Redwood Lumber Grades and Uses
There are over thirty different grades of redwood lumber including general purpose grades and specialized grades for a single use. There is a grade of redwood for almost any application suitable for wood. Redwood is graded by appearance and durability, with criteria defined by the Redwood Inspection Service.
Excellence of appearance
This is a major factor in the grading of redwood. Clearness (freedom from knots) is the determinant for the highest grades. Other grades are categorized by number, size, and nature of knots and the presence of other characteristics such as stains or manufacturing defects that may occur.
Resistance against insects and decay
Redwood is also graded by its color. Reddish-brown heartwood from the inner portion of the tree contains extractives that render it resistant to insects and decay. The cream-colored sapwood that develops in the outer growth layer of the tree does not possess heartwood’s resistance to decay and insects.
As a rule of thumb, all heartwood grades of redwood will have the word “Heart” in the grade name.
The architectural grades of redwood include Clear All Heart, Clear, Heart Clear, Heart B and B Grade. These grades are normally sold kiln dried (pre-shrunk and stress free) for the finest exterior and interior architectural uses.
No other wood equals these finish grades in beauty and dimensional stability. They are the choice grades for siding, paneling, trim and cabinetry where attractiveness and tight joinery are desired.
The garden grades of redwood include Deck Heart, Construction Heart, Deck Common, Construction Common, Merchantable Heart, and Merchantable. These grades are typically offered seasoned or unseasoned. They are frequently specified for exterior structures where knots or other characteristics have little or no effect.
For uses where the wood will be on or near soil, such as posts, bulkheads or patio grids, it’s essential to use one of the durable, heartwood grades – Clear All Heart, Heart B, Deck Heart, Construction Heart or Merchantable Heart.
For construction above ground where there is little danger of insect or decay issues, one of the sapwood containing grades – Clear, B Grade, Deck Common, Construction Common or Merchantable – will serve very well.