New Zealand Building Code: One National Rule Book on Chippy Tools

NZ Minimum Roof Pitch (E2/AS1): Tiles vs Metal

Fri, 31 Jul 2026 00:00:00 +0000

The requirement

Roof pitch is how steep your roof is. Lay it too flat for the material you’re using and water sits, or blows back under the laps, instead of running off. New Zealand’s national Building Code fixes this through clause E2 External Moisture, and the numbers actually used on site come from its Acceptable Solution, E2/AS1.

E2/AS1 doesn’t give one minimum pitch for “roofing.” It gives a different minimum for each material, because each sheds water differently:

Wet Area Waterproofing (NZ E3/AS1)

Fri, 31 Jul 2026 00:00:00 +0000

The requirement

E3/AS1 is the Acceptable Solution for Building Code clause E3 “Internal Moisture” — the recipe most bathrooms are built to. It sets impervious surfaces at different heights depending on what’s underneath them, not one number for the whole room (E3/AS1, Paragraph 3.3.1 “Showers” and Paragraph 3.2.2 “Joints between fixtures and wall linings”).

Where	What’s required (E3/AS1)
Shower walls	Impervious lining up to the higher of 1800 mm above the shower floor, or 50 mm above the shower rose
Shower floor	Impervious floor or floor finish, the full extent of the enclosure
No shower enclosure (open shower)	Impervious floor extends at least a 1500 mm horizontal radius from the shower rose
Walls next to a bath, basin, tub or sink	Impervious lining with a 150 mm minimum upstand, sides and back, sealed to the fixture

Inside the shower, the impervious wall lining has to be sealed to the wall behind it at its top edge — or run all the way to the ceiling — so condensation can’t get in behind the lining. Penetrations for tapware, mixers and roses have to be waterproofed with a proprietary flange or sealant that still allows access for servicing.

Does NZ Have a Minimum Ceiling Height?

Fri, 31 Jul 2026 00:00:00 +0000

The requirement

Here’s the short answer: the New Zealand Building Code does not set a minimum ceiling height for a house. There is no single number to hit.

The Building Code is performance-based. Instead of naming a height, clause G5 “Interior Environment” asks for an adequate, controlled interior temperature, and that habitable spaces have enough room for activity, furniture and any mobility aids (NZ Building Code G5, clause G5.3.3). It never states a floor-to-ceiling height in metres. The government’s own Verification Method G5/VM1 even says in plain words that no specific method has been set for checking G5. And the Acceptable Solution G5/AS1 has just one table of sizes — and that one is only for old people’s homes, with widths and floor areas, no ceiling height.

NZ House Foundations & 'Good Ground' (NZS 3604)

Fri, 31 Jul 2026 00:00:00 +0000

The requirement

In New Zealand, a standard timber-framed house is built to NZS 3604:2011. It’s the recipe most homes use, and the council accepts it under the Building Code (Clause B1 Structure, via B1/AS1). But there’s a catch that comes before any footing dimension: your block has to be “good ground.”

What “good ground” means. Good ground is soil or rock that can permanently hold an ultimate bearing capacity of 300 kPa — roughly 100 kPa once you take off the standard safety factor. That’s the number in NZS 3604:2011 clause 1.3. Just as important is what good ground is not: any ground that could move 25 mm or more for any reason is out. That rules out expansive clay, uncontrolled fill, soft or loose soil — and frost heave. If your site isn’t good ground, NZS 3604 stops applying and the footing goes to an engineer.

NZ Ramp Gradients (NZBC D1)

Fri, 31 Jul 2026 00:00:00 +0000

The requirement

New Zealand does not set one ramp slope for a house and another for a shop. The rule book — D1/AS1, the Acceptable Solution for Clause D1 Access Routes — sorts ramps by the job the ramp does. Pick the type that matches your ramp, then read the slope off the table.

Ramp type	Where it’s used	Max slope
Accessible ramp	step-free access routes	1:12
Common ramp, can get wet	outside, or anywhere it can be rained on	1:10
Common ramp, stays dry	indoors, kept dry	1:8
Service ramp	plant / service access only	1:3 (footholds needed if steeper than 1:8)

There is no “house ramp” number. D1/AS1’s table has no private, residential or household category — the types are keyed to accessible, common and service use. A ramp into a home fits none of them cleanly. So do not quote a single “NZ residential ramp gradient”: there isn’t one. In practice, if you want a step-free entry, build to the accessible 1:12. If it’s a plain dry ramp, the steepest walkable figure is 1:8. If it can get wet, don’t go past 1:10.

NZ Stair & Barrier Rules: Riser, Tread, Handrails, Barriers

Fri, 31 Jul 2026 00:00:00 +0000

The requirement

A stair has to be steep enough to fit the space, but shallow enough to climb safely. The New Zealand Building Code sets this with two numbers you set out with a tape — the riser and the going — plus rules for headroom and the handrail. These come from the D1/AS1 Acceptable Solution, the deemed-to-comply path.

Riser — how tall each step is.
Going — how deep each step is, the flat part you stand on (some call it the tread).

For the main stair in a house, each riser can be no more than 190 mm and each going must be at least 280 mm deep. Keep every step the same height so the stair is safe to climb. Secondary and service stairs are allowed to be a bit steeper — see the table.