How big can a Tiny House be in NZ?

Updated: Nov 24, 2020

Probably THE most frequently asked question we get is some variation of “how big or how wide can my tiny house be?”, the answer is not as straightforward as you might think!

The short answer

= 8m long x 2.4m wide x 4.3m high - Reference NZTA

If like most people, you want your tiny house on wheels (THOW) to….

  • Be identifiable as a vehicle and therefore exempt from the Building act, and…

  • Be road legal (warranted and registered and able to be towed on the road on its own chassis), and…

  • To have a loft / mezzanine level, and…

  • Be built like a house not like a caravan (i.e. using building materials and construction techniques typical in NZ e.g. light gauge roll formed steel framing, lightweight vinyl cladding, insulation, double glazing, colour steel roofing etc)…

… then in our experience the largest trailer size we would recommend is 8m long x 2.4m wide x 4.3m high. The legal requirements for a light simple trailer can be found here in factsheet 13D.

Until we see more clarity about the rules on over-width and overweight tiny homes, we will continue to advocate that THOW’s be built within the restrictions of weight and size for the class of vehicle that it has been registered as. So that means sticking to 2.55m wide and less than 3500kg for a light simple trailer. We feel that this gives our clients the greatest level of confidence that they are operating within the rules, and the best level of defence should the status of their THOW as a vehicle be called into question by any regulatory body. 

Keep in mind, that even using quality lightweight materials, all our previous builds at this size still required many items to be removed from the tiny house (such as appliances and removable cabinetry) and be transported separately. This was in order to get the THOW down to 3500kg so that it can be transported legally on the road on its own chassis. It may be possible to build heavier and wider than this but there are many caveats and some amount of risk you need to understand before making a decision to go wider or heavier, if you are considering this, please read the long answer below…

The long answer

Because the Tiny House movement is still in its infancy here in NZ, there is little guidance available on what criteria a THOW should meet. To ensure our customers are well informed, we’ve written the below as a guide to help people considering building over 3500kg or wider than 2.55m wide, to understand the likely and possible implications of this choice. It’s important to us that our customers are educated in this area, we appreciate that it’s long, but if you’re going to be investing your money in an oversize or overweight tiny home, it’s important that you understand the situation as well as any of us can. We’ll endeavour to keep this brief, and up-to-date as things evolve.

The Building Act: In New Zealand, all building work is regulated under the Building Act 2004. Within the Act, there is a clause that states that vehicles are exempt from the Building Act. Tiny homes on wheels seek to meet the definition of a vehicle under the Building Act in order to be considered exempt. Section 8(1)(b)(iii) of the Building Act states a building includes:

“a vehicle or motor vehicle (including a vehicle or motor vehicle as defined in section 2(1) of the Land Transport Act 1998) that is immovable and is occupied by people on a permanent or long-term basis.” 

So if you plan to occupy your THOW permanently, it’s very important that you ensure that the tiny house remains movable to ensure it remains exempt from the Building Act. You can find more info about this in a document called “when is a structure a vehicle or building?”. There is also an interesting MBIE determination (2015/004) on this topic with a useful decision tree in the appendix that you can use to determine if the building act applies to your tiny house build. 

Land Transport Act 1998: The definitions of 'vehicle' and 'motor vehicle' in section 2(1) of the Land Transport Act 1998 are: 

“Vehicle – (a) means a contrivance equipped with wheels, tracks, or revolving runners on which it moves or is moved... Motor vehicle – (a) means a vehicle drawn or propelled by mechanical power, and (b) includes a trailer…”

NZTA: You will notice that the above definitions do not give us any criteria regarding the size, weight and safety features that a vehicle/motor vehicle must meet in order to be considered a vehicle under the Building Act. Those types of regulations are found within the NZTA "Vehicle equipment standards classifications” There are more than 20 different classifications of vehicles here, and each one comes with its own criteria regarding size, weight and safety. You could pick any one of these classifications to build a tiny house to (we’d love to see a tiny house moped, or a tiny house side car!), however the most commonly used vehicle class for registering tiny homes is “TD - Light Simple Trailer” this is because it requires a WOF (not a COF), and is basically a blank canvas that can be built onto. It should be noted that there is some evidence to say that a tiny house on wheels may not need to be warranted or registered or meet one of the NZTA vehicle classifications in order to still be considered a vehicle under the Building act, as the building act does not state this… more on that later.

