How changes in glazing practice have reshaped site sequencing in New Zealand

The shift toward on-site glazing has altered construction workflows, exposure risk, and protection requirements on live projects.

Over the past decade, glazing practices in New Zealand construction have undergone a quiet but significant shift. Where aluminium joinery was once commonly delivered to site fully glazed, it is now increasingly standard practice for units to be installed unglazed and glazed on site.

This change has had a material impact on site sequencing, exposure risk, and how completed areas are managed during construction.

Pre-COVID glazing practices: factory glazing with limits

Historically, factory glazing was widely used across residential and light commercial projects. Glazing units in a controlled factory environment offered clear advantages in quality control, weather protection, and installation efficiency.

However, even prior to COVID-19, the widespread adoption of double glazing introduced practical constraints. Larger insulated glass units significantly increased the weight and fragility of completed window assemblies. Transport, handling, and storage risks made on-site glazing more attractive for large panes, sliders, and commercial joinery.

As a result, on-site glazing had already become more common through the 2010s, particularly where unit size or access constraints made factory glazing impractical.

COVID-era disruption and the normalisation of on-site glazing

During the COVID-19 period, glazing practices shifted further. Supply chain disruption, shipping delays, and workforce limitations made just-in-time delivery of fully glazed units increasingly difficult.

In many cases, joinery frames were installed ahead of glass availability to avoid holding up programmes. Glass was then fitted on site once supply became available. While this approach was often a pragmatic response to uncertainty, it reinforced on-site glazing as the default sequencing model on many projects.

Rather than being a temporary workaround, this sequencing approach became embedded across parts of the industry.

Post-COVID: renewed interest in factory glazing

As supply chains have stabilised, there is growing discussion within the industry about reintroducing factory glazing where feasible.

Several factors are driving this renewed interest:

• Higher thermal performance requirements under updated H1 provisions

• Increased use of prefabricated and panelised construction systems

• A desire to reduce on-site labour, congestion, and weather exposure

In some projects — particularly prefabricated façades and panelised builds — windows are once again being glazed in factory conditions and delivered to site as complete assemblies, allowing buildings to be enclosed more quickly.

However, factory capacity, storage space, handling equipment, and transport risk remain limiting factors. As a result, off-site glazing is not universally suitable and must be assessed on a project-by-project basis.

How glazing practice affects site sequencing

Whether glazing occurs on site or in the factory has a direct influence on sequencing:

• On-site glazing introduces extended exposure of frames, sills, and adjacent finishes during high-traffic stages of the build.

• Factory glazing reduces exposure time but increases handling, transport, and coordination requirements earlier in the programme.

Both approaches require careful planning. When glazing is delayed, completed joinery is often installed well before surrounding works are finished, increasing the risk of surface damage unless managed appropriately.

Implications for surface protection

As on-site glazing remains common practice across many New Zealand projects, temporary surface protection has become increasingly relevant during the period between joinery installation and final handover.

Protection strategies must account for:

• Duration of exposure following installation

• Trade overlap and access routes

• Weather exposure

• Sequencing of glazing, finishing, and commissioning activities

Rather than being a substitute for good sequencing, protection acts as a support measure during unavoidable overlap between completed and ongoing works.

Key takeaway

Changes in glazing practice have reshaped how construction sites operate. While factory glazing offers advantages in quality and enclosure speed, on-site glazing remains a practical reality for many projects.

Understanding how these approaches affect sequencing and exposure is essential when planning protection measures on live construction sites.