Western red cedar (Thuja plicata): the premium joinery timber
Western red cedar (Thuja plicata) is the premium AU joinery timber: low density, naturally durable DC2 above-ground, dimensionally stable, paint-grade or clear-finish.
Ask Chalkline about this →Western red cedar (Thuja plicata) is the premium softwood for Australian residential joinery, mainly imported from North America. It is the high-end choice for timber windows, external doors, internal joinery, and weatherboard cladding, sitting above dark red meranti and well above treated pine in both price and reputation. For cladding-specific install detail see western red cedar cladding; this article covers the timber as a species across joinery and finish applications.
What it is
Western red cedar is a softwood from the Cupressaceae family, native to the Pacific Northwest of North America. The relevant species traits for builders:
| Property | Typical value |
|---|---|
| Density (air-dry) | ~370 kg/m³ |
| Natural durability (above-ground heartwood, AS 5604) | DC2 (high) |
| Natural durability (in-ground) | DC4 (low, not for ground contact) |
| Dimensional stability | High (low moisture-cycling movement) |
| Workability | Easy to saw, machine, plane, sand |
| Finish acceptance | Paint, oil, clear coats all accept well |
The low density makes large sashes and tall door leaves manageable in service (a 1,500 mm-high meranti sash weighs noticeably more than the equivalent cedar). The high dimensional stability is what keeps the finished joint tight as the seasons cycle.
Where it suits
Windows and external doors. The dominant Australian cedar joinery use, often through brands like Stegbar (Timberaul) and other custom timber-window manufacturers. The natural durability gives a 15-40 year service life on heartwood-rich members without preservative treatment, provided the surface coating is maintained.
Internal joinery and cabinetry. Where the look is wanted and the budget allows. Less common than meranti or radiata pine because of cost, but the workability and finish-acceptance make it a pleasure to work with.
Weatherboard cladding. Covered in detail in the cladding article, including the fixings rule (stainless or silicon-bronze only; ordinary galvanised stains the surface within months due to tannin reaction).
Outdoor pergolas, screens, lining. Where DC2 above-ground durability is enough and ground contact is avoided.
What it is not for
- Ground contact (posts, ground-fixed beams, retaining members): the in-ground rating is DC4 (low). Use a ground-rated species or treated pine.
- Structural framing: cedar is too soft (low density, low MoE) for span-table applications. Use radiata pine framing.
- High-impact wear surfaces (treads, sills with heavy traffic): cedar dents and scuffs more readily than hardwood; choose harder species for high-contact use.
Maintenance cycle
Cedar’s natural durability assumes the surface coating is maintained. Builder and client should expect:
- Initial coating at install (factory primer plus site-applied finish coats; oil, stain, or paint per design).
- Recoating every 3-7 years depending on exposure (sun, weather, salt). North-facing and exposed elevations cycle faster than south-facing or sheltered.
- Inspection of sapwood-exposed faces: heartwood is DC2, sapwood is lower durability. Mill-supplied joinery typically uses heartwood-rich sections, but cut edges and finger-jointed members can expose sapwood. Re-coat exposed sapwood proactively.
Skipping coats accelerates surface checking, sapwood decay, and tannin leaching. The maintenance interval is what keeps the 30+ year service life real.
How it compares
| Western red cedar | Dark red meranti | Accoya (modified pine) | |
|---|---|---|---|
| Density | ~370 kg/m³ (low) | ~600 kg/m³ (medium) | ~510 kg/m³ |
| Durability (above-ground) | DC2 | DC3 | Extended via acetylation |
| Cost | Premium | Mid | Premium |
| Dimensional stability | High | Medium | Very high |
| Paint and stain acceptance | All finishes | Good for paint | All finishes |
| Best for | Large sashes, heritage look | Volume window joinery | Hard-service exposed work |
Meranti is the volume choice for cost-driven jobs; cedar is the look-and-stability choice; Accoya is the engineered alternative when extended service life with painted finish matters.
For a builder
- Specify by species and grade. “Western red cedar, kiln-dried, heartwood-rich, vertical grain where visible” tells the joinery shop the quality level. Generic “cedar” can mean anything from heart-WRC to Eastern white cedar.
- Lead time matters. Custom cedar joinery (Stegbar Timberaul, Trend) runs 6-12 weeks. Order at frame stage, not at lock-up.
- Coat at the factory. A factory primer keeps the sapwood from absorbing moisture before site coatings go on. Site-only coating is a maintenance and warranty downgrade.
- Brief the client on the cycle. The 3-7 year recoat is part of cedar ownership; clients who expect “natural” cedar with no maintenance get unhappy.
References
- Standards Australia, AS 5604 Timber, Natural durability ratings (verified 2026-05-29).
- Mortlock Timber, Timber Durability Classes Explained (verified 2026-05-29).
- Stegbar, Timberaul timber windows range (verified 2026-05-29).
Related
See also
Last updated: 2026-05-29. Verified: 2026-05-29. Quarterly review for currency.