Special Offer for the New Zealand Agricultural Show 2019

In Christchurch, we have the The New Zealand Agricultural Show (used to be called the Canterbury A&P Show) happening this week (13-15 November 2019).

To celebrate, we are offering a special offer on our Cosy Homes: we will beat any other quote by $1800! Offer ends on 13th December 2019.

So bring us an authorised quote for a similar product from anyone else, and if we are not already cheaper (which is usually the case), then we will match their quote, and upgrade your kitchen by $1800. So for the price of a basic melamine kitchen, you will get a premium European made kitchen with high gloss, thermo-wrapped doors, moisture resistant board, soft closing doors and extra cabinetry.

If we are already cheaper than your provided quote, we will still give you a free shower dome and install, valued at $400.

And of course, you will get all the benefits of working with Cosy Homes, which include:

  • High quality finishing by our experienced builders, supervised by a Licensed Building Practitioner (LBP).
  • A huge choice of customisation – over 100 pre-priced options to choose from, or anything else you might need at a tailored rate.
  • Our “go the extra mile” attitude, which translates into numerous small benefits you will benefit from day to day, including:
    • 32Amp power supply instead of the standard 16Amp, so that you can run twice as many appliances at once.
    • Three smoke alarms instead of just one.
    • Smoke alarms with 10 year batteries – no hassle of testing and replacing them every year.
    • Ceramic vanity and all tap ware and mixers have a 10 year warranty.
    • An access conduit from the switchboard down to the chassis, so that any future electrical upgrades you might want are easy to install.
    • Careful use of thermal breaks to significantly improve insulation.
  • Access to unique options developed in-house that are not available anywhere else, like our Cosy Feet: earthquake resistant, adjustable-height feet made from double reinforced concrete.

Managing Moisture and Condensation in Modern Homes

Condensation is a common problem now that homes are getting more airtight. 50 years ago, with old wooden windows and gaps under the front door, there was a lot of accidental ventilation from draughts. But now, with rubber seals everywhere, there is not.
Living generates a huge amount of moisture – breathe on a pane of glass and you will see the condensation in one breath! We breathe out something like 1-2 litres of water a night when we sleep. Then there is cooking, showers, etc. And household furniture and carpets can store a surprising amount of condensation, for example a bed can store up to 10 litres of moisture!
And too much moisture causes multiple problems, from condensation on the windows, to causing black mould, to making the home far harder to heat which will cost you money every day in winter.

