What Are Different Grades of Redwood Lumber?

Redwood, a type of evergreen tree native to the western United States, produces a high quality timber valued for its appearance, light weight, resistance to insects and decay, and low flammability.

Clear All Heart

Giant redwoods are some of the largest and oldest trees in existence.Giant redwoods are some of the largest and oldest trees in existence.
Redwood lumber comes in several grades, divided into appearance and structural grades. Redwood lumber grades may also be categorized by whether they contain only heartwood, the denser wood at the center of the tree, or some sapwood, the softer wood closer to the bark.

The highest quality architectural grade, clear all heart redwood is entirely heartwood, and certified to be free of defects on at least one face. According to California's Redwood Inspection Service, this wood is best for siding, trim, and high end garden structures.

Heart B

This grade of lumber contains only heartwood, but has some knots and other visual defects not permitted in the higher grade. It makes attractive siding and paneling, and also works well in trim, decks, garden structures and other outdoor buildings.

Deck Heart

This heartwood-only lumber contains imperfections, such as knots, and is further graded for its strength characteristics. Intended specifically for use in decks and railings, this specialty grade of redwood lumber comes only in 2x4 and 2x6 dimensions.

Construction Heart

The appearance of this lumber is similar to that of deck heart. However, construction heart comes in a wider range of shapes and sizes. It's best used in decks, retaining walls, posts and other applications that require the wood to come into soil contact.

Merchantable Heart

This garden grade redwood lumber may include splits, large knots and holes, but is much less costly than other types. It works well in retaining walls and forms, fences and any structure where decay or insect damage are a concern.

Clear

Redwood lumber labeled simply as clear contains some sapwood, but is generally clear of knots and other imperfections on at least one face. It works well for above ground uses like decking, soffits and panels.

B Grade

This redwood sapwood lumber may include limited small knots and imperfections, but must be structurally stable and lack large imperfections. It does well when used as molding, siding, fascia and decking, but should not be used below or in contact with the ground.

Deck Common

Similar to deck heart grade, this lumber is meant for use in decks, but contains some sapwood. Like deck heart lumber, it comes only in a few sizes and has been graded for strength as well as appearance. It's most often used in railings and in portions of decks that do not touch the ground.

Construction Common

This redwood lumber is similar to construction heart lumber, with the addition of sapwood. Like other sapwood lumber, it does poorly when in contact with the ground, and should be reserved for railings, decking and similar uses.

Merchantable

Merchantable sapwood is an economical grade, which may contain splits, large knots, holes and other appearance problems. As it has a lower insect and rot resistance than pure heartwood, it's best used in fence boards, railings and temporary structures.

About the Author

G.D. Palmer is a freelance writer and illustrator living in Milwaukee, Wis. She has been producing print and Web content for various organizations since 1998 and has been freelancing full-time since 2007. Palmer holds a Bachelor of Arts degree in writing and studio art from Beloit College in Beloit, Wis.