Why Medium Density Housing?


Aotearoa New Zealand is a fresh field for medium density housing (MDH). Common in many countries around the world – Europe, Asia, America, and even Australia – in our country we have cherished separateness, proudly living in individual houses until recent times. Our country is not used to MDH and many of our people have little experience of MDH, so it is unsurprising that we are not yet skilled at designing and building MDH. Most of you reading this will not be living in MDH yourself, yet you are interested to know more.

Over the last 30 years Aotearoa has attracted nearly two million more immigrants, who have brought with them different attitudes to living. We have been one of the more sparsely-populated countries in the world, but that is swiftly changing in the big cities. In the last couple of years, MDH in parts of NZ has sky- rocketed: figures from Auckland Council show that since the creation of density-focused housing zones, building consent applications in 2021 were far greater for townhouses and apartments than for individual houses. Also in 2021, the Government changed the rules considerably to allow – or even to force – density upon our biggest cities. Density is here to stay and this book will help you design it better.


Definitions for MDH differ greatly from country to country. What we discuss as medium density here in NZ would be called low density in many other countries, but we need to find a level that works well for us. We need to make sure that what we do, we do well.

BRANZ have undertaken considerable research into MDH during this century and have a website dedicated to this research area. In Defining medium-density housing, an early research paper from BRANZ Study Report SR376 (Bryson and Allen, 2017), the authors examined how NZ defined MDH and what we understood about the subject. What they found was a little disturbing – there was no common viewpoint. BRANZ noted that amongst NZ government departments there were no fewer than 13 different definitions of MDH, with varying versions involving height of building, number of people, number of units, density and overall size. None of the definitions completely agreed with the others. Some aimed at a figure of 30-60 du/ha, others settled on a maximum house size of 350m². In the end, BRANZ settled on a simple all-encompassing definition of MDH: “multi-unit housing up to six storeys high.” BRANZ then divided this into three key categories:

Category One:

1-2 storey attached houses, such as duplexes or semi-attached townhouses

Category Two:

2-4 storey terraced houses, such as attached terrace housing

Category Three:

3-6 storey apartments. Although not stated as such, this implies that high density housing is confined to apartment buildings that are over six storeys tall and also that low density housing is restricted to single detached houses.

Quarter-Acre Dreams

Figure 1.1

Figure 1.1 Quarter Acre Dreams

Measuring density

What then is density? In many countries, density is used as the measure of MDH, but awkwardly, there are different methods to measure density. Figures for urban density are generally calculated by dwellings per area, rooms per area, or the number of people per area. The first question is, what size area to use? American and some older British calculations are measured using the acre as a unit of area, while some other worldwide figures use square kilometres. The most useful, relatable unit at this smaller scale (and used by most of the world) is the hectare. There are 2.47 acres to a hectare, and 100 hectares in a square kilometre. Let’s stick with metric, and stick with hectares.

Area size comparison between metre², hectare, kilometre², acre, square mile

Table 1.1

AREA hectare km² acre square mile
1 0.0001 0.000001 0.000247 0.000000386
hectare 10,000 1 0.01 2.471 0.003861
km² 1,000,000 100 1 247.105 0.3861
acre 4,046 0.404685 0.00404685 1 0.00156
sq mile 2,589,988 259 2.59 640 1

The other more variable measurement used in density calculations involves calculating the number of people within an area. There is no agreed formula for people per house, instead there is a range: assuming a minimum of one person per house, the maximum number can vary hugely. These days two to four people per house assumes just one or two children per nuclear family unit.

At the other end of the scale, there are now many more single people wanting their own home. While some of these may be older people living in retirement villages, there is also a significant rise in the population of people (of all ages) living alone. The growth of single-person housing in Aotearoa is a significant factor in our need for more housing, especially more smaller housing. This is a need that is not being met at present.

Counting population is always going to involve guesswork, while counting actual houses is far simpler and more factual. As the number of people per dwelling can vary hugely, in this book, all figures will be quoted in dwelling units per hectare (du/ha).

Note: gross density includes all the roads and open spaces in an area, while net density includes just the building area on the site itself. It is useful to be clear about whether you are quoting a net density or gross density figure.

Applying standard methods of measurement, Auckland’s ‘low’ density, is classified as ‘very low’, or even ‘super-low’ in international comparisons, and incapable of generating an urban environment (Jacobs, 1961; Turner, 2010).

