Sunlight to gardens and amenity space in a scheme layout

The sunlight amenity space assessment is an area test, not a window test, and the figure that matters is simple: at least half of an amenity area should receive at least two hours of sunlight on 21 March. Miss it and the reporting has to show how far short the space falls and what the layout did to try to avoid it. Meet it across the courtyards and gardens of a scheme, and one of the more predictable objections disappears before it is made.

Most schemes that fail this test fail it for reasons fixed in the first massing sketch.

The two hour test and what it applies to

BRE 209 recommends that at least half of an amenity area should receive two hours of sunlight or more on 21 March. For existing spaces affected by a proposal, it adds a second limb: where the sunlit area falls below half and also drops to less than 0.8 times its former value, the loss will be noticeable.

The guidance applies this to gardens of existing dwellings, and to open spaces within and around a scheme, including parks, playing fields, children's play areas and sitting-out areas. It does not apply to every scrap of external space. A service yard, a bin store forecourt and a 1.5 metre strip between a building and a boundary fence are not amenity areas, and treating them as such to lift the average across a site is the sort of thing that gets noticed in a review.

Identify the assessed areas on a drawing, name each one, and say what it is for. That drawing does more for the credibility of the assessment than the analysis itself.

Why 21 March is the reference date

The equinox sits midway between the extremes. Shadows on 21 March are longer than at midsummer and far shorter than at midwinter, so the date gives a representative rather than a flattering or punishing picture.

It also means the test is sensitive to building height and to north-south spacing in a way that a June assessment would hide. A courtyard that works beautifully in July can be in shadow for most of a March afternoon, and March is when people start using outdoor space again.

Some authorities ask for supporting plots at 21 June and 21 December to show the range. Those are useful context and they are not the test. Keep the compliance statement anchored to 21 March and present the others separately.

Communal space against private gardens

Private gardens and communal courtyards behave differently, and reporting them as a single pooled figure is a common weakness.

A private garden serves one household and cannot be substituted. If it fails, that household has no sunlit outdoor space. A communal courtyard serves many, so a well sunlit portion can carry real amenity value even where the overall area falls short, provided the sunlit part is usable and accessible rather than a triangle behind the cycle store.

Report both separately, with each private garden identified individually rather than averaged. Then say, in one paragraph, what the sunlit portion of each communal space is actually used for in the landscape design. Where a scheme provides private outdoor space to a policy minimum, check what the adopted plan requires: the London Plan, for instance, sets a minimum of 5 m² of private outdoor space for one and two person dwellings with an addition for each further occupant, and many authorities outside London set their own figures.

Podium gardens and roof terraces

Amenity space raised above ground is usually the best performing space on a dense scheme for sunlight and the worst for everything else.

A podium garden sits above the surrounding streets, so it clears local obstructions and receives sunlight the ground level courtyards cannot. It is also exposed. Wind conditions on a podium between two tall blocks can make a sunlit space unusable, and pedestrian comfort criteria for sitting and standing are a separate assessment with its own conclusions.

Report the two together where the scheme relies on podium amenity. A space that passes the two hour test and fails wind comfort for sitting has not delivered amenity, and a committee report that presents only the sunlight figure will be corrected by an objector.

Depth of growing medium is the third constraint, because planting that would soften a terrace needs substrate the structure has to carry.

Trees and planting in the model

Handle existing trees explicitly rather than quietly.

On 21 March most deciduous trees in England are not in leaf, so their shading effect is limited at the reference date and the honest approach is to model the built form, state the assumption about planting, and describe any evergreen or dense planting separately in the text. Including a mature deciduous canopy at full leaf in a March model overstates the shading and invites a challenge.

New planting raises the opposite question. A landscape plan showing semi-mature trees across a courtyard will, in fifteen years, shade a space the assessment shows as sunlit. Say so. It is not a reason to refuse and it is a reason to think about where the trees go.

Layout moves that change the result

By the time a scheme reaches detailed design the sunlight outcome is largely fixed, so the useful work happens at massing stage.

• Step building heights down towards the southern edge of a courtyard, so the tallest element is on the north side casting shadow away from the space.
• Open the southern or western corner of a courtyard rather than closing the perimeter block completely.
• Locate the main communal amenity to the south or west of the tallest building, not tucked to its north.
• Set back upper storeys on the southern arm, which recovers midday sunlight at the cost of a small amount of floorspace.
• Widen the gap between facing blocks rather than reducing height, where the site allows it.

Test these at sketch stage with a simple shadow study. The technique for doing this early, before the model is built, is set out in obstruction angles and the early massing test.

Where a shortfall is accepted

BRE 209 is advisory guidance and says so. In dense urban contexts, authorities and inspectors regularly accept shortfalls against the two hour test where the scheme delivers other benefits and where the amenity provided is of reasonable quality.

The argument works when three things are present: the shortfall is stated openly with figures rather than buried, the design has demonstrably been tested against alternatives that would have performed better, and the residual amenity is usable space rather than a technical area on a plan. It fails when the assessment reads as though the author discovered the problem after the design was fixed.

An Overshadowing Study covers the amenity area analysis, and a Daylight and Sunlight Assessment covers the window based tests alongside it. Both sit better with a case officer when the amenity argument is made in the same terms as the outlook and overbearing assessment.

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.