Quick answer
A multigenerational kitchen in Browns Bay or Mairangi Bay is two cooking zones sharing one ventilation plan. If one generation cooks at high heat every night — wok, deep-frying, pressure cooker — that cooking needs its own room, with a door, and a rangehood ducted outside. A recirculating hood pulls out grease and odour, then hands the heat and the water vapour back to the room. Acceptable Solution G4/AS1 asks for mechanical extract of at least 50 litres per second over a cooktop, exhausted outside, and says natural ventilation alone will not do it. Design the duct run first: the island, the second sink and the door swing all follow it.
Key points
- A recirculating rangehood filters grease and odour, then returns the heat and the water vapour to the room you were clearing.
- G4/AS1 asks for mechanical extract of at least 50 litres per second over a cooktop, exhausted outside, and says natural ventilation alone is not adequate.
- Tenancy Services is blunt for rentals: recirculating systems, and fans that do not extract outdoors, do not meet the healthy homes ventilation standard.
- The second kitchen earns its keep by having a door, because a space removing contaminants should sit at negative pressure to the rest of the house.
- Route beats spec: a short rigid run through an external wall beats a long sagging flexible one, and the roof space is never allowed.
A recirculating hood hands back the heat and the steam.
There is a version of this house on half the cross streets off Beach Road, and another dozen on the ridge above Mairangi Bay. Brick and tile, seventies or eighties, extended once at the back. Three generations in it now, kids walking down East Coast Road to Rangitoto College, nobody moving. They want a kitchen where dinner is cooked the way it has been for forty years — wok on full heat, six o'clock, every night — without the smoke alarm going.
So the brief arrives as “we'd like a second kitchen”. Fair enough. But that is an answer, and nobody has said the question out loud: where does the air go? Get it wrong and you have paid for a second room that smells exactly like the first. Confirm anything consent-related with Auckland Council or your LBP first.
The second kitchen is a ventilation decision, not a lifestyle one
Start with the physics, because the physics does not negotiate. High-heat cooking throws off three things you want gone: grease aerosol, odour, and a serious volume of hot water vapour. A recirculating hood — ductless, carbon filter — handles the first two. Air goes through a grease filter, then activated carbon that takes the smell out, then straight back into the kitchen. The heat comes back. The steam comes back. BRANZ's Level guidance puts outdoor humidity on coastal New Zealand sites at 70–80% year round, and the Bays are coastal. So the second kitchen is not a luxury line on the schedule — it is where the cooking that needs a duct and a door goes, so the room everyone lives in stays open plan. That is a different argument from the usual scullery and butler's pantry one about hiding mess. Mess is storage. Steam is air, and air has rules.
What the Code actually asks for
G4/AS1 is specific. Spaces in household units containing cooktops must have mechanical extract fans, and the fan — including its ducting — must have a flow rate of not less than 50 litres per second, exhausted outside. It carries a comment worth reading twice: within that acceptable solution, natural ventilation on its own is not adequate to remove moisture generated from cooktops. Sliding the ranchslider open is not a ventilation strategy.
Then comes the paragraph most people never reach, and it justifies the door. Where mechanical ventilation removes or collects contaminants, that space is to be maintained at negative pressure relative to other spaces in the building. Air should move into the wok kitchen and out through the duct, never the reverse. You cannot do that when one side of the room is a 2,400mm opening to the dining table. The door is what makes the extract work.
If the house is a rental, or becomes one, the healthy homes ventilation standard applies, and it is unusually direct: recirculating systems, and fans that do not extract outdoors, are not suitable to meet it. Fans installed after 1 July 2019 in a room with a cooktop need a minimum diameter, including ducting, of 150mm, or an exhaust capacity of at least 50 litres per second. The landlord's version is in the healthy homes kitchen rules.
| Option | Grease and odour | Heat and water vapour | Healthy homes standard |
|---|---|---|---|
| Recirculating hood, carbon filter | Mostly, while the filter is fresh | No — back to the room | Not suitable |
| Ducted hood, short external-wall run | Yes, outside | Yes, outside | Meets it at 150mm or 50 L/s |
| Ducted hood, long flexible run | Yes, outside | Yes, but flow drops with every bend | Verify the achieved flow |
| Hood ducted into the roof space | Out of the kitchen | Into your insulation | Not suitable |
| Continuous mechanical extract outdoors | Yes, outside | Yes, outside | Meets it if it satisfies the criteria |
Where the duct runs
Once the wok cooktop needs 50 litres a second going outside, its position stops being a styling call. It is a hard constraint, locked before anyone draws an island. The appliance side is covered in ducted versus recirculating rangehoods; this is the building side. The good case is a cooktop on an external wall: short, straight, rigid duct through the cladding, done. Level is blunt about the failure — extraction must not vent into a ceiling or roof space, and moist air must be discharged outside, not into another building space. A hood terminating in the roof cavity is a moisture problem parked above your insulation.