Density comparison between du/ha, du/kilometre², du/acre, du/square mile

Table 1.2

DENSITY (dwelling units per area) du/ha du/km² du/acre du/sq mile
  1 100 0.40 259
  2 200 0.81 518
NZ: One house per acre (4,048m²) 3 300 1.21 777
  4 400 1.62 1,036
  5 500 2.02 1,295
  6 600 2.43 1,554
NZ: Tauranga large lots aims for 7.5 du/ha 7 700 2.83 1,813
  8 800 3.24 2,072
  9 900 3.64 2,331
One house/quarter-acre (1,012m²) 10 1,000 4.05 2,590
Start of ‘community’ threshold (25-30 du/ha)
(Christchurch aims for 15 du/ha)
20 2,000 8.09 5,180
UK: Typical detached suburb (30-100 du/ha) 30 3,000 12.14 7,770
UK: Typical duplex houses 40 4,000 16.19 10,360
UK: Typical double-stacked / maisonettes 50 5,000 20.23 12,950
UK: Typical triplex 60 6,000 24.28 15,540
  70 7,000 28.33 18,130
  80 8,000 32.38 20,720
UK: Below 90 is considered low density 90 9,000 36.42 23,310
UK: Typical pre-WWII London flats four storeys 100 10,000 40.47 25,900
  110 11,000 44.52 28,490
  120 12,000 48.56 31,080
  130 13,000 52.61 33,670
  140 14,000 56.66 36,260
UK: London flats now 150 15,000 60.70 38,850
  160 16,000 64.75 41,440
  170 17,000 68.80 44,030
  180 18,000 72.85 46,620
  190 19,000 76.89 49,210
UK: Typical flats eight storeys 200 20,000 80.94 51,800
  210 21,000 84.99 54,390
  220 22,000 89.03 56,980
  230 23,000 93.08 59,570
UK: Below 250 is considered medium density 240 24,000 97.13 62,160
UK: London high density from here up 250 25,000 101.17 64,750
  260 26,000 105.22 67,340
  270 27,000 109.27 69,930
  280 28,000 113.31 72,520
  290 29,000 117.36 75,110
Hong Kong: Still way higher than this 300 30,000 121.41 77,700

(Levitt and McCafferty, Housing Design Handbook, 2019)

Why do we need MDH?

MDH is needed in our cities because with low density housing, we suffer from sprawl. It’s hard not to have sprawl in a city where the main mode of transport is the car, and when the city has grown up around the car. There was a long-held tradition in NZ that each house should be built on a quarter-acre section (1012m², or just over a tenth of a hectare). There was even a book – The Half-Gallon Quarter-Acre Pavlova Paradise (Mitchell, 1972). Those days are long gone.

“External space on all sides of the house became the preferred form of site layout, effectively separating the house from the public space of the street for privacy, and, behind the house, retaining garden space of sufficient size to grow vegetables and fruit, as well as, in many cases, to accommodate livestock.” (Turner, 2010, p112).

Single houses on a quarter-acre section equate to a density of only about 10 du/ha and it is now untenable to imagine good urban sites being ‘wasted' in this manner. Indeed, having buildings only one storey in height anywhere except in the countryside makes little economic sense today. We must go upwards – but not in a panicked way. We must build carefully and build well, for these houses will last us at least the next 50 years and quite possibly double that. Whether you call it a ‘housing crisis’, or the more politically acceptable ‘housing challenge’, one thing is clear: we urgently need more housing. What we build now will be Aotearoa for the future, so we have got to get it right. The recent rule change to allow three houses per section, up to three storeys high, makes that even more important.


Don't look back in anger

The wave of middle-class British settlers to Aotearoa after 1840 were looking for a rural land that was uncluttered and would have no need for dense urban housing. Coming fresh from the densely packed metropolises of London, Liverpool, Newcastle, Manchester, and Glasgow, where filth and pestilence crowded the streets and packed out the buildings, or from overcrowded small-holdings scratching a living at the edge of grand estates, New Zealand was seen as a green idyll away from all the old ways. Quarter- acre housing here was commonplace and houses were not joined by a common wall. Apartment flats were seen as abhorrent and abnormal. For decades in Auckland there were only a handful of apartment buildings – the Mayfair in Parnell, Courtville and Old Courtville in Anzac Crescent, and a handful of others elsewhere. A similar story played out in Wellington and Christchurch, where suburban settlement meant individual houses only.

“By 1900 the villa with as many decorative features as the buyer could afford had become the standard suburban house. Site design was regularised to a frontage of 15m – 18m and a depth of 40m – 60m... In most instances, the standard 18 metre section frontage has made vehicular access to rear gardens possible... The 1000m² site area provides space for workshops and sheds for garden equipment, and serves as a base from which maintenance and alteration work can be carried out.” (Turner, 2010, p180).

