Custom Granny Flats SA 2026 - Bespoke Design, Costs, and Approval Guide

When Custom Design Is Worth It for SA Granny Flats

The decision between a custom-designed granny flat and a builder's standard plan is not simply about quality or aesthetics - it is about whether the specific constraints of the SA project can be addressed by an off-the-shelf solution.

For a significant proportion of suburban Adelaide lots in General Neighbourhood or Suburban Neighbourhood zones with a conventional brief, a builder's standard plan at 50 to 65 square metres will satisfy the Planning and Design Code SA's DTS criteria, fit the site with adequate setbacks, meet NCC 2022 7-star NatHERS requirements for Climate Zone 5, and produce a functional, well-finished granny flat at a lower total project cost than a custom commission. SA property owners who commission custom design primarily for aesthetics on standard lots often find that the design fee adds $5,000 to $12,000 to the project without a commensurate improvement in function or planning outcomes.

Custom design delivers genuine and cost-justified value on SA granny flat projects in several specific situations. The first is the Character zone inner-suburban lot, which covers parts of Norwood Payneham St Peters, Unley, Walkerville, Prospect, and the City of Adelaide council areas. In these zones a performance-assessed development application is required regardless of size, and the design must demonstrate compatibility with the established character of the street and neighbourhood. A standard prefab module or catalogue plan designed for a contemporary outer-suburban lot rarely demonstrates this compatibility convincingly, and a Character zone application built around one is more likely to face objection and conditions that increase cost. A custom design developed specifically for the streetscape, materials palette, and roof form of the Character zone precinct is the appropriate approach and is more likely to achieve a smooth assessment outcome.

The second situation where custom design is clearly justified is the difficult or constrained SA lot. An irregular allotment shape, a significant cross-fall or side-to-rear slope, a rear laneway access requirement, a heritage overlay constraint, a narrow side-yard access, or a lot configuration where the standard plan dimensions simply do not satisfy all the required setbacks simultaneously are all cases where a custom design can solve problems that a standard plan cannot. The building designer works from the actual lot shape, the principal dwelling's position and footprint, the required setbacks, and the access constraints to produce a layout that maximises the allowable GFA within a buildable footprint. On difficult SA sites, the design fee is often recovered in avoided construction complications and approval delays.

The third clear justification is an atypical brief. A purpose-designed accessible granny flat with wider doorways, a step-free entry, and bathroom grab-rail provisions for an ageing parent requires design input beyond selecting the closest catalogue option. A dual-living configuration where the principal dwelling and granny flat are architecturally integrated requires design coordination that a separated standard plan cannot achieve. A granny flat designed to be architecturally consistent with an existing distinctive principal dwelling - a character home, a mid-century modern house, or a high-end contemporary build - is better served by a designer who can work with the established language of the existing building than by a catalogue plan that ignores it.

The SA Custom Granny Flat Design Process

A custom granny flat design commission in SA typically moves through four stages: briefing and feasibility, concept design, design development and documentation, and approval coordination. Understanding each stage and what it should include helps SA property owners engage designers effectively, evaluate fee proposals on a like-for-like basis, and avoid the common experience of scope creep that inflates design fees beyond the initial estimate.

The briefing and feasibility stage involves the building designer reviewing the property's planning constraints - zone, applicable overlays, setback requirements, site coverage limits, GFA allowance, and planning pathway - against the client's brief and budget. A good SA building designer will check the PlanSA ePlanning portal for the specific address before the first briefing meeting and will have a view on whether the brief is achievable within the site's constraints before any fees are committed for design work. Feasibility assessments that reveal planning constraints incompatible with the brief at this stage save money compared to discovering them during documentation or, worse, during assessment. The building designer should also advise at this stage whether the project is likely to follow the DTS planning pathway or will require a performance-assessed application.

Concept design translates the brief into a floor plan and external form that responds to the site, the principal dwelling, and the planning requirements. A SA custom granny flat concept design should include a site plan showing the proposed position, setbacks, and relationship to the principal dwelling; a floor plan at a scale sufficient to evaluate the room layout and circulation; and external elevations showing the proposed form, roof type, and materials. These drawings are sufficient to assess the concept's merit and identify whether any adjustments are needed before progressing to the cost of full documentation. SA building designers typically charge $1,500 to $4,000 for the concept design stage depending on project size and complexity.

