The Urban Greening Factor (UGF) is the London Plan's scoring system for how much genuine greening a development delivers. Under Policy G5, major developments in London must treat urban greening as a fundamental element of site and building design — and the interim targets are concrete: a UGF of at least 0.4 for predominantly residential schemes and 0.3 for predominantly commercial schemes. Miss the target without good justification and expect officer pushback, redesign requests, or a refusal reason.
This guide explains how the UGF calculation works, which surfaces score what, and the practical moves that lift a failing score — the same questions we answer every week when preparing sustainability statements for London applications.
What is the Urban Greening Factor?
The UGF is a simple area-weighted ratio. Every surface in the proposed scheme is assigned a factor between 0 and 1 according to its greening value, and the calculation is:
UGF = Σ (surface factor × surface area) ÷ total site area
A site covered entirely in semi-natural vegetation would score 1.0; a site fully sealed in concrete scores 0. Real schemes land in between, and the design task is to push the weighted average over the policy target. The method comes from the London Plan and is fleshed out in the Mayor's Urban Greening Factor London Plan Guidance, adopted in February 2023, which standardises how boroughs apply the policy and how surface types are defined and evidenced.
Selected surface factors
The guidance contains the full table; these examples (from the London Plan's published factor list) show the spread:
| Surface type | Factor |
|---|---|
| Semi-natural vegetation maintained or established on site | 1.0 |
| Wetland or open water (semi-natural, not chlorinated) | 1.0 |
| Intensive green roof or vegetation over structure (substrate ≥150 mm) | 0.8 |
| Extensive green roof (substrate ≥80 mm, meeting GRO Code) | 0.7 |
| Flower-rich perennial planting | 0.7 |
| Hedges | 0.6 |
| Amenity grassland | 0.4 |
| Permeable paving | 0.1 |
| Sealed surfaces (concrete, asphalt, standard roofing) | 0 |
Two things stand out. First, quality matters more than quantity: a wildflower-rich planting bed scores nearly double amenity grass. Second, roofs are where constrained urban sites win or lose — on a dense site the roof plane is often the largest single surface available for greening, and the difference between a standard membrane (0) and an extensive green roof (0.7) can carry the whole calculation.
Who does Policy G5 apply to?
Policy G5 directs boroughs to apply the UGF to major developments — broadly, schemes of 10 or more homes or 1,000 m²+ of floorspace. But the direction of travel is wider: boroughs are expected to set their own UGF requirements through local plans, and several London boroughs now apply UGF expectations to smaller schemes or set higher local targets. Always check the borough's validation list and local plan policy alongside the London Plan — the sustainability statement should address both.
Outside London, there is no national UGF requirement, but the concept is spreading: several councils across England have adopted or are consulting on urban greening factor policies modelled on the London approach. If you are building outside the capital, the equivalent pressures usually arrive through biodiversity net gain and local green infrastructure policies instead.
UGF, BNG and your sustainability statement
The UGF sits alongside — not instead of — the 10% biodiversity net gain requirement of the Environment Act 2021. They measure different things: BNG counts habitat units and their ecological value; the UGF counts greened surface area and its urban benefits (cooling, amenity, surface-water management). A green roof can help both scores; a chlorinated water feature helps neither. Because the same drawings feed both calculations, it is far cheaper to design them together than to bolt one on after the other fails. In practice the UGF calculation, BNG position, water efficiency and any BREEAM requirement are all evidenced in one place: the sustainability statement submitted with the application. For circular economy requirements on referable schemes, see our guide to London Plan Policy SI 7.
How to lift a failing UGF score
- Green the roofs first. Extensive green roofs at 0.7 are the biggest single lever on constrained sites — and they support SuDS and BNG cases at the same time.
- Upgrade planting quality. Swapping amenity grass (0.4) for flower-rich perennial planting (0.7) raises the score with no extra land take.
- Un-seal the ground plane. Every square metre moved from sealed surface (0) to permeable paving (0.1) or planting (0.4–0.7) counts, including parking areas.
- Use boundaries. Hedges (0.6) along boundaries and between plots outscore fences at zero.
- Add trees strategically. Tree planting scores through its canopy or pit area, so well-placed street trees over generous soil volumes contribute meaningfully — and support borough tree-canopy targets.
- Evidence it properly. The GLA guidance expects a UGF calculation table referenced to a landscape plan, with substrate depths and specifications shown — an unevidenced number invites a holding objection.
How Fortress Associates can help
Our sustainability statement service produces a free, site-specific sustainability statement for UK planning applications in minutes. It covers energy, water efficiency with the 110 litres-per-person-per-day Part G calculator, the 10% biodiversity net gain requirement under the Environment Act 2021, urban greening — including the Urban Greening Factor for London sites under Policy G5 — and BREEAM where required. It covers every UK local authority, for new homes, extensions, commercial and mixed-use schemes. Contact us to talk through a scheme that needs a bespoke greening strategy.
Sources & further reading
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