Garage Conversion Cost Calculator NZ | Free 60s Estimate
Garage Conversion Cost Calculator NZ — Your Estimate in 60 Seconds
Free cost calculator
How much will a garage conversion cost?
Get an instant Auckland price range for your project — no details required to see it.
Quick answer: Get a personalised garage conversion cost estimate emailed straight to your inbox in under 60 seconds. No phone calls, no sales pitches, no waiting on a builder’s diary. Tell us your project basics, and we’ll send back a project-specific number based on real 2026 Auckland pricing.
You’re staring at the garage. The car’s parked on the drive most weeks anyway. What if that space became a teenager’s bedroom, a home office, a rental income stream, or somewhere for your mum to live closer without moving in?
The first question is always the same — what’s it actually going to cost? You’ve probably already pulled up a few ranges online. They span $30K to $180K. Useful as a wall poster. Useless for planning. Once you’ve estimated your budget, see how turn an Auckland garage into a consented, habitable room, from the first drawing to the final inspection.
What you need is a number that fits your garage. Your section. Your conversion type.
That’s what this calculator gives you.
Get Your Personalised Estimate
Sixty seconds, a few quick questions, and a tailored estimate hits your inbox. Free. No follow-up sales call.
Why a Calculator Beats a Generic “Per m²” Estimate
Most online sources will tell you a garage conversion in Auckland costs $40,000–$180,000. That’s accurate. It’s also useless for budget planning.
The range is that wide because “garage conversion” covers wildly different projects. Converting a single garage into a teenager’s bedroom on a flat section in Albany sits at the bottom. Turning a double garage into a self-contained granny flat with kitchen, bathroom, and separate entry on a leaky-era home in Glen Eden sits near the top. Both are “garage conversions in Auckland.” Both technically inside that $40K–$180K spread. Both cost vastly different amounts.
The headline range alone doesn’t tell you which one you are.
That’s where the calculator earns its keep. Instead of giving you a number that covers everyone, it asks the specific questions that move your number, type of room, size of garage, whether you need plumbing, the condition of what’s already there — and gives you a tailored estimate based on what those choices actually cost in Auckland right now.
It takes about a minute. Results land in your inbox.
What Goes Into the Estimate
The calculator works through the same variables we use when we’re pricing a real project. None of it’s guesswork, every input maps to a cost driver we’ve seen on completed Superior Renovations jobs.
Built from data across hundreds of Auckland renovations completed since 2018, including garage conversions, granny flat builds, sleepouts, and minor dwelling additions.
Type of conversion. This is the single biggest driver. A dry-room conversion, bedroom, study, gym, sits at $40,000–$60,000. Add a bathroom and you’re at $80,000–$110,000. Full granny flat with kitchen, bathroom, and separate entry runs $120,000–$180,000. The jump isn’t linear, wet areas need plumbing, drainage connections, waterproofing, ventilation, and higher-spec fixtures.
Size of the garage. Single garages typically run 18–22m². Double garages 36–40m². A double conversion costs more in absolute terms but the per-m² rate often comes down because fixed costs (consent fees, design, structural assessment) spread across more floor area.
Foundation and floor condition. Most Auckland garages were built with a concrete slab that wasn’t designed for habitable use, no damp-proof membrane, no insulation underneath. Bringing the floor up to habitable standard means either insulating over the existing slab (loses ceiling height) or breaking out and re-pouring (adds $8,000–$15,000). Volcanic clay sections in Mt Eden or Mt Albert can complicate this further.
Insulation and weathertightness. Turning a garage into habitable space brings the H1 energy-efficiency clause into play, so walls, ceiling and floor all have to hit current R-values. The current documents (H1/AS1 and H1/VM1, 6th edition) took effect on 27 November 2025, and the previous 2022 editions stay valid only for consents lodged up to 26 November 2026 — worth asking which edition your design is being drawn to. Garages built before 2008 will typically need full re-insulation, and adding windows tightens the spec again.
