Case Study: Section 4.55(2) modification in Russell Avenue, Sans Souci

Homeowners often need to fine tune an approval after detailed design or early construction.

A Section 4.55(2) modification is the NSW pathway for changes that are more than a minor error yet still keep the project substantially the same.

This case in Russell Avenue, Sans Souci shows how a careful package of architectural refinements can improve internal amenity, confirm Building Code of Australia compliance, and protect flood resilience without changing the approved envelope or planning impacts.

Prepared by Town Planning Sydney.

Project snapshot

The approved development is a dual occupancy with two attached secondary dwellings in the R3 Medium Density Residential zone under the Bayside Local Environmental Plan 2021.

The site area is 742.1 sqm.

The original consent set the overall building form and heights, including ridgelines up to 10.52 m approved by Council through the original DA process.

The modification kept the same footprint, setbacks, maximum height and overall massing profile. It also slightly reduced the secondary dwelling floor area, which improves the proposal’s density position against the 0.7:1 FSR control.

What changed and why it matters

Amenity upgrades to openings and light: The most visible refinements are increases to the height of several glazed doors. D05 and D06 increased from 2,100 mm to 3,000 mm, while D12 and D13 rose by 500 mm. These vertical increases sit entirely within the approved ceiling levels and roof profile. They boost the light transmitting area in key rooms and, alongside new skylights to corridors and stair voids, help exceed BCA Part 3.8.4.2 minimum natural lighting requirements. Tinted glazing was noted for west facing windows to assist thermal comfort.

Minor GFA reduction: The secondary dwelling area decreased from 52.28 sqm to 50.68 sqm. With the building envelope unchanged, this reduction supports compliance with the 0.7:1 FSR and confirms there is no intensification of density.

Privacy improvements: Additional privacy measures strengthen performance against Bayside DCP guidance. These include a 1.7 m full height brick wall to the alfresco, 2.2 m screening in sensitive locations, and bathroom sill heights revised to 1.8 m. The horizontal sight lines to neighbours did not change because setbacks and window locations in plan remain as approved.

Construction clarity and code notes: The plans now show smoke alarms, mechanical ventilation to wet areas, and party wall fire separation to underside of roof and to footing in line with NCC provisions. Notes confirm non combustible eave lining and compliant vertical separations. These clarifications improve buildability and demonstrate code alignment without altering the approved external form.

Landscape and conditions housekeeping: The modification maintains the approved landscaped area and adds explicit tree protection fencing notes. Driveway details were annotated to reflect two 3 m wide crossings with 6 m separation and 0.5 m public domain clearance to address a consent condition.

Flood resilience retained

The site is flood affected and the original consent imposed strict controls.

The modification keeps the finished floor levels and does not introduce new openings below the flood planning level.

Air conditioning units are now explicitly noted to be at least 500 mm above the 1% AEP flood level, aligning with the consent conditions.

Raising door head heights does not affect sill heights, so the critical flood clearance remains intact.

“Substantially the same” test

For a Section 4.55(2) pathway, Council must be satisfied the development as modified is substantially the same as the approved scheme and that environmental impacts are minimal.

Here, the land use stays as dual occupancy with attached secondary dwellings in the R3 zone.

The envelope, ridgelines, setbacks and floor plates are unchanged.

Shadow outcomes remain consistent with the original approval, with three hours solar access to the private open space on site and at the adjacent properties still achieved during key dates.

Privacy is improved rather than diminished.

Traffic, access, and parking arrangements are maintained with condition aligned refinements only.

On that basis, the identity, scale, and impact profile of the development are preserved while internal amenity is improved.

BASIX implications

Because the modification introduces changes to glazing and skylights and relocates or specifies mechanical services, the BASIX assessment must be updated.

The revised certificate will confirm that water, energy, and thermal comfort targets continue to be met or exceeded for the modified design.

This is standard practice whenever glazing quantities or performance characteristics change in a BASIX affected project.

Outcome and takeaways for homeowners and builders

• Keep the envelope steady: Maintaining the approved height, setbacks, and footprint is the strongest foundation for a Section 4.55(2) case.

• Show clear benefits: Upgrades that improve daylight, ventilation, thermal comfort, and privacy help demonstrate a net amenity gain without extra impact.

• Address code and conditions on the plans: Including NCC notes, flood clearances, and condition specific details reduces assessment risk and speeds decision making.

• Update BASIX when glazing changes: Any change to the light transmitting area or high performance glass triggers a refreshed BASIX certificate.

This Sans Souci modification demonstrates a practical pathway to refine an approval, improve liveability, and satisfy Council that impacts remain minimal while the development stays substantially the same as first approved.