Could my building be leaky?

There are certain factors that increase or decrease the risk of a building developing weathertightness issues. These include:

Reduced Risk

• Protection of wall cladding by roof eaves, the wider the better.
• Drained and ventilated cavity behind cladding, e.g. brick veneer.
• Traditional and simple designs.
• Separation of cladding from ground, paving and tiled surfaces.
• Traditional boron treated timber framing.

Increased Risk

• No roof eave protection of walls.
• Exposed sites.
• More complex designs, i.e. lots of junctions and corners.
• Monolithic claddings, e.g. stucco plaster, fibre cement, etc.
• Tiled balconies and ‘solid’ handrails.

Highest Risk

• Chemical free (untreated), H1-LOSP and Douglas fir timber framing, in combination with any current monolithic cladding system.
  
  

What is the problem with leaky buildings?

All buildings will leak to some degree, either from imperfections in the design and construction, or subsequent actions that breach the building’s weathertight envelope such as adding an outside light or TV aerial, or that affect drainage such as raising garden levels too high.

Moisture can be retained behind the cladding when it is not able to drain and dry out. This moisture is hidden, usually on the back of the cladding, so the owner or occupant can be quite unaware of its presence.

Retained moisture can lead to mould growth on building materials, decay of timber framing and rusting of steel fixings and framing.

With timber not treated against decay, the chance of decay occurring is very high. The nature of some of these decays is of great concern, e.g. dry rot.

When did the building industry start using untreated framing timber?

NZS 3602, the Standard which permitted the use of kiln dried untreated pine was published in September 1995. The use of untreated timber likely started from 1996 onwards. Douglas fir has always been allowed without any treatment, however it is more durable than untreated kiln dried pine.

View a timeline of the leaky building issue here, which indicates the construction years presenting most risk of weathertightness issues.

Why was untreated framing timber allowed?

Prior to the 1990s, issues of water ingress and fungal decay were not considered in the treating of timber. Treatment was only intended to prevent insect attack. After a field study, it was considered that kiln dried timber was unpalatable to borer, so untreated kiln dried timber was deemed satisfactory for use as framing.

How long does it take for problems to occur with untreated framing timber?

This depends on many factors. The low moisture levels that can cause certain decays mean it could take many years for the problem to surface. However, significant decay has been found in buildings built less than one year ago. Some decay has even been found in buildings still under construction.

Do all buildings with untreated framing timber have problems?

It all depends on how much moisture penetrates and accumulates behind the cladding. The biggest safety factor is the roof eave – the wider the better. However, any moisture entry is of great concern and there is no protection against decay.

If I know I have a leaky building and sell it, is this legal?

You will need to take advice from a legal professional on this.

If my building leaks and rots, will my insurance cover this?

Every insurance policy is different, however, most insurance policies do not cover gradual damage. You should review your own policy wording, and consult a legal professional if you need further advice.

What can I do if I own a leaky building?

Seek professional advice as soon as possible. There are time limits on legal action, and the longer the problem is left, the greater the damage and subsequent repair costs are likely to be.

You may be able to bring the parties involved in the construction to account. Unfortunately, this may mean expensive legal action. If those involved will not assist, your best ‘bang for buck’ will generally be to spend money on repairs, and then trying to recover costs via litigation.

You can contact our team of professionals at Prendos for expert advice on your options, by calling 0800 PRENDOS or emailing prendos@prendos.co.nz.

You can also contact the Building Research Association of New Zealand (BRANZ) at www.branz.co.nz and the New Zealand Institute of Building Surveyors (NZIBS) at www.buildingsurveyors.co.nz.