What Information Is Needed to Prepare Shadow Diagrams?

Shadow Diagrams

If you have been asked to provide shadow diagrams, one of the first questions is often what information you actually need to send. Architectural drawings are usually the starting point, but survey information, site conditions and the applicable planning requirements can all affect how accurately the proposed shadows can be documented.

In Brief

Preparing shadow diagrams usually requires enough information to establish the proposed building, its position and levels, the orientation of the site and the surrounding context relevant to the study. Architectural drawings and survey information commonly provide this foundation. The applicable planning requirements are also important because they may specify the dates, times, neighbouring areas or drawing formats that need to be shown. The exact information required depends on the project.

What information is usually needed for Shadow Diagrams?

If you are preparing to commission shadow diagrams, you do not necessarily need to assemble every document associated with the development. What matters is having enough reliable information to represent the proposed built form and its relationship to the site.

This will commonly include architectural drawings showing the proposed development, together with survey or site information that establishes boundaries, orientation, levels and relevant existing conditions.

Information about surrounding buildings may also be needed where shadows extend beyond the subject site or where neighbouring conditions need to be represented in the drawings.

Just as importantly, any planning controls, council requirements or requests for information relating specifically to the shadow assessment should be provided where available. These can determine what the finished diagrams need to show.

Why are architectural drawings important?

The shadow cast by a development depends on its physical form. If the height, position or shape of the proposed building changes, the shadow it produces can change as well.

Architectural drawings provide the information needed to understand that form. Depending on the project, this may include the site plan, floor plans, elevations, sections, roof form, setbacks and nominated building or floor levels.

Other built elements may also matter. Screens, awnings, balconies, parapets, fences or similar features can contribute to the shadow condition where they form part of the proposed development.

The objective is not simply to have a set of plans on file. The drawings need to contain enough dimensional and level information for the relevant built form to be represented correctly.

A shadow model can only represent the project information it is built from. Architectural drawings establish the proposed form; survey and site information establish where that form sits.

Why is survey information important?

A proposed building does not cast shadow in isolation. Its position on the land, orientation and relationship with surrounding levels all influence where the shadow falls.

Survey information can establish the site boundaries, true north, ground levels and the location and height of relevant existing structures. These details help place the proposed development within the correct physical context.

Orientation is particularly important because the shadow direction is determined by the relationship between the built form and the position of the sun at the nominated date and time. Incorrect site orientation can therefore affect the direction in which the modelled shadow is cast.

Levels matter for a similar reason. Differences in ground and building levels can change the spatial relationship between the proposed development, surrounding land and nearby structures.

Is information about neighbouring properties needed?

Sometimes. The amount of neighbouring information needed depends on the project and what the shadow diagrams are required to document.

Where proposed shadows extend beyond the subject site, surrounding property boundaries, buildings and other relevant features may need to be represented so that the drawings clearly show where those shadows fall.

For some assessments, the applicable planning requirements may ask for particular neighbouring features to be identified. The necessary level of detail should therefore follow the purpose and scope of the shadow documentation rather than assuming that every surrounding property requires the same level of modelling.

Where reliable neighbouring information is limited, that may also affect what can reasonably be represented and should be identified before the assessment is finalised.

Do you need to provide the planning requirements?

If you have received a specific council request, planning condition or request for additional information relating to shadow diagrams, it is useful to provide it with the project drawings.

The reason is simple: technically accurate modelling still needs to answer the planning question being asked. The relevant requirement may nominate particular assessment dates, times, views, surrounding properties or presentation methods.

These requirements are not necessarily identical from one project or planning authority to another. A date or time convention used successfully on another development should not automatically be assumed to apply to yours.

For example, 21 June is commonly used as a winter reference condition, but the dates and times required for a particular project should still follow the applicable planning requirements. For more on this distinction, see Why Is 21 June Used for Shadow Diagrams in Australia?

What if some drawings or project information are missing?

You do not necessarily need to know whether every document is sufficient before asking for the shadow assessment to be reviewed.

In some cases, the available architectural and survey information may already contain what is needed. In others, a missing level, dimension, neighbouring condition or planning requirement may need to be clarified before reliable diagrams can be completed.

The important distinction is between information that is simply unavailable and information that is necessary to establish the geometry or assessment condition. Where an important input is uncertain, silently replacing it with an assumption can introduce uncertainty into the resulting shadow documentation.

Providing the most current drawings and available planning information at the outset makes it easier to identify any genuine information gaps before unnecessary modelling or revisions occur.

Does every project need the same information?

No. The information needed should be proportionate to the development and the purpose of the shadow assessment.

A relatively simple residential alteration may not require the same amount of surrounding site information as a larger or more complex development. Similarly, a project where the relevant shadow remains largely within the subject site may raise different documentation needs from one where surrounding properties need to be represented in detail.

Planning pathways can also differ. Some projects may have clearly nominated shadow diagram requirements from the outset, while others may receive more specific requests during the assessment process.

This is why a project-specific review is more useful than treating a generic document checklist as a universal requirement.

How does the project information affect accuracy?

Shadow modelling can calculate the relationship between the sun and built form with a high degree of geometric consistency, but the result still depends on the information represented in the model.

If a building height, site level, orientation or surrounding structure is represented incorrectly, the resulting shadow may also be represented incorrectly. Accurate input information therefore forms an important part of reliable shadow documentation.

This does not mean every project requires exhaustive modelling of everything around it. The information needs to be sufficiently accurate and complete for the particular shadow condition being documented.

The reliability of shadow diagrams, including the relationship between modelling inputs and the finished drawings, is considered separately within the wider Shadow Diagrams knowledge series.

What should you send when starting a Shadow Diagram assessment?

If you already have the current architectural drawing set and survey, these are usually the most useful place to start.

You should also include any planning correspondence or documentation that specifically refers to shadow diagrams, overshadowing requirements, nominated assessment dates or requested drawing information.

Where additional information about the site or neighbouring development is already available, providing it can help establish the relevant context without requiring the project team to identify it later.

You do not need to determine the complete technical scope yourself before making contact. Starting with the current project information allows the available inputs to be reviewed and any additional requirements to be identified in relation to the actual development.

Project information within the wider shadow assessment

Good shadow documentation starts before the first shadow is calculated. It starts with establishing what is being modelled, where it sits and what the assessment needs to demonstrate.

Architectural drawings establish the proposed built form. Survey and site information establish its physical context. Planning requirements establish the dates, times and documentation conditions that may need to be addressed.

The exact combination will vary between projects, which is why the appropriate inputs should be determined from the development itself rather than from a universal checklist.

Once those foundations are established, the shadow diagrams can provide a clearer and more reliable representation of the existing and proposed shadow conditions relevant to the project.