MGP10SpanTables
MGP10 Guide

How to Read MGP10 Span Tables (Step by Step)

Updated 2026-01-16 · MGP10 Span Tables

Diagram of a timber beam spanning between two supports under loadSpan (L)Load ↓  ·  Deflection (δ) · Support reactionsThe span is the clear distance a member bridges between supports
How to Read MGP10 Span Tables (Step by Step)
How to read an MGP10 span table — the short version
  1. Identify the member you are designing (floor joist, bearer, rafter, lintel and so on) and choose the matching design table.
  2. Confirm the stress grade is MGP10 — use the MGP10 table, not an MGP12, MGP15 or F-grade table.
  3. Determine your member spacing (for example 450 or 600 mm centres).
  4. Decide whether the member is a single span or a continuous span, and read the correct column for that case.
  5. Find your wind classification (N1–N4 or C1–C4) and, for floors and roofs, the floor load width or roof load width and roof mass.
  6. Read down to find the smallest member size whose listed maximum span meets or exceeds your required span.
  7. Cross-check against the current official tables and have the design verified by a qualified engineer or building certifier.

A page of span tables can look like a wall of numbers, but every one of them follows the same logic. Once you know which questions the table is asking, reading it becomes routine. Here is the step-by-step method — and the inputs you need before you start.

Diagram of a timber beam spanning between two supports under loadSpan (L)Load ↓  ·  Deflection (δ) · Support reactionsThe span is the clear distance a member bridges between supports
A span is the clear distance a member bridges between supports. The table tells you the largest span a given size and grade can manage for your loads.

The inputs every lookup needs

Before you open a table, gather these. Missing one is how people read the wrong value:

  • Member type — joist, bearer, rafter, lintel, etc. Each has its own table.
  • Stress grade — MGP10 here. Use the matching grade's table.
  • Timber size — e.g. 90×45, 140×45, 190×45 mm.
  • Spacing — the centre-to-centre distance between members.
  • Single or continuous span — a critical column choice.
  • Wind classification — N1–N4 or C1–C4 for cyclonic areas.
  • Load width — floor load width (FLW) or roof load width (RLW), and for roofs the roof mass (sheet vs tile).

Reading the table, step by step

  1. Pick the right table. Match the member you are designing to its design table.
  2. Confirm the grade. MGP10 reads from the MGP10 table only.
  3. Set your spacing. Find the row or block for your centres (e.g. 450 or 600 mm).
  4. Choose single or continuous. Read the column that matches your real support arrangement.
  5. Apply wind and load width. Narrow to the column for your wind class and (for floors/roofs) your load width and roof mass.
  6. Find the size that works. Read down to the smallest size whose listed maximum span meets or exceeds the span you need.
  7. Verify. Cross-check against the current official tables and have it signed off.
Comparison of common MGP10 timber cross-section sizes90x45140x45190x45240x45290x45Deeper members span further — common MGP10 sizes (mm)
Deeper members span further. The table lets you trade size against span for your fixed loads.

Build your lookup without missing anything

Forgetting an input is the most common way to read the wrong span. The Span Spec Builder walks you through every parameter and produces a tidy specification you can take straight to the official table or your engineer. It deliberately does not invent a span figure for you — that number must come from the authoritative table for your exact case.

Where the official tables live

The authoritative MGP10 span tables are published in AS 1684 (Residential Timber-Framed Construction) and its supplements, with equivalent data from industry bodies such as WoodSolutions and from timber manufacturers. Always work from the current edition — standards and load criteria are revised over time.

Next steps

Ready to apply it? Dig into the member you are working on: floor joists, bearers, rafters and roof members, or lintels and beams.

Frequently asked questions

What information do I need to use a span table?
At minimum: the member type, the stress grade (MGP10), the timber size, the spacing, whether it is a single or continuous span, the wind classification, and — for floors and roofs — the load width and (for roofs) the roof mass.
What does NS mean in a span table?
NS means 'Not Suitable' — that size and grade combination is not adequate for the spacing and loading in that column. You need a larger size, a higher grade, or closer spacing.
Why are there separate columns for single and continuous spans?
A member continuous over three or more supports behaves differently from one that simply spans between two. The tables list them separately because a continuous member can often span further — but only if it is genuinely continuous and lapped or joined correctly.
Where do I find the official MGP10 span tables?
The authoritative tables are in AS 1684 (Residential Timber-Framed Construction) and its supplements, with equivalent data published by industry bodies such as WoodSolutions and by timber manufacturers. Always use the current edition.

Keep reading

Build your lookup

Use the Span Spec Builder to assemble the exact parameters for this member, ready for the official tables or your engineer.

Open the Spec Builder