chalkline. Snap the line. Build to it.
glossary Glossary 3 min read

Seasoned timber

Seasoned timber is dried to 15% moisture or below before delivery. Standard for pine framing; reduces shrinkage and frame distortion. AS 1684 separates seasoned tables.

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

Ask Chalkline about this →

Seasoned timber is structural timber dried, by kiln (KD) or air, to a moisture content (MC) of 15% or below before delivery to site. The drying brings the wood to a state close to its in-service equilibrium moisture content, so the framing does not shrink significantly after install.

Unseasoned (or green) timber is delivered at higher moisture content, typically 25% to over 50%. Green timber continues to lose moisture in situ until it reaches equilibrium with the building’s interior environment. The shrinkage between delivery and equilibrium is what causes the visible problems in finished framing.

Why seasoned matters on a residential build:

  • Less shrinkage after fixing. Pine framing shrinks roughly 0.1% per 1% moisture-content drop in the radial and tangential directions. A green plate at 30% MC drying to 12% MC shrinks ~1.5% across its width: noticeable in a 90 mm plate.
  • Fewer screw pops in plasterboard. Most pops trace back to framing that shrank and pulled away from the screw head.
  • Tighter joints at corners, T-junctions, and floor-to-wall meetings.
  • Less twist and bow in long members (top plates, studs over 2.7 m).
  • Reduced re-trim risk. Architrave, skirting, and cabinet returns that match a frame at handover may gap or crack if the frame keeps drying.

AS 1684 implications. AS 1684 publishes separate span tables for seasoned and unseasoned timber. Seasoned-pine F-grade tables and the MGP-graded tables are not interchangeable with unseasoned tables. Using a seasoned table for unseasoned timber is a structural compliance breach because the strength values differ between the two states.

How to confirm seasoning. Two signals:

  1. The grade stamp carries a seasoning indicator: KD (kiln-dried), SD (seasoned, air-dried), or no marker (unseasoned).
  2. A moisture meter reading at delivery. Two-pin contact meters or pinless capacitance meters give a quick read. Spec calls for 15% or less at delivery, allowing some tolerance.

For builders.

  1. Specify “MGP10 KD” or “seasoned pine” in the quote. “MGP10” alone does not commit the supplier to dry.
  2. Reject high-MC deliveries. A pallet reading 25% or more at the meter is too wet for a seasoned-pine application.
  3. Site storage matters. Even seasoned timber re-wets if stored uncovered in rain. Cover stockpiles, store off the ground on dunnage, and ventilate.

Other species and applications.

  • Hardwood: seasoned hardwood is the standard for floor joists, flooring, and visible structural beams. Unseasoned hardwood is sometimes used for bridge timbers and railway sleepers, not residential.
  • Engineered timber (LVL, Glulam, I-joist) is manufactured at low controlled MC and is treated as seasoned for span-table purposes.

Also known as: KD timber, kiln-dried timber, dry timber, seasoned framing.

Category: Materials / timber / moisture.

See also

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

Related articles