Some building systems promote breathable walls, but this will never be enough by itself to control moisture and it can easily go badly wrong – unless this is very carefully designed and carefully built to specification, this can lead to moisture condensation inside the walls, which is terrible for insulation and causes rotting.  Other building systems use vapour barriers, either in the wall linings, or in the insulation itself, i.e. with polystyrene insulation. Either way, if you have a modern home with no accidental draughts, condensation needs to be actively managed.
So pretty much all new homes and tiny homes should actively think about and manage condensation. A good goal is to replace all of the air in the home at least 2-3 times per day.
There are a variety of approaches. I’ll list some, starting at the easiest (but often the least effective) and working up:
  • Install a shower dome over the shower – this makes the condensation from the shower stay in the shower and re-condensate there where it should. It also makes it warmer. This is reasonably cheap (about $300) and very effective, but not a complete solution by itself.
  • Leave two windows open a crack – they should be at opposite ends of the home to let wind create a flow. Think about the flow – it should cover the whole home – if it is just opposite sides of one room, it will mostly only help that one room. The more open windows the better, but it will still struggle to give 2-3 air changes per day, especially when there is not much wind. Opening one window a crack will not help much, as there is no chance for flow of fresh air in, because the is no place for the air to flow out elsewhere. Or vice versa depending on the wind direction.
  • Leave the bathroom and/or kitchen extractor on while you are away for the day. But think about where the fresh air is coming in to replace the extracted air, e.g. leave a window open a crack at the opposite end. If the rest of the home is sealed, the fan will struggle to push out anything. Remember that a bathroom and/or kitchen extractor that is turned off can be a inlet of fresh air IF it does not have a vent flap preventing this. This can be pretty effective, but requires you to remember to do it daily and this type of fan may not be as power efficient as a dedicated fan, and may not be designed to run for long periods, so it may fail earlier.
  • Use a dehumidifier, or put the aircon on to dehumidify mode while your away. This is ok in summer, as aircons in cooling mode will be dehumidifying as a byproduct of cooling. But this is not an ideal solution in winter, as all dehumidifiers work by cooling down the air (that is what makes the moisture condensate). These solutions are also more costly to run, dehumidifiers require you to manually empty the water out, and you don’t get the benefits of fresh, oxygenated air.
  • Install one or more ventilation fans. At its simplest, it is a quiet fan (so can stay on while you sleep) combined with a vent at the opposite end of the home, to get air flow through the home. You can either install an ultra-quiet fan (more expensive) anywhere, or install a reasonably quiet fan (i.e. quieter than a typical bathroom extractor) in a place further away from where people sleep, or ideally mount it outside – under the floor. If you go for just one fan, make sure you have an unblocked air flow through the whole home when doors are closed – you might need to install small vents through walls, or ideally make sure there is a small (~5mm) gap under any doors that are closed, or leave doors slightly open. Also, make sure the fan/s are big enough to achieve 2-3 air changes per day – they will have a stated air flow per minute etc, BUT this is based on not having to push against any air pressure (i.e. no restrictions to air flow at all, i.e. wide open doors and windows), so in reality, you need to divide the stated air flow by about 4 to get the real air flow. Most people get an expert to do this (like Moisture Master), but some can try it more themselves. Could easily cost $1000.
  • Install a heat exchange ventilation system. This is like the previous option except the outgoing air goes through a heat exchanger which captures the warmth from the outgoing air and uses it to heat up the incoming air, which saves on power bills and stops cold drafts from the incoming air vent. This could easily cost $2500 to $5000.
Whichever option you choose, it is important to think about condensation in your home, choose an option, and monitor the changes – learn and adapt. But do bear in mind what I said earlier about furniture and carpets storing moisture – you can often find that you see an improvement for a few weeks, then it seems like the condensation is worse than ever – this is probably not actually the case – this is probably the moisture levels in the air getting low enough that the water in the furniture and carpets is starting to evaporate into the air, which is actually a good thing – after a few more weeks, you home will be fully dried out, feel noticeably better and also be much easier to heat.

Do portable buildings need a Building Consent?

Table of Contents

Executive Summary
Case Study
The Determination Regarding “Vehicle”
The Determination Regarding “Immovable”
The Determination Regarding “Permanent Occupation”
Related Issues
      Does a Vehicle have to be Registered, Warranted, or Towable on the Road?
      Specific Mention of Caravans
      Is Moving a Home onto Site Considered Building?
      Are two Vehicles Locked Together a Building?
      Does Building a Deck Require Building Consent?


With public pressure and even government attention turning to affordable and diverse housing options, it is becoming increasingly important for everyone involved to be clear about what is and is not possible within the law. One issue that keeps coming up, and is often misunderstood by local councils, is when a portable building is considered to be a building or a vehicle, with regards to requiring a Building Consent.

To be clear, Cosy Homes understands that Building Consents can serve a valuable purpose, and that quality homes are important – this is why Cosy Homes are built to Building Code by licensed builders. However, we are also aware that there are many cases where the act of getting a Building Consent is an unnecessary and undue burden (e.g. the owner does not plan to keep the unit in that location for very long, or the requirements for earthquake safe foundations are irrelevant because the vehicle on wheels is already earthquake safe). Therefore, we think it is important that people have the option to not get a Building Consent, and we believe the central government has made this possible in their nationwide legislation (within appropriate guidelines), therefore it is local councils that often need help to interpret this carefully designed legislation and support the rights of their citizens.

Executive Summary

Broadly speaking, the Department of Building and Housing is consistently clear that a home does not need a Building Consent if:

1. It is a vehicle (i.e. has wheels, a towbar, and is movable), and one of the following is true:

a. The vehicle is not fixed to the ground in any way that needs a professional tradesperson to detach it, OR

b. The vehicle is not permanently occupied.

It also clarifies a few related points:

  • A vehicle does not have to be registered, warranted, or towable on the road.
  • Caravans and mobile homes are specifically mentioned as examples of vehicles.
  • Moving a vehicle onto a site does not need a Building Consent.
  • Locking two vehicles together typically makes them immovable, so would require them to get a Building Consent. However solutions to this are discussed.
  • Building a deck does not require a Building Consent.

