Redwood (Sequoia sempervirens) is a wonderful evergreen species, with mature trees commonly reaching 300 feet high and 12 feet in diameter. (Giant sequoia is even larger and is a different species.)
In North America, redwood grows primarily in California. Although much of the California redwood forests have been harvested or are now reserved, there are still good supplies, albeit expensive, of redwood logs available from replanted forests, sometimes called second growth, both here in California and in New Zealand. In fact, in New Zealand redwood trees grow so rapidly that within 50 years they are gigantic and ready for harvest. Interestingly, for such a large tree, the cones are scarcely 1 inch in length!
The wood itself, which is mostly heartwood, is lightweight and even grained. It is very red appearing, although second growth may be somewhat lighter in color and in weight. I believe the key properties of redwood lumber that have made it so popular are its low shrinkage (meaning good paintability, little warp in use, and so on) and its natural decay and insect resistance. There are more than 30 lumber grades for redwood lumber.
In addition to sawing logs into lumber, there is also active manufacturing processes using old timers and old lumber that is remanufactured into products for today.
Some old-growth redwood logs are available from forests where the trees have been blown down.
Redwood veneer products are also popular, although only a little redwood is used, with the core veneers being a more available for lumber production at times.
Processing suggestions and characteristics
Density. Redwood weighs about 23 pounds per cubic foot.That’s about 1-1/2 pounds per board foot, kiln-dried and surfaced.
Drying. Drying requires care to avoid severe end splits and collapse. Slow careful drying is the rule, with end coating being essential. With older growth, water pockets and areas of collapse are common. Shrinkage from green to 10 % MC is only about 3 percent. Final moisture contents can be 10-12 % MC.
Gluing and machining. Redwood glues very easily. The open structure requires a little more adhesive than with heavier woods. Avoid excessive pressure. Machining is excellent if tools are sharp. Sharp sandpaper is also important using light pressure.
Stability. Low shrinkage means the wood is very stable when the MC changes in use. This means low warp in-use. It also means that when painted, there will be little stress on the paint film, so paint will adhere and last for years.
Strength. Its strength (MOR) is approximately 7,900 psi, which is a little weaker than Eastern white pine (8,600 psi). Its stiffness (MOE) is 1.1 million psi. Hardness is 420 pounds.
Color and grain. Redwood is almost all heartwood, which is very red in color. The outer rings of the tree are white sapwood, but little of this is included in lumber. Typically, the wood is soft and fine grained. The grain is straight and not as distinctive as with most pines.
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