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MGP12

MGP12 is machine-graded pine with a characteristic modulus of 12,000 MPa, roughly F8. Used for bearers, lintels, longer-span floor joists where MGP10 spans run short.

By Chalkline. Last updated 14 May 2026. Verified 14 May 2026.

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MGP12 is a stress grade in the Machine Graded Pine (MGP) system, with a characteristic modulus of elasticity of 12,000 MPa, roughly equivalent to F8 in the visual-grading F-system. MGP12 sits in the middle of the residential MGP range: stronger than MGP10 (the volume framing default) and weaker than MGP15 (highest strength residential pine).

Where MGP12 is used on residential builds:

  • Bearers under floor joists, particularly where joist spacing requires more bearer stiffness than MGP10 allows.
  • Lintels over openings up to ~3.6 m where MGP10 sections run shallow or wide.
  • Top plates on longer-span walls.
  • Floor joists at longer spans (over ~4.2 m), where MGP10 spans would exceed AS 1684 limits.
  • Roof beams and ridge supports where the engineer’s design accepts MGP12 in place of LVL.

The MGP system is the modern residential pine grading; MGP10 is the most common. MGP12 is the next step up and is often specified in the AS 1684 span tables as the alternative when MGP10 doesn’t reach the required span.

How MGP12 is produced. Pine logs are sawn, kiln-dried, then run through a machine grader (e.g. CookGrader, Metriguard E-Computer, Brookhuis Timber Grader Goldeneye) that measures each piece’s stiffness non-destructively. Pieces meeting the MGP12 stiffness threshold are stamped MGP12. The machine grade replaces the visual grader’s eye with consistent, repeatable measurement.

Span advantage over MGP10. Indicative single-storey timber-framed dwelling, single span:

  • Floor joist, 240 × 45 mm, 450 mm centres: MGP10 spans ~3.6 m; MGP12 spans ~4.0 m.
  • Lintel, 240 × 35 mm, light wind, single storey: MGP10 reaches ~2.7 m; MGP12 reaches ~3.2 m.

(Indicative only; consult AS 1684 span tables for the exact design.)

Visible identification. MGP12 grade stamp appears on every length, often inked in a green or blue stripe for visual identification at the framing yard. The stamp includes:

  • MGP12 designation.
  • Species code (typically RP for Radiata Pine, P for general pine).
  • Treatment hazard class (e.g. H2 for internal framing).
  • Seasoning indicator (KD for kiln-dried).
  • Mill identifier.

Cost. MGP12 is typically 10 to 20% more expensive than MGP10 per linear metre, depending on size and mill. The premium pays off where it lets the design use a smaller section depth or wider joist centres.

For builders.

  1. Don’t substitute MGP10 for MGP12 in span tables. The strength values are different; using MGP10 where MGP12 was specified is a structural compliance breach.
  2. Confirm at delivery. A pallet of MGP10 visually identical to MGP12 is easy to confuse. The grade stamp is the only safe identifier.
  3. Engineered timber alternative. LVL beams can often substitute for MGP12 in lintel and beam applications where appearance is not a factor and the section depth needs to be minimised.

Also known as: MGP12 pine, machine-graded pine 12, MGP-12.

Category: Materials / timber / framing.

See also

Last updated: 2026-05-14. Verified: 2026-05-14.

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