The Truth - “Approval-Free” Granny Flats Under 70m²
One of the most common questions we receive at TBARCH is this:
“Is it true that granny flats under 70m² don’t require council approval?”
The short answer is no. This is one of the most misunderstood and frequently misrepresented topics in residential development today.
Unfortunately, many homeowners are being misled by marketing claims from companies selling prefabricated granny flats. These claims often suggest that if the granny flat is under 70m², it does not require approval. This is not accurate, and acting on this misinformation can result in serious legal, financial, and compliance consequences.
This article explains the truth, based on Western Australian planning and building regulations.
Where the 70m² Myth Comes From
The confusion originates from the Residential Design Codes of Western Australia (R-Codes), which allow ancillary dwellings, commonly known as granny flats, up to 70m² to be approved under deemed-to-comply provisions.
This means that if the granny flat meets all planning requirements, it may be approved without requiring planning discretion.
It does not mean that approval is not required.
It simply means the approval pathway is more straightforward.
There is a critical difference.
Planning Approval vs Building Permit: Two Separate Legal Requirements
In Western Australia, there are two separate approvals that may apply:
1. Development Approval (Planning Approval)
This is issued by the local council and assesses:
• Location on site
• Setbacks from boundaries
• Privacy and overlooking
• Site coverage and open space
• Compliance with R-Codes and local planning policies
If the granny flat meets all deemed-to-comply standards, Development Approval may not be required.
However, this must be assessed professionally. It is not automatic.
Many properties do not fully comply due to boundary setbacks, site constraints, or local planning variations.
2. Building Permit (Always Required)
This is issued under the Building Act 2011 and is mandatory for all habitable structures, including granny flats, regardless of size.
The Building Permit confirms compliance with:
• Structural safety
• Energy efficiency
• Fire safety
• Waterproofing
• Health and safety requirements
• National Construction Code compliance
There is no exemption based on size.
A 30m² granny flat requires a Building Permit. A 70m² granny flat requires a Building Permit. A 100m² granny flat requires a Building Permit.
The size does not remove this legal requirement.
Why Some Companies Say Approval Is Not Required
Many prefab suppliers focus on selling the structure itself, not the legal approval process.
Their marketing often refers to planning approval exemptions under ideal conditions. This is then misunderstood or misrepresented as meaning no approval is required at all.
This is incorrect and dangerous advice.
The responsibility for compliance always rests with the property owner, not the supplier.
If a granny flat is installed without proper approval, the council may require:
• Retrospective approval
• Structural certification
• Costly modifications
• Or complete removal of the structure
These situations are far more expensive than doing it properly from the beginning.
The Real Risks of Building Without Approval
We frequently assist clients who unknowingly relied on incorrect advice and now face serious consequences.
Common issues include:
• Difficulty selling the property due to unapproved structures
• Bank refusing refinancing due to non-compliance
• Council issuing compliance notices
• Insurance claims being rejected
• Costly retrospective approvals requiring structural inspections
In some cases, retrospective approval can cost significantly more than obtaining approval initially.
A Real Case We Encountered
A homeowner purchased a prefabricated granny flat advertised as “no approval required under 70m².”
After installation, they discovered they could not obtain occupancy certification due to missing approvals and structural documentation.
The bank refused refinancing. The council required retrospective approval. Engineers and surveyors had to inspect and certify the structure after construction, which was complex and costly.
The homeowner ultimately paid significantly more than if the project had been properly designed and approved from the start.
This situation is unfortunately common.
The Correct and Safe Process
A properly compliant granny flat involves:
• Site assessment and planning review
• Professional architectural drawings
• Structural engineering certification
• Energy efficiency assessment
• Building Permit approval
• Proper construction and certification
This ensures the structure is legal, safe, insurable, and adds real property value.
How TBARCH Helps Protect Homeowners
At TBARCH, we specialise in compliant, approval-ready granny flat design.
We provide:
• Full compliance assessment based on your property
• Professional architectural drawings
• Coordination with engineers and building surveyors
• Complete Building Permit documentation
• Approval-ready solutions that protect your investment
We ensure your granny flat is fully compliant, legally approved, and adds long-term value to your property.
The Bottom Line
There is no such thing as a fully approval-free granny flat in Western Australia.
Granny flats under 70m² may be exempt from Development Approval in some cases, but they always require a Building Permit.
Any claim suggesting otherwise should be treated with caution.
Proper approval protects your investment, your property value, and your peace of mind.
Thinking About Building a Granny Flat?
If you are considering a granny flat and want to understand exactly what approvals apply to your property, contact TBARCH for a professional assessment.
We will provide clear, accurate advice based on your site and ensure everything is done correctly from the start.
TBARCH
Precision. Clarity. Design with purpose.
