Granny Flats NSW 2026 - Get Free Quotes

Granny Flats in New South Wales

New South Wales has more secondary dwellings than any other state, and the reason is a planning framework that has made them comparatively straightforward to approve. That has produced a deep builder market, a wide range of standard designs and genuine competition on price. It has also produced a great many households who commit to the idea before working out what they actually want the building to do, which is where most of the disappointment in this area comes from. The framework has been amended several times since it was introduced, so what a neighbour built five years ago is not necessarily what you can build now. Treat their experience as encouragement rather than as guidance. Approvals have run into the thousands annually across the state for well over a decade now.

Two questions come before any conversation about cost or design. The first is purpose, because a dwelling for a parent who may need care in five years, a unit intended for rental and a home studio are three different buildings that happen to look similar. The second is eligibility, since the planning criteria exclude a meaningful proportion of blocks and finding that out after paying for plans is an expensive lesson. Answering both takes a few days and costs very little, and it determines whether everything after it is worth doing.

This page is the starting point rather than the detail. Pricing in depth sits under granny flat costs, while the criteria a proposal must satisfy are set out under granny flat rules. What follows is the material that helps you decide whether to proceed at all and in what form. Each of those covers its subject properly rather than in summary, and the material below deliberately avoids repeating them. Read this one first and the others when you have a specific question.

What a Secondary Dwelling Actually Is

Granny flat is the household term and secondary dwelling is the planning one, and knowing both is useful when you start reading council documents or talking to a certifier. The planning definition describes a self contained dwelling established in conjunction with a principal dwelling on the same lot, which means it has its own kitchen, bathroom, living and sleeping areas and can be occupied independently. That self contained requirement is what separates it from a bedroom with an ensuite. Using the planning term when you contact a council or a certifier gets you a faster and more accurate answer than the colloquial one does. Builders use both interchangeably in their marketing, which adds to the confusion rather than reducing it.

It may be detached from the house, attached to it, or created within the existing building, and all three arrangements are secondary dwellings in planning terms. Detached is what most people picture and what most builders offer, attached suits smaller blocks where a separate structure will not fit, and conversion of existing space suits properties with a substantial garage or outbuilding already in place. The route chosen affects cost and approval more than it affects the finished experience. Which one suits depends on your block far more than on preference, and a designer will usually identify the answer within a site visit.

The critical characteristic is that it remains part of the same lot as the house. A secondary dwelling cannot be separately sold, cannot be subdivided off, and does not create a second property title, which surprises a proportion of owners every year. If separate ownership is the goal, dual occupancy development with subdivision is the pathway to investigate instead, and it is a considerably larger undertaking with different requirements. Lenders treat it accordingly, valuing the improved property rather than adding a second asset to your balance sheet. Grasping that changes how the whole budget should be read.

One secondary dwelling is permitted per lot under the standard arrangements, so this is not a route to multiple rental units on a suburban block. Councils also apply provisions about whether the dwelling can be strata titled or leased separately from the main house in some circumstances. Where a property already has an approved secondary dwelling, adding another is generally not available. Verify the position for your land rather than assuming, because these details vary.

Terminology matters in one more respect, which is that a studio, a cabin, a rumpus room or a shed with a bathroom is not a secondary dwelling unless it has been approved as one. Building something that functions as a dwelling without approval creates problems at sale, with insurance and with council. If the intention is somewhere for someone to live, get it approved as a dwelling from the outset. Structures without that intent sit under shed and garage construction. Purchasers' building inspectors look specifically for unapproved habitable structures, so the problem surfaces at exactly the wrong moment.

Why Households Build Them

Accommodating a parent or an adult relative is the most common reason and it shapes the brief in specific ways. Someone in their seventies today may need mobility support in a decade, which argues for step free entry, a bathroom laid out so rails can be added, doorways wide enough for a walker and a layout that works with a carer present. None of that is expensive when designed in and all of it is expensive to retrofit. That thinking is covered further down. Families who design for today rather than for a decade ahead are the ones who end up paying for modifications within a few years. The move itself is often prompted by a change in health, which compresses the timeline considerably.

Adult children living at home are the second driver and the requirements differ. Independence and separation matter more than accessibility, a separate entrance and its own outdoor space make the arrangement workable, and durability matters less than for a rental. These arrangements are frequently temporary in intent and permanent in practice, so building something that will still be useful when the arrangement ends is worth thinking about at design stage. A dwelling designed only around a twenty five year old is harder to rent or repurpose later than one designed with some flexibility.

