Can I Build a Granny Flat? Site Assessment Checklist (2026)

TL;DR: Not every property can accommodate a granny flat. Before spending money on designs, run through this 12-point checklist covering lot size, zoning, slope, access, services, overlays, setbacks, easements, and more. Most issues can be identified for free using your state’s online planning portal and your property’s title documents. This checklist helps you catch deal-breakers early and avoid costly surprises.

Key takeaways

• Minimum lot size varies by state: NSW requires 450sqm, Victoria has no minimum (but 300sqm+ for permit exemption), WA has no minimum, SA requires 600sqm for fast-track approval.
• Zoning must be residential — check your property’s zone on your state’s planning portal before doing anything else.
• Slope adds cost: a fall of more than 1 metre across the building area can add $20,000–$50,000+ to your build.
• Access matters: you need at least 1.5m wide x 2.1m high clear access to the build site for materials and construction.
• Services proximity (sewer, water, electricity) directly affects connection costs — the further from existing infrastructure, the more expensive.
• Overlays (flood, bushfire, heritage, landslide) can add requirements, costs, or even block construction entirely.
• Use the grannyflatcost.com calculator to factor your site conditions into a realistic cost estimate.

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The 12-point site assessment checklist

Print this checklist or save it to your phone. Work through each item before engaging a designer or builder. Items with a cost estimate show where site conditions directly affect your budget.

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1. Lot size — does your property meet the minimum?

This is the first pass/fail test. If your lot is too small, you cannot build a granny flat regardless of how much you want one.

State/Territory	Minimum lot size	Notes
NSW	450sqm	Must have 12m frontage
Victoria	No minimum	300sqm+ for planning permit exemption
Queensland	450–600sqm	Varies by council
South Australia	600sqm (DTS pathway)	Smaller lots assessed on merit
Western Australia	No minimum	Removed April 2024
Tasmania	No specified minimum	Must accommodate setbacks and open space
ACT	No minimum	Removed — any size block eligible
NT	Varies by zone	Check with your local council

How to check: Your property’s lot size is on your Certificate of Title (available from your state’s land titles office) or measurable from your state’s online mapping portal.

Checklist item: [ ] My lot meets the minimum size requirement for my state/territory.

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2. Zoning — is residential development permitted?

Your property must be in a zone that permits secondary dwellings. Most granny flats are allowed in residential zones, but not all zones qualify.

Zones that typically allow granny flats: R1 General Residential, R2 Low Density Residential, R3 Medium Density Residential, R4 High Density Residential, R5 Large Lot Residential (often DA required), General Residential Zone (Victoria), Neighbourhood Residential Zone (Victoria).

Zones that typically do not allow granny flats: industrial zones, commercial/business zones (unless mixed-use), environmental/conservation zones, and special purpose zones.

How to check: Use your state’s online planning portal:

State	Planning portal
NSW	NSW Planning Portal
Victoria	VicPlan
Queensland	Council-specific — search “[your council] planning scheme”
South Australia	PlanSA SAPPA
Western Australia	PlanWA
Tasmania	LIST Map
ACT	ACTmapi

Checklist item: [ ] My property is zoned for residential use that permits secondary dwellings.

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3. Slope assessment — how flat is your building area?

Slope is one of the biggest cost variables in granny flat construction. A flat site is straightforward; a sloping site requires additional engineering, earthworks, retaining walls, or specialised foundations.

Slope grade	Description	Cost impact
0–2% (flat)	Ideal — standard slab construction	No additional cost
2–5% (gentle)	Manageable — minor cut and fill may be needed	+$5,000–$10,000
5–10% (moderate)	Requires engineering — stepped footings or split-level	+$10,000–$25,000
10–15% (steep)	Significant engineering — retaining walls, suspended slab	+$20,000–$50,000
15%+ (very steep)	Major challenge — specialist design, pier systems	+$50,000–$100,000+

How to assess slope: A visual check can get you started — a 1-metre drop over a 10-metre span is a 10% slope. Your state’s mapping portal often shows contour lines (typically at 1m or 2m intervals). For anything serious, a licensed surveyor can provide a contour survey for $1,500–$3,000. This is the most accurate method and is typically required before any real design work can happen.

The critical figure is the fall across the building footprint, not the overall property slope. A steeply sloping property might still have a flat area in the backyard that works perfectly.

Checklist item: [ ] I have assessed the slope of my proposed building area and understand the cost implications.

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4. Access assessment — can materials and equipment reach the site?

Your builder needs to get materials, equipment, and potentially a small crane or excavator to the building site. Restricted access increases costs significantly.

Minimum access requirements: at least 1.5 metres wide and 2.1 metres high, with a surface that can support delivery vehicles or wheelbarrows.

Common access issues include narrow side gates or passageways (very common on older properties), low-hanging trees, power lines, or eaves blocking overhead clearance, steep or unstable ground along the access path, and fences or structures that need temporary removal.

