Quick answer
In most Avondale and New Windsor houses the kitchen sits in the dark back corner because that is where the drainage was cheapest to run when the street went up, not because anyone designed it there. You can move it to the sun, but it is a drainage decision before it is a design one. Under Acceptable Solution G13/AS1 a 40mm sink waste is not permitted at 1:50 or 1:60 at all, so 1:40 is the flattest it goes: 25mm of fall for every metre it travels. Any individual fixture discharge pipe over 3.5m long running to a gully trap also needs venting with an open vent or an air admittance valve. So the test is this. If the new sink lands within roughly 3.5m of the existing gully trap and there is height under the floor for the fall, move it. If it doesn't, open the wall between the kitchen and the north-facing room instead, because borrowed light gets you most of the gain for a fraction of the spend and the sink never moves.
Key points
- New Windsor was officially called Avondale East until 1984, and both suburbs filled in with low-density housing through the 1950s and 60s on plans that stacked kitchen, laundry and bathroom into one service core so all three could share a single drain run.
- G13/AS1 Table 4 does not permit a 40mm discharge pipe at 1:50 or 1:60, so the flattest gradient available to a kitchen waste is 1:40, which burns 25mm of height for every metre of horizontal run.
- Any individual fixture discharge pipe over 3.5m long that discharges to a gully trap requires venting by either an open vent or an air admittance valve, per G13/AS1 Table 5.
- The gully trap is a fixed point you plan around: for Housing, the top of the dish must sit no less than 150mm below the overflow level of the lowest fixture it serves, in a visible position, installed so surcharge cannot enter into or under the building.
- Opening one internal wall is exempt work under Schedule 1 exemption 11 unless the wall is load-bearing, a bracing element, a fire separation, part of a specified system or masonry, which is why it usually beats moving the kitchen on cost and on risk.
Every metre you move the sink costs 25mm of fall.
The house is a three-bedroom weatherboard off New Windsor Road, and you bought it because the north light comes into the lounge all afternoon and makes the place feel like it's worth more than you paid. Then you go and make a cup of tea. The kitchen is at the back, facing the fence and the neighbour's garage, and you're reaching for the light switch at ten in the morning to find the teaspoons. Everyone who walks through says the same sentence: the kitchen's in the wrong room. They're right. What nobody says is why it's in the wrong room, and that reason is exactly what makes it expensive to fix.
This is about the post-war stock through Avondale and New Windsor, the weatherboard and brick-and-tile houses that filled in as the market gardens got carved up and Rosebank turned industrial. Assume a standalone house, timber floor on piles, gully trap somewhere against the back or side wall. If you're on a slab, a cross-lease or a unit title, the drainage answers below shift and the consent answers shift with them. None of it replaces a conversation with Auckland Council or your LBP, so confirm your own situation before you order a single cabinet.
Your kitchen is in the dark room on purpose
Nobody hated you. They were being economical. Pull up the floor plan of almost any house of this era and you'll find the kitchen, the laundry and the bathroom stacked into one corner, usually the back one, usually sharing the same two walls. That's a service core. One drain run, one vent, one point where the pipes leave the building. A builder working through a subdivision at speed was never going to run a second drain to the sunny end of the house so someone could admire the garden while they did the dishes.
The sun side went to the rooms that made a house feel expensive: the lounge, the main bedroom. A kitchen was a work room, and a work room was somewhere you worked rather than somewhere you lived. Then open plan happened and the whole country decided the kitchen was the living room after all. The houses never got the memo. That's the gap you're standing in, and the same argument plays out across the bungalow belt with different weatherboards and a bigger number on the end.
So when you ask whether the kitchen can move to the north side, you're not asking a design question at all. You're asking whether you can move one end of a drain. Everything else follows from that answer, including the answer you get on price.
The number that decides it: 25 millimetres per metre
Here's the constraint nobody raises on the first site visit. A kitchen sink waste is typically 40mm. Under G13/AS1, the Acceptable Solution for foul water, Table 4 sets minimum gradients for discharge pipes by diameter and loading, and for a 40mm pipe the 1:50 and 1:60 columns are simply not available. The flattest a 40mm waste is permitted to run is 1:40. That's 25mm of fall for every metre it travels, and it isn't negotiable by anyone who wants to stand behind the job afterwards.
