Daylight and Sunlight Gardens and Amenity Spaces: BRE Guidance for Outdoor Areas

This article explores the BRE’s 2022 guidance on site layout planning for daylight and sunlight, focusing specifically on outdoor areas. It explains why daylight and sunlight matters in gardens and amenity spaces, outlines how to assess sunlight availability, and sets out best practices for layout design to preserve and enhance these areas.

Ensuring access to adequate daylight and sunlight in gardens and amenity spaces is a critical component of good urban design. The Building Research Establishment (BRE) guidelines advise planners and designers to ensure that outdoor areas such as gardens, courtyards, parks, and terraces receive sufficient natural light throughout the year.

While most conversations around daylight and sunlight focus on internal rooms, the quality of external spaces can significantly affect both residential satisfaction and the visual character of a development.

Why Daylight & Sunlight Matters in Gardens & Amenity Spaces

Sunlight plays a vital role in making outdoor spaces functional, attractive, and enjoyable. The BRE outlines several benefits of ensuring sunlight access in gardens and amenity spaces:

Enhancing visual appeal: Sunlight improves the aesthetics of a site, providing bright, sunlit views throughout the year.

Comfort and usability: Sunny areas make sitting out, socialising, and children’s play more pleasant during warmer months.

Horticultural benefits: Plants, lawns, and gardens flourish with good sunlight exposure, especially in spring and summer.

Ground maintenance: Sunlight helps dry out surfaces, reducing slime, moss, and damp ground.

Seasonal safety: In winter, it assists in melting frost, ice, and snow.

Everyday functionality: Sunlight can help dry clothes or surfaces all year round.

What Types of Outdoor Areas Should Be Assessed?

The BRE guide advises checking sunlight availability for a wide range of outdoor spaces where sunlight is necessary for comfort or functionality:

Private gardens (especially main rear gardens of homes)

Communal amenity areas, including courtyards and roof terraces

Public parks and playing fields

Children’s playgrounds

Outdoor swimming or paddling pools, and marinas

Sitting out areas in public squares or between non-domestic buildings

Nature reserves, especially where rare or light-sensitive flora are present

Core Assessment Criteria: The Two-Hour Sunlight Test

The benchmark for assessing sunlight in gardens and amenity areas is the “two-hour sunlight test.” The BRE recommends:

At least half of a garden or amenity area should receive a minimum of two hours of sunlight on 21 March (spring equinox).

If a new development reduces this area to less than 80% of its former size, the impact is deemed significant.

Tools and Techniques for Sunlight Assessment

To determine whether the two-hour sunlight threshold is met, practitioners may use:

Sunpath indicators, such as the BRE’s solar availability protractor

Shadow plotting, to visualise sun exposure at different times of the year

Computer simulations, particularly helpful for complex layouts

BRE recommends plotting shadow plans for 21 March, which represents average solar conditions. Plots for 21 June (summer solstice) and 21 December (winter solstice) can be used as supplementary analysis for seasonally used spaces.

Best Practice Site Layout Strategies

To enhance sunlight availability in outdoor spaces, the BRE offers practical guidance:

1. South-facing orientation: Position low-rise housing to the south and taller blocks to the north to maximise sunlight for amenity areas.

2. Courtyard design: Avoid enclosing courtyards on all sides; open them toward the southern half of the sky.

3. Reconfigure obstructions: Remove or realign extensions and high walls that cast persistent shade.

4. Gaps in structures: Use breaks in built form, particularly on the southern edge, to let in sunlight while preserving enclosure.

5. Flexible site use: Reserve the sunniest parts of a site for gardens or social areas; allocate shaded zones for car parking or utilities.

Consideration of Trees, Hedges, and Fences

The impact of vegetation and boundary treatments is nuanced:

Trees: Generally excluded from calculations unless they form a dense evergreen barrier.

Fences and walls: Opaque barriers over 1.5 metres high should be included in overshadowing calculations.

Hedges: Tall hedges can significantly block sunlight. Under the High Hedges provisions of the Anti-Social Behaviour Act 2003, local authorities can require their reduction if they cause a nuisance.

Designing for Seasonal and Daily Usage

BRE recommends tailoring sunlight assessments to reflect how occupants use outdoor areas:

For year-round use, assess sunlight on 21 March.

For seasonal use (e.g. outdoor dining areas or school playgrounds), assess based on their specific hours and months of activity.

Shadow Planning: Before and After Development

Where a large building is proposed, BRE encourages the use of “before and after” shadow plots. These show the extent of new shadow cast by a proposal, helping decision-makers and communities visualise the true impact on outdoor spaces.

Legal and Planning Implications

Although BRE guidance is non-mandatory, local authorities widely use it as a material consideration in planning decisions. Projects that fail to meet the two-hour sun test may face planning resistance, especially if they reduce sunlight in existing gardens or public spaces.

FAQs: Daylight & Sunlight Gardens & Amenity Spaces

What is the BRE two-hour sunlight test?
This test checks whether at least half of an outdoor area receives two or more hours of direct sunlight on 21 March. If not, or if a development reduces the area that passes the test to less than 80% of its former size, assessors consider the impact significant.

Do the guidelines apply to front gardens?
Not typically. BRE advises assessing only main rear gardens for houses, and communal spaces for flats. Assessorments usually exclude front gardens, especially those facing public roads.

Are trees included in the shadow calculations?
No, unless they are dense evergreens or part of a deliberately planted screen. The variable and seasonal nature of tree shade makes them less critical than built structures.

Can hedges cause a loss of light claim?
Yes. Under the High Hedges provisions of the Anti-Social Behaviour Act 2003, local authorities can take action where evergreen or semi-evergreen hedges over 2 metres in height are adversely affecting the reasonable enjoyment of a neighbour's property, including through loss of light.

What if a courtyard is shaded most of the year?
Shaded courtyards can feel grim and underused. Reorienting the courtyard, opening southern sides, or repositioning buildings can help bring in sunlight.

Is the BRE guide legally binding?
No. It is a best-practice guide. However, many councils incorporate its principles into local planning policy and design codes.

Can software be used for sunlight assessments?
Yes. Specialist 3D modelling tools and simulation software can accurately assess sunlight hours and produce shadow plots to support or contest a planning application.

What about rooftop terraces?
Rooftop communal amenity spaces should also be assessed using the same two-hour guideline if they are intended for year-round or frequent use.

Key Takeaways - Daylight & Sunlight Gardens & Amenity Spaces

1. The BRE Guide recommends that at least half of any garden or amenity space should receive two hours of direct sunlight on 21 March.

2. A reduction of more than 20% in sunlit area due to new development is deemed a noticeable and potentially unacceptable impact.

3. Shadow plots and sunpath tools are essential for assessing current and proposed site conditions.

4. Trees and fences can alter light availability but are assessed differently depending on type and function.

5. Proper design orientation and massing can dramatically improve sunlight access to outdoor areas.

Although the law does not enforce BRE guidance, planners and developers widely adopt it as a benchmark for quality and amenity.

For professional support with daylight and sunlight analysis for your development project - including garden and amenity space assessments - contact Anstey Horne, the UK’s leading specialists in daylight and sunlight assessment and analysis.

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