How to Specify Redwood How to Specify Redwood
Redwood's natural beauty and performance characteristics make it ideal for a wide variety of architectural projects. There is an ideal grade, grain, seasoning and pattern for every project. The information on this page discusses redwood properties and the descriptive details that comprise a complete specification.
Natural beauty is integral to every piece of redwood lumber. Redwood beauty is typified by rich cinnamon-colored heartwood, cream-colored sapwood, distinctive grain and performance that keeps projects looking good for years. Redwood offers a broad array of appearances giving specifiers several choices in color, visual texture and scale.
Natural stability is the key to redwood's long-lasting performance. Redwod out-performs other woods because it shrinks less. This means redwood is less likely to warp, cup, check and pop nails. Stability and little or no pitch content also help redwood hold finishes better. Redwood's stability is a guarantee of long-lasting beauty. The top quality architectural grades of redwood can be ordered "Certified Kiln Dried" which means they will exhibit little or no additional shrinkage in use.
Redwood heartwood provides resistance to both decay from fungus and damage from insect attack. The cinnamon-colored heartwood has decay resistance throughout the lumber, not just on the surface.
No other wood provides the complete performance of redwood. Beauty, stability, durability, finish retention, and workability ensure that redwood projects look better than others when they are new and after they have aged.
Redwood grades are established by the Redwood Inspection Service (RIS). For more detailed descriptions, contact the California Redwood Association or the Redwood Inspection Service.
Clear All Heart
Clear All Heart is the finest grade of redwood. It is all heartwood and the graded face of each piece is free of knots.
Clear is similar to Clear All Heart except that it includes sapwood in varying amounts. Some boards may have one or two small, tight knots on the graded face.
B Heart is an economical all-heartwood grade containing a limited number of small tight knots and other characteristics not permitted in Clear or Clear All Heart. It is graded on one face and one edge.
B Grade is similar to B Heart except that it permits sapwood as well as heartwood.
Lumber is considered vertical grain when the annual growth rings form an angle of 45 degrees or more with the surface. If the angle is less than 45 degrees, the lumber is flat grain. Vertical grain lumber is not susceptible to grain raising. Clear All Heart and Clear may be ordered either flat or vertical grain. Other grades are sold mixed grain.
Architectural grades are available in "Certified Kiln Dried" for top performance and minimal shrinkage. Redwood kiln dried to accepted RIS standards will include the words "Certified Kiln Dried" or "CKD" on the grademark of each piece.
Standard redwood patterns include: tongue & groove, bevel, rabbeted bevel, shiplap, channel shiplap and V shiplap. Board and batten patterns are laid up using standard dimension lumber.
Each pattern has a pattern number. To ensure delivery of the proper product, the pattern number should be included in specifications and on lumber orders.
Surfaced lumber has a smooth-planed face, emphasizing the wood's grain and color. Saw-textured lumber has a resawn face providing a rough textured appearance. Saw-textured redwood has a more even appearance and color and holds finishes longer than smooth surfaces.
To ensure delivery of the proper product, the specification should include: use, grade, grain, seasoning, pattern description, pattern number, and texture.
Redwood lumber for exterior siding shall bear the RIS grade-mark, Clear All Heart grade, vertical grain, Certified Kiln Dried, 1x6 Tongue & Groove, pattern #208R, with a saw-textured face exposed.