Design development and documentation takes the approved concept to construction-level drawings suitable for building consent. This includes detailed architectural drawings, a site plan with dimensions, sections, construction details, specification of materials and finishes, a shadow diagram for the planning application if required, and coordination with structural engineering and NatHERS assessment. The documentation package for an SA granny flat building consent application typically requires architectural plans, structural engineer's drawings, a NatHERS energy rating certificate, and a hydraulics plan showing service connections. The building designer typically coordinates the structural engineer and NatHERS assessor as subconsultants. The documentation stage represents the largest component of the designer's fee and typically costs $3,000 to $9,000 for a standard SA granny flat project, depending on size and complexity.

Approval coordination covers lodging the planning application through the PlanSA ePlanning portal, responding to council or assessment panel requests for information during the planning assessment, and coordinating the building consent with the private certifier or council. SA building designers typically charge this as an additional scope item rather than including it in the documentation fee. For a DTS planning assessment in a straightforward zone, the coordination effort is modest. For a performance-assessed application in a Character zone, the coordination scope is more substantial and should be quoted explicitly before engagement rather than negotiated partway through the assessment when the applicant has less leverage.

SA Character Zone Custom Granny Flat Design

SA's Character zones represent the most demanding planning context for granny flat projects in metropolitan Adelaide, and they are precisely the context where custom design delivers the clearest practical benefit. Character zones apply to portions of several inner Adelaide councils - most notably Norwood Payneham St Peters, Unley, Walkerville, Prospect, and the City of Adelaide - covering streets of Victorian, Federation, Edwardian, and interwar housing where the established streetscape character is a protected planning value. All development in these zones, including ancillary accommodation of any size, requires a performance-assessed development application because the DTS pathway does not apply in Character zones regardless of floor area.

The performance assessment for a Character zone granny flat is primarily a design quality assessment. The relevant Performance Outcomes in the Planning and Design Code require that the ancillary accommodation is designed to be consistent with and complementary to the established character of the street and neighbourhood. The assessment authority - typically the council's assessment panel or delegated planner - evaluates the proposed design's materials, roof form, scale, proportions, setbacks, and relationship to the principal dwelling and neighbouring properties. This is a qualitative assessment, not a checklist of objective criteria, and its outcome is directly influenced by the quality of the design documentation and the strength of the character compatibility argument presented in the planning application.

Effective SA Character zone granny flat design takes specific cues from the streetscape and the existing principal dwelling. In a Victorian terrace street in Norwood, the appropriate materials palette might include face brick or rendered masonry, a corrugated iron or terracotta tile roof, timber-framed double-hung windows, and a return verandah if the existing house has one. In an interwar bungalow street in Prospect, the cues might include horizontal weatherboard or fibre cement cladding, a modest gable or hipped roof in corrugated steel, and proportions consistent with the single-storey scale of the surrounding streetscape. The granny flat need not be a pastiche reproduction of the principal dwelling, but it should share enough formal and material characteristics to read as a coherent part of the site composition. A building designer who approaches Character zone work by adapting a generic contemporary design produces applications that are slower to assess and more likely to require design revisions. A designer experienced in the specific council's Character zone requirements develops a brief-responsive design from the outset and presents a more persuasive planning case.

Rear-of-lot positions that are not visible from the primary street are assessed less stringently on character compatibility than front or side-yard positions. SA property owners whose lot configuration allows the granny flat to sit entirely behind the principal dwelling with no direct street visibility have a more straightforward Character zone pathway than those whose site requires a visible side-yard or street-facing position. Confirming the lot's positional options before commissioning the design is a practical first step that the building designer should address at the feasibility stage.

Planning Pathways for Custom-Designed SA Granny Flats

The planning framework for all SA granny flat projects - custom or standard plan - is the Planning and Design Code SA under the Planning, Development and Infrastructure Act 2016. The Code defines granny flats as "ancillary accommodation," establishing the key requirements: the structure must be on the same site as an existing primary dwelling, must be subordinate to that dwelling, must contain no more than two bedrooms, and must not exceed 70 square metres GFA. The November 2024 Code Amendment increased the GFA limit from the previous 60 square metres and removed the prohibition on self-contained ancillary accommodation, meaning a custom-designed granny flat can now include its own bathroom, kitchen, and laundry without risk of reclassification.