New Zealand cities, especially Auckland, have traditionally been very low density and for many years Auckland was argued to be the least densely populated city on planet Earth. While probably a little stretching of the truth, Auckland’s sprawl meant that roads became crowded and blocked as people tried to get from one place to another. The implementation of motorway systems in Auckland and Wellington without the concurrent construction of high-speed public transit train systems has made the congestion even worse. The answer cannot always be to build more roads. Wellington was always constrained by topography, hemmed in between harbour and hillsides, with a resulting small size of many houses that persists to this day. Auckland’s outlying suburbs are full of state housing with (in many cases) a single house sitting on a quarter-acre section. Building more houses over our most productive land for food, as is already happening in the green fields of Pukekohe, is unwise. It is within New Zealand’s best interests for Auckland to stay within its city boundaries and densify. Sprawl must stop.

But despite making it seem as though housing is a problem unique to New Zealand, it is actually a world- wide phenomenon. Housing crises exist all over the world, on every continent, tied up together with global warming, climate change, excess liquidity and rapidly growing inequality. And the answers everywhere are the same. Consume less. Travel less. Live in smaller dwellings. Recycle. Densify.

In Toronto, they note:

“If we wish to reduce our carbon footprint, then the single most powerful tool at our disposal is middle-density intensification in established, walkable neighbourhoods.” (Bozikovic et al, 2019. House Divided. p229)

Why this book/resource?

Despite the recent boom in MDH in Auckland and (to a lesser extent) around Aotearoa, the building consenting system is not yet set up for good MDH outcomes in NZ. The New Zealand Building Code (NZBC) is currently ill-equipped to cope with buildings other than single family homes made from light timber framing, built to a maximum of three storeys high. It needs a huge amount of revision to be relevant to the modern world, instead of dismissing nearly everything MDH as ‘Alternative Solutions’. Our local authorities and Building Consent Authorities (BCAs) struggle with consenting for MDH, making life more difficult for all involved. But it is not just their fault.

The architects and designers involved are often not highly skilled or experienced in designing MDH,
as it is still a new phenomenon here – a recent survey has determined that there is a large number of less experienced designers working in the system, still feeling their way (Belu, 2021). The builders and labourers undertaking the work are also unfamiliar with good building practices around MDH. The new buildings often include new materials, new construction systems and new building processes. Nearly everyone working in this area in New Zealand needs to rapidly up-skill in the subject. The body of knowledge is still incomplete, or as Turner notes:

“Mature local knowledge based on experience in practice and application is sparse, leaving a void in which agreement about quality is elusive. Thus, the opportunity to prove theoretical propositions or to lay foundations for socially sustainable higher density housing is defeated by the mass of socially dislocated, un-imaginative, and technically sub-standard development.” (Turner, 2010, p285).

Harsh words perhaps, but I think, rather true in many cases.

Existing MDH design guides

There are a number of other design guides for medium density that should also be consulted – this Medium guide does not attempt to replicate them, but aims to work side-by-side to provide more detailed, technical information about certain aspects of the design and construction of MDH.

Crisis? What crisis?

We are not the only country suffering from a housing crisis. In House Divided (Bozikovic et al, 2019), Bozikovic details a three-goal solution to housing affordability proposed by the Ontario Association of Architects:

Goal A: Increase supply

Action: Increase density and free up land through:

  • Promote low-rise infill and intensification within neighbourhoods.
  • Expanding permission for semis, duplex, triplex, etc. i.e. basement suites, garden suites and laneway suites.
  • Promoting low to mid-rise intensification along corridors, particularly those with frequent public transport.
  • Promoting mid to high-rise intensification within centres.

Goal B: Make housing financially attainable

Action: Reduce construction costs through

  • Changes to Building Code (and remove regulatory hurdles)
  • Financial Model Opportunities

Goal C: Address the urgency

Action: Speed up delivery, expedite approvals, incentivise construction methods.

It seems that the NZ Government has been acting on all these fronts during 2021 – taking a leaf out of Toronto’s book. By avoiding our housing crisis for so long though, we’ve got a backlog of housing to build, so the problem won’t be going away any time soon. In the meantime, it is up to us, the design community, to help resolve this issue.


The crunch point of any housing scheme is the same the world over, ‘how much will it cost?’ Despite everyone's best efforts to bring house prices down, in New Zealand housing is now the most unaffordable it has ever been, propelled by sky-rocketing prices for land that has moved from a ratio of 1:5 (land to house) to more like 1:1 today. It is simply not affordable to build low cost housing on land that expensive, driving us to build higher and denser. The New Zealand housing market is also the most over-fuelled it has ever been, coinciding with worldwide product supply restrictions and Covid-driven difficulties in obtaining enough skilled construction labour. Prices will have to reverse a lot more before they become 'affordable'.

We all know that the answer lies somewhere in the golden triangle of cost, quality and speed. One of these must give way for a substantial change to occur. All too often the answer to lessen cost has been to either build to a lower quality standard, or to build a smaller house – or both at once. Small, badly built housing is not the right recipe for the future, it is a recipe for slums to occur later.

