Dual occupancy development has become one of the most common project types EMS Engineering Consultancy works on across Melbourne, as developers and builders respond to demand for higher-density housing on existing residential lots. It’s also a project type where structural engineering decisions early in the design significantly affect both cost and feasibility later on.

• 25 August 2026
• Komal Chauhan

Why Dual Occupancy Sites Present Unique Structural Challenges

Unlike a standalone new build, dual occupancy projects typically work within tighter site constraints — narrower lots, shared boundaries, existing services, and often the need to consider an adjoining property’s structure during excavation and construction. These constraints shape structural decisions from the footing design stage onward, not just the final building layout.

Footing Design Considerations Specific to Dual Occupancy

Footing design for dual occupancy sites needs to account for:

• Soil classification across the site, which can vary meaningfully even within a single suburban block
• Proximity to boundaries and adjoining structures, particularly where excavation near an existing building’s footings is involved
• Differential settlement risk between the two dwellings, especially where they share a party wall or are built close together
• Site access constraints, which can affect what construction methods and equipment are realistically usable

Getting footing design right at this stage has flow-on effects for the entire project — an inadequate assessment early on is one of the more common sources of costly redesign later in a dual occupancy build.

Coordinating Structural Engineering with the Planning Process

Dual occupancy developments typically require both planning permit and building permit approval, and the structural engineering documentation needs to align with what’s been approved at the planning stage. Significant design changes after planning approval can trigger the need for amended structural documentation, which is why early coordination between the architect, town planner and structural engineer tends to produce a smoother approval process overall.

What a Structural Engineer’s Scope Typically Covers on Dual Occupancy Projects

• Footing and slab design for both dwellings
• Structural design for any shared or party walls
• Retaining wall design where site levels require it
• Engineering documentation for the building permit application
• Liaison with the building surveyor where structural queries arise during the approval process

Managing Risk to Adjoining Properties

Where a dual occupancy development involves excavation or construction near an existing boundary, structural engineers also need to consider the potential impact on adjoining properties — an area that can involve additional survey and assessment work, particularly for older adjoining structures with less predictable footing conditions. This is a common source of project delay when it isn’t planned for early.

Why Early Engineering Input Matters for Feasibility

Because footing conditions, boundary constraints, and site access all affect what’s realistically achievable, involving a structural engineer during the feasibility and concept design stage — rather than after a design is finalised — helps developers and builders understand cost and constructability implications before they’re locked into a design that may need significant rework.

EMS Engineering Consultancy works with developers and builders across Melbourne on dual occupancy projects from concept through to permit-ready documentation, helping identify site constraints early enough that they inform the design rather than derail it.