Planning consent and building consent are both required for all SA ancillary accommodation regardless of size, zone, or design approach. There is no consent-free pathway for granny flats in established SA residential zones. The planning pathway is either DTS (Deemed-to-Satisfy) - where the proposed design meets all objective criteria in the applicable zone including the 70sqm GFA limit, minimum setbacks, maximum site coverage, and 20sqm private open space - or performance-assessed, where the design does not meet one or more DTS criteria and must be assessed on its merits against the relevant Performance Outcomes. Custom designs may follow either pathway depending on the zone and whether the design complies with DTS criteria. A custom design that is tailored to fit within all DTS criteria will follow the DTS pathway and achieve a faster, more predictable assessment. A custom design that seeks to vary from DTS criteria - for example, a larger footprint, a reduced setback, or a different form - will require performance assessment and should include a well-prepared planning case justifying the proposed variation.

The minimum lot size for ancillary accommodation in most SA residential zones is 600 square metres. SA lots below this threshold are not eligible for a granny flat, regardless of how well-designed the proposed structure is. Lots in the 600 to 700 square metre range are eligible but require careful layout planning to satisfy setback, site coverage, and private open space requirements simultaneously, and a custom design that optimises the building's position and footprint on the specific lot delivers clearer practical value on these constrained lots than a standard plan that may not fit the available envelope. The private open space requirement is 20 square metres minimum accessible to the ancillary accommodation, in addition to the private open space requirement for the principal dwelling.

Overlays add requirements on top of the zone-based rules for SA properties. The Bushfire Risk Overlay applies to properties in the Adelaide Hills, Barossa Valley, McLaren Vale, and other peri-urban bushland areas and requires the building to comply with AS 3959 Construction of Buildings in Bushfire-Prone Areas at the applicable BAL rating. Custom design allows the architect or building designer to incorporate BAL requirements into the design from the outset rather than retrofitting compliance onto a standard plan, which typically produces a better design outcome and more accurate construction pricing. The Heritage Overlay, Coastal Areas Overlay, and Flooding overlays each add specific requirements that a custom design can be developed around with full awareness from the briefing stage. Checking the PlanSA ePlanning portal for all applicable overlays on the specific SA property address is essential before commencing any custom design commission.

Custom Granny Flat Costs in SA

A realistic total project budget for a custom granny flat in metropolitan Adelaide in 2026 has five main cost components: design fees, planning and building consent fees, site preparation, construction, and service connections. Understanding each component and what drives cost variation within it allows SA property owners to budget accurately before engaging any professional and to evaluate quotes on a consistent basis.

Design fees for a custom SA granny flat commission typically range from $5,000 to $18,000 total across all design stages, depending on the scope of the designer's engagement, the complexity of the design, and whether the fee includes planning application preparation and coordination. A straightforward brief on a standard suburban lot with an experienced building designer is typically at the lower end. A Character zone commission requiring a more detailed performance assessment justification, or a brief with multiple revisions and an unusual site, is typically at the higher end. Design fees are separate from structural engineering ($1,500 to $3,500), NatHERS energy assessment ($500 to $900), and private certifier or council fees for building consent ($800 to $2,500).

Planning consent costs depend on the pathway. DTS applications processed by the council or regional assessment panel attract assessment fees that vary by council but typically range from $300 to $800 for a standard residential ancillary accommodation application in metropolitan Adelaide. Performance-assessed applications attract higher fees, typically $500 to $1,500, reflecting the additional assessment work involved. Character zone applications may also require a Heritage Impact Statement or Character Compatibility Assessment prepared by a heritage consultant or town planner, adding $1,500 to $4,000 to the planning application cost. The planning application fee is in addition to the design fee and is typically paid directly to the council or assessment panel on lodgement.

Construction costs for a custom SA granny flat in metropolitan Adelaide in 2026 range from approximately $3,000 to $4,500 per square metre of GFA for a standard specification residential build, reflecting current Adelaide labour and material costs. A custom 55 square metre single-storey granny flat to a good but not premium residential specification therefore has a construction cost in the range of $165,000 to $248,000 before site preparation, service connections, and professional fees. Premium specification - polished concrete floors, stone benchtops, high-grade cladding, feature timber elements - can push costs above $4,500 per square metre. Basic specification without premium finishes can come in below $3,000 per square metre on straightforward flat sites with standard soil conditions. These figures are for site-built construction; prefab and kit options have different cost structures covered in the dedicated prefab granny flat SA and granny flat kit homes SA guides.