If vehicle access is available via a wide side driveway or rear lane, construction is standard and materials can be delivered directly. If only pedestrian access is available through a narrow side path, costs increase by $5,000–$15,000+ due to manual material handling, smaller equipment, and longer build times. Prefabricated or modular granny flats may not be deliverable at all. If there is no access, a crane lift over the house may be needed for prefabricated builds ($5,000–$15,000 per crane day), or the build must use traditional construction methods with materials carried in by hand.

Checklist item: [ ] I have at least 1.5m x 2.1m clear access to the proposed building area.

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5. Sewer, water, and electricity — how close are existing services?

Connecting your granny flat to sewer, water, and electricity is mandatory. The distance from existing infrastructure directly affects cost.

Service	Typical connection cost (close)	Typical connection cost (far/complex)
Sewer	$3,000–$5,000	$8,000–$20,000+
Water	$1,500–$3,000	$5,000–$10,000
Electricity	$2,000–$5,000	$5,000–$15,000
Gas (if required)	$1,500–$3,000	$3,000–$8,000
Total (typical)	$8,000–$16,000	$21,000–$53,000+

A few things to check: identify where the sewer main runs through your property — if the granny flat is on the opposite side from the sewer, trenching costs increase substantially. In some states, granny flats must connect to the existing dwelling’s sewer connection rather than directly to the main. Properties at the end of long supply runs or at higher elevations may have low water pressure requiring a booster pump. Your existing electrical supply may need upgrading if the granny flat’s load exceeds the remaining capacity (a switchboard upgrade can cost $2,000–$5,000). Rural properties without mains sewer will need an on-site wastewater system, which can cost $10,000–$25,000+ depending on soil conditions and council requirements.

How to check: Your property’s drainage diagram (available from your water authority) shows the location of sewer and stormwater connections. Your Section 149 Certificate (NSW) or equivalent planning certificate in other states may also show service locations.

Checklist item: [ ] I know where my sewer, water, and electrical connections are and have estimated connection distances.

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6. Tree removal and vegetation

Trees on or near the proposed building area may need removal or protection, and both come with requirements and costs.

Tree removal is generally straightforward for non-significant species, trees not covered by a Tree Preservation Order (TPO), and trees that are dead, dying, or dangerous.

Tree removal is restricted or prohibited for heritage or significant trees (many councils maintain registers), trees covered by a TPO (you need council approval, which may be refused), trees on neighbouring property, and trees in environmental overlays (removal may require specialist ecological assessment).

Tree removal costs $500–$5,000+ per tree depending on size, species, and access. Stump grinding adds $200–$500 per stump.

If a significant tree is near (but not on) the building site, you may need a Tree Protection Zone (TPZ) fence and an arborist report ($500–$1,500). Construction activity within the TPZ is restricted.

Checklist item: [ ] I have identified all trees that may need removal or protection, and checked for Tree Preservation Orders.

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7. Flood zone check

Properties in flood-prone areas face additional requirements that can significantly affect granny flat feasibility and cost.

Flood zone implications: the granny flat may need to be built above the defined flood level, potentially requiring elevated construction; walls, floors, and finishes below the flood level may need to be flood-resistant; flood-affected properties typically require a more detailed planning application; and flood-prone locations may have higher or unavailable building insurance.

How to check: Search for “[your council] flood mapping” or check your state’s planning portal. Most councils publish flood maps showing the 1% AEP (Annual Exceedance Probability) flood extent.

Checklist item: [ ] I have checked whether my property is in a flood zone and understand any floor level requirements.

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8. Bushfire zone check

Properties in designated bushfire-prone areas must comply with additional construction standards that increase cost.

BAL rating	Description	Approximate cost impact
BAL-LOW	No special construction required	No additional cost
BAL-12.5	Ember attack — basic protection	+$5,000–$10,000
BAL-19	Increasing ember and radiant heat	+$10,000–$20,000
BAL-29	High radiant heat exposure	+$15,000–$30,000
BAL-40	Very high radiant heat	+$25,000–$50,000
BAL-FZ (Flame Zone)	Direct flame contact expected	Often not feasible for granny flats

How to check: Your state’s planning portal typically shows bushfire-prone land overlays. A formal BAL assessment ($500–$2,000) by a certified practitioner determines the exact rating for your building site.

Checklist item: [ ] I have checked whether my property is in a bushfire-prone area and know the likely BAL rating.

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9. Heritage overlays

Properties within heritage overlays face additional design restrictions and approval requirements.

Heritage overlays can mean: external materials and colours may need to match the existing streetscape character; roof form, pitch, and height may be prescribed; visibility from the street may be restricted (the granny flat might need to be completely hidden behind the main dwelling); heritage assessment by council advisors adds to the approval process; and the whole thing simply takes longer.

