Child yield and playable space in a Play Space Assessment

A child yield calculation for planning is arithmetic, not judgement: you take your unit mix, split it by number of bedrooms and tenure, apply the child occupancy rates for the relevant ward, and add up the children. Under London Plan (2021) Policy S4, that figure is then multiplied by 10 m2 to give the playable space the scheme must provide. On a 48-flat mixed-tenure block, the difference between a lazy yield and a properly derived one can be 60 or 70 m2 of podium space, which is the difference between a scheme that works on site and one that needs a section 106 contribution.

This matters early. Playable space competes with cores, cycle stores, refuse, substations and amenity terraces, and if the yield is only calculated after the layout is fixed, something has to give.

What Policy S4 actually asks you to prove

Policy S4 of the London Plan (2021) requires development proposals that include housing to make provision for play and informal recreation based on the expected child population the scheme generates, and to provide at least 10 m2 of good quality play provision per child. The supporting Mayoral guidance on play and informal recreation sets out the method: derive the child yield, split it by age band, and test whether each band's needs can be met on site or within an acceptable walking distance.

A Play Space Assessment is the document that shows your working. It should contain the unit schedule used, the yield rates applied and their source, the age-band breakdown, the resulting area requirement in m2, an audit of existing provision within the relevant catchments, and a schedule of what the scheme provides and where. If any of those five things is missing, the case officer will ask for it, and on a major application that is a delay measured in weeks.

Outside London the arithmetic is different but the logic is the same. Most local plans set an open space or children's play standard expressed either as m2 per person, hectares per 1,000 population, or a per-dwelling contribution formula in an open space supplementary planning document. Check the adopted plan and the council's own SPD before assuming a London-style per-child figure applies. Some authorities also draw on Fields in Trust benchmark guidance for equipped play, so ask which version the council uses.

Getting the child yield right

The Greater London Authority publishes a population yield calculator that returns child occupancy rates by ward, by number of bedrooms and by tenure. Those three variables do most of the work. A 3-bed social rented flat generates several times the child yield of a 1-bed market flat, so two schemes with identical floorspace and identical unit counts can produce very different requirements.

A few things go wrong repeatedly:

• Using borough-wide rates when ward rates are available. Ward selection changes the answer, and officers check it.
• Applying market rates to the whole scheme because the affordable tenure split is not settled. If the tenure mix is still moving, run the calculation for the worst case as well as the proposed case.
• Counting studios as 1-bed. They are not the same in most datasets.
• Ignoring build to rent, later living or student accommodation. These have their own yield behaviour and the assessment should say plainly which rates were used and why.

Record the exact inputs in an appendix table. When a scheme goes to committee 14 months later with a revised mix, you want to be able to re-run the calculation in an afternoon rather than reconstruct it.

The 10 m2 per child standard and how it splits by age

The 10 m2 figure is per child, not per dwelling and not per resident. Multiply the total yield by 10 and you have the headline requirement. The harder part is the age split, because each band has a different type of provision and a different acceptable walking distance.

The under-5 requirement is the one you cannot export. Doorstep space has to be genuinely on the doorstep, visible from homes, and reachable without crossing a road. If your layout cannot accommodate it, the design has a problem that no off-site contribution will fix.

Age-band proportions come from the same population data as the yield itself, and they vary by area. Do not assume an even split across three bands. In wards with a young demographic the under-5 share can dominate, which pushes more of the requirement into the hardest-to-deliver category.

What counts towards the area

Usable, safe, overlooked space counts. Left-over strips between a car park and a boundary fence do not, and neither does the setback in front of a ground-floor window. Landscaped areas can count where they are designed to be played in rather than looked at, which means specifying surfacing, planting that tolerates use, and sightlines from adjacent homes. Say so explicitly in the assessment, with an annotated plan keyed to the area schedule.

Illustrative example: 48 flats in an outer London borough

The following is illustrative. The yield rates below are assumed for demonstration and are not GLA figures; always run the published calculator for your ward and tenure mix.

Assume a 48-unit scheme: 30 market (12 one-bed, 14 two-bed, 4 three-bed) and 18 affordable (8 two-bed social rent, 4 three-bed social rent, 6 two-bed intermediate).

At 10 m2 per child the requirement is 237 m2. Apply an illustrative age split of 35 per cent under 5, 40 per cent aged 5 to 11 and 25 per cent aged 12 and over, and you get roughly 83 m2 of doorstep space, 95 m2 of local provision and 59 m2 of neighbourhood provision.

Notice what the tenure split does. The 18 affordable homes generate around 16 of the 23.7 children, two thirds of the requirement from just over a third of the units. A scheme that swaps four 3-bed social rented flats for 1-bed market units loses roughly 6 children of yield and 60 m2 of requirement, which is the sort of trade-off that surfaces in viability discussions and should be flagged to the client before it happens rather than after.

On a constrained urban site, 83 m2 of genuine doorstep space on a podium is achievable. Finding a further 154 m2 on site usually is not, which brings you to the shortfall argument.

When on-site provision falls short

The order of preference is on-site first, then improvement of existing off-site provision within the catchment, then a financial contribution. To argue for the second or third, the assessment has to audit what already exists.

A usable audit does three things. It maps every existing play facility within the relevant catchment distances for each age band. It records the type, condition, capacity and age suitability of each one, from a site visit rather than an aerial photograph. And it forms a view on whether the additional children from your scheme can be absorbed without degrading the facility for existing users.

1. Establish the requirement by age band in m2.
2. Audit existing provision within 100 m, 400 m and 800 m, with a plan and a condition note for each site.
3. Assess route quality: crossings, lighting, severance, whether an 8-year-old could reasonably get there.
4. Quantify the on-site provision the layout can deliver, keyed to a landscape drawing.
5. State the residual shortfall by band, and set out the proposed off-site improvement or contribution and how it was calculated.

Where a contribution is proposed, it has to satisfy the section 106 tests in regulation 122 of the Community Infrastructure Levy Regulations 2010: necessary to make the development acceptable, directly related to the development, and fairly and reasonably related in scale and kind. A contribution towards refurbishing a specific play area 300 m away, named and costed, is far easier to defend than a round sum into a general fund. Ask the council early whether play is covered by their CIL charging schedule, because if it is, a separate section 106 payment for the same infrastructure may not be available to them.

Where play space work overlaps the rest of the evidence base

The same child yield feeds several other documents in a major application. Education contributions, health impact work, open space provision and the amenity space calculation all draw on the population the scheme generates, and officers do notice when the Play Space Assessment says 24 children and the section 106 heads of terms assume 31.

Run the yield once, put it in one appendix, and cross-reference it from everywhere else. An Open Space Assessment covers the wider quantum and quality of open space; the play work sits inside it and should not contradict it. If the scheme is in London and referable to the Mayor, expect the GLA case officer to check the calculator inputs directly.

The landscape drawings need to agree with the area schedule to the square metre. A Play Space Assessment that quotes 237 m2 while the general arrangement plan hatches 198 m2 will come back, and the applicant will spend two weeks reconciling drawings that should have been coordinated at the outset. Fix the yield before the layout freezes, not after.

PlanScope's Play Space Assessment is one of the 66 report types covered by the guided flow, and it uses the site data and unit mix you enter to structure the assessment against GLA standards, flagging missing site facts rather than filling them in. Pricing is one free report, £50 per report or £150 a month for unlimited on the Professional tier. Enter your postcode to see which reports your site is likely to need.

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.