A secondary dwelling—commonly called a granny flat—is a self-contained dwelling established in conjunction with a principal dwelling on the same lot. It may be within, attached to or separate from the principal dwelling. Its legal classification depends on the approved use and documents, not a builder’s product name or the structure’s appearance.
This guide combines limited Ermington statistical context with statewide planning guidance. It does not treat the locality name as evidence that a particular parcel is suitable. The legal lot, responsible council, zoning, title, existing approvals, mapped controls, services and proposed design must all be verified before an approval pathway is selected.
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This guide is general information only. Obtain property-specific verification of zoning, overlays, title constraints, services and approval requirements before making design, purchase or construction decisions.
Local granny-flat overview
The locality record identifies Ermington as Australian Bureau of Statistics Suburbs and Localities geography code SAL11438, with an area of approximately 3.8596 square kilometres. SAL means the ABS Suburbs and Localities geography. SAL boundaries are statistical approximations designed to represent commonly recognised localities; they are not cadastral boundaries, planning zones or evidence of which controls apply to a legal parcel.
The 2021 Census All persons QuickStats for Ermington recorded 12,686 people, 4,790 private dwellings, a median age of 37 and an average of 2.8 people per household. These are historical 2021 Census observations for the statistical locality, not current population estimates or evidence about present housing demand, property values, rental performance or development capacity.
The supplied ABS geography records the statistical LGA name Parramatta as the sole overlap with the Ermington SAL. “Parramatta” in that dataset is an ABS statistical LGA name. City of Parramatta Council is the formal council organisation named in the supplied official source pack. The overlap is a useful search lead, but it must not be used to decide the responsible council for an address or to apply council instruments to a parcel.
Confirm the legal lot and deposited plan through current property records, then use the NSW Planning Portal Spatial Viewer to begin checking the address. If those checks establish that City of Parramatta Council is responsible, its official development information provides the local application starting point. The Parramatta Local Environmental Plan 2023 mapping route should likewise be applied only after the parcel and relevant planning authority have been confirmed.
Under the NSW secondary-dwelling guidance, a secondary dwelling operates with a principal dwelling and remains on the same lot. This development type does not create a separately subdividable or separately titled residence. A freestanding building is not automatically a secondary dwelling, and a garage, shed or studio cannot be treated as approved accommodation without checking its approval history and authorised use.
State guidance says secondary dwellings are permitted in residential zones R1, R2, R3, R4 and R5 and may be permitted in other zones where the applicable local environmental plan allows them. Permissibility is only an initial planning question. It does not establish that an address can accommodate the proposal or that a particular approval pathway is available. Rural and non-residential land requires direct review of the applicable local environmental plan rather than residential-zone assumptions.
Council rules and approval pathway
New South Wales provides two potential approval pathways. A development application is assessed by the responsible council. Alternatively, a complying development certificate may be issued by a council or appropriately registered certifier when every relevant statutory requirement is satisfied. Complying development is standards based; a certifier cannot disregard an exclusion, prerequisite or development standard.
For the Housing SEPP complying-development pathway, official guidance identifies a lot area of at least 450 square metres, except where the secondary dwelling is located entirely within an existing dwelling house. This is one bounded eligibility rule, not a universal minimum for a council-assessed application and not sufficient by itself to establish complying-development eligibility.
The proposal must be tested against the current State Environmental Planning Policy (Housing) 2021, including its relevant Schedule 1 provisions, and the State Environmental Planning Policy (Exempt and Complying Development Codes) 2008. The Department’s complying-development guidance explains the certifier’s role and the need to comply with certificate conditions. Superseded Affordable Rental Housing SEPP material should not be used for a current assessment.
Before choosing a pathway, obtain address-specific evidence for:
- the legal lot, title, deposited plan and lawfully approved principal dwelling;
- the responsible council, zoning and current environmental planning instruments;
- easements, covenants, restrictions, legal access and existing consent conditions;
- survey levels, boundaries, drainage, sewer and utility locations;
- mapped controls or constraints that actually affect the parcel; and
- whether the proposal is internal, attached, detached or a conversion.
Planning approval may not remove a private title restriction or authorise interference with an easement or utility asset. Existing structures also require an approval-record check before their conversion can be assessed.
