Posted at 12:31h
in Blog
by Oakvale Homes
Granny flats and secondary dwellings have become increasingly popular in recent years – and it’s easy to see why. Whether you’re looking to create space for extended family, give older children some independence, generate rental income, or add value to your property, a secondary dwelling can be a smart investment.
However, while the idea may sound simple, there are several important planning and design considerations to take into account before starting your project. Different councils have different rules, and what works on one block may not be possible on another.
At Oakvale Homes, we work with clients and the relevant regional councils within our build zone to help navigate the process and design secondary dwellings that suit both council requirements, budget and lifestyle needs.
What is a Secondary Dwelling?
A secondary dwelling – often referred to as a granny flat – is a self-contained dwelling located on the same lot as a primary residence.
Importantly, a secondary dwelling is considered subordinate to the main home and generally cannot be separately titled or sold independently.
Key Things to Consider Before Building a Granny Flat
Council Regulations Vary Between Regions
One of the biggest misconceptions about granny flats is that the rules are the same everywhere – they’re not. Each council has its own planning scheme, size limits, setbacks, and overlay requirements.
For example, some councils limit the maximum floor area differently depending on whether the property is residential or rural residential land, while others have varying setback or height requirements.
This is why one of the first steps should always be contacting your local council or speaking with the qualified building professionals at Oakvale Homes to understand what is achievable on your block.
Site Coverage Matters
A major consideration is total site coverage. In many council areas, the combined footprint of all buildings on the property – including the main dwelling, granny flat, sheds, patios, and outbuildings – generally cannot exceed 50% of the total site area.
This means that even if your block appears large enough, existing structures may already use a significant portion of your allowable coverage.
Careful site planning is essential to ensure your secondary dwelling can fit comfortably while still complying with council requirements.
Access to the Secondary Dwelling
Access is another important factor that is often overlooked in the early planning stages.
You need to think about:
How people will safely access the dwelling
Vehicle access and manoeuvrability
Privacy between the main dwelling and granny flat
Emergency and maintenance access
Some councils also regulate where a secondary dwelling can be positioned on the block, particularly in relation to the front of the main residence or property boundaries.
Car Parking Requirements
Most councils require provision for at least one designated car parking space for a secondary dwelling. This does not necessarily need to be an undercover parking space, but a defined accessible parking space.
Even where this isn’t strictly enforced under planning rules, practical parking considerations are important – especially on suburban blocks where street parking may already be limited.
Planning parking properly from the start can avoid future access and congestion issues.
Sewerage & Septic System Upgrades
One of the most commonly forgotten costs when planning a granny flat is sewerage or septic upgrades, although this only applies to blocks not connected to town sewerage.
Adding another kitchen, bathroom, and laundry increases the load on your property’s wastewater system. Depending on your site and existing infrastructure, you may need to:
Upgrade your septic system
Increase treatment capacity
Modify existing sewer connections
Install additional plumbing infrastructure
This can become a significant cost if not considered early in the planning process.
Overlays & Development Applications
Some secondary dwellings can be approved through a private building certifier without requiring a full development application – provided the proposal meets all council planning requirements.
However, if your property is affected by overlays or doesn’t comply with certain requirements, a formal development application (DA) through council may be required.
Common overlays that can trigger additional assessment include:
Flood overlays
Bushfire overlays
Environmental overlays
Heritage overlays
Character or neighbourhood overlays
These overlays can affect placement, height, materials, setbacks, and even whether a secondary dwelling is permitted at all.
Lot Size & Positioning Requirements
Some councils also impose minimum lot size requirements and restrictions on how far the secondary dwelling can be positioned from the main house.
Because these requirements differ significantly between councils and zoning types, it’s important not to assume what applies to one property will apply to another.
Planning Early Saves Time & Money
The earlier you investigate council requirements, overlays, access, sewerage capacity, and site coverage, the smoother the process will be.
At Oakvale Homes, we help clients work through these considerations from the very beginning – ensuring designs are practical, compliant, and tailored to suit both the property and lifestyle goals.
Whether you’re planning accommodation for family, an investment opportunity, or extra space for the future, a well-designed secondary dwelling can add enormous value to your property when done correctly.
Thinking About Building a Granny Flat?
If you’re considering a granny flat or secondary dwelling our team would love to help guide you through the process.
Contact Oakvale Homes today to discuss your block, your ideas, and what may be possible for your property.
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