Pink Timber Treatment New Zealand

Treating Timber’s Harsh Realities

Poorly designed and badly built homes in New Zealand caused more than a stir in New Zealand’s building industry from the mid 90’s  leading to some ill-thought-out policies being introduced that overcompensated for our shortcomings and lead to more problems then it solved. One of these implemented policies was the widespread use of treated timber in our builds.

Some may argue that there can’t be any downside to using treated timber throughout our builds because it won’t rot as quickly as untreated timber if left exposed to wet conditions or the risk of insect attacks like Wood Borer. The reality however is that we should have never been designing houses in the way we were – with no eaves for example – that was the trend in the Mid 90’s, and using external cladding systems that were not properly installed and sealed by the builders. My logic is we should be designing and building better with water ingress in mind and building inspectors should be picking up these issues before they begun. Also, the Wood Borer insect is usually only evident in damp places, usually under the house and is almost never present in dry untreated timber that adheres to the recommended building guidelines moisture content i.e. 12%.  Last week I checked a piece of ‘that day’ supplied H1.2 timber that was delivered by a local builders merchant, the moisture content was 35% which even for treated timber is not advisable to use and likely to split and warp during its several months, even possibly years drying if already installed in a wall. Furthermore, if this splitting does occur then this will lead to the substantial loss of the timber’s inherent mechanical strength.

log prices in New Zealand are the lowest they’ve been in 5 years, yet we are paying the highest price we have ever paid for treated pine

Also, there are many ways of treating timber and almost all of them use chemicals that are not good for our health, both the material handlers and the building occupants. It is quite interesting how few people that work in the industry really understand the potential health impacts of handling, particularly breathing in the light organic solvent-borne preservatives (LOSPs).

The New Zealand Timber Preservation Council are advocates for treating timber with LOSPs, but they themselves have published handling guidelines that should raise awareness of the apparent health impacts, such as:

  1. 1) LOSP treated timber should be stored in a well ventilated, under cover area with any protective wrapping removed.
  1. 2) Where possible packs should be opened a day or two before use to allow any residual solvent vapours in the inner boards to evaporate.
  1. 3) Some people may experience temporary skin irritation, headaches or light headedness when using LOSP treated timber. These undesirable effects are more likely if the timber is not solvent dry.
  1. 4) Wear gloves and long sleeves for protection against splinters and cuts during handling. 5) Treatment plant operators should wear solvent resistant gloves when handling timber that is still damp from treatment. Application of a chemical resistant barrier cream to exposed areas, particularly wrists and forearms, is strongly recommended.
  1. 6) Wear protective glasses and a filter mask when sawing, sanding or machining treated timber.
  1. 7) Working with solvent damp timber is inadvisable, however, an impervious work apron must be used to protect clothing if direct contact proves unavoidable.
  1. 8) If LOSP preservative or treated sawdust accumulates on clothes, wash separately before reuse.
  1. 9) Always wash hands after handling LOSP treated timber, especially before eating.
  1. 10) Do not transport LOSP treated timber in an enclosed environment.
  1. 11) If undesirable effects occur cease handling or using the material and review your personal protection measures.

I’ve been building with treated timber here in New Zealand for the last 2 decades since I moved back here from Europe in 2001 and I was not made aware of the risks of improper handling of treated timber by our suppliers – and nearly all my timber that I’ve received on site has been damp to the touch.

My biggest question is do we really need to be building with treated timber on internal partitions, exposed rafters or wall linings where water is very unlikely to be present? Can we just make sure we’re building properly and then use untreated timber like the rest of the world does? If we can use untreated timber in places where it’s not necessary then we will open up our market to more affordable and stronger timber varieties, better building systems (like mass timber) and drive more competition and open up more supply options.


Treating all our timber is costly, causes supply chain bottlenecks, especially when we send our timber to be treated offshore and then import back into our country for use. This is slow and transport alone is a huge added cost rife with problems and inefficiencies at the moment. Treating all our timber also limits market competition and only benefits a very few companies in New Zealand.

The most used timber variety we use in New Zealand for building is Pinus Radiata (Pine), it’s a fast growing timber species that is structurally weaker than most other timber varieties used internationally because the grains are wider which is also good for the chemicals to impregnate the timbers, whereas stronger timber varieties that grow slower and  have closer grains are not easily treated but are also less susceptible to water and pest damage. There is a strong argument from our timber suppliers in New Zealand to keep the status quo, they don’t want new competition and they can hike timber pricing when they feel like it.

At the time of writing this article log prices in New Zealand are the lowest they’ve been in 5 years, yet we are paying the highest price we have ever paid for treated pine. I don’t believe it will take much for our policy makers to sit down and think about this unnecessary building code policy and implement a revision that not only makes sense but makes our homes healthier, promotes more competition and drives timber pricing back down to realistic levels.