The NZ builder’s quick reference facts

These are the numbers and rules of thumb experienced NZ builders carry in their heads — grades, timeframes, coverages, and the counterintuitive ones that catch people out. They’re quick answers for pricing, ordering and sense-checking on site; the detail behind each lives in its own topic.

Timber grades & treatments

Two things to get right: the structural grade (how strong) and the treatment level (where it can go).

• SG8 – Stress Grade 8, the most common framing grade.
• SG10 – stronger, used for engineered jobs.
• H1.2 – LOSP-treated, indoor-only.
• H3.1 – LOSP exterior, above-ground.
• H3.2 – CCA exterior, above-ground — more durable, blue-green tint.
• H4 – below-ground (fence posts).
• H5 – ground contact (deck posts, retaining).
• H6 – marine.

Seismic zones & consent timeframes

NZS 3604 splits the country into seismic zones. A higher zone means more bracing units (BU) and heavier fixings.

• Zone 1 (low) – Auckland, Northland, parts of Waikato.
• Zone 2 (medium) – most of NZ.
• Zone 3 (high) – Wellington, Marlborough, lower North Island.

Building consent processing times

These are typical council turnarounds — plan around them, and add time for the inspections during the build.

• Auckland Council – 6–8 weeks standard residential; up to 12 weeks during the Sept–Nov peak.
• Tauranga – 4–6 weeks standard.
• Christchurch – 6–10 weeks.
• Allow an extra 4–8 weeks for inspections during the build (pre-pour, pre-line, pre-cladding, final).

Required inspections

A standard residential build steps through these inspections in order. Each one is roughly a $280–$380 council fee.

1. Pre-pour foundation.
2. Pre-line (framing & wraps).
3. Pre-cladding.
4. Final, plus CCC.

Additional inspections apply for wet-area waterproofing, gas/plumbing, electrical and drainage.

Paint, moisture & panel sizes

Paint coverage

Resene coverage runs about 1L to ~10m² on a smooth surface (SpaceCote, Lustacryl). Rough or fresh GIB needs primer first at ~8m²/L. Always finish with a minimum of two coats, and add 10–15% for wastage on cutting in and brush wash.

Moisture content

• NZ framing: 18% maximum moisture content at install (NZS 3604).
• Kiln-dried H1.2 framing is usually 14–16%.
• Wet timber installed = shrinkage cracks and GIB pops.
• Kwila, Vitex and Garapa hardwood decking: install at 12–15% MC — it’ll still move with the seasons regardless.

Standard panel & board sizes

• GIB 10mm – 2400×1200, 3000×1200.
• Plywood F8 19mm – 2400×1200.
• Particle board flooring T+G 22mm – 3.6×0.9m.
• Linea weatherboard 180×11 – 3.6m.

Always order 1 extra sheet or board per 10 to cover cuts and waste.

The ones that catch people out

Kwila and Merbau leach red tannin for 6–12 months — it stains the deck below, adjacent concrete, the works. Pre-soak the boards in water for 7+ days, or install in dry weather and get oil on them quickly. Vitex doesn’t leach as much, but still pre-treat it.