Density of Softwood Timber

Wood is the most variable structural material in common use. Kiln-dried spruce-pine-fir runs about 420–470 kg/m³, Douglas fir-larch 500–540, southern yellow pine 550–620, and dense hardwoods like white oak reach 750 kg/m³. Within a single species and grade, specimen-to-specimen scatter of ±15 % is normal, because density tracks growth-ring spacing and the ratio of latewood to earlywood.

Moisture content is the other half of the story and the usual trap. Wood density is only meaningful with a moisture content attached: green lumber at 40 % MC can be 50 % heavier than the same stick at the 12 % equilibrium moisture of a heated building, and the piece shrinks 3–4 % across the grain on the way down. Use 500 kg/m³ for estimating dead load and shipping weight, and use the species-specific specific gravity from the NDS supplement for anything structural: connection capacity in particular is computed directly from oven-dry specific gravity, not from this figure.