Redwood — Density, Movement, Workability & Cost

A redwood board cuts like butter under a sharp blade and crushes just as easily under a careless clamp — a combination of extreme stability and extreme softness that makes coast redwood (Sequoia sempervirens) simultaneously one of the easiest woods to mill and one of the most frustrating to handle carefully.

Stable and soft in a combination few other species share

At 26 lb/ft³ and 450 lbf on the Janka scale, redwood is light and gives easily under point pressure, so clamping with cauls and pre-drilling near board ends are standard precautions rather than optional extras. What sets it apart is dimensional stability: a low, well-balanced shrinkage profile keeps it flat and quiet through humidity swings that would move a less stable softwood noticeably more.

Movement, and old-growth versus young-growth grading

Radial shrinkage of 2.4% against a tangential figure of 4.7% gives a 2.0 ratio right at this site's movement-prone threshold, though the small absolute numbers keep real movement modest — FPL's own tables actually separate old-growth figures (2.6/4.4/6.8) from young-growth (2.2/4.9/7.0), and this page uses The Wood Database's average across both. Redwood fence pickets and lap siding are commonly milled at 8" nominal width, and that's where the low ratio pays off in practice: seasoning from a wet 15% down to a drier 9% sheds only about 0.075" (1.9mm) across the face — modest movement even by redwood's own low-shrinkage standard, and part of why old clear-heart fences stay flat for decades. Run a different width through the wood movement calculator. Milled 1" thick and 12 feet long for a deck run, the same board weighs about 17.3 lb — the wood weight calculator covers other decking sizes.

Gluing, and a finishing trap that catches people off guard

Redwood glues well, though the low density means end grain wants a sizing coat to avoid a starved joint. The real finishing hazard is tannin bleed: this species' natural tannins will bleed straight through water-based finishes and light-coloured paint, staining the topcoat from underneath — a stain-blocking primer or an oil-based finishing system is essential rather than optional if a light, even colour is the goal.

Durability that depends entirely on which grade you buy

Old-growth heartwood is very durable, genuinely worth using unprotected outdoors for decades. Young-growth sapwood has essentially none of that resistance, which makes grade — not just species — the deciding factor for any outdoor redwood purchase far more than it is for most other woods. It holds at roughly $9 per board foot, moderate on this site's scale. Decking and siding, outdoor furniture, hot tubs, fascia and trim, and garden structures round out its uses, virtually all of which depend on getting the heartwood-versus-sapwood grade question right.

Why grade matters more here than almost anywhere else

Old-growth coast redwood is now largely protected, and essentially all commercial supply is second-growth — a genuinely different product from the legendary old-growth material in both colour and durability. A buyer specifying redwood for ground contact or sustained outdoor exposure needs to confirm heartwood content specifically, since young-growth sapwood in the same board offers dramatically less protection despite carrying the same species name.

What people actually ask about redwood

How can I tell old-growth redwood from second-growth at a lumberyard? Ring count is the reliable visual tell — old-growth heartwood shows far tighter, more closely spaced growth rings from decades of slow growth, while second-growth boards show wider, more open rings; colour alone isn't a safe indicator since both age toward a similar reddish-brown.

Can existing tannin staining on a redwood deck be removed once it's shown up? Often, yes — stripping the finish and treating the surface with an oxalic-acid wood bleach before refinishing with an oil-based or stain-blocking system will lift most bleed-through staining, though a badly weathered board may need a light sanding pass first for the bleach to reach fresh wood.

What is "sequoiosis" and should I be worried about it? It's a rare hypersensitivity pneumonitis linked to prolonged, heavy exposure to redwood dust, documented mainly in workers with sustained occupational exposure rather than occasional hobbyist use — normal shop ventilation and dust collection are sensible precautions regardless.

Redwood's density, Janka hardness and shrinkage figures come from The Wood Database's 12%-moisture-content testing, which also cites the USDA Forest Products Laboratory's Wood Handbook (FPL-GTR-190, 2010) as its underlying source. Coast redwood also holds the record for tallest tree species on Earth, with documented living specimens over 380 feet — a scale that has nothing to do with the wood's stability at the bench, but explains why old-growth boards could once be milled in dimensions no longer commercially available.