The 8-step framework

1. STEP 1

   Start with the structure, not the wishlist

   The biggest input is the condition of the existing home. Book a structural engineer for a feasibility visit before you spend on design. Failing footings on reactive clay - common across Melbourne’s western and northern growth corridors - or a second storey needing underpinning can quietly tip a sound-looking extension into rebuild territory.

2. STEP 2

   Measure how much floor area you are adding

   The industry rule of thumb: when the work costs more than roughly 50-60% of a new build, a knockdown rebuild often becomes the smarter choice. If you are reworking most of the house to make the extension flow, you are effectively paying rebuild money for half a home.

3. STEP 3

   Compare land value against house value

   If your block is worth far more than the house on it - common in established middle-ring Melbourne suburbs - a rebuild unlocks that land value with a home that suits it. If the home is sound and the location is the whole point, extending protects what you already have.

4. STEP 4

   Check your planning overlays and permit path first

   Before you spend on design, check your property for a Heritage Overlay (HO), Neighbourhood Character or Significant Landscape Overlay on Vicplan or with your council. A heritage overlay can make demolition hard to approve (pushing you toward extending). Many straightforward works may qualify for a faster VicSmart permit; larger changes need a full planning permit.

5. STEP 5

   Price both paths on the same brief

   Get an extension quote and a rebuild quote against the same end-state - the bedrooms, living zones and finish level you actually want. Comparing a bare extension against a fully finished rebuild is the most common way Melbourne families talk themselves into the wrong answer.

6. STEP 6

   Factor the extension risks people underestimate

   Extensions on older Melbourne homes carry hidden-condition risk: asbestos in pre-1990 walls and eaves, non-compliant old wiring, and undersized footings. Add temporary accommodation if a second storey makes the home uninhabitable for a period, plus the cost of matching new work to old. Budget a 15-20% contingency.

7. STEP 7

   Factor the rebuild costs people forget

   A rebuild is not just the build. Budget demolition, service disconnections and reconnections, site preparation, and holding or rent costs across the build. In growth areas also check for a Growth Areas Infrastructure Contribution (GAIC) or a Section 173 agreement on title. The upside: a new 7-star NatHERS home with full structural warranties and Domestic Building Insurance cover - always built by a builder registered with the Victorian Building Authority (VBA).

8. STEP 8

   Weigh the lifestyle factors honestly

   Staying in your street, keeping the kids in the same school zone, and avoiding a year of disruption all have real value - sometimes enough to justify extending even when the raw numbers lean rebuild. Name these trade-offs with the whole household before you commit either way.

FAQs