Houses from the untreated framing years, about 1995 to 2005

When was untreated framing allowed in New Zealand?

Standards New Zealand's timeline gives the dates. NZS 3602:1995, from 11 September 1995, allowed untreated framing if it was kiln-dried and its moisture content in service would not exceed 18%. The Building Code's Acceptable Solution B2/AS1 cited that change from 28 February 1998. A Building Industry Authority directive then required treated framing for consents issued from 1 April 2004.

The window is therefore fuzzy at both ends, roughly 1995 or 1998 to 2004 or 2005. Not every house from those years was framed untreated; some builders kept using treated timber throughout.

Why does untreated framing matter for borer?

Because radiata pine sapwood is a host for the common house borer, and kiln-drying alone does not protect it. The NZ Farm Forestry Association lists radiata pine among the timbers the beetle attacks, with larvae spending about four years in its sapwood. Boron-treated H1.2 framing is treated to resist borer; untreated framing has no such protection.

Kept dry inside a sound building, untreated framing may never be troubled. The 18% moisture condition in the 1995 standard assumed exactly that. The risk rises where the framing gets wet or the air around it stays humid, since common house borer develops fastest above about 70% relative humidity, and damp untreated framing is also open to decay.

How did untreated framing connect to leaky homes?

The Bioeconomy Science Institute, formerly Scion, says the mid-1990s change allowing untreated framing made leaky-home damage worse. Where water got behind cladding, treated framing had some protection against decay and untreated framing had none. That is why many buyers of houses from this era commission weathertightness checks as well as a standard building report.

Borer and decay are separate problems with a shared cause. A weathertightness specialist looks for water getting in; a borer inspection looks at the timber that can be seen. For a house with monolithic cladding from these years, Consumer Protection suggests a more specialised inspection by a registered building surveyor, and the building inspection guide explains how the reports differ.

How can you tell if a house has untreated framing?

Start with dates: the consent date and the completion date in the council property file or LIM tell you whether the house falls in the window. Then look where framing is exposed. NZS 3640 sets how treated timber is marked, and BRANZ notes that H1.2 boron framing is colour-coded pink. Untreated kiln-dried pine has no treatment marks and no pink tint.

• Council records: consent issue date, code compliance date, and any later alterations.
• Roof space: trusses and framing can often be seen from the hatch.
• Garage or unlined areas: sometimes the easiest place to see wall framing.
• Subfloor: on suspended floors, joists and bearers may show stamps or colour.
• Builder's paperwork: occasionally kept by an original owner.

Colour fades and stamps get covered, so a missing mark is a clue, not proof.

How does a borer inspection approach framing it cannot see?

It reports what it can reach and says plainly what it cannot. In a house from these years most wall framing sits behind linings and cladding, out of view. The inspection looks hard at the parts that are exposed, the roof space and any subfloor or garage, because the same timber supply usually went through the whole house. Those areas then stand in for the rest.

1. Dates

   Check whether the consent falls in the untreated window.

2. Exposed framing

   Roof space, subfloor and garage: treatment marks, colour, holes and dust.

3. Moisture

   Readings and visual signs of damp at reachable points, especially near wet areas.

4. Limits

   Wall framing behind linings recorded as not inspected.

5. Next step

   Treatment of exposed live borer, or a weathertightness specialist if moisture is suspected.

How those findings are laid out is described in reading a borer report.

Should buyers avoid houses from this era?

No. Many houses from the late 1990s and early 2000s were framed with treated timber, and many with untreated framing have stayed dry and sound. What the era does is raise the bar for due diligence: check the framing where it can be seen, understand the cladding and its weathertightness history, and read moisture findings carefully. The answers decide the house, not the decade.

For comparison, the earlier untreated era is the opposite case: villas and bungalows built before 1952 were framed in untreated native timber, and old borer is close to universal. The house borer by build year guide covers every era side by side.

Is there a year boron treatment became compulsory?

Not one that the primary sources show. Boron treatments were introduced in 1952 and the Timber Preservation Authority was set up in 1958, but no opened source states a year from which boron treatment of framing became compulsory. Claims of a single "compulsory boron" year are best treated with caution. The dates that can be stated precisely are the 1995, 1998, 2004 and 2005 ones.

For a buyer, the practical question is about the house in front of you, not the regulation history: what the council records say about its consent, and what the exposed framing shows. The borer inspection page sets out what is checked on the visit.

More on build era

• House borer by build yearWhich New Zealand houses carry house borer, era by era, and why the framing timber decides it
• Pre-purchase borer inspectionA borer check timed to your building condition, read alongside the building report
• Borer and moistureHow humidity, damp subfloors and timber moisture drive borer, and what moisture readings in findings mean
• Pre-purchase building inspectionWhat an NZS 4306 pre-purchase building inspection covers, what it leaves out, and where borer fits