At Cosy Homes, we have gone above and beyond to ensure we understand the law and comply with it. In particular, we are careful to comply with points 1 and 1a above.

Case Study


The most definitive definition and ruling on this question comes from the central government – The Department of Building and Housing (DBH). DBH administer the Building Act and the Building Code, and have ultimate responsibility in deciding how the Act is interpreted. Local councils who are unsure of interpretations can submit their case to the DBH, who will make a determination. Local councils are then legally obligated to follow the DBH determination.

To save a lot of individual hassles of local councils making incorrect interpretations and wasting the time of the council, the client and the DBH in asking for individual determinations, I thought it was prudent to do a literature review of past determinations that most closely relate to this question. While I have not looked at all DBH determinations, I have studied most of the 30 or so determinations in this area.


The following is perhaps the best example:

Determination 2015/044: Regarding the issue of a notice to fix for a prefabricated unit and whether the unit is a building or a vehicle.


Date issued: 8 July 2015.


A property owner contracted a manufacturer of small homes on wheels to build one on his site in Balfour. When it was partially finished, Southland District Council issued a “notice to fix” on the grounds that it was a building and therefore this was building work and a building consent should be obtained for it. The DBH determined that the home was in fact a vehicle, and overruled the Southland District Council. The council disagreed with the draft determination and gave their reasons, however the DBH gave clear logical responses and maintained their determination.


Section 2 details how the home in question was very similar to a Cosy Home in the following ways:

  • It was quite large compared to a traditional caravan or tiny home at 40sqm (Cosy Homes are typically 38 or 50 sqm).
  • It’s subfloor was built on a metal sub-frame with axles, inflatable tyres and a tow bar. Its sub-floor was timber joists, with sheet flooring installed over this. Cosy Homes also have metal sub-frame with axles, inflatable tyres and a tow bar. Cosy Homes’ sub-floor is of higher quality (steel joists with a thick insulated panel over this and then sheet flooring), but this does not materially affect the determination in any way.
  • It used aluminium window joinery and corrugated iron external wall cladding and roof. Cosy Homes typically uses uPVC window joinery and colorsteel roof – again higher quality, but functionally identical for this determination.
  • The unit was to be partitioned to provide separate sleeping, bathroom, and living areas. The latter to include kitchen facilities. Power was provided via a standard caravan lead, and water supplied from a hose to an external tap. LPG was used to heat water and for cooking. This is all functionally identical to Cosy Homes.
  • It used “levelling stays” to take the load off the tyres and provide more stability. Cosy Homes use “feet” that serve the same purpose.
  • The manufacturer refers to it as a caravan. And states their “caravans are designed to be towed with a tractor”. Cosy Homes are also designed to be towed with a tractor and we have pictures of us doing so if required.
  • As an aside, the manufacturer routinely constructs these units for holiday parks (section 4.3).

The Determination Regarding “Vehicle”

Section 5 has a detailed discussion on this, but it is well summarised in 5.1.8:

(italicised texts are direct quotes from the Determination)

5.1.8 To summarise the position as to when vehicles will be treated as buildings:
  – if something is a vehicle, and it is immovable and occupied by people on a permanent or long-term basis, it will be treated as a building
  – if something is not a vehicle, the question of whether it is to be treated as a building will fall to be considered under the main definition of building in section 8(I)(a) of the Act
  – if a person claims something is not subject to the Building Act because it is a vehicle, they must establish the thing is a vehicle or motor vehicle, and that it is movable or that it is not occupied by people on a permanent or long-‘term basis.

This is also summarised well in Appendix A, which contains a clearly defined decision tree.

The first check determines if it is a vehicle.

5.1.5: …”vehicle” is not defined in the Act, so the natural and ordinary meaning applies (Oxford Dictionary of Eng|jsh): “a thing used for transporting people or goods, especially on land, such as a car, lorry, or cart. …

5.1.6 The reference to vehicle in section 8(I)(b)(iii) also includes a “vehicle or motor vehicle” as defined in section 2(1) of the Land Transport Act 1998.  The relevant part of that definition provides:
    a) means a contrivance equipped with wheels, tracks, or revolving runners on which it moves or is moved;

5.2.2: The unit, although only partially constructed, has wheels and axles, and in my opinion is clearly designed to be capable of being towed.