Distance and shape matter too. Ductwork adds resistance, so a longer run needs a bigger fan to shift the same air. Keep the run short, the bends few and wide, and use smooth-walled duct — flexible duct sagging between hangers is a series of bends you never designed. The outlet is not free: fixed louvres cut airflow by around 30%, gravity louvres by around 50%. A backdraught shutter keeps draughts out without strangling the fan.
One more gets skipped: extract without replacement air does not work. Fans take air out and bring none in, so replacement is drawn through gaps, doors and windows. Pull 50 litres a second from a sealed room and the fan will not achieve it. In a wok kitchen with a door, that means a deliberate path — an undercut door, a trickle vent, a window on the far side. Design it, or everyone blames the appliance.
The duct route decides the kitchen, not the reverse.
Every “the rangehood's too noisy” callback I've been to turned out to be a duct problem. Nobody complains about the fan once the air's got somewhere to go.
Which cooking gets a door on it
You do not need two of everything. Split by heat and smell, not by meal. The main kitchen keeps what the family does together: the island, the good benchtop, the layout everyone circulates through. The second takes the wok burner, the deep-fry, the pressure cooker and a sink deep enough for a wok. A second full-height fridge is what usually ruins it — put one in an 1,800mm-wide room and the bench you needed is gone.
| Function | Main kitchen | Wok kitchen | Why |
|---|---|---|---|
| Rangehood | Ducted | Ducted, separately | Two cooktops means two ducts |
| Cooktop | Induction or gas | The high-heat burner | The burner making the steam belongs behind the door |
| Sink | Yes | Deep single bowl | A wok will not fit under a divided bowl |
| Dishwasher | Yes | Rarely | Dishes travel; a drawer unit only if the room is wide |
| Fridge | Yes | Under-bench at most | A second tall unit turns the room into a corridor |
| Oven | Yes | No | Ovens do not make the problem you are solving |
| Bin | Yes | Yes | Prep waste should not cross the main bench |
Benchtops in a wok kitchen take heat, oil and impact from someone not being precious about it. Laminate is the honest answer: materially cheaper, easy to replace in a decade, and nobody is photographing it. Stainless is better again beside a wok burner. Save the stone for the main bench. And engineered stone is still perfectly legal here — Australia banned it in July 2024 and New Zealand did not follow. MBIE consulted on options including licensing and a ban, and WorkSafe has tightened the exposure standard for respirable crystalline silica, but no ban is in force. The risk sits with whoever cuts it, making it a dust-control question. The benchtop comparison has the detail.
The grandparent end of the brief
Multigenerational means the kitchen works for someone in their thirties and someone in their seventies at once, without either feeling the design is about the other. Mostly that is reach and light. Drawers rather than base cupboards. A run of bench workable at seated. Task lighting over the boards, because older eyes need noticeably more of it. Lever taps. Nothing heavy above shoulder height. It costs close to nothing at design stage and a lot after the carcasses are cut — our accessible and universal design piece has the detail. If the grandparents do the high-heat cooking, the wok kitchen gets the good lighting, not the show kitchen.
If the second kitchen is a granny flat
Since 15 January 2026 you can build one detached self-contained dwelling of up to 70m² with no building consent and no resource consent, provided the design is simple, the work is carried out or supervised by licensed building professionals, and plumbing and drainage go to registered plumbers and drainlayers. Take a PIM from council before you start, and notify council on completion with final plans, Records of Work and certificates of compliance. It need not house family.
Three things people get wrong. The exemption is for a new build — MBIE says it cannot be an addition, alteration or conversion of an existing structure, so turning the garage into Mum's flat does not qualify. A mezzanine counts as another storey and disqualifies it. And no consent does not mean no Building Code: G3 food preparation and G4 ventilation still apply, and development contributions do too. MBIE separates a granny flat from a sleepout because a sleepout lacks the facilities to be self-contained — a bathroom or a kitchen. The kitchen is what makes it a dwelling.
