Paul King | Freelance Architect

Leaky Building Syndrome, And How To Avoid It

Horror stories about poor construction standards in homes built during the 1980’s to early 2000’s dominated the news for many years. Popularly known as “leaky-building- syndrome “, this phenomenon sent shock waves through the New Zealand building industry and shivers down the spines of many potential buyers of houses built during that period.

Many prospective home buyers are left wondering ” is it worth the risk?” and, “if things go wrong, who’s to blame?”

To put things into perspective, it is worth remembering that buildings around the world have always been subject to leaks of one sort or another; sometimes because maintenance has been inadequate, other times due to extreme weather events. However, here in New Zealand and overseas there has been a significant increase in leak problems that can’t be explained this way.

Various groups have been blamed — builders, building materials manufacturers, city councils, the government, architects and other designers, and even homeowners themselves. In reality, most problems have arisen due to a number of factors and cannot be attributed exclusively to one agent or authority. If we are aware of these factors and take them into account during a new home’s design and construction, leaky-building-syndrome is entirely avoidable. As always, good professional design and advice ahead of time, coupled with a good standard of construction is the best insurance against potentially serious leak problems – now, and into the future.

How Leaky-Building-Syndrome actually happens

Geographical location

The vast majority of New Zealand “leaky building” problems have emerged in the north of the North Island – where high rainfall & high humidity have exposed problems that would not arise as quickly (or at all) elsewhere. It seems that an overheated property market in the North, particularly in the Auckland area, had fostered a “cowboy” culture in which builders, owners and developers were taking short cuts to build more quickly and cheaply.


Certain materials used in buildings are blamed more often than others. Particularly strong criticism has been made of the use of plaster on polystyrene wall linings directly fixed to untreated timber wall framing. If this construction technique is employed, only the outer painted surface provides for weather tightness. This weakness is compounded by the fact that if water does get through the surface, there is no easy way for it to get back out again, meaning it can remain trapped in the interior of the wall.

As a result of prolonged exposure to dampness, untreated timber framing within walls, floor or roof can develop mould and start rotting – often without any visible sign from the outside until it has become quite extensive. Luckily, better construction techniques can ensure that water resistance is not just dependant on a layer of paint – for example by providing drainage cavities allowing any water that does penetrate the surface as result of extreme weather conditions, to drain back out again.

Bad design details

All too often the quickest, easiest and lowest cost “standard” methods of construction in recent years have been the most leak prone. Over-reliance on sealants and poorly designed or installed window flashings are common faults, made worse on buildings without wide eaves to shelter the walls and windows from rain, or on complex buildings where there are more joints that can develop leaks. Good techniques do exist to prevent leaking on any building, but these cost more to design and build properly and may not be well understood by some designers & builders.

Lack of ventilation

Older New Zealand houses have always leaked – often more than the new “leaky buildings” we hear about!

Also,  moisture in the air generated inside the building by its occupants through showering, cooking, and even just breathing, can introduce just as much water through internal condensation,  as any leaks might introduce from the outside.

However, in order to save on heating bills, newer buildings are usually much better sealed against draughts, and have wall cavities filled with insulation. Ironically, this means they can be less able than older houses to ventilate away any moisture that does collect within walls and roof spaces, and consequently, any trapped water is much more likely to sit for long periods and cause rot and other damage.

Building Regulations

The New Zealand Building Code is “performance based”. It is flexible enough to allow for the use of new technology and innovation within a framework of generalised safety and durability requirements. However, while the code does offer guidance for many specific situations, it cannot hope to cover all of the huge range of situations, and all of the construction materials and systems that are available in any detail – this is left to the skill and experience of the designer and builder selected. The code also only sets minimum standards. Builders and owners who opt to build just to the minimum standards required by law allow themselves less margin for error. Mistakes do happen and purely price-driven decisions frequently do result in problems for home-owners – and not just from leaks!

Lack of oversight by local authorities

The checking of building consent applications by local authorities provides only minimal protection for home-owners. Under current legislation the owner bears final legal responsibility for meeting all building and planning regulations, or for engaging builders and designers as required to achieve this. As a result, and for some years before the crisis emerged, domestic building consents were often granted based on fairly minimal architectural drawings and details submitted.

This is fine where the owner delegates his or her responsibilities to competent designers and builders who actually know the Code, understand the ramifications of each choice, and have the skills and judgement to select appropriate construction materials, details and methods in every situation – but in a price driven market the cheapest rather than the most competant designers and builders are often chosen.

As a result of “leaky building” publicity, local authorities now require much more thorough and detailed design information and drawings up-front, to catch more problems before they arise.

While some problems that emerge can be picked up later during construction on site, the reality is that Council building inspectors simply don’t have the time or funding to visit all building sites often enough to ensure that every problem is detected in time, so good drawings are essential!

Inadequate training and knowledge of builders

Some builders and tradespeople — most often the cheapest ones — have limited training or little overall understanding and knowledge outside their own trade. This means they are often only familiar with minimum standards of construction and may have little detailed understanding of how all a building’s parts need to work together. This can be made worse when a homeowner or project manager or developer with even less training tries to co-ordinate all the different trades involved in the complex process of building a new home.

Inadequate training and knowledge of building designers

Price is usually a reflection of quality, and builders and designers who offer the lowest prices are often those least qualified to do the job. It’s the age-old rule—you get what you pay for.

This rule is particularly important in New Zealand, because until fairly recently there was no minimum legal level of competence required to design and build houses here. Thankfully, a mandatory “Licensed Building Practitioner” regime covering a range of designers & trades people is now in operation to address this, and exclude some of the Cowboys operating in the Industry.

However some argue that the bar has been set far too low. Currently Architects are still the only designers of houses obliged to meet proven academic and professional standards.

Lack of input from Architects

The statistics show that problems for a given level of building complexity are very much more likely when home owners choose not to use the services of a genuine Registered Architect.

Building a home is not a project to be undertaken lightly and an Architect’s input is essential if design and detailing issues are to be well resolved ahead of time. An Architect can also monitor quality of work and building costs independently during construction to forestall any problems that do emerge.

Conclusions: Getting what you pay for

In a nutshell, it seems that much of the “Leaky Building Syndrome” has resulted from a combination of four main factors:

  1. The desire of home owners and developers to save money and time.
  2. The availability of a wide range of new and cheaper building materials.
  3. The availability of a wide range of cheap tradespeople and designers in the construction industry.
  4. A tendency for owners and developers to “do it themselves” by hiring and managing each trade separately during construction, foregoing the traditional single experienced contractor who would otherwise take full responsibility for and manage all construction, and foregoing an independent Architect who has the skill and experience to champion design and build quality from the outset.

The ever-increasing range of cost cutting options clearly carries with it an increased level of risk, and at the end of the day, while building practitioners must be held to account for what they do, home-owners must also take more responsibility for choosing wisely.

If the true long-term costs and benefits are considered rather than just the lowest short-term cost, most problems disappear.

Compared with buying a used home, particularly one from the ‘leaky building era’ where long term durability and performance are unknown, a new, well designed and well built home will generally give the very best protection against leaks – and other problems.

It can also be a wonderful lifestyle option that, in the long-term, provides many New Zealanders with a sound investment and lasting value for their money.