My response is different. We need to build better homes, to higher standards, that will last longer. We need to not only build smaller homes to save on square metre cost rates, but also to design those homes well so that space is not wasted. We need to build smarter, using prefabrication of standard components on a large scale – not just prefab wall frames, but complete prefab wall panels complete with windows, flashings, insulation, etc. And not just prefab basic vanities in the bathroom, but entire prefabricated bathrooms such as those advocated by First Light Studio with the Unipod (First Light Studio, 2014).

There are some alternative strategies for creating housing that is more affordable. One is to build smaller units, in terms of square metre floor area, but taller so that the tenant has the choice to inhabit vertically as well as horizontally. Gary Chang is the leader in this field in Hong Kong, where building small has always had to go hand in hand with building clever (Chang, 2008). Designing loft beds over storage areas, and mezzanine studies above wardrobes, etc. can make the most of vertical space. Design smarter. Build better.

Another option is to change our land ownership model, by bringing back leasehold use, so that the exorbitant price of land is reduced. This would need to be strictly controlled to avoid abuse as has happened in some areas of Auckland where this was trialled in the early 2000s. Potential saviours on the horizon include councils, Government, and local iwi, who may all have larger bank balances and longer views on the future than the more time-driven focus of many private developers. Build-to-rent projects are starting to be seen, like the 26 Aroha project in Auckland, where great housing is backed up by long-term owners. Community-led housing projects like the Nightingale apartments in Melbourne are also starting to be seen here. Southcombe thoroughly explores co-operative housing in Counterfutures 9 (2020).

The boom in creating unit title housing via a body corporate has been sullied in Wellington and other earthquake-prone cities by the eye-watering prices being charged by the few remaining insurers, leading to a movement back to fee simple title ownership. Apartment housing is unaffordable long-term if the insurers cannot be controlled in their greed. Nonsensical developments are likewise hindering progress, such as the infamous Paddington scheme, where in the very heart of the urban growth area for Wellington city, a meek two-storey development has been allowed to grow – wasting land and tempers alike.

Another tactic is to just supply the absolute basics. Create shell apartments – just four walls and a fixed services riser, leaving the purchaser the chance to install items such as internal walls, bathrooms, kitchen, wardrobes etc. I was lucky enough to purchase my apartment in central Wellington this way affordably (Croxley Mills, Custance, 2001). Alejandro Aravena uses this method in Chile with the Elemental housing project, where the developer builds a shell and fits out only half the house, while the tenant can complete the house if they want, later. Jean Nouvel also used this method as seen in the Nemausus building in Nimes, where basic multi-storey concrete floor slabs, façade and bathrooms were provided by the housing provider and the immigrant settlers infilled the rest. This does not mean it has to be ugly, all three projects listed above have won architectural awards. Clever can be both beautiful and affordable. 

Recent (July 2021) Government actions

Recent proclamations from the Minister of Housing and from the Government have reinforced this attitude. The National Policy Statement on Urban Development (NPS-UD), the Government Policy Statement on Housing and Urban Design (GPS-HUD), and the surprise October 2021 Resource Management (Enabling Housing Supply and Other Matters) Amendment Bill (RM-EHS) freeing up the rules around urban density, have all combined to give effect to a potential massive change in NZ society. The NPS-UD removed the requirement for minimum parking requirements on sites all over NZ and raised the cap on minimum building heights, while the GPS-HUD advocated for better quality dense residential development.

The government bill RM-EHS was passed through parliament at great haste, permitting 'Tier 1' cities (Auckland, Wellington, Christchurch, Hamilton and Tauranga) to have three dwellings per site, up to 11m tall, with only 1m side yards, to a maximum of 50% site coverage without having to gain a Resource Consent. While this involves only small changes to Auckland’s Unitary Plan guidelines, it will have bigger effects elsewhere in cities that have been, up to now, largely suburban. No one is yet sure what lasting effect it will have, but it will likely grow in importance over the coming years. Densification this way will take careful, cautious design to get the best results for everyone, but sadly there is no guarantee of any of this extra housing being ‘affordable’. Still, it may increase housing supply somewhat, especially in outer areas like Upper Hutt where site coverage is currently at a maximum of only 30%.

Medium Density Residential Standards (MDRS) will affect everything. The years of kicking and screaming about density are over, the lightning bolt has been cast: we will densify. The only real question is: can the design community make it perform better and look better?

We need to have confidence that architects and architectural designers can make a significantly better effort than they have to date, for all MDH dwellers. Some current MDH schemes in some parts of Auckland are real shockers, with some really badly planned, exceptionally ugly and functionally inefficient rows of two-storey townhouses being produced. However, there have also been some truly wonderful examples of MDH recently and we feature some of these game-changers in the final chapters of this book.

We also need to move on from just two-storey townhouses. To inhabit a truly MDH world, we need to look to the next phase of MDH – housing of three to six storeys. And that is the key focus of this book.