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    AS 1684 / AS 2878 reference · Australia

    F17 Hardwood Sizing Reference Guide

    Timber grades, section sizes and questions for professional review. No allowable span values are provided; consult official sources and a qualified designer.

    Indicative reference only, not engineering advice

    This page is educational and does not reproduce the official AS 1684 span tables, which are copyright Standards Australia. The tables below show common F17 sizes only — every allowable span must be read from the published AS 1684.2 table for your wind classification and loading, and confirmed by a structural engineer. This is not engineering or certification advice.

    What is F17 hardwood?

    F17 is a stress grade for seasoned hardwood timber assigned under AS 2878 (Timber — Classification into strength groups). It is specified where higher strength or longer spans are needed than softwood grades like MGP10 can achieve. Common Australian species graded F17 include Spotted Gum, Blackbutt and Sydney Blue Gum, typically supplied seasoned and dressed.

    F17 ceiling joist reference guidance

    Common F17 hardwood ceiling joist sizes at 450 and 600 mm centres. This page does not publish allowable spans — read each from the official AS 1684.2 ceiling joist table for your project loading.

    • 90 × 45
      Spacing (mm)
      450
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2
    • 90 × 45
      Spacing (mm)
      600
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2
    • 120 × 45
      Spacing (mm)
      450
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2
    • 120 × 45
      Spacing (mm)
      600
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2
    • 140 × 45
      Spacing (mm)
      450
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2
    • 140 × 45
      Spacing (mm)
      600
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2
    • 190 × 45
      Spacing (mm)
      450
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2
    • 190 × 45
      Spacing (mm)
      600
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2
    • 240 × 45
      Spacing (mm)
      450
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2
    • 240 × 45
      Spacing (mm)
      600
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2

    F17 rafter reference guidance

    Common F17 hardwood rafter sizes at 450 and 600 mm centres. This page does not publish allowable spans — read each from the official AS 1684.2 rafter table for your wind classification.

    • 90 × 45
      Spacing (mm)
      450
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2
    • 90 × 45
      Spacing (mm)
      600
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2
    • 120 × 45
      Spacing (mm)
      450
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2
    • 120 × 45
      Spacing (mm)
      600
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2
    • 140 × 45
      Spacing (mm)
      450
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2
    • 140 × 45
      Spacing (mm)
      600
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2
    • 190 × 45
      Spacing (mm)
      450
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2
    • 190 × 45
      Spacing (mm)
      600
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2
    • 240 × 45
      Spacing (mm)
      450
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2
    • 240 × 45
      Spacing (mm)
      600
      Max single span (m)
      Verify against AS 1684.2
      Max continuous span (m)
      Verify against AS 1684.2

    F17 vs MGP10 — which is stronger?

    A grade comparison alone cannot establish an allowable span or suitable substitution. Compare verified product properties and ask a qualified designer to assess the load case, connections and serviceability. Obtain current prices from suppliers rather than assuming a fixed cost ratio.

    Where to buy F17 hardwood in Australia

    F17 hardwood is available through specialist hardwood timber merchants and some Bunnings Trade outlets. Confirm species certification and stress-grade markings with the supplier before ordering, as not all "structural hardwood" is graded F17.

    Related reference guides
    MGP10 reference guide
    Full MGP10, MGP12, MGP15, F7 and F17 reference tables.
    Timber types and grades
    How F-grades, MGP grades and stress grades are assigned in Australia.
    Ceiling joist reference guide
    Sizes, spacing and how to read a ceiling joist span table.
    Roofing timber best practices
    Installation, fixings and AS 1684 compliance tips.