Shadow Diagrams
A shadow diagram needs to show more than a shaded area on a plan. To understand what the shadow represents, the drawing also needs enough information to establish the development condition, assessment date and time, site orientation and relevant surrounding context. The exact documentation required will depend on the project and the requirements applying to it.
In Brief
A shadow diagram will commonly identify the site, the relevant development condition, the shadow being modelled, the assessment date and time, site orientation and enough surrounding context to understand where the shadow falls. Clear titles, legends, boundaries and drawing conventions help make that information understandable. The exact content and presentation can vary according to the project and assessment requirements.
A useful shadow diagram should provide enough information to understand the shadow condition being represented. The shaded area is only one part of that information. The reader also needs to be able to establish what is casting the shadow, when the shadow occurs and where it falls in relation to the site and relevant surroundings.
This commonly means showing the proposed development or relevant built form, the subject site, the assessment date and time, site orientation and the shadow generated under those conditions. Where surrounding properties or buildings are relevant to understanding the shadow extent, they may also form part of the drawing context.
The precise information required is not identical for every project. Planning authority requirements, the type of development and the purpose of the assessment can influence what needs to be documented and how it is presented.
The objective is not to place as much information as possible onto the drawing. It is to provide enough relevant information for the shadow condition to be understood clearly.
The shadow shown on a diagram needs to be understood in relation to the development that produces it. The relevant proposed building form or other development geometry should therefore be identifiable within the drawing.
The subject site also provides an important spatial reference. Property boundaries, building outlines or other site information can help establish where the development sits and how the modelled shadow extends beyond it.
Where surrounding buildings, properties or other features are relevant to the assessment, showing that context can make the shadow extent easier to understand. A shadow extending beyond the subject site has much more meaning when the drawing makes clear what lies beneath and around it.
This is different from the information used to build the shadow model. Architectural drawings, survey information and other project inputs are considered in What Information Is Needed to Prepare Shadow Diagrams? Here, the focus is on what the completed drawing communicates to the reader.
A useful Shadow Diagram does more than display a shaded area. It provides enough context to establish what is casting the shadow, where it falls and the assessment condition being represented.
A shadow diagram represents a particular solar condition, so the date and time are fundamental to understanding what is shown. Without them, the shape and direction of the shadow lack an important part of their context.
Shadow diagrams may be prepared at several nominated times so that the movement of shadow can be seen across part of the day. Each drawing should make clear which time it represents, allowing equivalent conditions to be identified and compared.
In Australia, 21 June is commonly encountered in shadow assessment because it represents the winter solstice period, when winter shadow conditions are of particular interest. It should not, however, be treated as a universal date for every assessment.
The appropriate assessment date and times depend on the requirements applying to the project. The reasons behind the common winter reference date are explored further in Why Is 21 June Used for Shadow Diagrams in Australia?
Site orientation is another essential reference when interpreting a shadow diagram. A north point or other clear orientation marker allows the drawing to be related to the actual site rather than read as an isolated graphic.
This helps the reader understand the direction in which the shadow extends and where surrounding properties or spaces sit in relation to the proposed development.
Orientation also provides an important check on the relationship between the site, the represented building geometry and the modelled shadow condition.
The north point does not need to explain the solar geometry behind the assessment. Its role on the drawing is simpler: it establishes how the shadow diagram is oriented in relation to the site.
Where an assessment compares the site before and after a proposed development, the drawing set may distinguish between existing and proposed shadow conditions.
The existing condition establishes the relevant baseline, while the proposed condition shows the modelled shadow with the development included. Some documentation may also identify additional shadow so that the change between the two conditions can be seen more directly.
These conditions may be shown on separate drawings or differentiated through linework, hatching, colour or another graphical convention. Whatever method is used, the drawing should make the represented condition clear.
The distinction is important because the total shadow shown in a proposed condition is not necessarily all new shadow. See Existing vs Proposed Shadow Diagrams: What Is the Difference? for a closer look at how the two conditions are compared.
Property boundaries help establish where the modelled shadow falls in relation to the subject site and surrounding land. Without this spatial reference, it may be difficult to tell whether a shadow remains within the site or extends beyond it.
Surrounding buildings can also provide important context. Where relevant to the assessment, their outlines can help the reader understand the relationship between the proposed development, neighbouring built form and the shadow shown on the drawing.