Rental income motivates a substantial share of these projects and it brings the most exacting requirements. A tenanted dwelling needs separate metering where practical, its own entrance and outdoor area, durable finishes, adequate storage and enough separation that neither household feels observed. It also brings a legal relationship with obligations, and the numbers deserve honest modelling rather than optimism. Letting the dwelling out is examined at granny flat rental income. Vacancy, maintenance, insurance, agent fees and the periods between tenants all belong in the calculation alongside the rent. Modelling the return on conservative rent rather than the best figure an agent mentions is the safer approach.

Working from home has driven a newer category, being a studio or office that is genuinely separate from the house. Where the requirement is a workspace rather than accommodation, a full secondary dwelling may be more than is needed, and a studio without a kitchen is a simpler proposition to approve and build. Consider what the building has to contain before defaulting to a full dwelling, since the difference in cost is substantial. Approval for a studio without cooking facilities is usually a simpler exercise, though it still needs to be approved rather than assumed.

Downsizing in place is the least discussed use and among the most practical. Older owners move into the secondary dwelling and let family occupy the main house, which keeps them in their neighbourhood and their networks while reducing what they maintain. It works well where the relationship is sound and the arrangements are documented, and it needs the same care about future mobility as any other later life housing decision. It also raises questions about ownership and inheritance that are far better settled at the outset than left to be worked out later.

Whether Your Block Is Likely to Qualify

A meaningful proportion of properties cannot take a secondary dwelling, and establishing which side of that line you sit on is the first thing worth doing. The criteria applied to these proposals cover matters including the size of the lot, its width, the floor area of the proposed dwelling, how far it must sit from boundaries, how much of the site can be built on and how much must remain as landscaped area. Failing any one of them changes the pathway or ends the project. Contractors report a steady stream of enquiries from households whose blocks were never eligible, which is time wasted on both sides. Finding out early is not a setback, it is the point of asking.

The figures attached to those criteria have been amended more than once in recent years and continue to be reviewed, which makes any number published on a website a starting point rather than an answer. A minimum lot size in the order of four hundred and fifty square metres has been commonly cited historically, along with a minimum width and a maximum floor area, and each of those has been subject to change. Confirm the current position for your property rather than relying on figures from any source including this one. This is genuinely the one area where secondhand information is worth nothing, because a figure correct in one year may not be correct in the next.

The reliable way to find out is a conversation with your council or a registered certifier, both of which can give you an answer specific to your land in a short call. Councils publish local provisions that sit alongside the state framework, and those local documents can affect the outcome. Property and planning services are accessible through Service NSW, and the detailed criteria sit under granny flat rules. Ask specifically about local provisions as well as the state framework, since councils apply their own controls alongside it. Most councils have a duty planner, an assessment officer rostered to answer public enquiries, available for exactly this kind of question.

Beyond the numbers, characteristics of the land itself disqualify or complicate a proposal regularly. Heritage listing or location within a heritage conservation area, bushfire prone land, flood affected land, easements, being registered rights over part of your land held by an authority or a neighbour, running through the only viable building area, protected trees whose root zones cover the space, and steep or unstable ground all matter. Some of these mean a different approval route rather than a refusal, and some genuinely end the idea. A title search and a look at your council's online mapping will surface most of these in an afternoon, and the routes available afterwards are compared under granny flat approval.

What already sits on the property counts too and owners frequently overlook it. Existing structures consume site coverage, meaning the proportion of the block permitted to be built on, while a pool takes both that and landscaped area, and driveways and paving reduce what remains permeable. A block that would qualify if empty may not qualify as it stands, and removing a structure to make room is itself a project. Walk the yard with a tape and a plan before assuming there is space. Measuring the space you think is available, then subtracting the setbacks, is a sobering exercise worth doing before you fall for a design.

If a Granny Flat Is Not the Answer

An attached addition is the most direct alternative where a detached dwelling will not fit. Built off the side or rear of the house, it can be self contained with its own entrance while sharing a wall, which suits narrow blocks and properties where site coverage is tight. It costs more per square metre than a detached build because it involves working into the existing structure, and it is a genuine solution rather than a compromise. This route sits under granny flat additions and broader work under home extensions. It also shares services with the house, which reduces connection costs compared with a dwelling at the rear boundary. It can also be designed to be reintegrated into the house later if circumstances change.

