Green infrastructure evidence for a school expansion

A school expansion is usually proposed on the only part of the site that is open, which is why green infrastructure evidence decides so many of these applications. Playing field, tree belt, informal grass, hedgerow along the boundary: those are the things the new teaching block has to displace, and each of them brings a different consultee and a different test.

Start with the land, not the building. Draw the green infrastructure of the existing site before the architect draws the extension, because the sequence of those two drawings determines how much of the following year you spend defending the layout.

Why a school site is treated as green infrastructure

School grounds are often the largest area of continuous open land in a residential area. They hold mature trees planted when the school was built, informal grassland that is habitat whatever the mowing regime says, boundary hedgerows that connect to gardens, and permeable surface that handles rainfall the surrounding streets send nowhere.

So the loss of 2,000 m2 of playing field reads differently depending on who is looking. To the local authority as education provider it is the cost of extra classrooms. To the planning authority it is a loss of open space, a reduction in canopy cover, a biodiversity baseline reduction and an increase in impermeable area, all at once.

Set out that multiple function in the evidence rather than letting four consultees discover it separately. A Green Infrastructure Plan is the document that holds the whole picture, with the technical reports sitting beneath it.

Playing field loss and the statutory consultee

Sport England is a statutory consultee under the Development Management Procedure Order on development likely to affect land used as a playing field. The trigger is use of the land as a playing field, which includes land used within recent years, so a pitch that has been left unmown is still a playing field for consultation purposes.

Sport England will object unless the proposal falls within one of the exceptions in its published playing fields policy. The exception most often relied on for school expansion is replacement by provision equivalent or better in quantity and quality, in a suitable location, with equivalent or better accessibility and management arrangements.

Three things decide whether that argument works.

1. Whether the replacement is on the same site or elsewhere, and if elsewhere, whether pupils and community users can actually reach it.
2. Whether the replacement pitch is of comparable playing quality, which for natural turf means drainage, levels, soil profile and a maintenance regime rather than an area figure.
3. Whether the arrangement is secured, by condition or by obligation, including community use where the existing pitch was used by clubs.

Engage before the application. Sport England's pre-application involvement is the difference between a holding objection that stops determination and a consultation response that supports the scheme with conditions.

Replacement provision and what counts as equivalent

Area for area is the starting point and rarely the end of it. A smaller artificial grass pitch can carry many more hours of play per week than the natural turf it replaces, which is a quality argument worth making with the hours set out. It also brings floodlighting, fencing and noise questions that natural turf does not, so the gain in one assessment becomes a cost in another.

Reference the authority's own playing pitch strategy where one exists. That document states the local supply and demand position by sport, and an argument built on it is far harder to dismiss than one built on an area table. School area guidance published by the Department for Education sets out the expected playing field and informal area allowances for mainstream schools, and showing the post-development position against that guidance answers the educational side of the same question.

Trees on a constrained site

Commission a survey to BS 5837:2012 before the layout is fixed, covering every tree on the site and those on adjoining land whose root protection areas reach into it. The survey categorises trees A to C and U, and the root protection area, calculated from stem diameter, is the constraint that moves buildings.

School sites raise two particular issues. Mature trees in the middle of a site, often planted as specimens, which are the highest category and the most awkward to design around. And tree belts along boundaries, usually category B or C individually but functioning as a screen for neighbours, where the amenity value of the group exceeds the value of its parts.

A tree survey prepared after the layout is drawn tends to produce a method statement full of compromises, and the arboricultural officer reads those compromises as accurately as you wrote them.

Biodiversity on school grounds

Mandatory biodiversity net gain applies to the permission rather than to the applicant, so a school expansion needs a 10 per cent gain measured by the statutory metric unless an exemption applies. The de minimis exemption, which covers development affecting below a stated small area of on-site habitat and a short length of hedgerow, catches some small internal works and almost no new teaching blocks.

The baseline is the problem. Amenity grassland scores low, which sounds helpful, but boundary hedgerows and scattered trees score higher and are precisely what a boundary extension removes. Hedgerow units are assessed separately from habitat units and have to be addressed in their own right, so a scheme that removes 40 metres of species-diverse hedge cannot make it up with wildflower seeding.

The metric has to be completed by a competent person under the Environment Act 2021 regime, and an AI-assisted draft of a Biodiversity Net Gain Assessment is a starting point for that person rather than a replacement. Get the ecologist on site in the growing season, because a winter baseline assessed from aerial photography will be challenged.

Canopy cover, shade and outdoor learning

Two arguments carry weight with officers and are often left out. Shade, because playgrounds without canopy are unusable in a heatwave and the school will raise it eventually. And outdoor learning space, which several authorities now reference in their own education or design guidance.

In London, the urban greening factor in the London Plan sets target scores for major development and provides a numerical framework for the replanting case. Elsewhere the equivalent argument is canopy cover before and after, stated as a figure and shown on a plan, with new planting counted at mature rather than planted size and the interval between the two acknowledged honestly.

Air quality is the quiet companion to all of this. Schools are sensitive receptors, and the approach to receptor identification in an air quality assessment matters where the expansion brings classrooms closer to a busy road or increases vehicle movements on site.

What the authority and the consultee need to see

Assemble the pack so each consultee can find its own answer without reading the others.

• A green infrastructure plan showing existing and proposed, with areas quantified by type.
• Playing field areas before and after, pitch provision by sport, and the replacement proposal with its management arrangements.
• Tree survey, impact assessment, method statement and protection plan, with canopy cover figures.
• Ecology appraisal and the completed statutory metric, with hedgerow units shown separately.
• A drainage strategy reflecting the loss of permeable area, where the approach to climate change allowances in a drainage strategy sets the attenuation sizing.
• A construction management plan that protects what is being retained.

And one short section that reconciles them, because the common failure is a landscape plan showing twelve new trees while the arboricultural report counts eight and the biodiversity metric assumes fifteen. Officers check. Illustrative example: a two form entry primary adding a six classroom block over the corner of a grass pitch, replacing the lost area by re-levelling and draining an under-used rear field, retaining the two category A oaks by moving the block 4 metres, and offsetting hedgerow loss by planting a new native hedge along the extended boundary.

Browse the 66 report types to see which of these documents a school expansion needs, then draft the narrative ones and send the ecology, arboricultural and drainage work for professional review.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required.