Handling & safety. Contains plicatic acid and other compounds. Elevated rate and severity of allergic reactions compared to other commercial woods, particularly occupational asthma.
Properties
| Latin name | Thuja plicata |
|---|---|
| Species type | Softwood |
| Origin | Pacific Northwest United States and Canada |
| Density | 370 kg/m³ |
| Janka hardness | 1,560 N |
| Modulus of rupture | 51.7 MPa |
| Elastic modulus | 7.66 GPa |
| Crushing strength | 31.4 MPa |
| Specific gravity | 0.37 |
| Porosity | Non-porous (softwood) |
| Movement class | Low |
| Tangential shrinkage | 5% |
| Radial shrinkage | 2.4% |
| Volumetric shrinkage | 6.8% |
| T/R ratio | 2.1 |
| Durability (EN 350) | Class 2 |
| Relative cost | Mid |
Density and mechanical properties are typical values at around 12% moisture content. Shrinkage figures represent total dimensional change from fibre saturation to oven dry. Individual boards vary.
Description
Its strengths are practical: it’s easy to machine, relatively stable for exterior boards, and naturally decay resistant, which is why it’s a classic for cladding, shingles and exterior joinery. The flip side is softness—it dents and scratches easily—and it can sand unevenly because of the density difference between earlywood and latewood.
Western red cedar is chosen when you want an exterior timber that stays light, stable and long-lasting without chemical treatment. It’s an “exterior specialist” softwood: not structural powerhouse timber, but superb when the job is weathering and longevity.
Anatomy
- Porosity: Non-porous
- Vessel Arrangement: N/A — softwood. Thuja plicata (Cupressaceae) lacks normal resin canals — a key diagnostic feature distinguishing it from Pinaceae softwoods like pine and spruce.
- Vessel Description: N/A — softwood. Normal resin canals absent (characteristic of Cupressaceae). Traumatic resin canals may occur in response to injury.
- Parenchyma: Axial parenchyma present; in Cupressaceae often in fusiform strands adjacent to resin canals (when present).
- Rays: Uniseriate to biseriate; ray cells are usually square to upright (procumbent ray cells less common than in Pinaceae). Typically 1–20 cells high.
Durability
- Durability Class: Class 2 — Durable
Rated as durable to very durable in regard to decay resistance, though it has a mixed resistance to insect attack.
Odor
Has a strong, lingering, aromatic scent when being worked.
Uses & Availability
Common Uses
Shingles, exterior siding and lumber, boatbuilding, boxes, crates, and musical instruments.
Pricing & Availability
Moderately inexpensive for construction-grade lumber, though higher grades of clear, straight-grained, quartersawn lumber can be more expensive.
Conservation
- CITES Status: Unlisted
- IUCN Status: Least Concern
Lookalikes & Substitutes
Coast redwood (Sequoia sempervirens) has closest weight, appearance, and similar geographic distribution, but tends to have darker heartwood and lacks the characteristic scent of western red cedar.
Working the timber
Easy to work with both hand or machine tools, though it dents and scratches very easily due to its softness, and can sand unevenly due to the difference in density between earlywood and latewood zones. Glues and finishes well. Iron-based fasteners can stain and discolor the wood.
Finishing & gluing
Western red cedar contains water-soluble extractives that can bleed and cause tannin-like staining under some paints and water-based finishes, so a stain-blocking primer is worth it on light-coloured coating systems. It’s very soft and has strong earlywood/latewood density differences, so over-sanding can leave a washboard surface that telegraphs under clear coats—light pressure and a sharp finish scraper help. Outdoors, expect rapid colour fade to silver; if you want to hold the warm reds, use a UV-resistant exterior oil/stain and accept regular maintenance.
Cedar usually glues well with PVA and PU, but its softness makes joint fit and clamp pressure critical—over-clamping crushes fibres and can starve the joint. Freshly prep the surfaces (don’t glue over burnished planer sheen) and de-dust thoroughly, as the low-density earlywood can hold sanding debris. For exterior work, PU or epoxy is often the more durable choice as joints cycle wet/dry.