Plumbing and electrical. Running new water, waste, and drainage to a detached garage is more expensive than to an attached one — sometimes $5,000–$12,000 just for the connections. Electrical needs to be brought up to current Standards and usually means a new sub-board.
Finish level. Standard GIB and vinyl, or feature timber lining and engineered flooring? Premium finishes add $10,000–$25,000 on most conversions.
💡 Quick tip: The cheapest conversion isn’t always the smartest one. A $60K dry-room conversion can become a $120K rework two years later when you realise you needed a bathroom. Plan for what the space will actually do, not just what you can afford this year.
See Your Personalised Number
Inputs take a minute. The estimate hits your inbox right after.
What You Get in Your Inbox
A couple of minutes after you submit, you’ll receive an email with a project-specific estimate. Here’s what’s in it:
A low-to-high range based on the inputs you provided. Not a single point estimate, because no honest builder gives you one before a site visit. The range shows you where your project realistically sits.
A breakdown of the main cost categories, structural, finishes, professional fees, consents, services, so you can see where the money goes and where the biggest swings are.
Notes on what the estimate doesn’t include. Typically GST, resource consent (if triggered), development contributions for new dwellings, and any unforeseen ground or structural issues that only become visible once construction starts. We’d rather flag the limits than pretend they don’t exist.
It’s not a quote. Quotes need site visits, drawings, and detailed scope. The estimate is the layer before that, the number that tells you whether your project sits in a budget you can work with, or whether you need to rescope before going further.
If the number looks workable, the next step is usually a feasibility consultation, where we walk through your specific garage, what you’re trying to achieve, and what’s realistic on your section. That’s a separate conversation — and one you can book after you’ve seen the estimate, not before.
Single, Double or Detached: What Your Garage Type Changes
Two things about your garage set the shape of the whole project before anyone talks about finishes: how big it is, and whether it is attached to the house.
Single Garage Conversions (roughly 18–22m²)
A single garage gives you one good room. A bedroom, a home office, a gym, a studio. It is the cheapest conversion available and it sits at the bottom of the $40,000–$60,000 dry-room band, but the per-square-metre rate is the highest of any conversion type, because the consent, design and structural assessment cost the same whether you are converting 20m² or 40m².
If you want a bathroom in a single garage, be realistic about what is left. Take out 3–4m² for a compact bathroom and the habitable room that remains is small. That is usually the point at which people either accept a dry room or start looking at the double.
Double Garage Conversions (roughly 36–40m²)
This is the footprint that makes a genuinely self-contained unit work: open-plan living, a bedroom, a bathroom and a kitchenette without any of it feeling like a corridor. It also spreads the fixed costs across twice the floor area, so the per-m² rate drops even though the total goes up.
Attached vs Detached: The Services Question
An attached garage is almost always the cheaper conversion, and the reason is plumbing rather than structure. Water, waste and drainage are already a few metres away, and the wall between garage and house is often already close to a habitable build-up.
A detached garage at the back of the section is a different job. Water, waste and drainage have to be trenched out to it, and that alone can run $5,000–$12,000 in connections before anything happens inside the building. Power usually means a new sub-board and a run out to the structure. Detached conversions also tend to be the ones that hit boundary, height-to-boundary and impervious-area rules, because they sit near the edge of the section.
| Garage | Typical footprint | What it realistically becomes | Band |
|---|---|---|---|
| Single, attached | 18–22m² | One good room: bedroom, office, gym | $40,000–$60,000 |
| Single, with bathroom | 18–22m² | Bedroom plus compact bathroom, tight | $80,000–$110,000 |
| Double, attached | 36–40m² | Self-contained unit with room to move | $120,000–$180,000 |
| Detached, any size | — | Add services trenching and boundary-rule risk | +$5,000–$12,000 on connections |
Converting a Garage Into a Bedroom
This is the most common brief we get, and it is the cheapest useful thing a garage can become. There is no plumbing, no drainage, no waterproofing, so the whole wet-area cost jump never happens.
