Child yield and play space calculation explained

Play space requirements are calculated from the number of children a scheme will house, not from the number of dwellings, and in London the benchmark is at least 10m² of playable space per child. The London Plan applies that to schemes of ten or more dwellings, with the child population estimated from the unit mix and tenure using published yield data. Outside London the method is the same even where the standard differs, because every authority's standard still has to be applied to an estimated child population.

Two numbers decide the answer: children per dwelling type, and square metres per child. Everything else is presentation.

Why child yield drives the requirement

A scheme of 50 one bedroom flats and a scheme of 50 four bedroom houses contain very different numbers of children, so a requirement expressed per dwelling would be arbitrary. Yield data converts the mix into a population.

That has a design consequence worth flagging early. Increasing the family housing in a mix increases the play requirement and reduces the developable area at the same time, which is why play provision should be sized at the point the mix is agreed rather than at reserved matters. Leaving it to reserved matters means designing, costing and securing it under time pressure.

Yield figures come from census based analysis of household composition by dwelling size and tenure. In London the Greater London Authority publishes a yield calculator for this purpose. Elsewhere, authorities either publish their own figures in a supplementary planning document or expect the applicant to derive them from census data for the relevant area.

Deriving yield from unit size and tenure mix

Set the calculation out as a matrix, because that is what a reviewer wants to check.

Rows are the unit types by bedroom count. Columns are tenure, usually market sale, intermediate and affordable rented. Each cell holds a yield rate for children in each age band. Multiply the number of units in each cell by the rate, and sum the columns.

Three rules keep it defensible:

• Use the same source for every cell. Mixing a published local rate for market units with a national rate for rented units produces a number nobody can replicate.
• State the age bands the source uses, because they vary, and the bands drive the provision types.
• Round at the end, not at each step, and show the unrounded total.

The tenure effect is substantial. Affordable rented family units typically yield more children than market sale units of the same size, so a scheme where the affordable housing is concentrated in larger units generates a higher requirement than the unit count alone suggests.

The area per child benchmark and its source

The London benchmark of at least 10m² per child comes from the London Plan's play and informal recreation policy, and it is applied to the total child population across all age bands.

Take the figure and the policy wording from the plan that applies, since authorities outside London set their own standards in local plan policy or a supplementary planning document, sometimes as area per child, sometimes as area per dwelling, and sometimes as a quantum of open space per thousand population with play as a sub category. Those three formulations give different answers for the same scheme, so identify which one applies before calculating anything.

Age bands, distance thresholds and provision types

Play provision is not one space. The policy framework divides it by age and by distance from home, because a three year old and a thirteen year old need different things at different distances.

The London framework works to doorstep playable space for under fives within a short walk, local provision for five to eleven year olds somewhat further, and neighbourhood provision for older children and teenagers further still, with indicative distances of around 100m, 400m and 800m respectively. Check the current guidance for the distances and bands, since they are set out with qualifications.

The distance test is the one applicants forget. A single large play area in one corner of a 300 unit site can satisfy the area requirement and fail the distance requirement for half the dwellings, which is why doorstep provision is usually distributed and neighbourhood provision is usually singular or off site.

Inclusive provision runs across all three tiers rather than sitting in one of them. Accessible routes, equipment usable by children with limited mobility, seating for carers and quiet spaces away from the busiest equipment all belong in the specification, and the reasoning overlaps with the material in our note on access and inclusion in an equalities impact assessment.

Off site contributions where on site provision fails

Where the site cannot accommodate a tier, a financial contribution towards an existing or proposed facility is the normal answer, secured by section 106.

Three things have to be evidenced for the contribution to be lawful and defensible. The facility it will be spent on, named and identified. The basis of the calculation, usually a published cost per square metre or per item from the authority's own schedule applied to the shortfall area. And the connection between the development and the facility, which in practice means the facility is within the relevant distance threshold for the age band concerned.

A contribution calculated as a round sum with no shortfall area behind it is the version that gets challenged, and it is also the version that fails the statutory tests for obligations.

Evidencing the calculation in a short appendix

The whole calculation should fit on two pages, and a reviewer should be able to reproduce it without asking a question.

1. The unit mix table by bedroom count and tenure, matching the accommodation schedule exactly.
2. The yield rates with the source named, dated and referenced.
3. Child numbers by age band, shown unrounded and then rounded.
4. The area standard with the policy reference.
5. The total requirement in square metres, by age band where the policy splits it.
6. The proposed provision by type and area, with a plan showing each space and its distance catchment drawn.
7. The shortfall, if any, and the contribution calculation with its source.

Keep it consistent with the rest of the submission. If the accommodation schedule changes during determination, the play calculation changes with it, and an officer who finds a mix in the Play Space Assessment that does not match the drawings will query the whole appendix. The same discipline applies to the wider Open Space Assessment, where double counting the same square metres as both play space and amenity space is the commonest error, and to the capacity evidence described in our note on utilities capacity evidence for a residential scheme.

Reports drafted on PlanScope are AI-assisted and should be reviewed before submission, and we do not guarantee planning approval. Where the scheme raises wider community and wellbeing effects, the method in our note on health determinants inside a health impact assessment runs alongside this one.