The call usually goes something like this. Someone has three quotes for a 2 bedroom granny flat sitting on the kitchen bench, and the cheapest is a fraction of the dearest. Same number of bedrooms, same backyard, much the same floor area. They want to know which builder is having them on.
Usually nobody is. The quotes just aren’t pricing the same thing. 2 bedroom granny flat prices look wildly inconsistent online because one number is a kit, another is a shell and a third is a finished home with a tenant ready to move in. Once you know what sits inside each figure, the spread makes a lot more sense, and you can work out which quote is actually cheaper for your block.
The same 2 bedroom flat gets priced three different ways
Search for prices this year and you will see advertised figures for two bedroom designs ranging from the tens of thousands to several hundred thousand. Those numbers are not really competing with each other. They describe different products.
Kit price. Materials only: frame, cladding, roof sheets, windows, sometimes a flat pack kitchen. You still pay for the slab, every trade, approvals, connections and the certifier. Kits suit owner builders with time, skills and the right permits. For most people they are a starting figure, not a finished one.
Build only or lock up. A builder constructs the flat but leaves things out. Approvals, site works, service connections or the internal fit out might sit with you. These quotes often look sharp right up until you reach the exclusions page.
Turnkey. Designed, approved, built, connected and handed over with keys. This is the number that actually tells you what the project costs, and it is the only fair way to compare one builder against another.
If you only remember one thing from this post, make it this: before you compare two prices, check they belong in the same column.
NSW size rules mean the flat itself is rarely the big variable
In NSW a granny flat (the planning term is secondary dwelling) can have an internal floor area of up to 60 square metres. To use the faster complying development certificate route, known as a CDC, the lot generally needs to be at least 450 square metres and at least 12 metres wide at the building line.
That 60 square metre ceiling matters for price. A sensible 2 bedroom layout needs most of that area, so most 2 bedroom designs land close to the limit. Two flats of near identical size use a similar amount of slab, frame, roofing and plasterboard. Finishes move the price a little. Kitchen and bathroom choices move it a bit more.
The big swings almost always come from the ground the flat sits on. We have a broader guide to what granny flats cost across NSW if you want the full picture across sizes. This post sticks with the two bedroom question and the site costs that change it.
Site costs are where Illawarra quotes split apart
Two identical flats can carry very different price tags once they leave the drawing board. In our part of the world, these are the usual reasons.
Slope
Blocks running up toward the escarpment in Thirroul, Austinmeer, Bulli and Helensburgh are rarely flat. A sloping site can need more excavation, retaining walls, extra engineering or a raised floor on piers instead of a simple slab. None of that shows up on a flat block in Dapto. All of it shows up in the quote.
Sewer and stormwater
Plenty of older Wollongong suburbs have a Sydney Water sewer main running across the back of the yard, often right where the owner pictures the granny flat. Building over or near a main needs Sydney Water sign off and can mean deeper footings or a shifted footprint. Stormwater is the other half. Water from a new roof has to go somewhere legal, and on a block that falls away from the street that can mean a pump or an easement through a neighbour’s land.
In the Southern Highlands, water and sewer come under Wingecarribee Shire Council rather than Sydney Water, and some rural edge blocks are not on reticulated sewer at all. That changes the plan completely.
Power
A second dwelling adds real load to the property. Some older homes need a switchboard or supply upgrade before the flat can be connected. On some jobs it is a modest line item. On others it is the surprise of the quote.
Bushfire and flood mapping
A lot of Southern Highlands land is mapped as bush fire prone. That triggers a Bushfire Attack Level assessment (BAL for short), and the higher the rating, the tougher the construction needs to be: ember screens, specific glazing, particular cladding. Each step up costs more. On the coast, some low lying blocks near creeks and Lake Illawarra are flood mapped, which can affect floor heights and the approval path.
Access
If the only way into the backyard is a 1 metre gap beside the house, materials get carried in by hand or lifted over by crane. Either way that is time and money a corner block with a wide driveway never pays.
What a complete 2 bedroom quote should list
When we sit down with an owner to compare quotes, this is the checklist we work through. A quote that doesn’t mention one of these is either including it silently or leaving it for you.
