The legal definition of “natural ground level” (NGL) remains elusive within Victoria’s building and planning framework. However, recent decisions by the Building Appeals Board (BAB) and the Victorian Civil and Administrative Tribunal (VCAT) are helping to shape a more coherent approach, with practical consequences for developers, consultants and building surveyors. 

Determining NGL is a threshold issue and a critical starting point when assessing building height, setbacks and overall compliance under the Building Regulations 2018 (Vic) (Regulations). Height limits in regulation 73 (building height), regulation 75 (setback), and planning schemes across Victoria frequently reference “natural ground level”, yet that phrase remains undefined in both the Building Act 1993 (Vic) (Building Act) and the Regulations.

This legal vacuum has led to competing methodologies in the field. In some instances, NGL is treated as the existing site condition at the time of permit application. In others, it’s assessed by interpolating pre-development contours from historical survey data.

 In a recent matter before the BAB, Martinez & Funez v Alexopoulos (BAB Case No. 456057, 25 July 2025) (Martinez), the applicants challenged a stop work order, which was said to arise from the building height exceeding 9 metres under regulation 73. That assessment hinged on what constituted “natural ground level” beneath the building's highest point.

The BAB considered competing expert evidence, pre-development survey data, and whether subsequent excavation invalidated the reduced levels (RL) used. Ultimately, the Board found:

• There is no statutory definition of NGL, and no binding methodology;

• pre-development survey evidence, in Martinez, a 2011 feature survey, was the most reliable benchmark;

• interpolation between boundary levels along a consistent gradient is an accepted method for determining NGL;

• minor title or survey inconsistencies, if immaterial, do not prevent a finding on NGL; and

• the correct RL at the relevant point was RL 71.17, based on the evidence led by the applicants.  

This approach aligns with a developing body of case law, including:

• Shire of Gisborne v King [1994] 1 VR 364: Where the Supreme Court distinguished between natural and altered topography and emphasised the factual nature of determining whether land had been modified by human intervention.

• Mrocki v Bayside CC [2015] VCAT 1371: Which preferred the pre-disturbance level that existed prior to any development.

• Faversham Mews Pty Ltd v Boroondara CC [2016] VCAT 1954: Which rejected the “existing condition” test and instead defined NGL as the level before excavation, levelling or fill for development.

• Coda One Pty Ltd v Stonnington CC [2024] VCAT 1022: Which reaffirmed that interpolated or reconstructed survey data is acceptable where original levels have been disturbed.

Across these decisions, a shared principle emerges: “natural ground level” is a question of fact, not convenience, and is to be determined by reference to how the land existed in nature or before human intervention.  

Martinez shows that:

• Height disputes under regulation 73 hinge entirely on the NGL determination;

• feature surveys and expert input are essential;

• relevant building surveyors (RBSs) must engage with objective survey data; and

• the BAB will favour historically anchored evidence over speculation.

Incorrectly determining NGL can derail a project, trigger stop work orders and cause costly redesigns. However, with early planning and proper documentation, many disputes can be avoided altogether, particularly on sloping or previously excavated land.

Sloping blocks pose particular risk when it comes to complying with height limits under regulation 73. The 9-metre height limit applies to the vertical distance between NGL and the highest point of the building.

On a gradient, that height can vary significantly along the length of a wall or roofline, and any error in defining the NGL may result in an erroneous finding of a breach of the Regulations, even where the design appears compliant on paper. 

To avoid costly disputes and enforcement action, consultants should:

• Obtain a feature survey before any site works commence;

• capture existing contours, RLs and gradients before any disturbance occurs;

• use consistent interpolation methodology;

• note that interpolation between known RLs at boundaries along a defined gradient is standard and acceptable;

• clearly mark NGL on all design documentation;

• not assume it is self-evident or that existing ground levels will be accepted as “natural”;

• discuss NGL assumptions with the RBS early;

• engage in pre-permit dialogue or obtain written confirmation where needed;

• not equate existing condition with NGL, as courts have confirmed “natural” refers to pre-disturbance, not a site’s current condition; and

• involve licensed surveyors where needed. A short expert report or diagram validating NGL assumptions can help avoid disputes later.  

Despite its significance, “natural ground level” has never been given a clear statutory definition.

Practitioners are often left to interpret guidance from scattered tribunal and court decisions, as well as industry practices that vary across projects. This ambiguity introduces uncertainty at key development stages, from design and planning applications to compliance checks and enforcement actions. Inconsistencies between planning scheme definitions, building regulation applications, and RBS interpretations mean that consultants must proactively address the risk of misalignment.

Building height is not merely an aesthetic or design consideration; it is a regulatory control mechanism. For dwellings on sloping land, or in established neighbourhoods subject to height-sensitive overlays, exceeding the permissible height limit can have serious consequences. These include stop work orders, enforcement notices, permit refusals or VCAT appeals. In Martinez, the stop work order was triggered by a height non-compliance allegation based entirely on a disputed NGL.

Resolving that single data point (RL 71.17) proved determinative. This underlines the importance of robust early-stage survey work and documentary clarity.  

RBSs have significant discretion in interpreting regulatory compliance, especially where the Regulations are silent on methodology.

To reduce exposure to enforcement, designers and property owners should actively engage with their RBS to agree (or clarify) the proposed approach to NGL.

Many height disputes emerge not from bad faith, but because different professionals apply different standards. It is not uncommon for an RBS to take a more conservative approach when assessing NGL, while designers rely on interpolated data accepted in prior developments. Clear dialogue and agreement on methodology, supported by feature surveys and architectural annotations, can de-risk this dynamic. 

As digital modelling and site-scanning technologies improve, consultants have more tools than ever to document and justify site conditions. Drone surveys, 3D scans and LiDAR-generated topography maps can provide precise digital evidence of pre-construction levels. These tools are particularly useful in dispute contexts, or where earlier survey records are limited. Nevertheless, the regulatory system still relies on professional judgment, standard practice and expert interpretation.

Technological outputs must be presented in a format that RBSs, tribunals and consultants can understand and rely on.  

If future amendments to the Regulations seek to clarify the definition of NGL, they should draw on the accumulated findings of cases such as King, Mrocki, Faversham, Coda and Martinez.

Codifying accepted methodologies, such as interpolation across boundary RLs and reliance on pre-disturbance feature surveys, would provide consistency across projects and jurisdictions. Until then, the best defence remains methodical documentation, transparent assumptions and informed coordination between designers, surveyors and RBSs.

The lessons from Martinez offer a template for navigating this grey area with professionalism and evidence.

If you would like to discuss the implications of NGL determination, regulatory compliance, or strategies to manage building height disputes, please contact our Construction & Engineering team.