Heritage overlays are most common in inner-city and older suburban areas across all states. They can apply to individual properties or entire precincts.

How to check: Your state’s planning portal will show heritage overlays on the property map. Your property’s planning certificate will also list any heritage controls.

Checklist item: [ ] I have checked whether my property is affected by heritage overlays and understand any design restrictions.

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10. Setback requirements — can you fit the granny flat?

Setbacks define the minimum distances your granny flat must be from property boundaries and the main dwelling. After applying setbacks, the remaining “buildable area” determines what size granny flat you can fit.

State	Front	Side	Rear	Between dwellings
NSW (<900sqm)	Behind main dwelling	0.9m	3m	1.8m (or fire-rated wall)
NSW (>900sqm)	Behind main dwelling	1.5m	5m	1.8m (or fire-rated wall)
Victoria	Behind main dwelling	1m	3m	No minimum (fire rules apply)
SA (DTS)	500mm behind front line	Zone TNVs	Zone TNVs	No minimum specified
WA	Behind main dwelling	R-Code requirements	R-Code requirements	No minimum specified
Tasmania	4.5m (or streetscape)	1.5m	3m	Fire separation applies

How to calculate your buildable area: Get an accurate site plan (from your title or a surveyor). Draw in all setback lines from each boundary. Mark the position of the main dwelling and required separation. The remaining area is your buildable envelope. Check if your desired granny flat size fits within it.

Drawing it on graph paper or using Google Earth to measure your backyard works well as a starting point. A professional site plan from a surveyor ($500–$1,500) gives the most accurate result.

Checklist item: [ ] I have calculated my buildable area after setbacks and confirmed my desired granny flat size fits.

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11. Easements and covenants

Easements and covenants are restrictions on your property that may prevent or limit construction.

Easements to watch for include sewer easements (a strip of land typically 1–3m wide where the sewer main runs — you generally cannot build over one), drainage easements (similar restrictions for stormwater infrastructure), right-of-way easements (access rights for neighbours or utility providers), and power line easements (overhead or underground power corridors).

Covenants to watch for include building covenants on the title that restrict the number of dwellings, building materials, or minimum build quality; developer covenants in newer estates that sometimes prohibit secondary dwellings or outbuildings of certain sizes; and restrictive covenants that may limit building height, setbacks, or even colours.

How to check: Easements and covenants appear on your Certificate of Title and deposited plan. Order these from your state’s land titles office or check with your conveyancer/solicitor. Some easements also appear on drainage diagrams from your water authority.

If an easement runs through your proposed building area, you may need to relocate the granny flat (if space allows) or apply for easement diversion/removal — which is rare and expensive ($10,000–$50,000+).

Checklist item: [ ] I have checked my title for easements and covenants that may restrict where I can build.

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12. How to read your planning certificate

Every property has a planning certificate that summarises the planning controls affecting your land. This is your most useful document for assessing granny flat feasibility.

State	Document name	How to get it	Typical cost
NSW	Section 10.7 Certificate	From your local council	$53–$180
Victoria	Planning Property Report	Through VicPlan (free) or council	Free–$50
Queensland	Planning and Development Certificate	From your local council	$50–$200
SA	Planning Certificate	Through PlanSA	$50–$100
WA	Zoning Certificate	From your local council	$50–$100
Tasmania	Planning Certificate	From your local council	$50–$100

What to look for on your planning certificate: zone classification (confirms what development is permitted), overlays (flood, bushfire, heritage, environmental, acid sulfate soils), minimum lot size, maximum site coverage, height limits, setback requirements, contaminated land history, and road widening reservations.

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Quick decision matrix

After completing the 12-point checklist, use this matrix to assess your situation:

Result	What it means
All 12 items pass	Strong candidate — proceed to design and quoting
1–2 items need resolution	Likely feasible — address the specific issues before committing to a builder
3+ items have issues	Complex project — engage a town planner or building designer for a feasibility assessment before proceeding
Lot size or zoning fails	Cannot build — a granny flat is not possible on this property under current rules

What to do next

1. Complete the checklist — work through all 12 items using the resources linked above
2. Estimate your costs — use the grannyflatcost.com calculator to get a detailed cost estimate that accounts for your site conditions, state, and desired granny flat size
3. Get a site survey — if your checklist reveals potential setback or slope issues, invest $1,500–$3,000 in a professional contour and feature survey
4. Engage a professional — a building designer or town planner can provide a formal feasibility assessment for $500–$2,000, confirming what is achievable on your specific site
5. Lodge your application — once design is complete, submit through your state’s planning portal or local council

The site assessment phase is the cheapest part of the entire granny flat process. Spending a few hours (and a few hundred dollars on a planning certificate) now can save you tens of thousands in redesign costs, unexpected site works, or — worst case — discovering your property simply cannot accommodate a granny flat after you have already paid for designs.