How Long Does It Take to Build a Granny Flat? Stage-by-Stage Timeline
Summary
Most people asking how long it takes to build a granny flat are really asking how long until they have a tenant or a parent moved in, and that is a longer answer than the build alone. In 2026, the whole job from first drawing to handover runs roughly 4 to 7 months on the fast approval pathway, and longer if your project needs a full council application or your site is difficult. The construction itself is the predictable part, about 8 to 16 weeks from slab to completion. The months that surprise people are hiding before the build even starts, in design and approval, and they are decided by your approval pathway and the quality of your documentation, not by how fast anyone can lay bricks. This guide walks the timeline stage by stage, shows where the delays actually live, and explains what you can control. For the full rules and costs, start with our Australian granny flat guide.
Table of Contents
The honest answer up front
A granny flat takes about 4 to 7 months from the day you start drawing to the day you get the keys, assuming a reasonable site and the fast approval pathway. That is the number, and now the caveat, because the range is wide for a reason and the reason matters.
People hear “how long to build” and picture the construction, the slab and the frame and the trades. That part is fairly honest and fairly fixed, around 8 to 16 weeks once it starts. The trouble is that construction is maybe half the total clock. The other half is design and approval, which happen before a single tool comes out of the ute, and which most people forget to count. When a project that “should have taken three months” took eight, it was almost never the building that blew out. It was the approval, and the approval was slow because the paperwork was wrong. Hold that thought, because it is the whole game.
The full timeline at a glance
Here is the realistic shape of a granny flat project in 2026, on the fast pathway, on a site without nasty surprises. Treat these as typical durations that overlap slightly in practice, not as a sum you add up to the day.
| Stage | Typical duration | What happens |
|---|---|---|
| Design and drafting | 2–4 weeks | Concept, site and title check, full documentation, energy and BASIX |
| Approval | 2 weeks to 5 months | CDC or building permit (fast) versus a council DA (slow) |
| Site preparation | 2–4 weeks | Soil test, site cut, service applications, set-out |
| Slab | 1–2 weeks | Footings and slab pour, cure |
| Frame and lock-up | 3–5 weeks | Frame, roof, windows, external cladding, frame inspection |
| Internal fit-out | 4–6 weeks | Waterproofing, tiling, cabinetry, trade fit-off, painting |
| Completion and handover | 1–2 weeks | Final inspection, Occupation Certificate, making good |
Add the fast-pathway version up and you land around four to five months. Swap the fast approval for a full council DA, or add a difficult site, and you are closer to six or seven, sometimes more. The build barely moves between those two scenarios. The approval is the whole difference.
Stage by stage, start to finish
The sequence matters as much as the duration, because each stage depends on the one before it being done properly. Here is what actually happens, in order.
Design and drafting (2–4 weeks)
This is where the project is won, and where people try to save the wrong fortnight. Good drafting starts by reading your title and planning certificate, then designs to your block and your approval pathway, and produces a complete set including the energy documentation, which in NSW means a BASIX certificate. Rush this stage with a cheap or incomplete set and you do not save two weeks. You lose two months later when approval bounces.
Approval (2 weeks to 5 months)
This is the swing stage, and your pathway decides it. In NSW, a compliant 60m² secondary dwelling can be approved as Complying Development through a private certifier in around 10 to 20 business days. In Victoria, a small second dwelling under 60m² on a qualifying lot skips the planning permit entirely and needs only a building permit, which a surveyor can usually turn around in a few weeks. A full council Development Application, which you hit when your site or design falls outside the fast pathway, runs anywhere from six weeks to three to five months. Same build, wildly different wait, decided here.
Site preparation (2–4 weeks)
Once approved, the block gets ready. Soil testing should already be done, because it shapes the slab and you do not want surprises now, and the site is cut and levelled, service connection applications go in, and the build is set out. On a sloping or rocky site this stage stretches, which is one more reason the site costs we cover in the Sydney cost guide tend to surprise people.
Slab (1–2 weeks)
Footings go in, the slab is poured, and then it cures, which is not a step you hurry. This is quick and predictable on a prepared site.
Frame and lock-up (3–5 weeks)
The frame goes up, the roof goes on, windows and external doors are installed, and the external cladding is completed, at which point the building is weathertight and “locked up.” A certifier frame inspection happens here, one of the mandatory hold points, and the build cannot proceed past it without sign-off.
Internal fit-out (4–6 weeks)
The slow, detailed stage. Waterproofing goes in and gets inspected, because it is the most common defect and nobody sane skips the check, then tiling, cabinetry, the electrical and plumbing fit-off, internal linings, and painting. This is where finishes and trade availability decide your pace, and where ordering the kitchen too early or too late costs you.
