Western hemlock trees reach height of 200 feet, with diameters of 3 feet. An exceptional specimen was recorded at 259 feet tall, with a diameter of 108 inches. The heartwood and sapwood of western hemlock are almost white with a purplish tinge. The sapwood, which is sometimes lighter in color, is generally not more than 1 inch thick. The wood often contains small, sound, black knots that are usually tight and stay in place.
Western hemlock is moderately light in weight and moderate in strength.
It is moderate in its hardness, stiffness, and shock resistance. It has moderately large shrinkage, about the same as Douglas-fir. Green hemlock lumber contains considerably more water than Douglas-fir, and requires longer kiln drying time. The wood is intermediate in nail holding ability and has a tendency to split when nailed. It is satisfactory with respect to being glued and in taking stains, polish, varnish and paint.