If City of Parramatta Council is confirmed as responsible, review its current development-application requirements and the applicable local environmental plan, development control plan, contribution arrangements, stormwater requirements, waste provisions, fee schedule and driveway or vehicle-crossing processes. Council material and digital maps should be checked again when the application is prepared because instruments, fees and lodgement requirements can change.
The Housing SEPP does not itself require additional parking for a secondary dwelling. The design must still address any existing consent conditions, removal of existing parking, safe access, driveway impacts and other controls applying to the site.
After planning approval, the project may require construction certification, appointment of a principal certifier, prescribed inspections and completion evidence. Service NSW explains that an occupation certificate is required before occupying or using a new building, or using an existing building following an approved change of use. A concept plan, quotation, BASIX certificate or builder statement is not a development approval or occupation certificate.
Costs and budgeting
There is no verified suburb-wide construction price that can reliably represent an Ermington project. A useful budget starts with an investigated parcel, coordinated design and written scope. Access, levels, ground conditions, demolition, existing-building work, service distances, authority requirements and finishes can materially change the amount payable.
Build the budget in separate categories:
- title, planning, survey and service investigations;
- design, engineering and specialist reports;
- application, Planning Portal and certifier charges;
- council contributions and authority fees where applicable;
- demolition, excavation, retaining and site preparation;
- building work, fixtures, finishes and BASIX commitments;
- stormwater, sewer, water, electricity and communications;
- paths, driveways, fencing, landscaping and waste removal;
- inspections, certificates, insurance and finance expenses; and
- an allowance for unresolved scope and documented site risks.
Obtain itemised quotes based on the same drawings, specifications and reports. Ask each tenderer to identify exclusions, provisional sums, service allowances, excavation assumptions, external works, utility-provider charges and responsibility for approvals and certificates. Separate confirmed prices from allowances so that apparently similar quotations can be compared on a like-for-like basis.
The current Building Commission NSW residential building contract guidance requires a written contract for work costing more than $5,000, with more extensive large-job contract requirements above $20,000. It also states that the maximum deposit is 10%. Read the Consumer Building Guide, check the contract form and ensure progress-payment stages correspond with completed work.
Home building compensation cover applies where required for residential building work valued at $20,000 or more, including GST. Before paying money or allowing work to start, use the official HBC Check to verify the certificate. Match the insured builder’s legal entity, work and property details to the signed contract rather than relying on an application receipt or generic insurance statement.
Design and site considerations
Design should begin with an accurate survey and a confirmed description of the proposed use. Establish whether the secondary dwelling will be within, attached to or separate from the principal dwelling, or whether an existing structure is proposed for conversion. This affects planning classification, construction details, servicing and the correct BASIX secondary-dwelling project type.
Map the boundaries, levels, existing buildings, access, significant trees, easements and known services before fixing a footprint. Assess the relationship between both dwellings, including usable outdoor space, privacy, overlooking, daylight, ventilation, noise, pedestrian access, waste storage, clothes drying and maintenance routes. Where the proposal changes parking or vehicle manoeuvring, test the resulting arrangement against the property’s applicable controls.
Check floor area, setbacks, height, landscaped area, site coverage and earthworks against the exact pathway and current instruments. The Housing SEPP contains secondary-dwelling site and floor-area provisions, while other controls may become relevant because of the parcel, zone or proposal. A standard copied from another council, a different development type or an old approval guide is not a sound design input.
Resolve stormwater and wastewater arrangements during feasibility. Confirm lawful discharge, sewer connection requirements, utility capacity and authority approvals before finalising levels or construction systems. Locate infrastructure before excavation and ensure the design respects registered easements and access rights.
Investigate hazards or overlays through official address-level mapping and records. Discuss flood, bushfire, heritage, biodiversity, contamination, trees or other constraints only when evidence shows that they affect the parcel. Where one applies, incorporate the authority’s requirements and any necessary specialist report into the design brief.
The official BASIX guidance addresses water, energy use and thermal performance for applicable residential development. Integrate its commitments into orientation, glazing, shading, insulation, ventilation, fixtures and services. Approved commitments should appear consistently in the drawings, specification, building contract and completed work.
