Renovating homes built during the 1970s

ARTICLE Kelly Moran 

Fantastic wallpapers, crazy colour combinations and textured carpets come to mind when thinking about 1970s homes. Most of these will have long been updated, but the typical features of the houses as such remain. Styles include 'colonial', 'ranch', 'Mediterranean' and 'contemporary'. Many were built by developers as speculative houses. They were typically small and plain, rectangular or L-shaped, comprising of three good sized bedrooms with fitted wardrobes, one bathroom with separate toilet and laundry, an open plan kitchen/living room and a separate living room. Metal roofs, aluminium joinery, timber cladding and concrete floor slabs were commonly used.

Design and layout

The original design and layout of a 1970s home may not have incorporated an organised indoor/outdoor flow. For most of these houses, renovations will focus on upgrading comfort and energy efficiency, adding space, improving layout and orientation, improving indoor/outdoor flow, upgrading services, and replacing outdated fixtures and finishes.
Any new building work must comply with the Building Code and may involve consideration of compliance with current Resource Management Act constraints for side yards and site coverage. Where existing load bearing walls are removed, the basement is excavated or another floor is added, a specific engineering design may be required.

Common problems and remedies

Most 1970s houses are likely to be weathertight and structurally sound, with large eaves that give good weather protection, airtight windows and ventilated subfloors. However, some design and structural issues may need consideration as part of a renovation. In particular, some houses may require strengthening. Check to see if load bearing walls have been removed, if bracing is adequate, and if there is other evidence of structural problems such as floors slumping.
Weathertightness can be an issue if cladding has been poorly maintained, is damaged or deteriorated, or around windows, especially when no flashing has been used. When renovating, pay special attention to ventilation to ensure that internal moisture does not become a problem.
1970s houses were typically built rectangular of L-shaped comprising of three good-sized bedrooms.
Few houses built in the early 1970s were insulated, and where insulation was installed it is unlikely to meet modern requirements. Insulation may be required as part of a renovation project, and in any case will provide comfort and health benefits. Fire safety should also be considered. 
While wiring is likely to remain in good condition, many 1970s houses will not have enough power and light outlets. Low pressure hot water systems may need to be upgraded to mains pressure. Pipes and fittings such as mixers may need replacement to cope with the higher pressure. Any copper pipes will probably not need replacement but plastic pipes may - have them checked and watch for any signs of leaks.
Some piled foundations may lack adequate earthquake bracing. Check for unevenness, moisture and other signs of damage or deterioration. Original floors and wall cladding may remain in good condition, but should be checked for borer, rot, moisture damage or other signs of deterioration.
Original windows are unlikely to be double-glazed. Frames may be in poor condition. Metal elements such as roofing, fixings and flashings may have corroded, which can affect structural performance. Original roofs may need maintenance or replacement. Consider the condition of the cladding, whether there are signs of water entry, and whether drainage is adequate.

Health risks

Asbestos cement was in use in the 1970s and 1980s for wall and roof claddings, flooring and textured ceilings. It’s no longer used as it becomes a health hazard when old materials containing it are being removed or break down, allowing the fine particles to become airborne and breathed in. As a general rule of thumb, sheets that are pre-1988, or have a corrugated profile for roofing or a dimpled back surface on wall cladding sheets, are likely to contain asbestos fibres and need to be removed by specialists.
Lead was used in house construction in external and internal paintwork, flashings, valley gutters and nail heads. The use of white lead in paint was banned in 1979 but some special-purpose paints still contained red lead. It is not possible to identify lead-based paint from its appearance, but if a building is over 25 years old, assume that it has been painted with lead-based paint.
During the 1970s, boric treatment was used to protect against insect attack for interior use and for exterior painted timber such as trims, fascias and weatherboards. Copper chromium arsenic treatment may be found in decks, piles, fencing and poles. These chemicals may be hazardous to people, so care must be taken when working with treated timbers.

This article by Kelly Moran featured on page 106 of Issue 003 of Renovate Magazine. Renovate Magazine is an easy to use resource providing fresh inspiration and motivation at every turn of the page.

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*All information is believed to be true at time of publishing and is subject to change.