- Design, drafting and engineering
- CDC or DA approval, certifier fees and BASIX (the NSW energy and water rating every new dwelling needs)
- Site preparation, excavation and any retaining
- Slab or pier footings
- Frame, roof, cladding, windows and doors
- Kitchen, bathroom, laundry and flooring
- Electrical, plumbing and connection to sewer, stormwater, water and power
- Smoke alarms and the final occupation certificate
- Paths, landscaping and fencing, if included
Watch for provisional sums. These are allowances a builder puts in for work they can’t price yet, such as rock in the excavation. They are not fixed. If the real cost comes in higher, you pay the difference. A quote heavy with provisional sums can look cheapest on day one and finish dearest of the lot.
You can see how we put our 2 bedroom granny flat builds together on the service page, including what we check on site before a price is locked in.
A fixed design takes most of the guesswork out of the price
We build fixed design, CDC approved granny flats for owners across the Illawarra and Southern Highlands, and the reason is mostly price certainty. When the plans are already resolved and engineered, there is very little left to discover halfway through the build. The design is a known quantity. What changes from one job to the next is the site.
That is also why we don’t publish a single headline number for a 2 bedroom flat. A figure without a site inspection would be one of those kit or build only numbers we warned about above. We would rather give you one honest price for your actual block than a nice round one that grows later. Our builds are backed by Jaya Builds, a local Illawarra construction company, so the trades and systems behind each quote are the same ones that turn up to build it.
Is the second bedroom worth paying for?
For most of the owners we work with, yes, but it depends on why you are building. A second bedroom widens the pool of people who can live there: a couple with a child, two sharers, or a parent with a carer who stays over. It also gives the family flexibility down the track. The extra cost over a one bedroom design is real, though, and on a tight or awkward block a one bedroom can be the smarter fit. We’ve laid that decision out in our comparison of 1 and 2 bedroom layouts.
How to compare two quotes without getting caught out
Put them side by side and go line by line against the checklist above. Anything missing from one quote, ask about in writing. Then ask each builder three plain questions. Was this price based on a visit to my block? What is excluded? What happens if you hit rock, a sewer main or soft ground?
Check the contract side too. In NSW, residential building work over $20,000 needs a written contract and home building compensation cover (insurance that protects you if the builder can’t finish the job or fix defects). A complete granny flat build is well over that threshold, so if a builder is vague about either, take that as your answer.
The cheapest quote is sometimes the right one. It just needs to still be the cheapest once everything is in it.
Get a price for your block, not an average
The quickest way to a real number is to have someone look at the slope, the sewer, the access and the power before quoting. Book a free site inspection and we will walk your yard, check what sits under it, and price one of our two bedroom granny flat designs for the block you actually own. You can also call us on (02) 4203 3554, Monday to Friday, 7:00 AM to 5:00 PM.
Common questions about 2 bedroom granny flat prices
How much does a 2 bedroom granny flat cost to build?
It depends far more on the block than on the flat. Published prices across NSW this year run from kit figures in the tens of thousands to turnkey figures several times higher, because they include different things. The only number worth planning around is a turnkey quote based on an inspection of your site.
Can I build a granny flat for $100,000?
A complete, approved and connected 2 bedroom flat from a licensed builder at that figure is unlikely in the current market. Budgets around that level usually mean a kit, a smaller design, or a quote that leaves out approvals, site works or connections. Ask exactly what is excluded before you rely on it.
How much does a Bunnings or kit granny flat cost?
Kit prices cover materials only, so the advertised number is just the start. You still need a slab, licensed trades, a certifier, approvals and service connections, and you take on the coordination yourself. Add those up before comparing a kit with a builder’s turnkey price.
Is it cheaper to extend or build a granny flat?
It varies with the house and the block. A granny flat on a qualifying lot can often go through the faster CDC approval path, while an extension may need a DA and has to tie into the existing structure. A granny flat also gives you a separate dwelling that can earn rent, which an extension usually can’t.
Can a granny flat have 3 bedrooms in NSW?
The 60 square metre internal floor area limit applies whatever the bedroom count. Fitting three bedrooms into that space leaves very little living area, which is why 2 bedrooms is the practical maximum for most designs.
Why do 2 bedroom granny flat prices vary so much between Wollongong builders?
Mostly because the quotes are scoped differently. One may include approvals, excavation and connections while another lists them as exclusions or provisional sums. Sloping blocks, sewer mains and tight access also change the price from one Illawarra street to the next.