Over-width - 3m wide THOW:

While factsheet 13D for light simple trailers does give a clear maximum width for the vehicle of 2.55m, there are provisions for vehicles and loads to be wider than this... see factsheet 53a. To summarise the relevant information from the document…

  • Over-width vehicles: if a vehicle needs to be over-width in order to perform its primary function, then it may do so as a ‘specialist over dimension vehicle’ (examples of this are chip spreaders, forklifts, mobile cranes, snow ploughs, ground spreaders/sprayers etc). While we do not know of anyone who has tried, it’s very unlikely that NZTA would find that a tiny house meets the requirements for a ‘specialist over dimension vehicle’, as it does not need to be over width to perform its primary function.

  • Over-width loads: A standard size motor vehicle is allowed to transport an over dimension load. A load wider than 2.55m but less than 3.1m must display hazard panels (these panels must meet certain criteria also), and a load 3.1m or wider must display hazard panels, an over-width sign, and also have a pilot vehicle. 

Based on the provision above for vehicles to carry over-dimensioned loads, many have built 3m wide tiny homes, stating that their tiny house is a ‘load’ being transported by a vehicle (the trailer). We love 3m tiny house designs, and the extra width really does give so many more options for layout and increase the liveability of the space. But we still have a few questions that we feel haven’t been proven or answered satisfactorily, and thats why we're hesitant to recommend our clients follow suit. Here are our questions...

  • Can a 3m wide tiny house be built under 3500kg? Most if not all 3m wide tiny homes currently on the market weight significantly more than the 3500kg weight limit for light simple trailers. This means that it would be illegal and dangerous to tow it on the road using its own chassis and braking system. Most of these tiny homes are instead transported by being lifted onto the back of a Hiab truck, rather than being towed on its own chassis. This is a good solution but can be a much more expensive transportation method, as you need to hire a professional tow company, and you will need to get an over-height permit if the total height of the truck deck and the tiny house exceeds 4.3m.

  • Will it still get a WOF at 3m wide? No, you will not be able to get a WOF for a tiny house that is wider than 2.55m. BUT to get around that, most over width tiny homes are built in a way that the trailer is detachable form the house, therefore the trailer itself is detached and WOFd by itself. (more to come about detachable trailers.) 

  • Is it still a vehicle? Is a 3m wide tiny house still considered a vehicle under the Building Act if it is considered a ‘load’ on a trailer by NZTA? Here is where things start to get a little grey, there is nothing within the Building Act or the Land Transport Act that covers this question. Until recently, we were left to speculate on this issue, but we can now look at legal precedents set by a recent court decision. On the 19th of Feb 2020, a case was heard in the Christchurch District Court in the case of Alan Dall (Defendant) and MBIE (Respondent). MBIE determined that Alan’s THOW was a building under the Building Act, Alan then decided to challenge this decision in court, and the judge ruled in his favour. Alan's case is of note here, because his tiny house was over-width and permanently attached to the trailer. We’ve extracted some of the salient points from the judges decision here, and will discuss the highlighted points below and the contradictions they seem to pose. We do recommend you read it in full, and you can do so here: Alan Dall v MBIE CIV-2019-085-000404.

