The 1970s saw 279,000 houses built in New Zealand. Architectural styles that had developed during the late 1950s and 1960s influenced the design and appearance of mass housing.

1970s houses were built during a period of expanding suburban development. Many were built by developers as speculative ('spec') houses, and many others were built from plan books offering styles such as 'colonial', 'ranch', 'Mediterranean' and 'contemporary'.

The spec houses were typically small and plain, rectangular or L-shaped in plan, and built from lower-cost materials. Typically they were built from standard plans and many were not particularly suitable for the site, or were poorly oriented for sun, views, privacy or wind shelter. At the same time, houses in the more affluent areas were increasing in size.

Although the period was characterised by the introduction of new materials and methods, some features were typical of the era, including:

• Open plan living
• Increased prevalence of two-car garages and internal access
• Lower roof pitches typically (12-15°)
• Metal roofs
• Aluminium joinery
• Timber cladding - in particular, rusticated weatherboards
• Concrete floor slabs.

Increasingly, houses were drawn and built to metric dimensions, although some materials were still only available in imperial sizes.

Though most houses were built on-site, prefabricated framing became more common - initially for roof trusses and, later in the decade, for wall framing. Modular construction also became more common, as did factory-built housing. Factory-built houses were typically fairly small, and were used to develop new towns such as Twizel, Turangi and Cromwell, as well as parts of cities such as Auckland.

Other developments and influences included:

• Regulatory changes - In 1978, NZS 3604 Timber Framed Buildings was introduced, and this gave the design requirements for timber framing. Also at the end of the 1970s, NZS 4218 Minimal thermal insulation requirements for residential buildings, introduced mandatory levels of insulation in new homes.
• A reduction in the availability of flat sites - this contributed to the development of split-level designs and, in places such as Wellington, to 'vertical' building styles often using timber post-and-beam construction, external bracing and steeply pitched roofs.
• Alternative construction methods such as the Lockwood™ construction system and the use of concrete block construction for housing (Figure 1), pioneered by architects such as Warren and Mahoney, Peter Beaven, and James Beard.

Figure 1: Concrete construction

The 1970s generic style of housing continued into the mid to late1980s, when there was a distinct change with the adoption of monolithic claddings, style changes such as parapets and membrane roof decks, and the use of sealants.

1970s houses today

Many 1970s houses built for lower income homeowners may have had little alteration carried out since their construction. Where the increasing capital value of properties has justified it, houses may have been substantially altered and renovated, in particular to increase living space, improve orientation of living spaces to the sun, upgrade bathrooms and kitchens, add an ensuite bathroom, extend living spaces, or to add one or more bedrooms.

In general, the houses built during the early to mid 1970s had little or no insulation, although a range of insulation materials was available. Those built after 1978 will have some insulation as it became compulsory, but they are unlikely to meet current standards for energy efficiency.

Therefore, many of the houses built during the 1970s will require significant upgrading to improve their energy efficiency.