How much surrounding information needs to be represented depends on the purpose and scope of the assessment. A drawing does not necessarily need to reproduce every feature beyond the subject site simply because it exists.
The relevant question is whether enough surrounding context is shown to understand the shadow extent and satisfy the documentation requirements applying to the project.
Building outlines and relevant geometry help connect the shadow to the built form that generates it. On a plan-based shadow diagram, this may include the footprint or roof form of the proposed development together with the site and surrounding building outlines needed for context.
Depending on the drawing format and assessment purpose, relevant levels, heights or other annotations may also be included. These can help clarify the geometry represented where that information is important to understanding the documentation.
Not every geometric input used in the underlying model needs to appear as an annotation on every finished shadow drawing. The output needs to remain readable while providing sufficient information to identify the relevant development and shadow condition.
The level of detail should therefore reflect the purpose of the drawing rather than turning the shadow diagram into a duplicate of the complete architectural or survey documentation.
Clear labels allow the reader to establish what each shadow diagram represents before interpreting the shaded areas themselves. The drawing title, assessment date and time, represented condition and relevant annotations can all contribute to that clarity.
Where more than one type of shadow is shown, a legend becomes particularly important. Different hatching, tones, outlines or colours may distinguish existing, proposed or additional shadow, but those graphical conventions should not be assumed without checking how the drawing defines them.
Consistent labelling across a drawing set also makes comparisons easier. If several times or conditions are presented, the reader should be able to move between the drawings without having to reinterpret the graphical language each time.
For a step-by-step explanation of these elements from the reader's perspective, see How to Read a Shadow Diagram.
Relevant neighbouring properties may need to be represented where they provide necessary context for the shadow assessment or where the applicable documentation requirements call for them to be shown.
For example, if the modelled shadow extends beyond the subject site, surrounding property boundaries and built form may help establish where that shadow falls. The appropriate level of detail depends on what the assessment needs to communicate.
This does not mean that every neighbouring feature must always be documented in the same way. The extent of surrounding context should be appropriate to the project, the shadow being assessed and the requirements applying to the documentation.
Showing relevant context helps locate the shadow. Determining what that shadow means for solar access or planning performance is a separate assessment question.
No. There is no single drawing layout or information set that should be assumed to apply identically to every shadow assessment.
The documentation can vary according to the type and scale of development, the site context, the purpose of the assessment and the requirements of the relevant planning authority or approval pathway.
One project may require a relatively straightforward series of plan-based diagrams at nominated times. Another may require additional views, conditions or contextual information to communicate the shadow change appropriately.
For this reason, a generic checklist can be useful for understanding common drawing elements, but it should not replace checking the requirements that apply to the particular project.
A shadow diagram is primarily a representation of where modelled shadow falls under defined conditions. It does not, by itself, answer every planning or environmental performance question associated with that shadow.
For example, seeing shadow extend across an adjoining property does not automatically establish whether the development satisfies or fails a particular solar access requirement. That requires the relevant planning criteria and the affected areas or periods to be considered.
Similarly, a shadow diagram should not be treated as an indoor daylight assessment. Daylight performance within a building involves different questions, metrics and modelling methods.
The diagram establishes the spatial shadow condition. Other forms of analysis can then use that information where the project requires a broader assessment of solar access, overshadowing or building performance.
A clear shadow diagram brings the essential parts of the assessment together in a form that can be understood: the represented development condition, relevant geometry, site orientation, date and time, modelled shadow and sufficient site context.
Titles, legends, boundaries and consistent graphical conventions help explain how those elements relate to one another. Where existing and proposed conditions are compared, the documentation should also make that distinction clear.
The aim is not to make every shadow diagram look identical. It is to make the relevant shadow condition unambiguous while meeting the documentation requirements applying to the project.
Once that information is clearly represented, the drawings can provide a reliable visual basis for understanding where the shadow falls and for any further assessment required by the project.
Continue Reading
The information shown on a shadow diagram is one part of the wider assessment. Explore how shadow diagrams are prepared, what they represent and how they support planning and development documentation.
Explore the Shadow Diagrams guide →Shadow Diagrams
Clear shadow documentation should show the relevant development condition, assessment time and site context in a way that makes the modelled shadow easy to understand.
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