Site preparation costs depend almost entirely on the SA lot's topography and soil conditions. Flat suburban Adelaide lots with Class M or M-D reactive clay soil (common across the northern suburbs including Salisbury, Para Hills, and Davoren Park) require an engineered slab designed for reactive soil conditions, typically adding $3,000 to $6,000 to the slab cost compared to a standard slab design. Steeply sloped lots require cut-and-fill earthworks before construction can begin, with costs ranging from $5,000 to $25,000 or more depending on the slope, access, and soil type. Adelaide Hills properties on limestone-based or rubble fill soils require soil testing before footing design. Properties in Prospect, Nailsworth, and Enfield commonly encounter limestone subsoil at shallow depth, which may require rock breaking for service trenching and footing excavation. A geotechnical investigation ($800 to $1,500) before finalising the custom design is worthwhile on any SA lot with known or suspected soil challenges.

Service connection costs for a custom SA granny flat include the SA Water connection fee for a new water meter or extension of existing services ($2,000 to $5,000 depending on the property's current connection), SA Power Networks connection or board upgrade ($1,500 to $4,000 if a new meter or upgrade is required), ATCO Gas Australia connection if gas is specified ($1,200 to $3,500), and sewer connection or extension of the existing sewer line from the rear of the lot to the new structure (typically $2,000 to $5,000 depending on run length and depth). Properties on the SA Water sewer network use the standard connection process. Properties off-sewer - typically rural and outer-rural lots in regional SA - require an approved wastewater treatment system (AWTS) from a supplier such as Taylex or Everhard, with SA Health approval required, adding $8,000 to $15,000 to the service cost. Custom designs can be developed with full awareness of these service requirements from the outset, with the building designer coordinating service authority requirements into the design and documentation.

SA Site-Specific Cost Variables for Custom Granny Flats

South Australia's geology, climate zones, and planning overlays create site-specific cost variables that are absent or less pronounced in other Australian states. A SA property owner budgeting for a custom granny flat project needs to understand which variables apply to their specific lot before relying on any indicative cost range, because some of these variables can shift the total project cost by $15,000 to $50,000 compared to a straightforward metropolitan Adelaide lot.

Reactive clay soils affect a substantial proportion of suburban Adelaide lots, particularly in the northern suburbs. Salisbury, Elizabeth, Davoren Park, Para Hills, Andrews Farm, and Smithfield Plains are among the areas commonly identified with Class H1, H2, or E highly reactive clay soils that experience significant volume change with moisture variation. An engineered slab design for reactive clay soil conditions costs more than a standard design, and the degree of engineered treatment required - standard reactive clay provisions, articulated or stiffened raft slab, or deep pier footing - depends on the soil test result. A custom design commission should include a geotechnical investigation to confirm the soil classification before finalising the footing design, because the difference between a Class M standard design and a Class H or E design in construction cost is material. The building designer and structural engineer can develop the footing design once the soil test result is available, producing a more accurately priced construction documentation set.

BAL-rated properties in the Adelaide Hills, Barossa, McLaren Vale, and Fleurieu Peninsula require construction materials and details that comply with AS 3959 at the applicable BAL rating. BAL-19 compliance - the minimum rating above which standard construction practices change - requires ember-resistant construction details and some upgraded window and door hardware. BAL-29, BAL-40, and BAL-FZ add progressively more demanding requirements for non-combustible cladding, external window and door frames, roof vents, and sub-floor protection. A custom design for a BAL-rated SA property should incorporate the required construction details from the initial design stage, with the designer selecting materials and details that comply with the BAL assessment while achieving the desired aesthetic outcome. Retrofitting BAL compliance onto a design developed without BAL awareness adds cost and typically forces materials compromises that a design-from-the-start approach avoids.

Asbestos-containing materials (ACM) in the principal dwelling or existing structures are a significant cost variable for SA conversion and extension projects and can affect new detached builds on older suburban lots if existing sheds, garages, or outbuildings contain ACM and must be partially demolished or disturbed for the new granny flat's position or service runs. Pre-2000 structures on SA lots require an asbestos inspection before any demolition or significant work. The identification and removal of ACM is subject to SafeWork SA requirements under the Work Health and Safety Regulations 2012 (SA), and bonded asbestos removal by a licensed removalist is required for areas above 10 square metres. Including an asbestos inspection in the feasibility stage for any SA project involving older structures avoids cost surprises during construction.

NCC 2022 and 7-Star NatHERS Compliance for Custom SA Granny Flats

All new SA granny flat construction is required to comply with the National Construction Code 2022 (NCC 2022) following SA's adoption from 1 May 2023. The NCC 2022 introduced a 7-star NatHERS energy efficiency minimum for new Class 1a residential buildings including ancillary accommodation, replacing the previous 6-star standard. In Adelaide's Climate Zone 5, achieving 7 stars requires thoughtful design attention to orientation, glazing, insulation, and shading rather than simply increasing insulation quantities. A custom design commission is an opportunity to optimise these elements from the outset of the design process rather than retrofitting compliance onto a pre-designed layout.