5.2.3: I also accept the manufacturer’s submission about the circumstances in which the unit can be towed, and that the unit’s construction is sufficiently robust to enable this to happen.

5.2.4: As a result, I consider that the unit is a vehicle, both within the natural meaning of that term, and as defined by the Land Transport Act 1998.

5.1.7: If a particular structure is a vehicle, it will then only be treated as a building for the purposes of the Act if it also satisfies the two further requirements in section 8(1)(b)(iii) of the Act.  These are that the vehicle must be ‘immovable’ and ‘occupied by people on a permanent or long-term basis’

The Determination Regarding “Immovable”

Therefore, the next relevant test becomes is it “Immovable”.

5.3.3: Whether a vehicle is immovable is a question of degree that will turn on a range of factors such as:
  – Whether the vehicle is attached to the ground and how easily those attachments can be removed;
  – Whether the vehicle has been connected to services and how easily those can be removed;
  – Whether the vehicle has retained its wheels and the ability to be towed or to move itself;
  – Whether structures have been attached to the vehicle, such as decks, verandahs, or additional rooms, and how easily these can be detached.

This is why, at Cosy Homes, we have made the following careful design decisions:

  • We developed our patent pending feet (only about 40kg each), to ensure they cradle the home and do not attach it to the ground – the home can be lifted off the feet with no detaching required whatsoever, or the feet can also be removed while the home is still in place.
  • We ensure all services are easily detached, e.g. gas, power and water are easily unplugged, waste water is connected with a flexible, quick-release coupling (more details available on request).
  • Our wheels and towbar are retained by each customer. While the towbar can be telescoped into the sub-frame to keep it out of the way, it is very easy to extend again.
  • We ensure that any possible decks or verandahs are preferably completely free standing, but at the least, are very easy to detach.

Therefore, none of our Cosy Homes are immovable when delivered to the client. What happens after that is up to the client, but we ensure each client is aware of the regulations and implications.
In this determination, the home is not considered to be immovable:

5.3.4: As stated in paragraph 5.2.2, the unit is clearly designed to be capable of being towed…

The levelling stays used to keep it stable and take load off the wheels (in 2.6) are not considered to change this determination, as they are easy to remove (4.3).
In this case, sewage had not yet been connected, so we have to refer to other determinations for this guidance.

In a different Determination (2014/025), section 4.3.3 found the home to be immovable because:

…the unit also has permanent services connections that would require the services of a person authorised under Plumbers, Gasfitters, and Drainlayers Act 2006 to disconnect.

This makes it clear that the logical test used by the DBH is that it is immovable if the services can only be removed by a person authorised under Plumbers, Gasfitters, and Drainlayers Act. Therefore, more broadly, a home is considered movable as long as none of the connections need to be removed by a qualified tradesman.

This is why Cosy Homes only need one thread loosened in order to remove plumbing fittings and why Cosy Homes use a Caravan Style plug, which can be disconnected by any fit adult.

The Determination Regarding “Permanent Occupation”

If the home is considered to be a vehicle, then it can only be considered to be a building if it is both immovable, and “occupied by people on a permanent or long-term basis”.

In this determination (Determination 2015/044), permanent occupation is not discussed in detail, because it is irrelevant, as it was already determined to not be immovable, therefore not a building.

However, we can confirm this decision path in a different Determination (2014/025) where the vehicle was immovable, but used temporarily. Section 4.4.1:

The unit is designed and fitted out for habitation. The owner has stated his intention to construct a dwelling on the site at a later date and that the unit is meant to be temporary and would be occupied for ‘occasional/holiday/weekend use’. Given that it is not intended to be occupied by people on a permanent and long term basis I am of the view that it doesn’t met the test under section 8(1)(b)(iii) of the Act.

Which therefore reaches the conclusion that it is not a building in section 4.5.1:

In conclusion, although the unit can be moved it has permanent services connections that are not easily disconnected.  However the intended occupancy is not on a permanent or long term basis but for occasional use only.  Taking into account the features of this particular unit in these circumstances, I consider that the unit is not a building under section 8(1)(b)(iii) of the Act.

