of October 2026 than they were back in December 2025. At almost the same moment, new biodiversity net gain (BNG) rules for nationally significant infrastructure projects came into force. Put the two together and you get a genuinely two-speed story for biodiversity units: Rightmove new homes developments down biodiversity units on the housing side, but a new wave of long-term demand opening up from major infrastructure.
For landowners, habitat bank operators and developers planning 2027 applications, this is not background noise. It is a shift in who buys biodiversity units, how much, and for how long.
Key Takeaways
- Rightmove reported new-home developments on site down 6% between December 2025 and end-October 2026, with New Homes revenue expected to fall below last year's level.
- Rightmove cut its 2026 ARPA growth guidance from £110-£120 to £100-£110, blaming weaker housebuilder spending entirely.
- From 2 November 2026, NSIP applicants (reservoirs, roads, railways, energy networks) must deliver at least 10% BNG, secured for a minimum of 30 years.
- The Autumn Budget (28 October 2026) confirmed a BNG exemption for brownfield housing sites up to 1.5 hectares, further softening small-site unit demand.
- Supply planning should now reflect two buyer types: smaller, price-sensitive housebuilders and larger, long-duration infrastructure promoters.
Rightmove's Figures Confirm Housebuilders Are Pulling Back
Rightmove's trading update, published 6 November 2026, sets out a clear slowdown in housebuilder activity. The number of new-home developments on site was 6% lower at the end of October 2026 compared with December 2025. Rightmove expects New Homes revenue to come in below last year's level as a direct result.
The company also cut its 2026 average revenue per advertiser (ARPA) growth guidance from £110-£120 to £100-£110, and trimmed overall revenue growth guidance from 6-8% to 6-7%. Rightmove attributed the entire guidance cut to weaker housebuilder spending, not to any wider weakness in its core estate agency business.
Wider housing market indicators support the picture. Rightmove reported buyer demand down 10% and sales agreed down 9%, with asking prices at end-October 0.3% below a year earlier against record stock levels. The average five-year fixed mortgage rate rose from 5% at end-June to 5.5% by 31 October, adding pressure to buyer affordability. Rightmove CEO Johan Svanstrom said: "We are on track to deliver revenue and profit growth within our previous full-year guidance."
These figures sit alongside separate construction data. The UK construction PMI fell to 43.6 in October, reflecting a housebuilding slump, and the RICS Q3 2026 Construction Monitor recorded private housing workloads at -18%. Savills, in a forecast published 4 November 2026, expects UK house prices to fall 1.5% in 2027, with a recovery from 2028 and transaction volumes also falling in 2027.
Why Rightmove New Homes Developments Down Biodiversity Units Matters for Unit Supply
Fewer new-home developments on site means fewer housebuilders actively seeking biodiversity units to discharge their own BNG obligations. When Rightmove new homes developments down biodiversity units becomes the headline trend, it directly reduces one of the two main sources of demand that habitat bank operators and landowners have relied on since mandatory BNG began.
This matters because small and medium housing sites have historically been steady, if modest, buyers of off-site units. If housebuilders are starting fewer developments and delaying others in response to softer buyer demand and higher mortgage rates, their appetite for securing units now is likely to soften too.
The Autumn Budget's confirmation, on 28 October 2026, of a BNG exemption for brownfield housing sites up to 1.5 hectares adds a second layer to this softening. Brownfield schemes under that threshold will no longer need to deliver or buy BNG at all, removing another slice of expected housing-sector demand.
NSIP Biodiversity Net Gain Rules: A New Source of Long-Term Demand
While housing demand softens, a new category of buyer has just entered the market. From 2 November 2026, applicants for Development Consent Orders for nationally significant infrastructure projects in England, new reservoirs, roads, railways and energy networks, must deliver at least 10% biodiversity net gain.
Under the new rules, NSIP applicants must:
- Submit an outline biodiversity gain plan alongside their application
- Provide a biodiversity metric calculation supporting the proposed gain
- Comply with the relevant biodiversity gain statement for their project type
- Deliver gains on site, off site, or through a combination of both
- Legally secure, manage and monitor significant gains for at least 30 years
- Follow a simpler approach where the impact qualifies as temporary
As reported by Open Access Government on 6 November 2026, this requirement is expected to increase demand for off-site biodiversity units, because infrastructure projects often cannot deliver all required gains within their own site boundaries.
