Open Space Assessment outline and the quantum calculation
The document answers one question with a number. Establish the standard, audit the catchment, identify the deficiency, then apply the standard to the population your scheme generates.
An Open Space Assessment answers one question with a number: how much open space does this development generate a need for, and where is it going. Everything else in the document exists to make that number defensible. The structure follows the same four steps every time. Establish the local standard and its typologies, audit what exists in the catchment, identify the deficiency, then apply the standard to the population your scheme creates. Get those four right and the negotiation is about quality and management rather than quantum.
Local standards and the typologies used
Start with the adopted policy, quoted. Most councils express open space standards as an area per person or per thousand population, broken down by type of space, and the breakdown matters because a surplus of one type does not answer a deficit in another.
The typologies in common use descend from the audit tradition established in national guidance and carried into local plans:
- Parks and gardens.
- Natural and semi-natural green space.
- Green corridors.
- Outdoor sports facilities, including pitches and courts.
- Amenity green space.
- Provision for children and young people.
- Allotments and community growing space.
- Cemeteries and churchyards.
- Civic spaces.
Record for each typology the quantity standard, the accessibility standard expressed as a walking distance or time, and any quality standard the council applies. Where the plan is silent on a typology, say so rather than importing a figure from elsewhere, and reference the benchmark you are using instead with its source.
In London, the play space standard in the London Plan operates alongside borough open space policy, and a Play Space Assessment is usually needed as a separate document rather than a section of this one.
Existing provision audit within the catchment
The audit is the evidence half of the document, and it is the half that gets criticised.
Define the catchment first, using the accessibility standard for each typology rather than a single radius for everything. A local play space with a 400 m standard and a district park with a 1,200 m standard produce two different catchments from the same site, and mapping both is the point of the exercise.
Then audit what is inside each catchment:
- Site name, reference and typology.
- Area in hectares, measured from a defined boundary rather than estimated.
- Ownership and whether public access is secured or permissive.
- Condition and facilities present.
- Barriers on the walking route: a railway, a dual carriageway without a crossing, a river, a locked gate.
- Any restriction on use, such as club-only pitch bookings or seasonal closure.
Permissive access is the item that changes conclusions. A field used by the public with the owner's tolerance is not secured provision, and counting it as such is the fastest way to lose the argument at committee.
Deficiency analysis
Deficiency is quantity against standard, tested against accessibility, and moderated by quality. Report all three rather than collapsing them into one figure.
Set out the existing population of the catchment from published census data at the smallest sensible geography, the existing provision by typology in hectares, and the provision per thousand population against the standard. Then state whether each typology is in surplus or deficit, and by how much.
Accessibility deficiency is separate and often more useful. A catchment with adequate hectares can still have a deficiency where the space sits on the far side of a barrier, and that finding supports on-site provision even where the numbers suggest a contribution would do.
Quality comes last and it is the least contested. Use the council's own audit where it has published one, because arguing with a council's own quality scores is rarely productive.
Quantum generated by the development
This is the calculation the officer checks, so show every step.
Derive the population from the unit mix using an occupancy assumption per dwelling size, taken from census household data for the area, and state the assumption. A scheme of 60 flats with a bedroom mix weighted to one and two beds generates a different population from 60 houses, and using a flat average per dwelling overstates or understates the requirement depending on which way the mix runs.
Then multiply the population by the standard for each typology and report the requirement in square metres or hectares. Show the child population separately where a play space standard applies, since it is derived from a different part of the household data.
| Step | What to state |
|---|---|
| Unit mix | Numbers by bedroom count |
| Occupancy assumption | Persons per dwelling by size, with the source |
| Population generated | Total, and child population separately |
| Standard applied | Area per person or per thousand, by typology |
| Requirement | Area by typology, in square metres |
Keep this table consistent with the figures used in the Planning Statement and in any obligation schedule, because three documents with three population figures is a familiar and avoidable embarrassment.
On site provision against an off site contribution
The choice is a policy question answered with evidence, not a preference.
On-site provision is the default where the site can accommodate usable space of the right typology at the right size, and where the deficiency analysis shows a local need. Fragmented strips of amenity land that exist only to meet a numerical requirement are worse than no provision, and officers say so.
An off-site contribution suits cases where the site cannot deliver usable space, where the catchment has capacity that needs improving rather than extending, or where a nearby project would serve the development better. The contribution must satisfy the statutory tests for planning obligations: necessary to make the development acceptable, directly related to it, and fairly and reasonably related in scale and kind. Identify the receiving project, its cost basis and the calculation, because an unallocated sum is vulnerable to challenge.
Where the council operates a Community Infrastructure Levy, check what the levy already funds. Seeking a contribution for something the levy list covers is the objection to raise early rather than after the heads of terms are agreed.
Quality and accessibility measures
Quantum alone does not make good open space, and a short section on quality strengthens the whole document.
Cover the size and shape of each space proposed, its orientation and sunlight availability, overlooking for passive surveillance, entrances and step-free routes, seating and shade, planting and habitat value, boundary treatment, and lighting where evening use is intended. Where the space serves a play function, cover age ranges, equipment types and safety surfacing.
A Green Infrastructure Plan is the right vehicle where the open space also carries drainage, biodiversity or urban cooling functions, and cross-referencing it avoids repeating the same drawings in two documents.
Management and maintenance
Every open space proposal needs an answer to the question of who cuts the grass in year 12.
Three routes exist. Transfer to the local authority with a commuted sum covering a defined period, which needs the authority's agreement in principle before you rely on it. A management company funded by estate charges, which needs the charge mechanism and a schedule of works. Or transfer to a community body or trust, which needs the body to exist and to be willing.
State the route, the funding, the works schedule by year, and the replacement provisions for equipment and planting. Then say how it is secured, whether by obligation, condition or transfer agreement.
Illustrative example: a 48-dwelling scheme where the catchment audit showed adequate amenity green space in hectares but with the only park beyond a railway line with no crossing within 600 m. The assessment argued accessibility deficiency rather than quantity deficiency, and the approved scheme delivered a 0.12 hectare on-site space with a toddler play area and a commuted sum for a 15-year maintenance period, rather than the off-site contribution the council had initially sought.
Browse the 66 report types on PlanScope to see how an open space assessment sits alongside the other documents a residential application needs.
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
How is the open space requirement calculated?
Derive the population from the unit mix using an occupancy assumption per dwelling size taken from census household data, state that assumption, then multiply by the standard for each typology. Report the child population separately where a play space standard applies, because it comes from a different part of the household data.
Can existing informal open space be counted in the audit?
Only where public access is secured. Land used by the public with the owner's tolerance is permissive rather than secured provision, and counting it as available is one of the quickest ways to lose the argument at committee. Record ownership and the basis of access for every site in the audit.
What is accessibility deficiency?
A shortfall caused by barriers on the walking route rather than by a lack of hectares. A catchment can meet the quantity standard while the only park sits beyond a railway or a dual carriageway with no crossing. That finding supports on-site provision even where the numerical position looks adequate.
When is an off-site contribution appropriate?
Where the site cannot deliver usable space of the right typology, or where the catchment has capacity that needs improving rather than extending. The contribution must satisfy the statutory tests for planning obligations, so identify the receiving project, its cost basis and the calculation rather than offering an unallocated sum.
Who maintains the open space after completion?
One of three routes: transfer to the local authority with a commuted sum for a defined period, a management company funded by estate charges, or transfer to a community body. State the route, the funding, a works schedule by year and the replacement provisions, and say how each is secured.
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.