Secondary dwellings have become a genuine feature of the Melbourne property market — as rental income, multigenerational housing, or simply extra space. Whether you're buying a property with an existing granny flat or planning to build one, the due diligence involved is easy to underestimate.
An existing secondary dwelling carries its own set of risks separate from the main house — often built later, sometimes by different tradespeople, and not always to the same standard or with the same permits. Understanding what you're actually buying matters just as much here as it does for the primary residence.
The Core Consideration
A granny flat or secondary dwelling is a separate structure with its own foundations, services, and construction history — which means it needs its own genuine assessment, not just a glance while inspecting the main house.
What to Check on an Existing Secondary Dwelling
- 1Permit & Approval History
Confirm the structure was built with appropriate council approval — unpermitted structures can create complications at resale or with insurance.
- 2Structural Condition
Assess foundations, framing and roof independently — a separate structure means separate risk factors.
- 3Services & Connections
Understand how plumbing, electrical and stormwater connect to the main dwelling or to independent services.
- 4Build Quality & Standards
Secondary dwellings, particularly older or owner-built ones, can vary significantly in construction quality.
- 5Moisture & Pest Risk
Smaller, often lower-set structures can carry elevated moisture and termite risk if drainage wasn't well considered.
Buying vs Building: Different Priorities
| Buying a Property With an Existing Dwelling | Building a New Secondary Dwelling | |
|---|---|---|
| Key focus | Verifying permits, condition and compliance | Stage inspections during construction |
| Main risk | Unpermitted or substandard existing work | Site constraints, easements, service connections |
| Inspection type | Standard building inspection of the structure | Slab, frame and pre-handover stage inspections |
| Resale consideration | Confirm value is genuinely reflected in permits | Build to a standard that supports future resale |
Why Permit History Matters More Than It Seems
An unpermitted secondary dwelling isn't just a compliance technicality — it can affect your insurance cover, your ability to legally rent it out, and its contribution to the property's assessed value. It's worth confirming permit status with the relevant council before finalising a purchase that includes an existing secondary structure, alongside your physical inspection.
A Practical Checklist
Whether buying or building, these are worth confirming.
Confirm Permit Status
- Check with the local council whether the existing structure has appropriate approvals
Get It Independently Inspected
- Treat the secondary dwelling as its own structure requiring its own assessment
Understand Service Connections
- Clarify whether plumbing, power and drainage are shared or independent
If Building New, Use Stage Inspections
- Slab, frame and pre-handover inspections apply just as much to a secondary dwelling as a main home
Frequently Asked Questions
Does a granny flat need its own building inspection?
Yes — it's a separate structure with its own construction history and risk factors, and deserves its own genuine assessment rather than a quick look while inspecting the main house.
What happens if a secondary dwelling wasn't council-approved?
This can create complications around insurance, legal use as a rental, and future resale. It's worth confirming permit status with the council and discussing implications with your conveyancer before proceeding.
Are secondary dwellings generally lower quality than the main house?
Not necessarily, but construction standards can vary more than for a primary dwelling, particularly for older or owner-built structures — which is exactly why independent verification matters.
Should I get stage inspections if I'm building a granny flat myself?
Yes — the same logic that applies to a full home build applies here. Slab, frame and pre-handover inspections catch issues while they're still cheap and easy to fix.
Buying or Building a Secondary Dwelling?
Independent inspections that treat your granny flat with the same rigour as the main house.
Book Your Inspection