The stair
Treads and risers
Stringers
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or build your stair?
Send us your stair and we'll tell you if it works for your space, or what we'd change. If you'd like us to build it, we'll tell you what it would take.
How to use the
stair calculator
Pick the type of stair and enter the overall rise. Leave the run at 0 and the calculator picks the best number of risers for you, or enter the space you have and it fits the stair to it. Then choose your treads, risers and stringers. You get the stair's geometry, a drawing, a full stringer setout with cut angles, a spec and a materials list, all checked against the NZ Building Code.
Measuring the rise
Measure from the finished surface at the bottom to the finished surface at the top, such as ground or path to the deck boards. Allow for anything not built yet. Every riser and going in a flight has to be the same within 5 mm, so a small error in the overall rise shows up in every step.
NZ Building Code stair limits
Acceptable Solution D1/AS1 sets the limits for each type of stair:
| Type of stair | Max riser | Min tread | Max pitch | Max rise before a landing |
|---|---|---|---|---|
| Accessible | 180 mm | 310 mm | 32° | 2.5 m |
| Common, and main private | 190 mm | 280 mm | 37° | 2.5 m common · 4.0 m private |
| Secondary private | 200 mm | 250 mm | 41° | 4.0 m |
| Minor private, and service | 220 mm | 220 mm | 47° | 4.0 m |
Source: D1/AS1 Access Routes (Tables 6 and 7), building.govt.nz. The tread depth is the going plus the nosing projection.
Which type is my stair?
- Main private: the stair to frequently used rooms like living areas, kitchens and garages. Every outdoor stair at a house counts as main private, so deck and garden steps use these limits.
- Secondary private: a stair to a floor with only bedrooms, bathrooms or similar.
- Minor private or service: an out-of-the-way stair used now and then to reach a single room that isn't a living area or kitchen, or for maintenance access.
- Common: a stair shared by more than one household or used by the public.
What about 2R + G?
"Twice the riser plus the going" is a good guide to how comfortable a stair feels, and the calculator uses it to pick the best number of risers. It isn't a code check. D1/AS1 notes the rule doesn't always give a safe stair, so compliance is checked against the limits above.
This calculator sets out a straight flight of timber stairs. It isn't a construction drawing or a design certificate. Stringer sizes, fixings, barriers and footings must suit your site, and stairs that are part of larger work, or over 1.5 m high, may need building consent. Send us your stair and we'll check it.
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