Related Issues

Does a Vehicle have to be Registered, Warranted, or Towable on the Road?

In a different Determination (2014/025), in section 3.1 the local council felt that the home had to be a registered and warranted vehicle that could be towed on the road:

In the application for determination the authority submitted that it had applied the test ‘is it permanently occupied’, and ‘is it a vehicle or can it be towed if it had a warrant [of fitness] and a [vehicle registration]’.  The authority accepted that it was not permanently occupied, but believed that as the unit was 3.1m wide it could not be towed but needed to be transported as a load.

The DBH overruled the local council’s interpretation in section 4.2.10:

In my view, whether the unit can be considered a vehicle, does not turn on whether it is registered and has a current warrant of fitness. I consider that the unit is a vehicle, both within the natural meaning of that term, and as defined by the Land Transport Act 1998.

And then clarifies in Section 4.3.1:

The fact that a vehicle cannot be legally towed on a public road is not the same as being ‘immovable’ for the purposes of the Act.

It is therefore very clear that a vehicle does not have to be registered, warranted, or towable on the road.

(It is worth noting in the same Determination (Section 2.7), a response from NZTA states that:

any over-dimensioned vehicle … could be registered as a trailer but should not be able to obtain a warrant of fitness.)

Specific Mention of Caravans

In a different Determination (2016/019), caravans are discussed:

4.3.5: Caravans or mobile homes are clearly vehicles; while they perform a similar function as a dwelling, in that they are used for sleeping accommodation and may contain sanitary facilities

…A vehicle such as a caravan or mobile home only falls within the Building Act if it meets the test under section 8(I)(b)(iii), being that it was both immovable and occupied on a permanent or long-term basis.

So the DBH is very firm in their view “Caravans or mobile homes are clearly vehicles”. Cosy Homes are designed to be caravans or mobile homes, and are indisputably regarded as vehicles when delivered to a client. What happens after that (regarding “immovable” or “permanently occupied”) is up to the client, but we ensure each client is aware of the regulations and implications.

Is Moving a Home onto Site Considered Building?

In a different Determination (2017/065), this is discussed in detail:

4.5: In previous determinations I have considered the relocation of buildings and whether this constitutes “building work” under section 7 of the Act (see for example 2011/104 and 2014/0304).  I maintain the view set out in those determinations, that the act of moving or relocating a building and placing it on site is not “building work”.

4.7: “Building work” is defined in section 7 of the Act as:
  (a) means work—
  (i) for, or in connection with, the construction, alteration, demolition, or removal of a building; and
  (ii) on an allotment that is likely to affect the extent to which an existing building on that allotment complies with the building code; and
  (b) includes sitework; …

So while “Building work” includes “removal of a building”, it does not include moving a home onto a site.

It is therefore very clear that moving a home onto a site does not require a Building Consent. The DBH has consistently made this determination at least 3 times (2011/104, 2014/0304, 2017/065).

Are two Vehicles Locked Together a Building?

The matter of connected prefabricated units was considered in High Court in Te Puru Holiday Park Ltd v Thames Coromandel District Council (HC Hamilton CRI-2008-419-25, 11 May 2009, Duffy J):

[21]The unit on this site is described as a duplex; it comprises two [proprietary] units locked together to form a single dwelling.

And the result is (paraphrased):

when locked together, creates a new structure, which has no evidence to suggest that it could move or be moved on the road.

This view as upheld by the Court of Appeal in Thames-Coromandel District Council v Te Puru Holiday Park Ltd ([2010] NZCA 663).

So the connected structure was evaluated as a single whole structure, which was considered to be a building. As it is unlikely that two vehicles could ever be joined to create a single structure that is still a vehicle or movable, Cosy Homes would suggest that this should only be attempted if a Building Consent is obtained, which is a viable option as Cosy Homes are built to Building Code by licenced builders.

You can still enjoy the benefits of two or more vehicles without a Building Consent – just be careful no to physically connect them. We have seen fantastic examples of homes on wheels (aka vehicles), on either side of, or surrounding a shared deck and veranda (which should not require a Building Consent). This can create a beautiful, sheltered, outdoor living space. Just be sure to not fix your vehicles to the veranda or deck, and it is highly recommended that the vehicles are situated so that they are able to be towed away from the shared space if required.