NatHERS thermal performance modelling assesses the proposed building against a reference building with standardised internal loads in the specific climate zone. A custom SA granny flat designed with an energy-aware building designer can achieve well above the 7-star minimum with modest cost implications, by optimising the orientation of the main living and sleeping spaces relative to north, specifying double-glazing, designing roof overhangs for summer shading and winter solar access, and selecting wall and ceiling insulation appropriate for Climate Zone 5. These decisions are embedded in the design layout - effectively free at the design stage but expensive or impossible to correct after documentation is finalised.

NCC 2022 also introduced the Livable Housing Design Standard as a mandatory requirement for new Class 1a dwellings, including granny flats. The standard requires a step-free (flush) entry threshold at the main entrance, wider doorways and circulation corridors (850mm clear minimum for principal circulation), an accessible toilet on the ground floor, and reinforced bathroom walls capable of supporting grab-rails. For an ancillary accommodation design intended for an ageing parent or occupant with reduced mobility, the Livable Housing requirements are baseline rather than extras, and a custom design brief should specify accessible fitout elements that exceed the minimum standard: a wider shower recess, a ceiling hoist provision in the bedroom, or a step-free outdoor connection between the granny flat and the principal dwelling. A building designer with accessible design experience will develop these elements as integrated design features rather than compliance afterthoughts.

The NatHERS assessment for a custom granny flat is performed by an accredited assessor using software such as AccuRate or FirstRate5. The designer provides the building geometry, orientation, glazing areas and specifications, insulation R-values, and construction details; the assessor models the building and produces a certificate confirming the star rating. If the initial model falls short of 7 stars, the assessor can advise which design changes would achieve compliance and at what cost implication. For custom SA granny flat projects, the NatHERS assessment is typically commissioned at the end of the design development stage when the design is substantially fixed, and the NatHERS certificate forms part of the building consent documentation. The cost of a NatHERS assessment for an SA granny flat is typically $500 to $900.

What to Look Out For with Custom Granny Flat Projects in SA

Custom granny flat projects in SA expose property owners to several specific risks that are less common with standard plan builds. Understanding these risks before engaging any professional or signing any contract is the most effective form of cost and timeline protection.

Design fee scope creep is the most common financial issue in custom design commissions. A fee proposal that quotes design to a concept or schematic stage without specifying what additional fees apply for documentation, planning application, engineering coordination, and approval management will expand substantially through the project. Before engaging any SA building designer, obtain a fee proposal that specifies the fee for each stage, what is included in each stage, and what additional professional fees (structural engineering, NatHERS assessment, heritage consultant, town planner) are expected and in what amount. A transparent, stage-gated fee structure allows the SA property owner to make informed decisions at each stage rather than accumulating fees without a clear picture of the total commitment. Request that the fee proposal reference the relevant SA building designer registration requirements under the Architectural Practice Act 2009 (SA) and confirm the designer's current registration status with the Architects Board of SA or their relevant professional registration body.

Planning pathway misrepresentation - where a performance-assessed project is presented as DTS to make it appear simpler - is a real risk on Character zone and constrained-lot SA projects.

A project that requires performance assessment will encounter assessment delays and possible conditions if it is lodged as a DTS application. SA property owners should check the planning pathway for their specific address through the PlanSA ePlanning portal before accepting any professional's assertion, and confirm in writing with the building designer which pathway the project will follow and the basis for that determination.

Builder substitution of materials or products specified in the custom design documents is a recurring issue on custom granny flat projects and is harder to detect than on standard plan builds where the specification is typically better defined and more widely understood. A custom design specifies particular products for a reason - structural adequacy, NatHERS compliance, character zone compatibility, or owner preference - and substituting a lower-cost equivalent may affect any of these. Contracts for custom SA granny flat construction should specify that any material or product substitution requires the owner's written approval and, where the substitution affects the NatHERS assessment or building consent documentation, the building designer's written confirmation that the substitution is compliant. This clause protects the SA property owner from receiving a granny flat that differs materially from the approved design.

