Original details

Windows in 1970s houses were typically larger than the windows of houses built during the previous two decades.

Many houses early in the 1970s had timber-framed windows, but aluminium joinery quickly grew in popularity.

Timber frames

Timber windows were generally redwood or western red cedar, although miro and matai were sometimes used for window and door sills.

Timber windows were framed on the exterior with 100 x 25 mm facing boards, except for stucco-clad houses.

From the mid 1970s passive ventilator inserts were available in timber windows but these were not often used.

Aluminium frames

Aluminium joinery (Figure 1) was considered to be maintenance-free, although this was not strictly true. 

Aluminium was typically anodised with polished or satin, silver or bronze finishes. Aluminium joinery was generally installed without facing boards to maintain a slim frame appearance.

Figure 1: Typical aluminium awning-type sash window with aluminium reveals/architraves and fixing flange.

Early aluminium windows and sliding doors:

• had flanges that were fixed to the framing before the cladding was installed, particularly for range sliders (Figure 2)
• had plastic or aluminium glazing beads in early models that were easily removable from the outside 
• did not incorporate effective condensation drainage 
• may have had frames set into rebated reveals (Figure 3)
• had rimu reveals.

Figure 2: Typical sliding door section with timber floor and weatherboarding.

Figure 3: Aluminium awning sash window

From the mid 1970s, aluminium reveals, aluminium (patent) glazing bars, aluminium windows with integrated condensation channels, and aluminium windows with passive ventilator inserts were available but none were commonly used.

Around the mid 1970s there was a shift from reveals trimmed with architraves to the wider slimline reveal where the plasterboard lining was fitted into a groove in the back of the reveal.

In 1976, MDF reveals began to be used, however they showed early deterioration if they became damp, and their use largely ceased in the early 1980s.

Other frame materials

Also developed during the 1970s but not widely used were the JMF profile timber windows with a much slimmer section than traditional timber sections, designed to be more like an aluminium window in appearance and utilise friction stays on opening sashes.

From the late 1970s, steel windows were available but not often used.

Types

Awning-style windows were the most common type of opening sash, but louvred (Figure 4) and sliding windows were often installed.

Large units combining a ranch slider that provided access to the patio and opening sashes, were commonly installed in living areas.

Some architects designed clerestories to allow light and ventilation into the middle of a house. In a few cases builders copied the roof style, but without including the windows.

Figure 4: Typical adjustable louvre.

Glazing

Glazing was single, clear or tinted glass.

From the mid 1970s toughened glass and double glazing were available but not often used.

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Common modifications

Original windows may have been replaced with newer glazing units. These will typically be aluminium. If the replacement was done recently, insulating glass units may have been installed.

When replacing glazing, carefully consider thermal performance of the replacement glazing. One tool that can help with this is the Window Energy Efficiency Rating System (WEERS), a 6-star rating system for assessing the thermal performance of new residential windows.