Converting an existing garage or outbuilding is the cheapest route to self contained accommodation where a suitable structure exists. A double garage with sound footings, adequate wall height and a serviceable roof can become a dwelling for $60,000 to $130,000, since the shell already exists and the work is insulation, lining, glazing, a bathroom, a kitchen and services. The catch is that it still requires approval as a dwelling and must meet the standards applying to habitable space. Losing the garage matters too, for parking, for storage and occasionally for resale, so weigh that alongside the saving. Check the slab and footings first, since a garage slab is not always adequate for habitable construction.

Adapting rooms within the house suits households whose need is more modest than a full dwelling. A bedroom, an ensuite and a kitchenette give a family member somewhere of their own without creating a separate dwelling, at $25,000 to $70,000, and it avoids the approval process a secondary dwelling requires. It works where the relationship suits shared living and fails where genuine independence is the point. Bathroom work sits under bathroom renovation.

Dual occupancy development is the route where separate ownership matters. Two dwellings on a lot with the potential for subdivision into separate titles is a different planning proposition with different criteria, higher costs and a longer process, and it is the only route that produces something you can sell independently. Where the goal is an asset rather than accommodation, that is the conversation to have with a planner rather than a granny flat builder. Not all land is eligible for dual occupancy, and where it is, the criteria and the process differ substantially from a secondary dwelling.

Doing nothing deserves consideration alongside the others. Where the need is temporary, where the block barely qualifies, or where the numbers only work on optimistic rental assumptions, spending $150,000 on a building may not be the best answer to the problem. Renting elsewhere for a family member, or moving, sometimes costs less and suits better. A feasibility assessment at $500 to $2,500 is a cheap way to test the idea before committing. There is no obligation to build merely because the block qualifies, and the analysis is worth doing honestly.

What Living Alongside One Is Actually Like

Privacy is the thing households underestimate and it works in both directions. Windows facing each other across ten metres of lawn mean neither household can sit in their own living room unobserved, and an outlook onto the neighbours' clothesline is nobody's idea of a good design. Orientation, window placement, screening and planting all address this cheaply at design stage and expensively afterwards. Walk the site and look at what each window will actually see. Standing where each window will be, during a site visit, tells you more than any floor plan can. High level windows, obscured glazing and careful orientation each solve part of the problem.

Separate entry matters more than the plans suggest. A path to the secondary dwelling that does not pass the main house's living areas or bedroom windows makes the arrangement feel independent rather than supervised, and it matters enormously for a tenant. Where the only route to the rear is past the kitchen window, expect both households to feel it daily. That routing decision costs nothing to get right and cannot be changed later. Where a tenant is involved this stops being a preference and becomes a requirement.

Outdoor space for the secondary dwelling is frequently forgotten entirely. A dwelling with no courtyard, no private outdoor area and nowhere to sit outside is a poor place to live regardless of how good the interior is, and it is what happens when the building is sited to maximise what remains for the main house. Allocate a defined outdoor area with some separation, even a small one, and the arrangement works far better. A small paved courtyard with some screening is enough, and it costs a fraction of what the building does.

Parking and the driveway cause more friction between households than anything else. Where the secondary dwelling has no dedicated space, someone is moving cars, and where the driveway is shared, comings and goings become visible and audible. Councils may require a parking space for the dwelling in any case. Sort out who parks where before anyone moves in rather than discovering it in the first fortnight, and driveway work sits under driveways and paving. Where street parking is scarce, this becomes the defining practical issue of the arrangement. Agreeing it in writing at the outset sounds excessive and prevents years of low grade irritation.

Noise between two dwellings on one block is a real consideration, particularly where one is tenanted. Position matters more than construction, since separation and orientation do more than acoustic insulation ever will, and a bedroom window facing the neighbours' air conditioning unit is a poor outcome. Think about where the plant, the clothesline, the bins and the outdoor seating go relative to both dwellings. Air conditioning condensers, pool pumps and rainwater tanks all deserve a moment's thought about where they sit relative to bedrooms.

Family arrangements deserve documenting even when the relationship is excellent. Who pays for what, what happens if circumstances change, whether any contribution has been made toward construction and what that means at sale are all worth settling in writing while everyone is on good terms. Where money has moved between family members, legal advice is genuinely worthwhile. Residential tenancy and building disputes in this state are heard by NCAT. Circumstances change through illness, relationship breakdown, financial pressure and death, and an arrangement that was obvious to everyone becomes contested.

