MID-CENTURY SUBURBAN
From the 1960s onwards New Zealand built hundreds of thousands of homes in new suburban developments across all the main centres and towns. Most of these houses were built as “spec” houses by group developers, designed to standardised models and plans, with many using prefabricated roof trusses and wall framing – although there was increasing variation in external claddings and layouts.
The typical mid-century home is rectangular or L-shaped, with lower-pitched metal roofs, wide eaves, and larger windows than 1940s / 50s houses. They usually had three bedrooms with an open plan or interconnected living / dining / kitchen area. Many were split level, especially on sloping sites, with garage and service areas under the bedrooms. An innovation of this era was the ranch slider, leading out to a concrete patio or terrace or a timber deck for outdoor living space. Another feature of the 60s and 70s was a full height ceiling in living rooms or entries / stairwells following the line of the roof, often with exposed timber rafters.
Materials included weatherboards, brick veneer, concrete blocks, wood-grained asbestos-cement boards, asbestos-cement sheets, stucco, or the popular Hinuera stone. Floors were often particleboard, covered by wall-to-wall carpeting and linoleum, vinyl and tiles in kitchens and bathrooms – although some floors were timber or concrete slabs. Heating options included open fires, wood burners, electric storage heaters, or gas heaters. Insulation was not common until 1978 when regulations introduced minimum requirements for ceiling insulation – however in Christchurch a council bylaw established insulation requirements in 1973.
DEALING WITH PREVIOUS RENOVATIONS AND CHANGES
Some homes from the 1960s, 70s and 80s still remain today in their original state, but many renovation projects will have to deal with modifications that have already been made over the years. In many cases these changes – reflecting the techniques, materials and fashions of previous eras – will not be adding value to the performance, the charm or the liveability of the home. Some may be the result of dodgy if well-intentioned DIY projects and not up to basic standards.
Today’s methods and technologies can solve such messy problems – but the renovation process will need a careful review of any earlier changes and conversion work:
Extensions to add more bedrooms or living spaces
Remodelling of kitchen / dining / living areas
Converting a garage to an additional bedroom or living space
Replacing windows with double glazing
Retrofitting insulation in the roof space and underfloor
Reroofing and replacing external claddings
WHAT YOU MIGHT FIND IN YOUR MID-CENTURY SUBURBAN HOME – & RECOMMENDATIONS...
FOUNDATIONS & FLOORS
Timber piles (1970s) of treated radiata pine – likely deterioration
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Continuous foundation wall of concrete or concrete blocks – may have cracking or deterioration
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Deterioration of original damp proof course protecting the subfloor framing from concrete piles and foundation walls
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Original floor framing using green timber – shrinking as the timber dried over time
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Missing or inadequate piles and joists
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Sagging joists, squeaking or bouncy floors
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Uneven floors
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Cracked masonry
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Lack of ground clearance, poor access and poor subfloor ventilation
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Blocked or deteriorated ventilation grilles
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Underfloor insulation:
● None
● Compromised original foil underfloor insulation (now banned)
● Polystyrene blocks between floor joists – may be inadequate for today’s standards
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Sagging or unstable decks and porches
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Some concrete slab floors:
● Damp proof membrane – polythene sheet to protect concrete from ground moisture
● Reinforcing steel mesh
● No under-slab insulation
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FRAMING, INTERNAL WALLS & CEILINGS
Radiata pine treated with boron salts or insecticide
FIX – Retain if sound; treat for borer if needed
Exotic timbers – Douglas fir, redwood
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Particleboard flooring damage from underfloor moisture or leaking pipes
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Some timber floors – may be untreated native timber
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Plasterboard or hardboard wall and ceiling linings – may have deteriorated due to internal moisture, leaks or moisture in the roof space
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Textured ceiling finishes containing asbestos
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Exposed rafters in open high ceilings – may be treated timber – ceiling panels may have moisture damage around joints
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Insulation in roof space – not adequate for today’s standards – likely to have slumped or drifted over the years
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No insulation in walls
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Insulation may include urea-formaldehyde foam or glass wool
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Walls no longer square or out of plumb
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Draughts and gaps – no airtightness
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Dampness – mould and rot, mustiness and smells
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Borer
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Rodent nests
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CLADDING
Original waterproofing layers or building membrane may be compromised
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Timber weatherboards – may be cedar or redwood – possible moisture damage or rot
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Brick veneer – likely to have cracking
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Stucco – likely to have cracking
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Concrete blocks – likely to have cracking or mortar deterioration
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Concrete brick veneer – “Summerhill stone” – likely to have cracking
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Asbestos cement sheeting or boards with wood-grain look – likely to have cracking and moisture damage
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Corrosion / rust of metal flashings
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No insulation in walls
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Retrofitted insulation may include urea-formaldehyde foam
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Lead paint – banned in 1979
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Some exterior timber, fences, decks and piles may have been treated with CCA – Copper, Chromium, Arsenic – highly toxic
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Borer
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WINDOWS
Single glazing – condensation and heat loss
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Timber framing – likely to have rot or other deterioration
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Aluminium framing – ranch sliders – not thermally broken
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Louvre windows in bathrooms and laundries – flimsy adjustable aluminium frames – sticking or looseness
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Deterioration of rubber or plastic sealing structures and flashings – rubber may degrade releasing harmful VOCs (Volatile Organic Compounds)
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Jamming or sticking windows
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ROOFS
Corrugated iron
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Tiles:
● Decramastic tiles, galvanised steel base with a top layer of stone chips embedded in a bitumen coating – may contain asbestos (pre 1980 – likely to have dents and moss, mildew and mould growth
● Clay – likely to have cracking
● Slate – likely to have cracking
● Concrete – likely to have cracking
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Asbestos-cement panels or shingles – likely to have cracking or moss growth
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Translucent fibreglass or polystyrene roofing over verandahs and patios – likely to have cracked, clouded and deteriorated over time
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Inadequate or compromised original insulation
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Roofing underlay laid over wire netting over roof purlins – may have deteriorated
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Inadequate moisture control in ceiling space
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Leaks and historical roofing repairs
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Lead head nails and lead flashings – pre-1979
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Asbestos flashings
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VENTILATION
No ventilation system except draughts and opening windows
FIX – Add balanced MVHR system with low-VOC ducting
Stuffy interiors – smells and mould
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