What is shadow diagram?

What does a shadow diagram show?

A shadow diagram is a set of drawings that show exactly where a building’s shadow falls on the ground and on neighbouring properties, at specific dates and times of the year. Each diagram overlays two shadow footprints on the same site plan: the existing shadow cast by whatever is on the site today, and the proposed shadow cast by the new development. Planning officers compare the two directly to see how much additional shadow the new building would create, and where.

Planning authorities may specify particular analysis dates and time intervals depending on the project and applicable requirements. Midwinter, equinox or selected daytime intervals are commonly used in different assessment contexts. A typical shadow diagram set includes anywhere from 6 to 12 individual drawings, each one labelled with the exact date, time, and true north orientation.

When are shadow diagrams required for a DA or planning application?

In Australia, shadow diagrams are commonly requested where a proposal may affect solar access, neighbouring amenity or private open space. The specific requirement depends on the planning framework and development context. Where the state’s Apartment Design Guide (ADG) or ResCode applies, solar access to neighbouring private open space and windows becomes a specific, numeric test, not just a visual one.

In the UK, shadow diagrams typically accompany a planning application whenever a scheme could affect a neighbour’s daylight or sunlight — extensions, infill development, and anything built close to an existing boundary. Some UK projects require a formal daylight and sunlight assessment where the planning context, development scale or potential effects on neighbouring receptors warrant further analysis.

Shadow diagrams vs overshadowing analysis vs solar access

These three terms get used almost interchangeably, but they’re not quite the same thing:

• Shadow diagram — the visual output. A drawing showing where shadows fall at specific times.
• Overshadowing analysis — the written assessment that interprets the shadow diagrams against a specific policy or planning control, explaining whether the impact is acceptable.
• Solar access — the Australian planning concept (ADG, ResCode) that sets a minimum number of sunlight hours a neighbouring window or private open space must retain. This is usually assessed using shadow diagrams, but the solar access test itself involves a numeric threshold assessed against the applicable criteria, not just a picture.

In UK planning, daylight, sunlight and overshadowing may be assessed with reference to BR 209 guidance where relevant. VSC, APSH and NSL are separate analytical metrics and should not be treated as interchangeable with a standard shadow diagram.

What files are needed to prepare one?

To build an accurate shadow diagram, we need:

• Your site plan and proposed building drawings (DWG, PDF, or ArchiCAD/Revit source files)
• A survey or cadastral/OS extract confirming true north and site boundaries
• The neighbouring building heights and footprints, where relevant to the required study area
• Your council name, planning reference, or the relevant DCP/BRE brief — so we can confirm the exact reference dates and times required

Without a verified true north and accurate site geometry, a shadow diagram isn’t just imprecise — it’s not admissible for a planning submission, since a few degrees of error can change the outcome of the analysis entirely.

UK vs Australia: what’s actually different?

Solar geometry itself varies by location — sun angles, daylight hours and solstice dates differ between hemispheres and latitudes. Australia’s winter solstice falls in June; the UK’s falls in December. What’s consistent across both markets is the need to model that geometry accurately. What differs is the compliance framework each planning authority applies to the resulting shadow drawings:

• Australia — council DCPs, plus ADG (NSW) or ResCode (VIC) for solar access to windows and private open space. Reference dates are usually set by the specific council.
• UK — BRE 209 guidance (Site Layout Planning for Daylight and Sunlight), applied by the local planning authority, often alongside shadow diagrams at the equinox and winter solstice.

Working across both markets means understanding which set of rules applies before a single shadow is modelled — not adapting a generic template after the fact.

Get council-ready shadow diagrams

CasStudio has worked with architectural modelling and visual project documentation since 2008 and now provides specialist shadow diagram and shadow analysis services for planning projects in Australia and the UK. Formal daylight and sunlight assessment scope is confirmed separately where required.

See our Shadow Diagrams overview for pricing and process, or go straight to your market:

• Shadow Diagrams — Australia (Sydney, Melbourne, Brisbane, Perth)
• Shadow Diagrams — UK (London, Manchester, Birmingham, Leeds, and more)