You have decided to build a granny flat. Good. Now comes the bit that trips everyone up. Do you go with one of those standard plans that every second builder has on their website? Or do you pay extra and get a custom designed granny flat drawn up from scratch for your block?
It sounds like a simple question but it is not. The answer changes depending on your budget, your block, what you want to use the thing for, and honestly how much you care about ending up with something that actually feels like it belongs on your property.
Let’s work through it properly.
What Is a Standard Plan?
A standard plan is a pre drawn granny flat design that a builder already has ready to go. They have built it before, probably dozens of times. The layouts are proven. The approvals process is faster because the plans are already set up to meet NSW regulations. You pick one from a catalogue, make a few small tweaks if the builder allows it, and off you go.
What You Get
A floor plan that works. One bed, two bed, studio, whatever size you pick. The rooms are sensible. The kitchen and bathroom are in logical spots. Nothing weird. Nothing exciting either.
What You Don’t Get
A design that considers the actual shape of your backyard. Or where the sun hits in the morning. Or how the granny flat sits in relation to the main house. Or the slope. Or the trees you want to keep. Or the view from the bedroom window.
Standard plans are designed to work on as many blocks as possible. That means they are generic on purpose.
What Is a Custom Designed Granny Flat?
A custom granny flat is exactly what it sounds like. Someone, usually an architect or a building designer, looks at your actual block, talks to you about how you want to use the space, and draws up a plan that fits your property like a glove.
What You Get
A layout that works with your land, not against it. Windows facing the right direction for light and breeze. A floor plan that makes sense for how you live. Privacy from the main house built into the design instead of being an afterthought. A building that looks like it was always meant to be there.
What You Don’t Get
A cheap price tag. Or a fast turnaround. Custom takes longer and costs more. There is no getting around that.
How Much Do Granny Flat Designs Cost?
Here is where the numbers sit in Sydney heading into 2026.
Standard Plans
Most builders include a standard plan in their overall build price. You might pay $2,000 to $5,000 for the design and approval drawings as part of the package. Some builders absorb this cost entirely if you sign a build contract with them.
A turnkey one bedroom granny flat on a standard plan runs roughly $150,000 to $200,000 in Sydney. Two bedrooms is more like $180,000 to $250,000. These are ballpark numbers and they move around depending on the builder, the site, and what is included.
Custom Plans
Getting a custom designed granny flat drawn up costs more. Design fees alone can run $10,000 to $20,000 including all the plans, engineering, and council or certifier fees. On top of that, the build itself usually costs more because custom layouts often have shapes and details that take longer to construct.
A custom built granny flat in Sydney generally starts around $200,000 and can push past $300,000 for larger builds with premium finishes. Some projects in Eastern Sydney and the North Shore go higher again because the sites are more difficult and council requirements are tighter.
When Standard Plans Make Total Sense
Not everyone needs a custom job. Plenty of people build perfectly good granny flats from standard plans and are happy with them.
Your Block Is Flat and Simple
If you have a nice rectangular backyard with decent access and no major slope, a standard plan will fit just fine. The design does not need to be clever because the site is not throwing up any challenges.
You Are Building Purely for Rent
If the granny flat is going straight onto the rental market and you are not planning to live in it yourself, a standard layout is usually all you need. Tenants care about clean finishes, a functional kitchen, and a decent bathroom. They do not care whether the architect spent three weeks optimising the morning light.
Budget Is Tight
If every dollar matters and you want to get the most space for the least money, standard plans win. The design is cheaper, the build is faster, and builders can price it more accurately because they have done the same plan before.
You Want It Built Fast
Standard plans get through the approvals process quicker, especially if they meet complying development criteria in NSW. A complying development certificate can be issued in as little as 10 days. Custom designs that need a full development application can take months.
When You Should Go Custom
There are situations where a standard plan will actually cost you more in the long run because it does not suit the block and you end up spending money fixing problems that a good design would have avoided in the first place.
Your Block Is Awkward
Narrow lot. Steep slope. Weird shape. Big trees you want to keep. A standard plan does not care about any of that. It just plonks a rectangle down and hopes for the best. A custom design will work around the obstacles and use the tricky bits to your advantage. A good designer can turn a sloped block into an opportunity for split level living or elevated views. A standard plan on the same block would need expensive retaining walls and earthworks.
You or Family Will Live in It
If mum and dad are moving in, or you are building it as your own space, the layout matters a lot more. Which direction does the bedroom face? Is there somewhere nice to sit outside in the afternoon? Can you get to the bathroom without walking through the kitchen? These are things a custom design addresses properly. Standard plans are functional. Custom plans are liveable.
Privacy Is Important
On a lot of Sydney blocks the granny flat ends up quite close to the main house. Where you put the windows and doors makes a huge difference to how private both homes feel. A custom design places openings and outdoor areas deliberately so nobody is staring into each other’s living room. Standard plans cannot do this because they do not know where your main house sits.
You Want It to Look Good
Some people want their granny flat to match the main house. Same materials, same roof pitch, same vibe. A custom design can tie the two buildings together so the whole property looks planned and considered. Standard plans look like standard plans. They are fine. But they do not wow anyone.
The Middle Ground
Here is something a lot of people do not realise. You do not have to go fully custom to get something better than a stock standard plan. A lot of builders offer modified standard granny flat designs where they take a proven layout and adjust it to suit your block. Flip the floor plan. Move a window. Change the kitchen layout. Shift the entry point.
This costs less than a full custom design but gives you a much better result than picking a plan straight off the shelf. If your block has a couple of quirks but is not super complicated, this middle option is often the sweet spot.
Things to Ask Any Builder
Whether you go standard or custom, there are a few questions that will save you from nasty surprises.
What Is Actually Included?
A turnkey price should cover everything from earthworks and approvals through to the finished product ready to move into. Some builders quote low and then hit you with variations for site costs, connections, landscaping, and council fees. Get it in writing.
Who Does the Design?
Some builders use qualified building designers. Others use drafters. For a custom build, you want someone who has experience designing for your area and knows the local council requirements inside out.
What Happens If the Site Has Surprises?
Rock, bad soil, hidden services. These things pop up and they cost money. Ask how the builder handles variations and whether there is any allowance built into the quote for unexpected site conditions.
Can I See Finished Examples?
Any decent builder should be able to show you completed granny flats, both standard and custom. Ask to visit one if you can. Photos are one thing. Standing inside the actual building tells you a lot more.
So Which Is Worth It?
If your block is simple, your budget is tight, and the granny flat is for rental income, go with a good standard plan from a reputable builder. You will save money and time and end up with something that does the job well.
If your block has challenges, you or your family will be living in it, or you want something that genuinely fits your property, spend the extra on a custom designed granny flat. The design fee is a fraction of the total build cost and it pays for itself in a better outcome that you will be happy with for decades.
Either way, pick a builder who has actually built granny flat designs in Sydney before. Not a general builder who is having a go at their first one. This is a niche. Experience shows in the finished product. Ask around, check reviews, visit display homes, and do not sign anything until you are comfortable with who is building it and what you are getting for your money.