What it still needs, and what people underestimate: the slab has to come up to habitable standard, which means either insulating over it and losing ceiling height, or breaking it out and re-pouring at $8,000–$15,000. The walls, ceiling and floor all have to meet current H1 R-values. The garage door opening usually becomes a window or a wall, and that changes both the structure above it and the look of the street frontage. Ventilation and natural light have to satisfy the Building Code for a habitable room, which a garage was never designed to do.
💡 Quick tip: Check your ceiling height before you fall in love with the idea. Insulating over an existing slab eats 100mm or more, and a garage that started low can end up below the height a habitable room needs. Measure first, design second.
Whether the finished room can be rented, and whether it counts as a separate dwelling for rates and consent purposes, is a question for Auckland Council or a Licensed Building Practitioner rather than a calculator. If you are weighing the conversion against other ways of adding a room, our guides to converting a garage into a granny flat, container homes versus regular granny flats, and the cost of building a new garage cover the alternatives. If losing the garage is the sticking point, our garage build cost guide prices putting a replacement elsewhere on the section.
The Three Variables That Move Your Number the Most
If you’ve used the calculator and want to understand what drove your result, these three factors do most of the heavy lifting.
1. Whether you’re adding plumbing. 30–40% of the total. The single biggest jump in cost is the leap from dry-room conversion to wet-room conversion. Adding a bathroom alone takes a $50K project to $90K-plus. Adding a kitchenette on top pushes another $20K–$35K. If the goal is just usable floor space, a dry-room conversion gives you the best return per dollar. If you’re going self-contained, expect the budget to roughly double.
2. Condition of the existing structure. 15–30% of the total. Garages weren’t built to habitable standard. A garage with a sound slab, intact roof, good wall framing, and proximity to existing services converts faster and cheaper. A 1970s leaky-era garage with rotting bottom plates, asbestos cladding, or a cracked slab can swallow $20K–$40K in remediation before the conversion proper even starts. Worth getting a builder to assess before committing to a budget.
3. Labour and trade coordination — 35–45% of the total. Auckland trade rates currently sit at $90–$120 per hour depending on the trade. A typical 25m² conversion needs 350–600 trade hours across builder, electrician, plumber, gibstopper, and tiler. The reason fixed-price quotes look higher than charge-up isn’t margin, it’s the risk premium for guaranteeing the number. Charge-up budgets routinely blow by 15–25% on conversions because of unexpected condition issues behind the gib.
Knowing which of these three is the biggest factor on your garage tells you where to focus when you’re trying to bring the number down, or where to brace yourself if it has to stay where it is.
Convert the Garage, or Demolish and Build New?
This question matters more in 2026 than it did a year ago.
In January 2026, the government introduced the Schedule 1A Small Stand-alone Dwelling (granny flats) exemption, new dwellings up to 70m² can now be built without a building consent if they’re designed and constructed by licensed professionals and meet specific conditions. That’s a structural shift in the economics of adding a second dwelling to your property.
Here’s the awkward bit: the exemption applies to building new, not to converting existing structures. A garage conversion still triggers building consent because it changes the use of an existing building, involves structural alterations, and almost always involves plumbing and electrical work.
Which means homeowners now have a genuine choice:
Convert the existing garage. Cheaper if the garage is in good condition. Faster start. Keeps the existing footprint. Consent required. $40K–$180K depending on scope.
Demolish the garage and build a new 70m² SSAD-exempt dwelling. Higher upfront cost — roughly $200K–$280K for a turnkey dwelling. But no building consent. No consent processing delays. More floor area. Standalone status. The numbers can work out closer than they look once you factor in the consent fees and design timelines avoided.
The break-even point depends heavily on the condition of the existing garage. If it’s structurally sound with good services nearby, convert. If it’s rotten, undersized, or full of asbestos, the new-build pathway can be the cleaner answer.
The calculator gives you the conversion estimate. If you want to weigh that against a new-build SSAD option, that’s worth a feasibility conversation before you commit to either path.
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Sixty seconds. Tailored to your project. Sent to your inbox. No sales call.
Frequently Asked Questions
Is the garage conversion cost calculator free?