What goes wrong
- The hood gets ducted into the roof space because the installer could not reach an external wall. Not permitted, not visible, and it surfaces two winters later as damp insulation and a ceiling stain.
- A 150mm hood is necked down to smaller duct to fit between studs. The healthy homes rule counts the ducting in the diameter, so the spec on the box is not the spec on the wall.
- The carbon filter has not been changed since the kitchen went in. They are consumables, and a loaded filter both smells and chokes the airflow.
- The scullery gets a wide cased opening instead of a door because it looked better in the render. It cannot hold negative pressure, so the steam still reaches the living room.
- The cooktop lands on the island after the slab is poured and the ceiling framed, and there is nowhere for a duct to go that costs less than the island did.
- Nobody planned replacement air. The hood is rated at 50 litres a second, delivers well under it, and the customer concludes the appliance is rubbish.
What to ask before you sign
- Where does the duct terminate — which external wall or soffit, marked on the plan?
- What is the duct diameter at every point, including where it passes through the wall?
- Rigid or flexible, how long is the run, and how many bends?
- What flow rate will the hood achieve on that run, not the free-air number on the box?
- Where does replacement air come from when the door is shut?
- Is the outlet a fixed louvre, a gravity louvre or a backdraught shutter?
- Are both kitchens on one contract and one invoice?
Frequently asked questions
Do we really need a second kitchen, or would a better rangehood fix the wok problem?
A bigger hood over the same open-plan cooktop helps, but cannot solve the whole problem, because an open room cannot be held at negative pressure. G4/AS1's logic is that a space removing contaminants sits at negative pressure to the rest of the building, and that needs a door. If the high-heat cooking is occasional, spend on a properly ducted hood over the main cooktop. If it is every night, the second room with a door pays for itself.
Can we put the wok cooktop on the island in a Browns Bay house?
You can, if you decide early enough that a duct route still exists. That usually means dropping through the floor and out a foundation wall, or a ceiling bulkhead across to the nearest external wall. Both are cheap to draw and expensive to retrofit. On a slab with the ceiling lined, an island cooktop tends to end up with a recirculating hood by default — the exact outcome you were avoiding.
Does adding a second kitchen need council consent in Auckland?
It depends what you are doing, and this is worth checking rather than assuming. A like-for-like swap usually needs no building consent, but moving plumbing or electrical, altering structure, or cutting a new penetration through cladding can engage the Building Code and need consent and an LBP. Separately, a self-contained second kitchen plus bathroom can raise a planning question about whether another dwelling has been created. Ask Auckland Council first.
Is a recirculating rangehood ever acceptable?
In a rental, no — Tenancy Services states that recirculating systems and fans that do not extract outdoors are not suitable to meet the healthy homes ventilation standard. In an owner-occupied apartment with genuinely no duct route it is sometimes the only option, and then you manage it: keep the carbon filter fresh, cook lower and slower, ventilate hard. It should never be the default in a standalone Bays house with an external wall three metres away.
Can we build Mum a granny flat with a kitchen without consent now?
Since 15 January 2026 you can build one detached self-contained dwelling up to 70m² with no building consent and no resource consent, provided the design is simple, licensed building professionals carry out or supervise the work, and registered plumbers and drainlayers do the plumbing and drainage. Get a PIM first and notify council on completion. Two catches: it must be a new build, not a garage conversion, and a mezzanine disqualifies it. The Building Code still applies, G4 included, so that kitchen needs its 50 litres a second going outside.
Getting a real number on it
A second kitchen in the Bays is usually a small room — cabinetry, a sink, a cooktop, a hood and a duct — so it does not double anything. Entry grade sits in the lower five figures, mid-range climbs into the mid five figures, and premium goes well past that; a compact wok kitchen alongside a main one reads as a known step-up, not a second full price. All plus GST, and the honest number depends on the duct route more than the door colour. Fuller breakdown in what a kitchen costs in Auckland.
Send us the scope — a rough sketch, where the cooktop sits, and a photo of the wall you think a duct can go through. We price off that and come back inside 24 hours; drawings sharpen the number but are not a prerequisite. We manufacture in East Tamaki, supply and install under one contract and one invoice, and a kitchen goes in over five to seven days. Twenty-three years, two thousand-plus kitchens, ten-plus a week, no showroom. If your duct must run somewhere awkward, we would rather say so at quote stage than on install day.