Redwood Lumber is available in more than 30 different grades, from general-purpose grades to highly specialized grades intended for a single specific use. It is graded by appearance and durability, with criteria defined by the Redwood Inspection Service and now administered by the Western Wood Products Association. Grades are dependent on where the board is cut in a tree trunk, how old the tree is, how the wood was developed, and in what direction the board was cut.
There are two primary groupings of redwood grades: Architectural/Appearance and Garden/Structural, with each subcategorized by whether it was cut from heartwood or sapwood. The primary grades are:
Clear All Heart. The finest architectural heartwood grade, typically certified Kiln Dried (but also available unseasoned), well manufactured, and free of defects on at least one face. It comes surfaced or saw-textured. Uses: siding, paneling, cabinetry, millwork, outdoor structures.
Heart Clear. High quality grade similar to CAH, but with limited imperfections allowed. Usually KD, surfaced or saw-textured.
Heart B. Quality heartwood grade with few knots and other characteristics not permitted in Clear All Heart and Heart Clear. Available KD or unseasoned, surfaced or saw-textured. Similar uses.
Clear. Same general quality and uses as previous but contains sapwood in varying amounts and some imperfections not permitted in Clear All Heart.
B Grade. Similar to Clear, but with limited knots and other imperfections.
Construction Heart. Contains knots of varying sizes and other slight imperfections. Offered seasoned or unseasoned, surfaced or rough. Uses: decks, posts, retaining walls, fences, garden structures.
Deck Heart. Similar appearance and uses as Construction Heart, but it is also graded for strength and available only in 2×4 and 2×6.
Merchantable Heart. Economical grade containing slightly larger knots than construction grades, as well as checks, splits and some manufacturing flaws. Offered unseasoned, surfaced or rough. Uses: fences, retaining walls, garden structures.
Construction Common. Similar to Con Heart, but contains both heartwood and sapwood. Unseasoned or seasoned, surfaced or rough. Uses: decks, fences, above-ground garden uses.
Deck Common. Same as Con Common, but graded for strength and available only in 2×4 and 2×6.
Merchantable. Same characteristics as Merchantable Heart, but has sapwood in varying amounts. Unseasoned, surfaced or rough. Uses: fences, rails, above-ground outdoor uses