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NZ Building Code · StructuralReading NZS 3604 span tables without an engineer
Span tables let you size joists, bearers, rafters and studs straight from NZS 3604 — this page shows which table to use and how to read it.
Span tables are the heart of NZS 3604 — they let you size joists, bearers, rafters and studs without an engineer, as long as you’re inside the standard’s limits (good ground, ≤2 storeys / 10 m, wind up to Extra High). You read off the member size for a given span and spacing, then adjust for wind zone.
How a span table works
Each table cross-references a few inputs to give you a member size. Get the inputs right and the size falls out of the grid — there’s no calculation, just a careful read. The general steps are:
- Confirm you’re inside the standard’s limits (good ground, ≤2 storeys / 10 m, wind up to Extra High).
- Pick the correct table for the member you’re sizing.
- Read off the member size for your span and spacing.
- Adjust for wind zone — lower wind zones generally allow longer spans.
Toolie doesn’t reproduce the tables. It tells you which table to use and how to read it, then you look up the value in your own licensed copy of the standard.
Which table for which member
Floor & deck joists — NZS 3604 Table 7.1
- Read the joist size by span × joist spacing (400 / 450 / 600 mm) × timber grade × floor load.
- Decks use the wet-in-service column — Table 7.1(b).
Bearers — NZS 3604 Tables 6.4 / 7.4
- Bearers are sized by loaded dimension (≈ half the joist span on each side) and bearer span — not by spacing.
Rafters — NZS 3604 Table 10.1
- Read by span × rafter spacing × roof weight × wind zone.
- Lower wind zones generally allow longer spans.
Studs — NZS 3604 Table 8.2
- Read the stud size / spacing by wall height × wind zone × loadbearing / storeys.
The catch
Toolie names the tables only — it does not contain the span values. Read the figure off NZS 3604:2011 for your exact loading, or get an engineer’s PS1.
Plain-English guide, not advice. This page helps you understand and navigate the rules — it is general information, not design, engineering or consent advice, and it does not reproduce the copyrighted tables of NZS 3604 or any Standard. Always check the current Standard or Acceptable Solution and your BCA, and use a suitably qualified LBP, engineer or QS where it matters.
Do it in Toolie
Put this into practice with the NZS 3604 take-off · the lintel/beam span calculator · the rafter span calculator. Try Toolie free — no signup — or open this topic in the Toolie app.
Common questions
Can I size timber members without an engineer?
Yes — NZS 3604 span tables let you size joists, bearers, rafters and studs without an engineer, as long as you’re inside the standard’s limits: good ground, no more than 2 storeys / 10 m, and wind up to Extra High. Outside those limits you need an engineer’s PS1.
Which NZS 3604 table do I use for each member?
Floor and deck joists use Table 7.1 (with the wet-in-service column, Table 7.1(b), for decks). Bearers use Tables 6.4 / 7.4. Rafters use Table 10.1. Studs use Table 8.2.
How are bearers sized differently from joists?
Bearers aren’t sized by spacing like joists are. They’re sized by loaded dimension — roughly half the joist span on each side — and by the bearer span.
Does Toolie contain the actual span values?
No. Toolie names the tables and explains how to read them, but it does not reproduce the span values. Read the figure off your own licensed copy of NZS 3604:2011 for your exact loading, or get an engineer’s PS1.
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