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Table 28 — Underpurlins

AS 1684.2
Select inputs to see spans

Inputs

Timber Grade
Roof Type
Roof Mass (kg/m²)
Roof Load Width — RLW (mm)
Rafter Spacing (mm)

Maximum Underpurlin Span

AS 1684.2 Table 28 — Wind classification N1/N2

Size (D×B mm)Max Span (mm)
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Design Reference

Figure 7.25 — Underpurlins design parameters
Figure 7.25 — Underpurlins (AS 1684.2:2021)

Notes (AS 1684.2 Table 28):

i) Maximum spans are based on the support of roof mass only.

ii) Roof mass includes roofing, roof battens, insulation/sarking. The mass of the rafters is accommodated in the span calculations.

iii) Maximum allowable cantilever is 25% of the allowable span but not more than 33% of the actual backspan.

iv) Multiple members nailed together as per Clause 2.3.

v) Wind classification N1/N2 only. For N3/N4 or cyclonic areas, refer to the relevant wind classification supplement.