“[44] I am of the view that the Unit was not immovable , for the following reasons:

A. The Unit possesses wheels, chassis, axel, brakes lights, drawbar and trailer hitch. The functional design of the Unit enables it to be attached to a vehicle and moved or relocated with relative ease. I do not consider this to be the case where a structure that would otherwise be a building’s been equipped with wheels solely in an attempt to circumvent the provision of the Building Act;

B. Furthermore the Unit has a valid registration and warrant of fitness, although I accept that the unit was registered before the superstructure was constructed on the trailer. The decision maker considered the fact that the unit was “over dimension for use on the road” weighed in favour of a finding that the Unit was not a vehicle. However I accept the Appellant’s submission that the Unit is no less a vehicle (an no less movable) simply for the fact that it must comply with certain road safety requirements due to its dimensions in the event that it is to be moved;

C. The unit is incapable of being fixed to the ground. My finding on movability would be different if, for example, the Unit was designed so that it could be moved off the wheels and fixed to the land

While that all sounds really positive for THOW owners across the country (It is!), we feel the judges three points above don’t go into enough detail to be able to say with confidence that all 3m wide tiny homes are always going to be determined to be a vehicle under the Building Act. As with any court ruling, it only applies to the case at hand, (though it will likely be used as a precedent for any future similar cases) but also, we still feel there is an element of risk taken on by the client in building an over-width THOW for the following reasons…. 

  • Firstly, the judges' comments don’t cover the scenario where a tiny house is too heavy to be towed using its own chassis (when in excess of 3500kg). The judge stated that “The functional design of the Unit enables it to be attached to a vehicle and moved or relocated with relative ease” OK… so if the THOW can not be towed using its own drawbar and hitch for transport on the road, but rather necessitates being transported by Hiab due to its weight, would it then still be considered movable? Point A above does not adequately cover this scenario, therefore we can only speculate. 

  • Secondly, in point B, the judge cited that the unit having a valid WOF and Rego played into his decision on whether the unit was a vehicle or a building, so referring back to the NZTA section above, it seems like while there is evidence from various MBIE rulings that a THOW may not need to meet the criteria for one of the NZTA vehicle classifications to still be considered a vehicle, in this case it did play a part.

  • Point C is where we see a contradiction, the judge stated that if Alan’s trailer had been detachable, that this may have led him to deem the Unit a building. However, the fact that Alan’s trailer is not detachable WILL prevent him from getting a valid WOF in the future, as the maximum width for a light simple trailer is 2.55m, meaning that when his current WOF expires he may again be in a vulnerable position to having his tiny house deemed to be a building, again this is just speculation.


Until we see more clarity about the rules on over-width and overweight tiny homes, we will continue to advocate that THOW’s be built within the restrictions of weight and size for the class of vehicle that it has been registered as. So that means sticking to 2.55m wide and less than 3500kg, as we feel that this gives our clients the greatest level or confidence that they are operating within the rules, and the best level of defence should the status of their THOW as a vehicle be called into question by any regulatory body. 

If you can’t fit your needs into a 2.55m wide tiny house, and you’ve read and accepted the risks above as well as done your own research, then yes, we can build a 3m wide tiny house for you. But we recommend that you still do your absolute best to keep the house under 3500kg so that it can be legally towed on its own chassis, It will be very challenging, and will mean making compromises to the length of the THOW, or on the materials and construction methods used. We also recommend that you create a ‘permanent’ connection between the over-width tiny house, and the trailer. NZTA has advised that a permanent connection is one that requires tools to disconnect, (container locks do not require tools) so a series of bolts would suffice. These two tips will help to minimise the risk of your 3m wide THOW being classed as a building should it be put to the test, but it’s by no means a guarantee! And don’t forget that it needs to remain movable too. 

If you would like to see more clarity about how various regulations do and do not apply to tiny homes on wheels across the country we recommend that you become a member of the NZ Tiny House Association. The Association has been formed to represent members of the Tiny House community, with the aim to foster innovation, promote the growth of the tiny house movement in New Zealand, and empower people with information and resources to assist them while they are working with councils to apply for consent to live legally in tiny houses. Build Tiny Ltd are proud to be a founding member of the NZTHA. 

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