Run that against your own floor plan and it gets real quickly. Two metres of travel costs 50mm. Nine metres, roughly the trip from the back corner to the front of one of these houses, costs 225mm of drop before the pipe has even reached the gully trap. Under a timber floor you can run out of height long before you run out of house, and the crawl space is always shallowest where the ground rises, which on these sections is frequently the exact side you want the kitchen on.
A second threshold quietly reclassifies the project. Under G13/AS1 Table 5, for fixtures discharging to a gully trap, any individual fixture discharge pipe over 3.5m in length requires venting, by either an open vent or an air admittance valve. An AAV under the bench is a standard item, not a catastrophe, but it has to stay accessible, which means it eats into a cabinet, and it's the first honest signal that you've crossed from moving a sink into altering a drainage system. Push further and the run becomes a branch drain; the same table adds that branch drains connected to a vented drain exceeding 10m in length require venting with an open vent. An open vent is a pipe that goes up. Up through what is a question worth asking while the design is still on paper.
The gully trap is the boss of your kitchen plan
Go outside right now. Find the dish set into the ground near the back wall with a grate over it. That object has more authority over your kitchen layout than your designer does, and it's worth understanding why before you pay anybody to draw anything.
G13/AS2 sets out what it has to achieve. For Housing, every building must have at least one gully trap positioned so that the top of the gully dish is no less than 150mm below the overflow level of the lowest sanitary fixture served by the drainage system. It must have a grating that will allow surcharge. It must be located in a visible position. And it must be installed so that surcharge cannot enter into or under buildings. That last clause is the entire purpose of the thing: when the sewer backs up, the gully trap is the designated place for it to come out. Outside, on the ground, in daylight, where you can see it. Not through your new floor.
The dimensional rules stack on top. Waste pipe outlets sit at least 20mm above water seal level and at least 20mm below the grating. The top of the water seal sits no more than 600mm below the top of the dish, and there's a minimum of 600mm of clear access space above it so it can be cleared by hand. This is not a component you bury under a new deck because it's unsightly. Drains also have to be laid at the maximum practicable gradient, so you don't get to run something flat merely because flat suits the island you've fallen for.
The test: when the move is actually worth paying for
Moving a kitchen isn't wrong. It's sometimes the best money in the whole project, because a genuinely sunny kitchen changes how you use a house every day and it shows up again when you sell. But it has to be a decision you make with the numbers in front of you, not one you back into after the drawings are done and the emotional deposit is paid.
| What you're looking at | What it means underneath | Verdict |
|---|---|---|
| New sink lands within about 3.5m of the existing gully trap | Roughly 88mm of fall at 1:40, and no venting required at that length | Move it. This is the cheap window |
| New sink is 5-7m away, decent subfloor, gully can shift along the wall | 125-175mm of fall, plus an AAV or open vent, plus a drainlayer relocating the gully | Worth it if the light is worth a known step-up |
| New sink is across the house and the gully trap cannot move | A new branch drain around the building, possibly a new utility connection | Open the wall instead |
| Wall between kitchen and the sunny room is non-load-bearing and unbraced | Borrowed light, zero drainage work, Schedule 1 exemption 11 territory | Open the wall |
| Wall is load-bearing or a bracing element | Beam, engineer, consent. The wall now costs what the move costs | Price both, then choose on merit |
| House is on a concrete slab | Cutting and re-laying in-slab waste is the expensive path in every direction | Strong bias to leaving the sink where it is |
Nine times out of ten the drainlayer decides your kitchen layout, and he turns up three weeks after the designer's already sold you the island.
The 80 per cent move: open one wall
Here's the part you don't often get told, because there's less in it for the person telling you. You almost never need the kitchen to be in the sunny room. You need the kitchen to see the sunny room.
Borrowed light does most of the work. Open up the wall between the dark back kitchen and the north-facing room beside it and the kitchen stops being a cupboard you cook in. The sink stays where it is. The gully trap stays where it is. The 40mm waste keeps its short, steep, compliant run to the same place it's been running to since the house was built. You've bought the light and the connection to the rest of the house without buying the drainage, and the drainage is the expensive half.