Yes. No charge, no obligation, no follow-up sales calls. Built by Superior Renovations to give Auckland homeowners a realistic starting estimate without having to chase a builder for one.
How accurate is the estimate?
The calculator uses 2026 Auckland market pricing and reflects real Superior Renovations project data. It's accurate enough for budget planning and feasibility, but it isn't a quote. Final pricing depends on detailed scope, site visit, and the condition of the existing garage.
What's the average cost to convert a garage in Auckland?
Auckland garage conversions sit in three main bands. A dry-room conversion, bedroom, office, gym, runs $40,000–$60,000. Adding a bathroom takes the range to $80,000–$110,000. A full self-contained granny flat with kitchen, bathroom, and separate entry runs $120,000–$180,000. Condition of the existing garage and complexity of services connections move these figures up or down.
Does a garage conversion require building consent in Auckland?
Can I use the new Schedule 1A granny flats exemption for a garage conversion?
What's the difference between a garage conversion and a granny flat?
A garage conversion means turning an existing garage into habitable space, which can be a single room, a bedroom-plus-bathroom, or a fully self-contained unit. A granny flat is the self-contained unit at the top end of that spectrum, with its own kitchen, bathroom, and separate entry. Not every garage conversion is a granny flat. Every granny flat conversion is a garage conversion.
Can I convert a double garage into a self-contained unit?
Yes, and double garages convert into the best granny flats because the 36–40 square metre footprint gives you enough room for an open-plan living area, bedroom, bathroom, and kitchenette without feeling cramped. Expect $130,000–$180,000 for a turnkey double-garage granny flat in Auckland, depending on existing condition and finish level.
Does the estimate include GST?
The estimate is GST-exclusive unless otherwise specified. You'll need to add GST when comparing the estimate to other builder quotes. Architect fees, structural engineering, council consent fees, and development contributions are also typically excluded from the initial estimate, they get factored in during the detailed quoting stage.
How long does it take to get the estimate?
Under 60 seconds to complete the form. The estimate lands in your inbox within a couple of minutes.
What happens after I submit, will someone call me?
No sales call. The estimate lands in your inbox within a couple of minutes and that's it. If you want to take the next step, you book a feasibility consultation through the site — we don't chase you with phone calls or follow-up emails. Plenty of Auckland homeowners use the calculator to sense-check budget without ever speaking to us, and that's the point.
How much does it cost to convert a garage into a bedroom in NZ?
A dry-room conversion, which is what a bedroom is, sits at the bottom of the range at $40,000-$60,000 in Auckland. There is no plumbing, drainage or waterproofing, so you avoid the biggest cost jump in the whole project. The work that remains is bringing the slab up to habitable standard (insulating over it, or breaking out and re-pouring at $8,000-$15,000), meeting current H1 R-values in the walls, ceiling and floor, closing in or reworking the garage door opening, and satisfying the Building Code on ventilation and natural light.
Is it cheaper to convert an attached or a detached garage?
Attached, almost always, and the reason is services rather than structure. Water, waste and drainage are already metres away on an attached garage. Trenching those out to a detached garage at the back of the section can add $5,000-$12,000 in connections alone before any work happens inside the building, and power usually means a new sub-board plus a run out to the structure. Detached garages are also the ones that most often run into boundary, height-to-boundary and impervious-area rules, because they sit near the edge of the section.
Please note: Cost factors vary project to project, and the calculator’s accuracy depends on the inputs you provide. The estimate is a planning tool, not a quote. Rates and material costs shift with the market, and final project pricing requires a site visit and detailed scope assessment of the existing garage. While information is considered current at the date of publication, Superior Renovations isn’t liable for any decisions made solely on the calculator output.
Further Resources for your garage conversion
- Featured projects and Client stories to see specifications on some of the projects.
- Real client stories from Auckland
Need more information?
Take advantage of our FREE Complete Home Renovation Guide (48 pages), whether you’re already renovating or in the process of deciding to renovate, it’s not an easy process, this guide which includes a free 100+ point check list – will help you avoid costly mistakes.
Download Free Renovation Guide (PDF)
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