Does building a Deck Require Building Consent?

In a different Determination (2017/065), it states:

4.8: The construction of the deck would not require building consent because it is exempt as provided for in Schedule 1 of the Act.

It is therefore very clear that building a deck does not require a Building Consent by itself.
However, care still needs to be taken:

  • Not to attach a fixed deck to a movable vehicle. At least, not to attach it in a way that requires a qualified professional to detach it.
  • Not to design the deck in such a way that it makes the vehicle unable to be moved.


Numerous determinations, including Determination 2015/044 include a flowchart to clearly describe the decision tree that can be used. This is included below:

What are Mega Tiny Homes?

At Cosy Homes, We have been working on a bit of a different take on Tiny Homes we like to call Mega Tiny Homes 😏. The basic premise is to make a single-level unit with floor area as large as possible while still being reasonably easy to transport. While it does need a truck and pilot vehicle to transport (costs a few hundred dollars per move), it has numerous benefits over traditional Tiny Homes:

  • Roughly 2x to 3x the floor area (typically 12.1m x 4.2m = 50.8 square meters).
  • 2 large (3m x 4m) bedrooms
  • Single-level, so more accessible for older people who cannot climb
  • A full-sized kitchen (9 doors, 7 drawers, 3.6m of bench!)
  • Huge 3m wide x 2.2m high wardrobe and 2 other large cupboards

So our vision is that it might suit people who do not need to move as often, and would prefer to have more space, more storage and more accessibility, e.g. for middle aged or elderly. In essence, we believe the extra cost of moving once and a while is more than made up for by the benefits experienced living in it every day.

Our Mega Tiny Homes can have wheels and a towbar like a traditional Tiny Home. The main difference is that in New Zealand, anything over 2.55m wide cannot be legally towed or driven on the road, so it has to be transported on the back of a truck. Therefore, our wheels and towbar are only for moving the home off-road (e.g. some movement around the site), and they also make the home qualify as a vehicle, so it does not need Building Consent (more information about that in What Council Consents or Permits Might I Need?).

At Cosy Homes, we have worked in homes that are only 2.5 or 3 meters wide, and it is hard to describe in words how much more restricting that can feel. Even going from 2.5m to 3m makes a huge difference, and going up to 3.5 or 4m wide makes an incredible difference – the space feels a lot more relaxed, a lot more like a home. With multiple people in the home, it also allows for a lot more individual space, and room to move around eachother – we have had 20 people in one of our homes for an open home and did not feel cramped! It also allows for much more design freedom, for example, placing the bathroom and kitchen side-by-side in the same width, freeing up a lot more length for other full-width purposes, which we use to full advantage in our standard floorplan.

Price wise, you will often find that our Cosy Homes are a comparable price to traditional Tiny Homes, but with 2x to 3x more space!

I hope we do not offend some of the traditional Tiny Home community. We believe Tiny Homes are about having the freedom to live how you want to. So hopefully they understand that we are just offering some different options to people that can’t climb stairs, or struggling to downsize, etc. We would welcome any feedback and comments below.

We have more pictures in our gallery and more details around the rest of the Cosy Homes website about our unique benefits. We also welcome you to contact us to take a look at one for yourself – many visitors have commented that you need to experience it in person to fully appreciate the difference.

What Council Consents or Permits Might I Need?

Fundamentally, consents are introduced when regulatory organisations think certain levels of quality are required, to keep occupants healthy and safe.
There are various regulations to be aware of, but what can make it complex is that many people, including council staff want to form their own opinions, sometimes ignoring the regulations, which are often outside of their control (e.g. are NZ-wide). But if you know the regulations, you can remind them 😉
Broadly speaking, there are two possible consents: 1) Building Consent and 2) Resource Consent.

1) Building Consent:

This is determined by the Department of Building and Housing (a NZ-wide government department) and Councils need to follow/enforce these rules. In summary (contact us for more details), a Building Consent is not required if:

a) the home has wheels and a towbar (does not need to be road worthy) and
b) the home is not permanently anchored to the ground, directly, or via a structure like a verandha.

We have solutions for both of these requirements so that a Building Consent is not needed. We have had councils challenge this, and take it to the Department of Building and Housing) and have their challenge rejected. 