Prefabricated, modular or relocatable construction does not bypass planning, building, BASIX or certification requirements. For a conversion, verify the structure’s lawful status and obtain professional assessment of structural capacity, fire safety, waterproofing, insulation, ventilation and services before relying on it in the project scope.
Rental and investment considerations
Rental assessment should begin only after confirming the approved use, completed work and occupation certification. Check that the constructed dwelling corresponds with the approval and that all required conditions and certificates have been addressed. Utility connection or practical completion alone does not establish lawful occupation.
A secondary dwelling remains associated with the principal dwelling on the same lot. That legal arrangement should be considered when obtaining lending, valuation, insurance, taxation and estate-planning advice. The project should not be modelled as an independently titled property.
For an approved secondary dwelling rented under a residential tenancy, use current NSW Fair Trading guidance on residential tenancy agreements. It covers standard terms and landlord and tenant obligations. The governing legislation is the Residential Tenancies Act 2010. Check the current requirements for the agreement, bond, condition report, disclosure, repairs, safety obligations and notices before advertising or granting occupation.
Family occupation, licences, boarder arrangements, short-term accommodation and standard residential tenancies are not necessarily treated alike. Identify the intended arrangement and obtain current legal, Fair Trading and planning guidance relevant to that use.
Practical management should address separate access, acoustic and visual privacy, deliveries, bins, outdoor areas, maintenance and emergency contacts. Document who is responsible for gardens, shared paths, driveways and common services. If utilities are shared, establish a lawful and transparent method for calculating charges and maintaining infrastructure.
Use current, genuinely comparable local evidence when assessing possible rent, and distinguish advertised asking prices from completed leasing evidence. Obtain advice for finance, insurance, tax and property management based on the owner’s circumstances and the approved property configuration. Keep these assessments separate from the planning feasibility decision.
Choosing a granny-flat builder
Identify the legal entity that will enter the building contract, then use the official Service NSW facility to check the builder or tradesperson licence. Confirm that the licence is current, its category covers the proposed work and its entity name and number match the contract. An ABN, association membership or review profile is not a licence check.
Request recent references for comparable secondary dwellings, particularly projects with similar construction, access, servicing or conversion requirements. With the owner’s permission, inspect completed work where possible. Ask previous clients about communication, variations, site-cost handling, defects, documentation and post-completion service.
Give each tenderer the same drawings, specification, reports and requested scope. Compare:
- inclusions, exclusions, allowances and provisional sums;
- excavation, retaining and access assumptions;
- utility, drainage and external-work responsibilities;
- approval, certification and inspection responsibilities;
- nominated BASIX products and commitments;
- variation and extension-of-time procedures;
- defect correction, statutory warranty information and handover records; and
- responsibility for occupation-certificate documentation.
Clarify whether the price is based on approved construction documents or an early concept. Record who will coordinate consultants, answer council or certifier requests and supply compliance evidence. Informal promises should be incorporated into the written scope where they are intended to form part of the work.
Follow the contract and consumer-protection requirements described in the budgeting section. Read the Consumer Building Guide before signing, verify the applicable cooling-off and statutory warranty information, keep agreed variations in writing and align progress claims with completed contractual stages. Seek independent advice on unclear terms rather than relying on sales explanations.
Verify required home building compensation cover through the official register before payment or commencement. Confirm that the certificate matches the site, contracted work and builder entity. At handover, collect approvals, inspection records, certificates, warranties, product information, maintenance instructions, keys and defect records needed for occupation and future maintenance.
Planning and feasibility checklist
- Confirm the address, lot and deposited plan.
- Verify the responsible council and lawful principal dwelling.
- Obtain the title, survey and existing approval records.
- Check zoning and mapped controls in the Spatial Viewer.
- Review the current planning instruments for the legal parcel.
- Locate easements, drainage, sewer and utility assets.
- Define the proposal as internal, attached, detached or conversion work.
- Test both approval pathways with council or a registered certifier.
- Confirm design controls, reports and BASIX classification.
- Check current application requirements, fees and contributions.
- Compare itemised quotations on an identical scope.
- Verify licences, contract requirements, warranties and HBC cover.
- Obtain approval before starting work.
- Complete required inspections and approval conditions.
- Obtain the occupation certificate before occupation or use.
- Use current Fair Trading documents if granting a tenancy.