Designing for Someone Who May Need Care Later

Where the dwelling is for an older family member, the design should suit the person they will be in ten years rather than the one moving in this year. Mobility declines gradually and the point at which a home becomes unsuitable arrives suddenly, usually after a fall or a hospital stay. Building in the features that support later life costs very little during construction and a great deal afterwards, which makes this the single highest value design conversation on the project. An occupational therapist can advise on layout where needs are already known, and their input is inexpensive relative to the build. Retrofitting accessibility into a completed dwelling routinely costs multiples of what designing it in would have.

Step free access from the street to the front door and through it is the foundation. That means no steps at the entry, a threshold that a walker or a wheelchair can cross, a path wide enough and firm enough to use, and adequate lighting along it. Achieving this is largely about setting the floor level correctly relative to the ground, which is a decision made once at slab stage. Ramps added later sit under wheelchair and threshold ramp installation. Getting it wrong means a ramp later, which takes space and rarely looks like part of the original design.

The bathroom is where most later life difficulty concentrates and where design pays off most. A shower without a hob, laid out so a seat and rails can be added, with the floor graded to drain and enough clear space beside the toilet for assistance, costs no more than a conventional bathroom if specified from the outset. Installing noggings in the walls at rail height during construction costs almost nothing and makes fitting rails later straightforward. Rail work sits under grab rail installation. A bathroom above the minimum size is where extra floor area repays itself most reliably. Slip resistant flooring and good lighting belong in the same conversation.

Door widths and circulation space determine whether the dwelling still works with a walker or a wheelchair. Wider doorways than the minimum, clear turning space in the bathroom and beside the bed, and corridors that are not the narrowest permissible all matter, and the difference in construction cost is minimal on a small building. Widening doors afterwards means structural work. Modifications of that kind sit under door widening and accessible entry modifications. Furniture placement matters as well, since a room that works empty may not work once a bed and a wardrobe are in it.

Practical details finish the picture and cost little. Lever handles rather than knobs, light switches and power points at reachable heights, task lighting in the kitchen and bathroom, a hot water system with a tempering arrangement, and floor surfaces that are not slippery when wet all support independence. Consider where a carer would stand and whether a hospital bed could be delivered into the bedroom, since both questions have a way of arriving without notice. Making the list before the design is finalised is easier than adding items during construction as variations.

The Order Things Happen In

The first step is a feasibility check rather than a design, and it is the cheapest money you will spend on the project. A designer, certifier or granny flat builder can assess whether your block qualifies, what pathway applies and what site constraints exist, for somewhere between $500 and $2,500 depending on depth. That assessment either confirms the project or saves you the cost of plans for something that was never going to be approved. Some builders offer this at no charge as part of their sales process, which is useful information provided you understand its purpose. It also gives you something concrete to discuss with family members who are part of the decision.

Investigations come next and inform everything after them. A site survey establishes boundaries, levels and where existing structures and services sit, and a geotechnical report classifies the soil so footings can be designed. Both are required for approval and both determine cost, which is why a builder pricing without them is estimating. Paying for these yourself and giving the same reports to every builder produces genuinely comparable quotes. Both reports remain valid for a reasonable period, so they are not wasted if the project pauses. Commissioning them in your own name means they stay with you if the builder changes.

Design and documentation follow, turning the brief and the site information into a proposal that satisfies the criteria. This is where purpose matters, since the accessibility features, the orientation, the window placement and the outdoor space are all decided here. Standard designs from a builder's range cost less than a bespoke design and suit straightforward blocks well. Appearance decisions belong with granny flat designs and internal layout with granny flat floor plans. Changes made at this stage cost nothing compared with changes made during construction, so this is where to be difficult.

Approval is obtained through the applicable pathway, which is measured in weeks for a compliant proposal certified rather than assessed, and in months for a development application to council. Which applies depends on whether every criterion is satisfied. One route runs through granny flat complying development and the other through granny flat approval. Neither route waves anything through, and the finished building answers to the same standards as any house.

Construction runs three to six months for a site built dwelling and considerably less on site for a modular unit, with mandatory inspections at defined stages throughout. An occupation certificate is issued at completion and nobody may lawfully occupy the dwelling before it exists. Build that into your timeline if someone is waiting to move in. Build methods and programme belong with granny flat construction.

