Urban Greening Factor: how the score is calculated
The Urban Greening Factor weights each surface type by function and divides the total by site area. Here is the method, the targets and what officers check.
The Urban Greening Factor is a weighted score for how much of a site is covered by greening that actually functions, and in London a major development is expected to reach 0.4 where it is predominantly residential and 0.3 where it is predominantly commercial. The urban greening factor calculation is a single sum: multiply the area of each surface type by its factor, add the results, and divide by the total site area. The work is in choosing the surface types honestly and evidencing them.
This is a London requirement. Policy G5 of the London Plan introduced it, and it has no direct equivalent in national policy, although some authorities outside London have adopted their own versions.
What the factor measures
The factor is about function rather than appearance. It asks how much of the site contributes to surface water management, cooling, biodiversity and amenity, and it weights surfaces accordingly.
A sealed surface contributes nothing and scores zero. Permeable paving does a little for drainage and scores close to zero. Mown amenity grass does more, but is still well below a semi-natural habitat. Semi-natural vegetation, woodland and open water sit at the top of the scale at 1.0.
Between those anchors the London Plan sets out a full schedule of surface cover types with their factors, covering intensive and extensive green roofs, rain gardens and vegetated drainage features, standard trees in connected pits with adequate soil volume, hedges, green walls, flower-rich perennial planting and groundcover. Take the exact figures from Table 5.1 of the London Plan rather than from a consultant's spreadsheet, because the weightings distinguish between specifications that look similar on a drawing.
Working the calculation on a site area
The method is deliberately simple so that officers can check it.
- Establish the site area used in the calculation, and state it. This is normally the whole application site, and the figure must match the site area given elsewhere in the submission.
- Measure the area of each surface cover type in the proposed scheme, in square metres.
- Multiply each area by the factor for that surface type.
- Add the weighted areas together.
- Divide by the total site area to give the score.
An illustrative worked example on a 2,000 square metre residential site, using only the clearest anchor factors:
| Surface | Area | Factor | Weighted area |
|---|---|---|---|
| Sealed surfaces: roads, footways, roof terrace paving | 900 m² | 0.0 | 0 |
| Permeable paving to parking court | 300 m² | 0.1 | 30 |
| Amenity grassland, regularly mown | 400 m² | 0.4 | 160 |
| Semi-natural vegetation retained and created | 400 m² | 1.0 | 400 |
| Total | 2,000 m² | 590 |
That gives 590 divided by 2,000, or 0.295, against a residential target of 0.4. Converting 300 square metres of sealed surface into semi-natural planting would add 300 to the weighted total and lift the score to 0.445. The example is illustrative and the real calculation will use the full range of surface types.
The target scores and how they work
The London Plan expects 0.4 for developments that are predominantly residential and 0.3 for those that are predominantly commercial. Boroughs are directed to develop their own factor policies, and some have set higher targets or added local surface types, so check the borough's adopted local plan before assuming the London-wide figures apply.
The targets are expectations rather than absolute thresholds. A scheme that falls short can still be acceptable where the shortfall is justified, but the justification has to be specific to the constraints of the site rather than a statement that the layout is fixed. Basement extent, existing trees, servicing requirements and site levels are the constraints that carry weight.
Design towards the score rather than calculating it at the end. Landscape architects who are given the target at the outset will hold ground for it against the parking layout and the refuse strategy, which is exactly the argument that needs to happen early. A scheme measured at the eleventh hour almost always scores below target, and by then the only remaining moves are token planters.
Green roofs, rain gardens and tree canopy
Three elements do most of the heavy lifting on a constrained urban site, and each has a specification that determines its factor.
Green roofs are weighted by substrate depth and by whether they meet the recognised code for green roof construction. A thin sedum mat is weighted far below an extensive roof with proper settled substrate depth, and an intensive roof with deep substrate is higher again. Specify the depth on the drawings, because the factor follows the specification and not the label.
Trees are weighted by soil volume. A standard tree in a connected pit with soil volume proportionate to its expected canopy scores materially higher than the same tree in an isolated pit. Show the pit dimensions and any structural soil or root cell system in the landscape details.
Rain gardens and vegetated drainage features score well and do double duty in the drainage strategy. Coordinating the greening score with the Drainage Strategy means the same features count twice in the submission rather than competing for space.
Evidencing the score in a submission
Officers check three things: the site area, the measured areas, and whether the specification matches the factor claimed.
Submit a colour-coded surface cover plan keyed to the schedule, a table listing each surface type with its area, factor and weighted area, the total and the resulting score, and cross-references to the drawings where each specification is detailed. Where a surface type sits at a boundary between two categories, say which you have used and why.
The most common challenge is over-claiming. Amenity grass presented as species-rich grassland, a sedum blanket presented as an extensive green roof, and trees in small isolated pits claimed at the connected-pit factor are all picked up routinely. A Landscape Strategy that carries the specifications and the maintenance regime is what makes the claimed factors credible.
Where the factor meets other requirements
The greening score overlaps several other obligations, and coordinating them saves both area and fees.
Biodiversity net gain uses a different metric with different units, so a high greening score does not deliver net gain automatically, and the two must be calculated separately. Surface water requirements draw on the same green infrastructure. Play space, amenity space and tree canopy cover policies compete for the same ground. Fire service access routes and vehicle tracking take area out of the greening total, so resolve them before finalising the landscape layout. Podium and basement extent matters most of all, because a slab at high level limits substrate depth and therefore limits the factor available across a large part of the site.
Where a scheme includes a Green Infrastructure Plan, it is the natural home for the combined picture, with the greening calculation presented as one output among several.
But the practical rule is to run the calculation at concept stage and again at every design revision. The score moves every time a parking bay does.
This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.
PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
What Urban Greening Factor score do I need?
The London Plan expects 0.4 for developments that are predominantly residential and 0.3 for those that are predominantly commercial. Boroughs are directed to set their own policies and some have gone further or added local surface types, so check the adopted borough plan before relying on the London-wide figures.
How is the calculation actually done?
Measure the area of each surface cover type in square metres, multiply each by the factor for that type from the London Plan schedule, add the weighted areas together and divide by the total site area. The site area used must match the figure given elsewhere in the application, and the schedule should be submitted as a table.
Does a green roof count the same regardless of build-up?
No. Green roofs are weighted by substrate depth and by whether the construction meets the recognised code, so a thin sedum mat scores well below an extensive roof with proper settled substrate, and an intensive roof scores higher again. Specify the depth and build-up on the drawings, because the factor follows the specification.
Does a good greening score satisfy biodiversity net gain?
No. Biodiversity net gain uses the statutory metric with different units and a different baseline, so the two are calculated separately and neither substitutes for the other. A scheme can reach the greening target while failing to deliver the required biodiversity uplift, particularly where the baseline habitat was better than the proposed planting.
Is the Urban Greening Factor used outside London?
It comes from policy G5 of the London Plan and has no direct national equivalent. Some authorities elsewhere have adopted their own greening factor policies with different weightings and targets, so check the local plan rather than applying the London figures by analogy. National policy addresses greening through other routes.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.