Gas work under G11: what a builder needs to know

NZBC clause G11 (Energy & Lighting / Gas), together with the Gas Act and gas safety regulations, covers LPG and natural-gas installations. For a builder it comes down to two things: every gas appliance needs enough air to burn cleanly, and a way to get combustion products out. All gas work must be done and certified by a Certifying Gasfitter (PGDB-licensed), who issues a gas certification — so your job is to frame, flue and ventilate so their appliance goes in cleanly.

Flued vs unflued — the carbon monoxide difference

A flued appliance vents its exhaust outside. An unflued one — a portable LPG heater, some cooktops — dumps combustion products, including carbon monoxide and a lot of water vapour, straight into the room. That means it needs generous fixed ventilation, and it’s banned as fixed heating in rentals (see Healthy Homes).

CO is colourless and odourless. Correct flueing and ventilation isn’t optional.

General rules

• All gas work must be done by a Certifying Gasfitter or Authorised Person under supervision (Plumbers, Gasfitters, and Drainlayers Act 2006).
• A Gas Safety Certificate must be provided to the owner at completion of work.
• LPG cylinder setbacks: minimum 1m from openings, and 1.5m from drains and ignition sources.
• Natural gas (reticulated) is much lighter than air, so it escapes upward. LPG is heavier than air, so it pools in low spots.
• Combustion ventilation is required where an unflued gas appliance is operating — a habitable room needs ≥1 m³/kW of input rating.

Appliance types and how they go in

The flueing and install detail changes with the appliance. Here’s what to expect for the common ones.

• Cooktop (natural or LPG) — Not flued, just a rangehood. Direct connection, with an isolation cock within 600mm. Rangehood vented to outside (G4/AS1) at ≥50 L/s exhaust.
• Califont (continuous hot water) — Flued to outside through wall or roof. External wall mount, or internal with flue. Cold and gas connections, pressure-tested, with a TPR and relief drain.
• Storage water heater (gas) — Flued, class 1 flue. A larger floor-mounted unit; connection is like a califont but with a storage tank. Less common in newer builds.
• Gas fireplace — Flued, sealed combustion typical. Sealed combustion uses no room air (efficient and safe). Flue routed up and out, or direct through wall (DV).
• Gas heater, portable (LPG) — Unflued. Cylinder ≤9kg indoors by regulation, with adequate room ventilation required. Not acceptable for Healthy Homes Standard 1 (main living).