What Shapes the Project

Purpose drives the brief and therefore a good deal of the cost. Accessibility features add little when designed in, durable finishes for a tenancy add moderately, and a specification chosen to match the main house adds substantially. Deciding what the building is for before talking to builders means the brief is yours rather than theirs, which is worth more than any negotiating on price. Writing the brief down, even in half a page, changes the conversations you have with builders considerably. A brief written by you is harder for a builder to substitute their standard product into.

Route makes the largest single difference to the figure. A detached dwelling, an attached addition, a garage conversion and adapting existing rooms span a range from twenty five thousand dollars to three hundred thousand for outcomes that partly overlap. Pricing more than one route before committing is unusual among households and it is the step most likely to save real money, particularly where an existing structure can be used. A designer who is not selling a particular product is the best person to advise which route suits your block. Very few households price more than one route, which is why so many overpay.

Site conditions produce the widest variation within any route. Reactive ground calls for a stiffer footing, a fall across the block brings cut and retaining, rock turns a day of digging into a week, and a narrow gate decides what machinery gets in. None of it is visible from a street view, which is why investigations come before pricing. The scope of any site cut is dealt with under excavation. Neighbouring properties that have recently built are a useful source of information about what is underground.

Position on the block affects both cost and how well the arrangement works. Close to the house means short service runs and lower cost, while further away buys privacy and separation at the price of longer trenches for water, sewer, power and stormwater. That trade off should be made deliberately with both considerations on the table rather than defaulting to whichever the builder suggests. Marking the footprint out with pegs and string before finalising it makes the decision far more concrete.

Timing and market conditions move builder pricing in ways outside your control, and the sums involved make getting three quotes worthwhile. Trade availability, material prices and how busy a builder happens to be all affect what they quote, and a proposal put to market in a quiet period does better than the same one in a busy one. Shortlisting is dealt with under granny flat builders. Treat an outlier low quote as a question rather than a win, since the gap is almost always scope.

Granny Flats Across Sydney

More secondary dwellings are built in Sydney than anywhere else in the country, and the builder market reflects that with volume operators, specialist designers and a wide range of standard products. Where a project lands depends far more on the block than the postcode, since soil, slope, rock and access vary enormously across the city, and the areas with the most difficult ground are consistently the dearest. Visiting completed examples is straightforward here in a way it is not everywhere, and it is worth the afternoon. Given the sums at stake, fewer than three quotes is not a comparison.

Western and south western Sydney account for the majority of secondary dwellings in the state and the reasons are structural rather than cultural. Blocks are larger and more likely to satisfy lot size criteria, the land is generally level with straightforward access, rental demand is strong, and builders operating at volume keep pricing keen. Clay movement is the local tax there, paid through a heavier footing than sandier ground demands. Local agents in those areas can give realistic rental figures for a specific street, which beats any general estimate when modelling granny flat rental income.

Inner Sydney, the eastern suburbs and much of the lower north shore present the opposite picture. Blocks are frequently below the lot size threshold, heritage conservation areas cover substantial territory, rear access is often impossible for machinery, and sandstone sits close to the surface. Attached additions and conversions are more commonly the workable answer in those suburbs than a detached dwelling, which is worth knowing before falling for a standard design. Modular delivery is frequently impossible in those suburbs because a crane cannot reach a rear yard, which rules out modular granny flats before the design stage.

Granny Flats in Regional NSW

Larger blocks and fewer space constraints are what change beyond the metropolitan area, along with a shallower pool of specialist builders. Newcastle, the Hunter, the Central Coast and the Illawarra support established operators and price much as Sydney does, while further out general residential builders take on the work and modular delivery becomes a stronger option than it is in the city. Booking further ahead matters outside the city, since the better builders are committed months in advance. Bundling it with other work you were going to do anyway makes the journey worth a builder's while.

Rural and semi rural properties raise questions a suburban block does not. Zoning on rural land treats secondary dwellings differently from residential zoning, services cannot be assumed where a property runs on tank water and an onsite wastewater system, and a system sized for one dwelling frequently cannot take a second. Those assessments come before design rather than during it, and they can change the shape of the project entirely. A wastewater consultant rather than a plumber is usually the right first call there, well before engaging granny flat builders.

