Western Hemlock — Density, Movement, Workability & Cost

Move from eastern hemlock to western hemlock (Tsuga heterophylla) and you're working a genuinely different-feeling wood despite the shared name — straighter, finer, and dramatically less prone to the ring shake that plagues its eastern relative, which is exactly why the West Coast building trade treats it as a legitimate clear-trim species rather than just barn-siding stock.

The presentable hemlock

At 29 lb/ft³ and 540 lbf on the Janka scale, western hemlock is close in weight and hardness to its eastern cousin, but it machines to a clean, pale surface that's genuinely suitable for interior work meant to be seen. Black flecks — healed insect galleries — are the species' characteristic and expected defect, showing up in nearly every board without meaningfully affecting strength or appearance once finished.

Movement, and a typical interior-trim weight

Tangential shrinkage of 7.8% against a radial figure of 4.2% gives a 1.9 ratio, just under this site's movement-prone line — better-behaved than eastern hemlock's 2.3, consistent with the overall cleaner working character. A 10"-wide board moving from a 12% moisture content to a dry 6% loses about 0.156" (4mm) across its width; different widths run through the wood movement calculator. A 3/4"-thick, 4"-wide, 7-foot interior trim board weighs about 4.2 lb; the wood weight calculator covers other trim sizes.

Working it, and where it actually gets used

Gluing is reliable, with the coarse surface taking adhesive readily. It accepts both paint and clear finishes evenly, giving it real versatility that its downgraded eastern relative doesn't offer to the same degree — a pale, neutral ground that works whether the final look is natural or coloured. This versatility is exactly why it's the standard clear interior-trim and door wood across much of the West Coast building industry.

Durability, cost, and a wood that plays two roles

Western hemlock is non-durable, though it takes preservative treatment better than most true firs, giving it slightly more flexibility for borderline exterior applications than a species like white fir would offer. At roughly $4 per board foot it's inexpensive, priced close to red alder. Interior trim and doors, framing, plywood, staircases, and pulp round out its uses — the trim and framing uses both draw from the same species, graded and directed to whichever market a given log's quality supports.

Its place in a grading group, and what that means for buyers

Western hemlock is the dominant species in the hem-fir grading group sold across the western lumber trade, bundled together with several true fir species that share close enough structural properties to be treated as interchangeable for framing purposes — buying "hem-fir" studs at a yard doesn't guarantee this exact species, though it's the most common single constituent.

What people actually ask about western hemlock

Do the black flecks in western hemlock get worse or more numerous with the tree's age? Not meaningfully — the galleries form during a fairly narrow window of the tree's growth when it's most vulnerable to the responsible insects, so an older, larger tree doesn't show proportionally more flecking than a younger one milled at commercial size.

Is western hemlock a good substitute for pine in interior trim work? Yes, reasonably — it machines to a comparably clean, pale surface and takes finish evenly, though it lacks pine's long resin-streak character and has its own distinct black-fleck appearance instead.

How much more does treated western hemlock cost compared to leaving it untreated for a covered exterior application? Pressure or dip treatment typically adds a real but modest premium over the raw board price, and for anything under a roofline where sustained wet exposure isn't the issue, that added cost against a naturally durable species like western redcedar usually favours hemlock on price alone.

Why would a mill stamp lumber "hem-fir" instead of just labeling it western hemlock directly? Grading multiple similar species together lets a mill process whatever comes off a given truck without sorting logs by exact species first, and since the bundled true firs meet the same structural spec, there's no functional reason for a framing buyer to need species-level precision on the stamp.

Western hemlock has been Washington State's official state tree since 1947, reflecting how dominant it is across the wetter parts of the Pacific Northwest timber industry. (The Wood Database's 12%-moisture-content testing is the source for density and Janka hardness above; shrinkage is FPL's Table 4-3 figure.)