Under Schedule 1 exemption 11, building work in connection with an internal wall, including an internal doorway, in an existing building doesn't require a building consent unless the wall is load-bearing, a bracing element, a fire separation wall, part of a specified system, or made of masonry units laid to a bond and joined together with mortar. The Ministry's own worked example is a homeowner removing a non-load-bearing timber wall between the kitchen and the laundry to make a bigger kitchen. That is very nearly your project, described by the regulator.
The catch lives in the word unless. Plenty of internal walls in these houses are doing bracing work whether they look structural or not, and the guidance is explicit that a load-bearing wall between the hallway and the kitchen puts you straight back into consent. You do not eyeball this off a video. Get someone with the appropriate expertise to tell you which category your wall falls into, in writing, before the demolition saw comes out, because opening a kitchen to the living space is a structural question first and a lifestyle question a distant second.
Once the wall is open, the rest is layout and light. A galley that used to be a corridor becomes a working run with a peninsula on the end, and the layout options narrow fast once the sink is pinned to one wall. That's fine, because the pinned sink is what's paying for the rest of the kitchen. Light has to be specified rather than hoped for, since one new opening won't rescue a south-facing bench on its own, and layered task and under-cabinet lighting is what makes the room usable at six o'clock in July. Ventilation deserves the same scrutiny: a rangehood that used to duct straight out through the old back wall in half a metre may have a much longer run once the room changes shape, so settle ducted versus recirculating before you commit to a position, not after.
One wall gets most of it. The sink never moves.
What this does to your consent, honestly
The general shape is this. A like-for-like kitchen swap usually needs no building consent. The further you push from like-for-like, the more of the Building Code you engage, and the exemptions are narrower than the internet suggests. Two conditions do most of the work in a kitchen: an alteration to existing sanitary plumbing is exempt only where the total number of sanitary fixtures in the building is not increased, and where the alteration does not modify or affect any specified system. It also has to be carried out by an authorised person. Those two conditions are the hinges the whole thing swings on.
| The work | Usually exempt? | The condition that actually decides it |
|---|---|---|
| New cabinets, sink stays put | Yes | Fixture count unchanged and no specified system touched |
| Moving the sink within the same room | Usually | Authorised plumber, and the total fixture count is not increased |
| Relocating the gully trap a short distance | Usually | Authorised Drainlayer, and it must not be a new connection to a network utility operator's service |
| Adding a scullery sink as well as the kitchen sink | No | That increases the total number of sanitary fixtures, so the exemption is gone |
| Removing a non-load-bearing internal wall | Usually | Not load-bearing, not bracing, not fire separation, not a specified system, not masonry |
| Removing a load-bearing or bracing wall | No | Structural, so engineering and consent every time |
| Anything that could affect floor joists or wall framing | No | The performance of structural elements is engaged |
What goes wrong
The failures on these jobs are boringly repeatable. They arrive in roughly the same order every time, and every one of them is cheaper to prevent than to fix.
- The drawing dies on contact with the subfloor. A designer puts the kitchen on the sunny wall, the client signs it, and the drainlayer crawls under three weeks later and says there's no fall. Now you're redesigning a kitchen you already emotionally own.
- The fall gets fudged. Someone lays the waste flatter than 1:40 because it only has to go a few metres. It works for eight months, then it doesn't, and the callback is under a finished floor with cabinetry on top of it.
- The scullery kills the exemption. The move was exempt right up until a second sink appeared in the walk-in pantry, which increases the total number of sanitary fixtures. Nobody notices until the house is being sold.
- The gully trap gets landscaped over. It has to stay visible, with clear access above it and a grating that lets it surcharge. Deck over it and you've built a machine for pushing sewage under your house.
- The wall turns out to be bracing. Discovered mid-demolition, on a Friday, with the kitchen already on the truck from East Tamaki. Now it's an engineer, a beam and a consent, and the install slot is gone.
- The rangehood ends up with nowhere to go. The old one ducted straight out the back wall in half a metre. The new position has a long run, a joist in the way and a client who assumed it was free.
- Nobody prices the making-good: floor to patch where the old cabinets stood, gib stopping, skirting, paint in two rooms rather than one.