CBS SA licensing is the minimum qualification threshold for granny flat builders in SA under the Building Work Contractors Act 1995 (SA). A licensed building work contractor must hold a current CBS SA licence for the relevant class of work. Verify the builder's current CBS SA licence status at the CBS SA licence register before signing any building contract. The Building Work Contractors Act also governs warranty periods: a five-year warranty on structural defects and a one-year warranty on non-structural defects apply to all SA residential building work. Obtain written confirmation of the builder's insurance coverage, including public liability and contract works insurance, before construction commences. The CBS SA website provides guidance on builder licensing requirements and dispute resolution options for SA residential building projects.

Construction contracts for custom SA granny flat projects should be reviewed before signing for several specific provisions: the definition of practical completion and what the builder must demonstrate to claim it; the process for variations including how they are priced and approved; the dispute resolution process and how SACAT jurisdiction is engaged for building disputes; the retention amount and conditions for its release; and the provision for the final defects liability period. The Master Builders Association SA and the Housing Industry Association both publish standard-form residential contracts used by many SA builders, and engaging a building lawyer to review any non-standard contract before signing is worthwhile on projects above $150,000 in value.

Choosing a Building Designer and Builder for SA Custom Granny Flats

The quality of a custom granny flat design depends heavily on the building designer's experience with SA ancillary accommodation specifically, not just residential design generally. SA's planning framework for ancillary accommodation has specific requirements that differ from other Australian states - the 70sqm GFA limit, the mandatory planning consent pathway, the DTS versus performance-assessed distinction, and the Character zone performance assessment process - and a designer whose experience is primarily in NSW or Victorian residential projects may not navigate these correctly. Asking specifically about SA ancillary accommodation projects in the designer's portfolio, and requesting references from SA clients whose projects went through planning approval, is a more informative qualification check than general portfolio quality.

For Character zone projects in inner Adelaide councils, local experience is particularly important. The specific character requirements of Norwood Payneham St Peters, Unley, Walkerville, and Prospect each have distinct features that experienced local designers understand and that designers new to the council area do not. A designer who has previously had ancillary accommodation applications approved by the specific council is a substantially better choice for a Character zone project than an equally skilled designer whose SA work has been in outer-suburban standard zones. The council's assessment approach, the types of design responses that have achieved approval, and the questions the assessment panel is likely to raise are all knowledge that comes from direct experience rather than general competence.

Builder selection for a custom SA granny flat follows the same principles as any SA residential project: CBS SA licence verification, insurance confirmation, written references from previous SA granny flat builds, and a clearly scoped, fixed-price contract. The specific question for custom builds is whether the builder has experience executing work designed by an independent building designer rather than from their own catalogue. Some SA residential builders primarily work from their own standard plans and are less confident at pricing an independent documentation set accurately. A builder who has previously worked from a similar independent design commission is more likely to price the job correctly and execute the documentation without substitutions. Request that the builder confirm their experience and ask for a specific example project they can reference. The Fair Trading SA website provides guidance on SA residential building contracts and consumer rights when engaging builders and designers.

Getting Accurate Quotes for Custom SA Granny Flat Projects

Obtaining comparable, accurate quotes for a custom SA granny flat project requires the same documentation to be provided to every builder. A brief that describes the lot address, the proposed floor area, the intended planning pathway, the required specification level, and any known site constraints allows builders to price the same scope and prevents the apples-to-oranges comparison that results when different builders make different assumptions about site conditions, specification, or approval costs.

Providing every builder with the same design documentation ensures quotes reflect the same scope. At minimum, share the concept design drawings; ideally a full documentation set.

The project brief should specify the required floor area and number of bedrooms, the planning zone and any known overlays, whether a planning application is included in the builder's scope, the intended start and completion dates, the required fitout specification level, any known site constraints including soil type and slope, and the service connection requirements. Requesting that each builder itemise their quote by cost category - site preparation, slab, structural construction, fitout, service connections, approval fees - allows a direct comparison of components rather than just the total price.

Planning and approval cost transparency is the most common source of incomparable quotes on custom SA granny flat projects. A quote that excludes the planning application fee, or assumes DTS assessment when the project requires performance assessment, understates the true project cost and misrepresents the timeline. Ask every builder specifically whether their quoted scope includes the planning application, what planning pathway they are quoting on, and what the assumed approval timeline is. For Character zone projects, ask whether the builder's scope includes a heritage consultant or character compatibility statement and what the quoted cost is. Confirm that the NatHERS energy assessment is included, that the structural engineering fee is quoted, and that the SA Water and SA Power Networks connection fees are either included or quoted as separate allowances. A complete and transparent quote on a custom SA granny flat project will include all these items; a quote that is silent on several of them is not a lower price - it is an incomplete scope.