Completion and handover (1–2 weeks)
The certifier does the final inspection and, if all is well, issues the Occupation Certificate, which is the legal document confirming the dwelling is fit to live in. Landscaping and making good the yard finish the job. Keys.
Where the months actually hide
Strip the timeline back and almost every serious delay comes from one of three places, and none of them is the construction.
The first is approval pathway. A project designed to fit Complying Development in NSW or the permit-free threshold in Victoria is weeks. The same project nudged outside those thresholds, by a third bedroom over 60m² or a non-compliant detail, becomes a council DA and months. The pathway is chosen at the design stage, often without the owner realising a choice was even made. If you are not sure which pathway your site falls into, the permit checker is the fastest way to find out before it costs you a season.
The second is documentation. A set that is incomplete, unscaled, or non-compliant gets knocked back, and a knock-back does not just cost the redraw. It costs the requeue, because you go back to the end of the assessment line. This is the single most avoidable delay in the whole project, and it traces straight back to who drew your plans and how well.
The third is the site and the weather, which you control least. Rock, slope, a distant sewer connection, a wet winter, a trade shortage. These are real and partly unavoidable, but a good design anticipates the site ones rather than discovering them, which is the difference between a planned cost and a blowout.
What you can do to keep it on schedule
Most of the timeline is set before construction, so most of your influence is too. Get the soil test done early, so the slab design is right and the site holds no surprises. Insist on a complete set of drawings with the energy documentation included, because a half-set is a delayed set. Confirm your approval pathway before you finalise the design, so you are not accidentally building a DA project when a CDC was within reach. Choose your finishes early, since waiting on a back-ordered benchtop stalls the whole fit-out. And if you are running the build yourself, sequence your own work around the trades rather than ahead of them, which we cover in the granny flat DIY guide.
A prefab or modular build is the other lever. Because the unit is fabricated in a factory while site works happen in parallel, it can compress the construction stage, sometimes to a handful of weeks. It does not skip approval, and it suits some sites better than others, but if speed is your priority it is worth weighing. The build was never the slow part anyway. The approval was, and that is the same whether the box is built in a factory or on your lawn.
What Draftee does at this stage
Two of those three delays are decided at the drawing board. We design to the fast approval pathway wherever your site allows it and produce a complete, compliant set so approval does not bounce, which is the cheapest time you will ever save on a build. Tell us about your block and we will draw it to move.
Frequently Asked Questions
How long does it take to build a granny flat?
In 2026, about 4 to 7 months from the first drawing to handover on the fast approval pathway, and longer if your project needs a full council Development Application or your site is difficult. The construction itself is roughly 8 to 16 weeks from slab to completion. The rest of the time is design, which takes 2 to 4 weeks, and approval, which can be as little as 2 weeks on a fast pathway or several months through council. The build is the predictable part; the approval is where the time varies.
How long does granny flat approval take?
It depends entirely on the pathway. In NSW, a compliant 60m² secondary dwelling can be approved as Complying Development in around 10 to 20 business days through a private certifier. In Victoria, a qualifying small second dwelling skips the planning permit and needs only a building permit, usually a few weeks. A full council Development Application, triggered when the site or design falls outside the fast pathway, takes six weeks to three to five months. Choosing the fast pathway at the design stage is the single biggest time saving available.
What causes the most delays when building a granny flat?
Approval, not construction. The biggest avoidable delay is non-compliant or incomplete documentation that gets rejected, sending you to the back of the assessment queue. The second is unknowingly designing a project that falls outside the fast approval pathway and into a slow council application. The third is the site and weather, such as rock, slope, or a wet season, which a good design anticipates rather than discovers. Getting the drawings right is the cheapest way to protect the timeline.
Is a prefab granny flat faster than a custom build?
Often, for the construction stage. A prefab or modular unit is built in a factory while site preparation happens in parallel, which can compress the build to a few weeks rather than 8 to 16. It does not skip the design or approval stages, which is where most of the total time sits, so the overall saving is smaller than the construction saving suggests. Prefab also suits some sites better than others. If speed is the priority it is worth considering, but approval remains the gate.
How long from slab to completion?
Roughly 8 to 16 weeks for a standard granny flat, depending on size, finishes, trade availability, and weather. That breaks down into about 1 to 2 weeks for the slab, 3 to 5 weeks for frame and lock-up, 4 to 6 weeks for the internal fit-out, and 1 to 2 weeks for completion and handover, with certifier inspections at frame, waterproofing, and final stages. The fit-out is usually the slowest part, since it carries the most trades and the most detail.
Continue Your Research
House Extension Cost 2026: A Realistic Guide to Building Costs
1 Bedroom Granny Flats WA Price List 2026: Real Costs for a Perth Ancillary Dwelling
Shed to Granny Flat Conversion 2026: What You Need to Know
Last updated and changelog
Last updated: 18/6/26
Changelog:
– 18/6/26: Initial publication
