housing
Nigel Isaacs looks back nearly 400 years for answers to the drywall shortage staggering in New Zealand and around the world
Remark: It may not be entirely fair, but we could blame the French for the great drywall crisis of 2022.
Louis XIV of France, after the devastation caused by the Great Fire of London in 1666, decreed that wooden frames of houses should be covered with nailed boards and plaster, “both inside and out, in such a way as to withstand firework” .
Enter gypsum plaster — or to give it its chemical name, hydrated calcium sulfate.
With two molecules of water for every molecule of gypsum, it is highly resistant to fire. Plaster is often referred to as “Plaster of Paris” after the large deposits found in Montmartre in the French capital.
In addition to fire protection, gypsum plaster provided a smooth, clean, paintable surface. Compared to wood sarking, it was fairly airtight and kept pests out, although it provided no structural benefit.
What was not to like about it? The problem was the build time. The gypsum plaster was applied wet, so curing took time. This slowed down the construction process.
Finally, a solution came in the form of fibrous drywall that could be prefabricated and cured off-site. They were made by adding animal hair or vegetable fibers to the plaster to resist cracking.
The first hint of a fibrous plaster rival appeared in 1883, when New York’s Augustine Sackett patented a three-prong roofing paper — a continuous sandwich of paper, felt, and paper cemented together, then cut to size. Sackett’s first drywall appeared in 1894. Improved by other inventors around the world, modern drywall had arrived by 1920.
After the painful years
Until the 1930s, the majority of New Zealand councils allowed interior wall coverings of sarking (thin wooden planks) covered with jute linen with wallpaper attached. It had a trifecta of failure: it was unsanitary, unsanitary and highly flammable.
Fiber plaster and the new drywall offered a real improvement. Imported wallboards were available and by the 1920s local production was encouraged.
It was from this milieu that Gib board would arise.
In 1925, a new New Zealand company, Builders’ Composite Materials Limited, promoted its patented Vidite drywall as waterproof, moisture resistant, drill resistant, fire resistant and good for nailing. This company lasted only two years before the factory was taken over by NZ Wallboards Ltd, the direct ancestor of Winstone Wallboards.
In 1932 the name became Gibraltar Board with the slogan “As Solid as the Rock of Gibraltar”. The company made extensive use of advertisements promoting the strength and fire resistance of Gibraltar Board.
In 1938 new benefits were advertised, including insulation against heat and cold, soundproofing and, where used to clad walls and ceilings, the provision of reinforcement “three times stronger than weatherboards”. Since then, the product has continued to evolve.
Rewriting the rulebook
About the same time Gib Board began rolling out the factory door, the country’s first national building codes were being developed.
Over the following decades, these statutes have gone through several iterations – and they became more and more complex. They were largely prescriptive ‘do it this way’ rules, adapted to local circumstances and municipalities.
The introduction of the New Zealand Building Code in 1992 marked an important departure. Instead of ‘do it this way’, the code says ‘get this feat’, demonstrating that the building as designed will meet the national minimum performance requirements.
Where proof of performance is required by the building code, proof must be provided – based on the properties of the actual materials and techniques – before the building permit is issued.
According to the code, drywall may be specified for its structural, fire resistance, water resistance and/or noise control compliance, with any test proof of its suitable performance being required. It can also have non-regulatory functions, such as providing a low-maintenance surface suitable for painting or wallpapering.
Once permission is granted, a specific product, material or method must be used. Replacement of the product is generally not permitted unless it can be shown to be suitable by test results or other evidence. The Ministry of Business, Innovation and Employment has now published guidance on product replacement of plasterboard.
Risk management
While the emphasis today is on using one drywall product that is in short supply, the reality is that the same situation can arise for any product used in a design to comply with building codes.
Louis XIV saw plaster as a solution to a problem as a way to control the risk of fire. But the experience of the building code has made many involved in design and construction averse to any risk. The question remains whether the rules still adequately control the risk and are still fit for purpose.
You may be wondering, why not just change the design of the building to avoid using a product that is in short supply? For example, if the specified drywall is not available, the structural reinforcement roll can be replaced with plywood or other sheet material, as is done in other countries. This may involve additional material costs, but can easily be done during the design process.
But it’s not that easy to make a change when the design is approved or under construction. If there are no products that are considered equivalent, this may require redesign and re-approval, both of which involve significant time and financial costs.
Unapproved replacement could result in the building being denied a Code of Conformity Certificate resulting in future legal problems for the owner (and potential buyer) when the property is sold.
Is legal action the future?
The building code can be seen as the ‘fence at the top of the cliff’ with the legal system the ‘ambulance at the bottom’. This approach places great importance on the actions of the designer, builder and product supplier to ensure that all requirements are implemented.
It also reduces the freedom to replace products specified for code compliance – and therefore any replacement under it requires clear management of liability.
It will be unacceptable for prospective home buyers to find that a hasty replacement, even if “approved”, will cause their building to fail or fail due to an unforeseen omission.