Urban greening factor and how it is scored

The urban greening factor is a single number between 0 and 1 that describes how much of a site's area is covered by vegetation and permeable surfaces, weighted by how much each surface type contributes. London Plan 2021 Policy G5 sets a target score of 0.4 for developments that are predominantly residential and 0.3 for those that are predominantly commercial. You calculate it by multiplying each surface area by its factor, adding the results and dividing by the total site area.

That arithmetic is simple. Hitting the target on a tight urban plot is not, and the number tends to be the last thing anyone checks before submission.

What the score is actually measuring

The factor rewards depth and permanence rather than appearance. A square metre of semi-natural vegetation retained on site scores the full 1.0. The same square metre as an extensive green roof with shallow substrate scores a fraction of that, and as block paving it scores almost nothing.

Policy G5 applies to major development proposals, so a scheme of ten or more dwellings, 0.5 hectares or more of residential land, or 1,000 m² or more of other floorspace will be asked for a score. Boroughs routinely ask smaller schemes for the calculation as well, and several have written their own target into a local plan policy or a design code.

The score goes in the Landscape Strategy or the landscape chapter of the Design and Access Statement, with a plan showing each area measured and a table setting out the sums. Officers check the plan against the table. Mismatches between the two are the most common reason a calculation gets sent back.

The factor list and the arithmetic

The surface categories most often used on London schemes carry factors along these lines.

Treat that as the shape of the system rather than the authority on it. The definitive category wording, the substrate depths and the soil volumes sit in the Greater London Authority's urban greening factor guidance, which has been revised since the Plan was adopted, so check the current document on london.gov.uk before you build a schedule around it.

A worked example, clearly illustrative. Take a 1,200 m² site with a residential target of 0.4. An intensive podium garden of 300 m² at 0.8 gives 240. Shrub planting of 150 m² at 0.5 gives 75. Four standard trees in connected pits covering 60 m² at 0.8 give 48. An extensive green roof of 400 m² at 0.3 gives 120. The remaining 290 m² of hard landscape, mostly permeable paving, gives 29. Total 512, divided by 1,200, is 0.43. The scheme passes, and it passes because of the podium build-up rather than the roof.

Change the podium to a 150 mm substrate and the same scheme drops below target. Substrate depth is where the score is won.

Where schemes lose points

Four patterns recur.

The first is counting the same area twice, usually a tree canopy over planting beneath it. The calculation measures surfaces, not layers, so overlapping areas have to be allocated once.

The second is counting land outside the red line. Street trees on the adopted highway, an adjoining park and a neighbour's hedge all sit outside the site area and outside the numerator.

The third is tree pits that cannot support the tree. A standard tree only earns its factor where the pit is connected and the soil volume is realistic, which on a podium means a structural depth that the engineer has to agree early. Discovering at technical design stage that the slab cannot take 1 m³ per tree is an expensive way to lose a quarter of your score.

The fourth is the gap between the landscape drawing and the drainage drawing. Rain gardens score well, and they only score where the drainage strategy actually routes water to them. Where the two consultants have not spoken, officers notice.

How it differs from biodiversity net gain

These two are measured differently and secured differently, and conflating them wastes a lot of time on a London scheme because both apply.

The urban greening factor is an area-weighted score about greening and permeability, set by the London Plan, assessed against a target of 0.4 or 0.3 and secured by a planning condition. Mandatory biodiversity net gain is a statutory regime under the Environment Act 2021, measured in biodiversity units using the statutory metric, requiring a 10 per cent uplift and a biodiversity gain plan approved by the authority, with habitat maintained for 30 years. The metric is to be completed by a competent person, and a biodiversity gain plan is a legal requirement rather than a design aspiration.

A high greening factor does not deliver net gain. Amenity grassland and green walls score reasonably on one and poorly on the other. Native grassland left to flower, and retained scrub, do well on both. Designing for the metric first and then reading the greening score off the resulting plan is usually the cheaper order.

Securing the score by condition

Boroughs normally attach a condition requiring a detailed landscape scheme, the urban greening factor calculation as approved, and a maintenance and management plan for a defined period. Some tie the score to a specific drawing number. That is the version you want, because an open-ended requirement to achieve a score is harder to discharge than a requirement to build a drawing.

Watch the wording. A condition that allows the score to be varied later by agreement without a further application strays into the territory of tailpiece conditions, which the courts have treated as unlawful where they let the permission be changed outside the statutory process.

Most greening conditions are pre-commencement or pre-occupation, so they belong on the schedule of conditions you need to discharge before work starts. Budget for the discharge application fee and for the time the landscape officer takes, which on a podium scheme with structural implications is rarely quick.

Outside London

There is no national urban greening factor. The National Planning Policy Framework re-issued on 17 August 2026 expects development to provide green infrastructure and net gains for biodiversity, and the National Design Guide and National Model Design Code both deal with nature and greening, without prescribing a numeric factor. Verify the current policy codes on gov.uk rather than relying on older paragraph numbers.

Several authorities outside London have adopted their own green space factor or urban greening requirement in a local plan or supplementary planning document. Read the adopted policy rather than assuming the London figures apply, because the factor lists differ and so do the targets. Where no local target exists, a calculation can still be worth doing as evidence that the landscape proposals are more than decoration.

This is general guidance, not legal advice. Check the position with your local planning authority or a chartered landscape professional before relying on it.

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