A Two-Speed Market for Biodiversity Units
The result is a market splitting into two distinct demand profiles. Housebuilders, facing a slowdown and a brownfield exemption, are typically becoming more cautious and price-sensitive buyers. Infrastructure promoters, by contrast, are entering the market with large-scale, long-duration requirements secured for a minimum of 30 years.
| Buyer type | Current trend | Typical demand profile |
|---|---|---|
| Housebuilders (small/medium sites) | Softening, per Rightmove data | Smaller volumes, shorter planning horizons, more price-sensitive |
| Brownfield housing (under 1.5ha) | Exempt from BNG since Budget | No unit demand from this segment |
| NSIP infrastructure promoters | New requirement from 2 November 2026 | Larger volumes, 30-year secured gains, longer lead times |
For habitat bank operators, this suggests diversifying who they market units to rather than assuming housing will remain the dominant buyer group. For landowners weighing whether to enter unit supply, infrastructure-linked demand may offer more certainty over a longer horizon, even if the pace of individual transactions is slower.
What This Means for LPAs and Developers Planning 2027 Applications
Local planning authorities and developers preparing 2027 applications should treat this update as a prompt to revisit assumptions, not a reason to delay. Housebuilders still progressing schemes above the 1.5-hectare brownfield threshold remain subject to standard BNG requirements. Meanwhile, any developer or promoter connected to infrastructure projects should expect metric calculations and gain plans to come under closer scrutiny given the new 10% minimum and 30-year monitoring commitment.
Typically, earlier engagement with ecological data gives both housebuilders and infrastructure applicants more flexibility in how they meet their obligations, whether through on-site habitat creation or securing off-site units.
Practical Steps for Landowners, Developers and Habitat Bank Operators
- Commission baseline ecological surveys early, before site conditions change with the seasons
- Run biodiversity metric calculations well ahead of submission deadlines, particularly for NSIP applications
- Review whether a housing site qualifies for the brownfield exemption before assuming unit demand
- Habitat bank operators should consider marketing toward infrastructure promoters as well as housebuilders
- Landowners should factor 30-year legal securing and monitoring obligations into any unit supply decision
- Developers should check biodiversity gain statements relevant to their specific NSIP project type
- Build in time for the outline biodiversity gain plan where a scheme involves a Development Consent Order
FAQ
Does the brownfield exemption mean small housing sites never need biodiversity units?
Brownfield housing sites up to 1.5 hectares are exempt from BNG following the Autumn Budget confirmation on 28 October 2026. Sites above that threshold or on greenfield land typically still need to meet standard BNG requirements.
Do NSIP infrastructure projects have to buy off-site units?
Not necessarily. Gains can be delivered on site, off site, or through a combination of both, depending on what a project can achieve within its own boundaries.
How long must NSIP biodiversity gains be secured for?
Significant gains must be legally secured, managed and monitored for at least 30 years under the rules that took effect on 2 November 2026.
Why did Rightmove cut its 2026 guidance?
Rightmove attributed its entire guidance cut, including the ARPA growth reduction from £110-£120 to £100-£110, to weaker housebuilder spending rather than wider market weakness.
Is the housing market expected to recover soon?
Savills' forecast, published 4 November 2026, expects prices to fall 1.5% in 2027 with recovery beginning from 2028, alongside falling transaction volumes in 2027.
Conclusion
This November 2026, the market for biodiversity units is being reshaped from two directions at once. Rightmove's figures confirm that housebuilders are starting fewer developments and spending less, while the Budget's brownfield exemption removes a further slice of small-site demand. At the same time, new NSIP rules are opening a long-term, large-scale demand channel from infrastructure promoters. Landowners, habitat bank operators and developers planning ahead should reassess who their likely buyers are and adjust supply and survey timing accordingly. To understand how these changes affect a specific site or portfolio, contact Biodiversity Surveyors to book a baseline habitat survey or biodiversity metric assessment.