Two Rescode rules cause more Melbourne double-storey extension redesigns than every other combined: the equinox overshadowing test (Clause 55.04-5) and the 9 m overlooking cone (Clause 55.04-6). Neither is intuitive to a first-time home-owner briefing a designer. Here is how each rule actually works, with the practical design moves that satisfy them.
The equinox overshadowing test
Test date: 22 September (the spring equinox). Time: 9 am and 3 pm. Site: neighbour's secluded private open space (SPOS). Rule: your proposed extension must not add more than 5 m2 of new shadow on the neighbour's SPOS at either time - OR reduce their SPOS receiving 5+ hours of direct sun to less than 75% of the original area.
Design moves that satisfy the test:
- Set the second storey back 1.5-3 m from the ground-floor rear wall so the tall element does not overhang the neighbour's SPOS.
- Skillion or mono-pitch roof falling away from the south neighbour reduces the shadow footprint by 30-50% vs a gable roof of equal ridge height.
- Push living areas to the north side of the plan so the two-storey element ends up on the south (where it shadows your own roof, not the neighbour's yard).
- Cross-check with a shadow diagram at concept-plan stage - do not wait until council refers you back. A designer can generate shadow diagrams in Vectorworks / Revit / ArchiCAD in 20 minutes.
The 9 m overlooking cone
Rule: any habitable-room window or balcony on the first floor within 9 m (horizontal distance) of a neighbour's habitable-room window OR secluded private open space must be treated so it cannot be seen through at seated eye height (1.7 m).
Design moves that satisfy the rule:
- Obscure glazing to 1.7 m sill height. Cheapest option. Frosted or patterned glass to 1.7 m, clear above. Loses the view.
- Fixed high-sill windows (1.7 m sill). Preserves ventilation with no obscure glass. Reduces natural light.
- Fixed external screens (louvres, batons) with less than 25% transparency. Preserves view partly.
- Angle the windows away from the affected direction. If the window can only see a wall or the sky, the rule is satisfied.
- Move the window to the opposite wall. Most obvious. Costs floor-plan flexibility.
The bathroom loophole (not really)
Bathroom, laundry and toilet windows do not count as habitable rooms and are exempt. Kitchens, living rooms and bedrooms all count. Study rooms without a door count as habitable. Master ensuites count as bathroom (exempt).
The council daylight-plane variation
Some councils (notably City of Boroondara and City of Stonnington) also apply a stricter daylight-plane test at 32 degrees from any point on the neighbour's boundary. Check the specific planning scheme for your council BEFORE briefing your designer.
Where BuildPilot fits
We are not town planners. Our Rescode setbacks guide covers the sibling rules. Our Monash and Boroondara council guides cover local variations. Book a 1-hour consultation with a planning-experienced draftsperson before your builder starts detail design.