What to ask before you sign anything
- Where is the gully trap, and how far is it from the sink on this drawing — in metres, measured rather than estimated?
- Has a drainlayer physically been under the floor, or is the fall still an assumption?
- Does any discharge pipe here exceed 3.5m, and if so, where does the vent or AAV live in the cabinetry?
- Is the wall we're opening load-bearing or a bracing element, and who is putting that in writing?
- Does this design increase the total number of sanitary fixtures anywhere in the house?
- Does the plan require a new connection to the network utility operator's service?
- Who is making good the floor, the gib and the paint — this price, or a variation later?
- Is this supply-and-install under one contract, or am I coordinating a plumber, a drainlayer, a builder and a cabinetmaker myself?
Frequently asked questions
Do I need a building consent to move a kitchen sink in Auckland?
Often not, but it turns on two conditions rather than on how far you move it. An alteration to existing sanitary plumbing is exempt building work only where the total number of sanitary fixtures in the building is not increased and the alteration doesn't modify or affect any specified system, and it must be carried out by an authorised plumber. If the work could affect structural elements such as floor joists or wall framing, or if you add a fixture like a second sink, you're into consent territory. Confirm your specific job with Auckland Council before you commit to a design.
How far can I move a kitchen sink from the gully trap?
There's no single published maximum distance, but two numbers shape the answer. A 40mm waste has to fall at not less than 1:40 under G13/AS1, so every metre of run consumes 25mm of height, and once an individual fixture discharge pipe passes 3.5m it needs venting with an open vent or an air admittance valve. In practice the real limit is how much depth exists under your floor between the sink outlet and the gully trap. That's why ten minutes of a drainlayer's time under the house is worth more than ten hours of a designer's time on a screen.
Is it cheaper to open a wall than to move the kitchen?
Almost always, and often by a wide margin, provided the wall is non-load-bearing and isn't acting as a bracing element. Opening a wall leaves the sink, the waste, the vent and the gully trap untouched, which removes the entire drainage half of the project along with most of its consent risk. If the wall turns out to be structural, the gap narrows quickly once you add an engineer and a beam. Price both options properly rather than assuming either one is automatically the cheap path.
Why is the kitchen at the back of my Avondale house in the first place?
Because it was cheaper to build that way. Houses through Avondale and New Windsor went up quickly through the 1950s and 60s as the market gardens were subdivided, and the plans grouped kitchen, laundry and bathroom into a single service core so all three could share one drain run leaving the building at one point. The sunny rooms went to the lounge and the main bedroom, because a kitchen was then a work room rather than the social centre of the house. The logic was perfectly sound. It just doesn't match how anybody lives now.
Can I put the sink in an island in the middle of the room?
You can, but it's the most expensive place to put it in a house like this. An island sink means running waste out from the middle of the floor, which spends your available fall over the longest possible distance before the pipe even reaches an external wall, and it usually triggers venting because the run comfortably exceeds 3.5m. On a timber floor with reasonable subfloor depth it's frequently achievable; on a slab it's a serious piece of work. Put the sink on the wall and the hob or the seating on the island, and you'll get a better kitchen for less money.
Getting a real number on both options
This decision goes wrong so often because people only ever price one option. They fall for the sunny kitchen, get a number, wince, and never find out whether the alternative was half of that or nine tenths of it. Price both. Entry-grade cabinetry in a house like this sits in the lower five figures plus GST and mid-range climbs comfortably into the mid five figures, and the drainage decision is one of the biggest single levers on which band you land in — considerably bigger than the door finish everyone agonises over. If budget is the binding constraint, there are better places to save than the parts you can't see, and the same arithmetic plays out across the western suburbs.
Send us the address, a rough sketch or even a photo of each wall, and where the gully trap is if you've been out to find it. You'll get a trade-priced number back inside 24 hours. We can quote off a rough scope and drawings only sharpen it. We manufacture in our own workshop in East Tamaki, we supply and install under one contract and one invoice, and a single kitchen goes in over five to seven days, so there's no gap between the person who measured it and the person who hangs the doors. Twenty-three years and more than 2,000 kitchens means we've been under a lot of Avondale houses, and we'd rather tell you the sink can't move before you've paid for the drawing than after.