As an aside, at Cosy Homes, we build to well exceed the Building Consent regulations, but we also design our homes so that customers do not need to get a Building Consent if they do not want to, saving them considerable time and expenses. In fact, we believe the Building Consent regulations are often too low, e.g. for insulation requirements, and as a result, most homes are built to “Code Minimum”, instead of to what benefit’s the owners and occupants long-term.

Also note, if you cannot fulfil b), you can still avoid a Building Consent if you don’t live in it full time.

2) Resource Consent (RC):

This relates to supplying you house with services. This is not as easy to summarise as there are more variables.
Connecting your home to existing power and water can simply be a caravan power plug and a potable water garden hose (should be protected from frost) – so they don’t need Resource Consent. Creating a new supply of power (e.g. solar) and water (e.g. a well), is more difficult, and will be covered in a different blog post.
For greywater and sewer, the first question is are you using council services or supplying your own? If using council services, you are generally expected to ask for permission. Often, councils will want you to pay to use their services, which is called a Development Contribution (DC) and they will not try very hard to check if you don’t need to pay this, so it would pay for you to consider the following:
  • If the property has already paid a DC in the past (e.g. the old house was then torn down), then you should not need to pay it again.
  • Most councils have some exemptions for resource consents for minor dwellings. E.g. for the Christchurch City Council (CCC) here and  here.
  • And most councils have a discounted DC for small homes as they will not put such a large load on the council services. 
You are allowed to deal with Greywater yourself, if you follow certain regulations for health – there is a great introduction here – as far as I can tell, greywater is not mentioned in the NZ-Wide Resource Management Act (RMA), but is typically addressed in Regional Council Plans (not your Local Council) – this is a good example – in the Wellington Region, you don’t need a consent if you meet 3 criteria (e.g. less than 2000L per day).
You can make your own system (e.g. a holding tank with a submersible pump going out to a buried drip line), or buy greywater treatment systems, e.g. from EcoToilets for $3000+GST, which follow the regulations.
And advantage to dealing with Greywater yourself is that you can make a good use of that excess water, e.g. water gardens, rather than just flush it down the council sewer system. One quick tip: use liquid soaps (including for clothes washing), as solid soaps and powders produce a solid residue that can block pipes and are not good for the soil ph. 
Sewer is another quite complex topic, with many variables, which will be covered in more detail in another blog post, but I will try to summarise here.
If you are close to a council sewer system, they will often require that you use their system. For movable homes (e.g. Tiny Homes) and homes not anchored to the ground, council will often want the connection to be easily detached (e.g. a quick release system) and will want a flexible hose or connection between the Home and the sewer pipe so that any possible movement (e.g. from an earthquake) does not crack the pipe and cause a leak/health hazard. At Cosy Homes, we have solutions for these requirements.
If you are further away from a council sewer system, you can create your own system, that does need to meed certain health and safety standards. As with greywater, sewer regulations are addressed in Regional Council Plans (not your Local Council), so these vary per region. However, various septic tank and composting toilet companies produce systems designed to comply across all of New Zealand. So check with you Regional Council – you may not need a Resource Consent if you use a well recognised system that fits the criteria of a permitted activity.

How this Relates to Mortgages and Insurance

It is worth bearing in mind that Mortgage and Insurance companies can often be quite conservative, and want to know that your Home has the appropriate consents before they will provide you with a Mortgage or Insurance. If you plan to sell you home in the future, potential buyers will also want to know they are buying something safe and healthy.
Therefore, we would suggest that if you do not want to get a consent, that you still contact the Council and get a letter from them to acknowledge that what you are doing is a permitted activity and does not need consent. This “Permit” is the evidence you can supply to Mortgage and Insurance companies, and future potential buyers. It is also very useful to have this proof if a different Council staff member has a different interpretation in the future and wants you to have a consent – you can show evidence that the Council has already approved this as a permitted activity.

Communicating with Council

One last tip – often, different council staff can have very different interpretations of the same regulations, or even want to ignore the regulations in favour of their own opinion. Therefore, if one council staff member is giving you more resistance than you care to work through, you might want to consider talking to a different staff member if possible, e.g. calling reception, asking which Building Consent staff are available, and asking to talk to a different one.