Sunlight to public open space in a new scheme

Communal courtyards and public spaces get assessed for sunlight using the same test BRE 209 applies to a back garden: whether at least half the area receives at least two hours of sunlight on 21 March. On a perimeter block with six storeys around a narrow courtyard, that test is often failed before anyone has drawn a landscape plan, and by the time the overshadowing results arrive the massing is fixed. Testing the courtyard at concept design costs a morning. Testing it at planning stage costs a redesign.

Why sunlight to shared space is assessed at all

Amenity space that never sees the sun does not get used. Residents do not sit in it, children do not play in it, planting struggles in it, and the space ends up as a route between the bin store and the front door.

Planning policy treats usable outdoor space as part of the quality of the accommodation, and national design guidance expects new development to provide well-located, usable amenity space. Where a scheme relies on communal provision to justify small private balconies, the quality of that communal space carries more weight, not less.

There is a second reason. Public space that is permanently shaded is colder and, in winter, holds ice and damp. That affects the perception of safety and the cost of maintaining surfaces and planting.

Applying the sun on ground test to communal areas

The test is straightforward to run and easy to misapply.

Take the amenity area as defined on the landscape plan, model the surrounding built form as proposed, and calculate the proportion of the area receiving at least two hours of sun on 21 March. The threshold is half the area. Where an existing space is affected by new development, the guidance also asks whether the area still receiving two hours has fallen below 0.8 times its former value.

Three definitional choices decide the answer. What counts as the amenity area, since including circulation, service yards and planting beds flatters the result. What ground level is assessed, since a raised podium behaves differently from a lower courtyard. And whether trees are modelled, since a mature canopy in a small courtyard can be the dominant obstruction.

State all three in the report. An Overshadowing Study that defines the assessed area on a clearly annotated plan is far more useful to an officer than one presenting a single percentage.

Play space, seating and planting

Not all of a communal space needs the same amount of sun, and saying so in the design statement is more persuasive than claiming the whole area performs well.

Children's play space is where sunlight matters most. Play areas in permanent shade are used less and are colder, and doorstep play for younger children is often placed close to entrances where the building height is greatest. Where a scheme is providing formal play provision, a Play Space Assessment should describe where the provision sits relative to the sunlit area rather than treating quantity and location as separate questions.

Seating follows the sun. Place the main sitting-out area in the part of the courtyard that achieves the two-hour test, and place the areas that fail it where they can carry cycle parking, bin storage, shade-tolerant planting or a route.

Planting has hard limits. Amenity lawn does not establish in deep shade, and a landscape design specifying it in a permanently shaded courtyard will fail within two seasons. A Landscape Strategy that matches the planting palette to the shade analysis is the difference between a courtyard that looks like the visualisation in year three and one that does not.

Tall building courtyards

The geometry is unforgiving. As the ratio of building height to courtyard width increases, the proportion of the ground receiving direct sun falls quickly, and beyond a certain point no arrangement of planting or surfacing recovers it.

The move that works most often is stepping or breaking the block on its southern or south-western side. It is also the move that costs units, which is why it has to be made early, when the scheme is still an area schedule rather than a set of consented drawings.

Roof terraces are a real answer rather than a consolation. They receive sun the courtyard cannot, and they can take the seating and growing space while the courtyard takes circulation and shade-tolerant planting. What they need is proper access, supervision and wind mitigation.

Which brings in the other half of the question. A sunlit space that is uncomfortable in wind will not be used either, and on schemes above a certain height a Wind Microclimate Assessment should be read alongside the sunlight results rather than filed separately. The two studies frequently point at the same corner of the site.

Presenting the results

Design review panels and case officers respond to drawings rather than to tables.

Show hourly shadow plots across 21 March, with the amenity area outlined, so the reader can see where the sun is at 10am and at 2pm rather than only the summed result. Add 21 June and 21 December as context, labelled clearly as context rather than as the test.

Then show the design response on the same plan. Where seating sits, where play sits, where the shade-tolerant planting sits. A panel that can see the sunlight analysis has driven the landscape layout will accept a courtyard that fails the numerical test in part, because the reasoning is visible.

Report the failures. A study that presents only compliant areas invites the question of what happened to the rest, and the answer always emerges eventually.

Mitigation where sunlight is limited

Where the geometry cannot be changed, there are honest responses and dishonest ones.

Honest: relocate the primary amenity function to a sunlit roof terrace or an off-site contribution to nearby open space where policy allows it, use light-coloured surfaces and pale facade materials at low level to raise ambient light, specify shade-tolerant species, and design the shaded area for uses that do not need sun.

Dishonest: redefining the amenity area to exclude the shaded parts, assessing a date other than 21 March without saying so, or omitting the trees. Officers who deal with these studies regularly recognise all three.

An illustrative example: a courtyard scheme achieves the two-hour test over 38 per cent of its communal space. Stepping the southern block down by two storeys over a 12 m length lifts it above half, at the cost of six units. The scheme instead moves the play provision to the sunlit western end, converts the shaded northern strip to cycle parking and shade-tolerant planting, and adds a roof terrace. Both are defensible. The second one has to be explained.

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. Enter your postcode on PlanScope to see which amenity and landscape documents a scheme is likely to need.