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Policy G5 Urban greening

G5

  1. Major development proposals should contribute to the greening of London by including urban greening as a fundamental element of site and building design, and by incorporating measures such as high-quality landscaping (including trees), green roofs, green walls and nature-based sustainable drainage.
  2. Boroughs should develop an Urban Greening Factor (UGF) to identify the appropriate amount of urban greening required in new developments. The UGF should be based on the factors set out in Table 8.2, but tailored to local circumstances. In the interim, the Mayor recommends a target score of 0.4 for developments that are predominately residential, and a target score of 0.3 for predominately commercial development.

The inclusion of urban greening measures in new development will result in an increase in green cover, and should be integral to planning the layout and design of new buildings and developments. This should be considered from the beginning of the design process.

Urban greening covers a wide range of options including, but not limited to, street trees, green roofs, green walls, and rain gardens. It can provide a range of benefits including amenity space, enhanced biodiversity, addressing the urban heat island effect, sustainable drainage and amenity – the latter being especially important in the most densely developed parts of the city where traditional green space is limited.

A number of cities have successfully adopted a ‘green space factor’ to encourage more and better urban greening. The Mayor has developed a generic Urban Greening Factor model to assist boroughs and developers in determining the appropriate provision of urban greening for new developments. This is based on a review of green space factors in other cities[106]. The UGF is currently only applied to major applications, but may eventually be applied to applications below this threshold as boroughs develop their own models. London is a diverse city so it is appropriate that each borough develops its own approach in response to its local circumstances. However, the challenges of climate change, poor air quality and deficiencies in green space need to be tackled now, so while each borough develops its own bespoke approach the Mayor has recommended the standards set out above. Residential development places greater demands on green infrastructure, and as such, a higher standard is justified.

[106] Urban Greening Factor for London https://www.london.gov.uk/sites/default/files/urban_greening_factor_for_...

The Urban Greening Factor for a proposed development is calculated in the following way:

(Factor A x Area) + (Factor B x Area) + (Factor C x Area) etc. divided by Total Site Area

So, for example, an office development with a 600 sqm  footprint on a site of 1,000 sqm  including a green roof, 250 sqm  car parking, 100 sqm  open water and 50 sqm  of amenity grassland would score the following;

(0.7 x 600) + (0.0 x 250) + (1 x 100) + (0.4 x 50) / 1000 = 0.54

So in this example, the proposed office development exceeds the interim target score of 0.3 for a predominately commercial development under part B of Policy G5 Urban greening.

Table 8.2 - Urban Greening Factors

Surface Cover TypeFactor
Semi-natural vegetation (e.g. woodland, flower-rich grassland) created on site.1
Wetland or open water (semi-natural; not chlorinated) created on site.1
Intensive green roof or vegetation over structure. Vegetated sections only. Substrate minimum settled depth of 150mm – see livingroofs.org for descriptionsA.0.8
Standard trees planted in natural soils or in connected tree pits with a minimum soil volume equivalent to at least two thirds of the projected canopy area of the mature tree – see Trees in Hard Landscapes for overviewB.0.8
Extensive green roof with substrate of minimum settled depth of 80mm (or 60mm beneath vegetation blanket) – meets the requirements of GRO Code 2014C.0.7
Flower-rich perennial planting – see Centre for Designed Ecology for case-studiesD.0.7
Rain gardens and other vegetated sustainable drainage elements – See CIRIA for case-studiesE.0.7
Hedges (line of mature shrubs one or two shrubs wide) – see RHS for guidanceF.0.6
Standard trees planted in pits with soil volumes less than two thirds of the projected canopy area of the mature tree.0.6
Green wall –modular system or climbers rooted in soil – see NBS Guide to Façade Greening for overviewG.0.6
Groundcover planting – see RHS Groundcover Plants for overviewH.0.5
Amenity grassland (species-poor, regularly mown lawn).0.4
Extensive green roof of sedum mat or other lightweight systems that do not meet GRO Code 2014I.0.3
Water features (chlorinated) or unplanted detention basins.0.2
Permeable paving - see CIRIA for overviewJ.0.1
Sealed surfaces (e.g. concrete, asphalt, waterproofing, stone).0