Douglas fir

In natural stands in North America:

• grows 40–60m high
• reaches 1–2m diameter
• trunk is clear of branches for about two-thirds of its height, and therefore produces a high percentage of clear wood
• bark is very fibrous.

• Occurs naturally on the west coast of the USA and Canada.
• A plantation species in other countries, particularly New Zealand.
• Sawn timber is readily available.

Colour

• Heartwood ranges from yellowish through orange to deep red.
• Sapwood is sometimes distinctly paler.

Grain

• Generally straight.
• Obvious difference in colour between earlywood and latewood results in a very distinctive figure (pattern) when back-sawn.

Other

• Sapwood varies from 50mm wide in mature trees to 75mm in faster-grown plantation stems.

• Engineering: sawn timber in heavy building construction (must be protected from the weather).
• Construction: sawn timber in general house framing, flooring, lining, fascias, bargeboards and pergolas; not suitable for use in contact with the ground or for above-ground, weather exposed structures.
• Decorative: furniture, plywood, joinery, turnery, carving.
• Others: boat building (light), boat oars, scaffold planks, timber vats.

• Density:
  • North America: 560kg/m³ at 12% moisture content; about 1.8m³ of seasoned sawn timber per tonne
  • New Zealand: 480kg/m³; about 2.1m³/tonne.
• Strength groups:
  • North America: S5 unseasoned, SD5 seasoned
  • New Zealand: S6 unseasoned, SD6 seasoned.
• Stress grades when visually stress graded in accordance with AS 2858—2001: Timber—Softwood—Visually stress-graded for structural purposes:
  • North America: F4, F5, F7, F8, F11 (unseasoned); F7, F8, F11, F14, F17 (seasoned)
  • New Zealand F4, F5, F7, F8 (unseasoned); F5, F7, F8, F11, F14 (seasoned).
• Shrinkage to 12% MC: 5.0% (tangential), 3.0% (radial).
• Unit shrinkage: 0.38% (tangential), 0.23% (radial).
• Durability above-ground: Class 4 (life expectancy less than 7 years).
• Durability in-ground: Class 4 (life expectancy less than 5 years).
• Lyctine susceptibility: sapwood not susceptible to lyctine borer attack.
• Termite resistance: not resistant.
• Joint groups:
  • North America—J4 unseasoned, JD4 seasoned
  • New Zealand—J5 unseasoned, JD4 seasoned.
• Preservation: sapwood and heartwood are both very resistant to impregnating with commercial preservatives.
• Seasoning: satisfactorily dries using conventional air and kiln seasoning.
• Hardness: firm (rated 4 on a 6-class scale) to indent and work with hand tools.
• Machining: machines, and turns well, but keep planer blades sharp to avoid surface ridging.
• Fixing: nails may follow the growth rings; be careful using standard fastenings and fittings.
• Gluing: satisfactorily bonds using standard procedures.
• Finishing: some material has high resin content and earlywood/latewood ridging of dressed timber—carefully select timber for finishing and preparing surfaces for paint and varnish.

General characteristics

• Sapwood: usually paler than heartwood but sometimes indistinguishable.
• Heartwood: variable; yellowish to orange-red or deep red.
• Texture: fine with prominent growth rings; grain normally straight except where knots are present.

Wood structure

• Growth rings: very distinct; transition from earlywood to latewood is very abrupt; latewood ranges from very narrow to very wide.
• Resin canals: uncommon but occurring both in longitudinal and radial directions and visible only with a lens.
• Vessels: absent.
• Parenchyma (soft tissue): none visible.
• Rays: fine, not visible without a lens

Other features

• Odour: distinctive odour.

• Ilic, J 1991, CSIRO atlas of hardwoods, Crawford House Press, Bathurst, Australia.
• Queensland Government, DAF 2018, Construction timbers in Queensland: Properties and specifications for satisfactory performance of construction timbers in Queensland. Class 1 and Class 10 buildings, Books 1 & 2, Department of Agriculture and Fisheries, Brisbane.
• Standards Australia, 2008, AS 2858—2000: Timber—Softwood—Visually stress-graded for structural purposes, Standards Australia International, Strathfield, NSW.