Mapped bushfire land covers much of regional New South Wales, reaching both the approval and the build. A property carrying a bushfire attack level rating must be built to a matching standard, and that reaches the windows, the external cladding, any deck and the screening, with cost climbing as the rating does. Establish your rating early because it influences design decisions rather than simply adding a percentage at the end. Whether a property is on bushfire prone land can be confirmed through the council, and the mapping is publicly available.

Distance from family is the practical driver behind many regional projects and it changes the brief. Where a secondary dwelling is being built so an older parent can move from a distant town to be near family, the accessibility thinking matters more than usual because the move is often prompted by declining independence. Design for the situation that prompted the move rather than the one that existed a year ago. Proximity to medical services and public transport also matters more for an older occupant than the size of the dwelling does.

What to Look Out For

Confirm your block qualifies before spending on design. The criteria exclude a real proportion of properties, and the figures attached to them have been amended more than once in recent years, so any number you read anywhere including here should be verified against your council or a registered certifier for your specific land. A conversation costing nothing prevents paying for plans that cannot be approved. Get the answer in writing where you can, since a verbal assurance is worth little if circumstances are later disputed. This single step prevents the most expensive mistake available in this category.

Decide what the building is for before you look at designs. A dwelling for an ageing parent, a rental unit and a home studio are different briefs, and choosing a floor plan first means the purpose gets fitted around the design instead of the other way round. Households who skip this step are the ones who discover the bathroom will not take rails or the tenant has nowhere to park. Write it down in a paragraph and give the same paragraph to everyone you speak to.

Price more than one route before committing to a detached build. An attached addition, a garage conversion or adapting existing rooms may suit your situation better and cost considerably less, and very few households compare them. Where a sound garage already exists, the saving against a new build can be sixty thousand dollars or more for accommodation that serves the same purpose. Ask a designer rather than a builder which route suits, since one who only builds detached dwellings will recommend a detached dwelling, and compare against granny flat additions.

Do not build habitable space without approval. A studio, cabin or converted shed that someone lives in without being approved as a dwelling creates problems with insurance, with council and at sale, and unapproved works are routinely identified during a purchaser's inspection. The saving is illusory because the cost of resolving it later exceeds what approval would have cost. Retrospective approval is sometimes possible and is always more expensive and less certain than approval obtained first. Insurers may decline a claim relating to an unapproved structure, which is the risk people underestimate.

Take the family arrangement seriously as a legal matter. Where a relative is contributing to construction, occupying the dwelling long term or both, document what has been agreed and what happens if circumstances change, and take advice where money has moved between parties. Consumer guarantees on building work are administered by the ACCC, while builder licensing and contract requirements sit with NSW Fair Trading. Independent advice for each party is better than shared advice where the interests could diverge.

What to Look for in a Quote in NSW

At this stage the quote worth obtaining is for the feasibility work rather than the build. A useful feasibility response states what will be assessed, whether it covers the planning criteria against your specific land, whether it identifies site constraints such as easements, trees and services, whether it confirms which approval pathway applies, and what you receive at the end. Site constraints and pathway confirmation are what separate a real assessment from a sales call. Paying for an independent assessment rather than accepting a free one from a builder removes any conflict of interest. Build quotes come later, once you know what can actually be built.

Tell each of them the same three things about your property. Give the lot size and dimensions, describe what already sits on the block including the house footprint, driveway, pool and any outbuildings, and say what the dwelling is for and who will occupy it. A copy of your survey plan and a recent rates notice answer most of the rest, and providing them turns a general conversation into a specific one. Photographs of the intended area from a few angles help as well, particularly ones showing access and existing structures.

Someone who asks what the dwelling is for is designing rather than selling. A designer or builder who wants to know who will live there, whether the occupant may need mobility support, where you would want the entrance and how the outdoor space should be divided is thinking about a building that works. One who leads with a floor plan and a price has a product to sell and will fit your situation to it. Ask what they would recommend against, because a professional willing to talk you out of something is worth listening to.

Settle purpose, eligibility and route before engaging anyone to design. Confirm with your council or certifier that your block qualifies and on what basis, write down what the dwelling has to do and for whom, price at least one alternative route alongside the detached build, and commission the survey and soil test before asking for fixed prices. Compare the quotes on scope rather than on the bottom line. The national picture sits on the granny flat builders hub, with detailed pricing under granny flat costs.