Specifying Redwood


This page provides information and resources about the uses and applications of redwood, maintenance and finishing, and the various redwood lumber grades that are available. If you have additional architectural specification questions about redwood, feel free to Contact Us directly. Our Redwood Lumber and Timber Products profile may also be found on the ARCAT website, where product specifications, catalogues, videos, and LEED information may be found.

Exterior Applications

As an exterior material solution, redwood provides outstanding design and durability capabilities, as well as an excellent sustainable building material choice. Redwood integrates well with most other building materials, particularly materials with a natural aesthetic such as stone. Redwood also provides a material solution for integrating indoor and outdoor spaces within a cohesive design.

Several advantageous performance characteristics of redwood include:

  • Dimensional stability. Redwood has the least volumetric shrinkage of any commercial domestic wood; therefore, it can be subjected to considerably more change in moisture before it has the same change in dimensions as other commercial species. This means that projects manufactured with redwood will be much less subject to open joints, warping, cupping, splitting, and other defects associated with dimensional change.
  • Natural resistance to insects and decay. Redwood heartwood contains tannins which make it is naturally resistant to insects and decay.
  • Easy to finish. Redwood’s open-cell structure with little pitch or resin means it absorbs and holds finishes extremely well.
  • Available in a variety of redwood grades, dimensions, and lengths. Redwood provides architects with multiple design solutions for exterior appearance and style.

Interior Applications

The rich beauty of redwood provides interior spaces with a natural warmth and luxury. Designers have an array of redwood colors, grains, textures, and dimensions to choose from to create truly unique indoor settings with a sustainable interior design aesthetic.

Redwood has a number of inherent qualities that make it ideal as an interior building material:

  • Excellent workability. Redwood is extremely workable and versatile and can be crafted into detailed and interesting patterns in interior applications.
  • High degree of insulation. The low density of redwood means it has higher K and R values and provides a relatively higher degree of insulation than other materials. It also has excellent sound insulation properties.
  • Natural fire resistance. Redwood contains little or no volatile resin, is hard to ignite, and burns slowly. Redwood lumber meets Class II standards in the UBC and BOCA codes and Group I standards in the NBC and SBCCI codes. Redwood construction common and better decking grades are Class B fire rated for use in fire hazard severity zones throughout the state of California.

Maintenance & Finishing

Redwood’s natural durability makes it easy to maintain, so outdoor structures stay strong and beautiful for years with minimal work.

Redwood lumber can be allowed to weather naturally due to its inherent dimensional stability and resistance to decay. Learn more about the low maintenance option for exterior redwood applications.

Regular cleaning of redwood outdoor structures helps keep them looking good over long periods of time. Learn how cleaning redwood can be done with only basic household supplies.

Applying a finish to already naturally decay-resistant redwood can enhance its appearance and extend the time between maintenance.  Finishes can enhance redwoods natural weathering stability, and provide contrasting or complementary design elements with other materials. Exterior finishes include:

  • Clear water repellents with mildewcide
  • Bleaching or weathering stains
  • Semitransparent stains
  • Solid body stains
  • Paints

The California Redwood Association’s Exterior Finishes guide provides general finishing tips and information on finish application, maintenance, and restoration.

For interior surfaces, adding finishes can extend the wide spectrum of color effects that can be achieved in conjunction with different texture and grain patterns. While interior redwood can be left unfinished, a finish will enhance the visual appeal and protect the wood from surface damage. Interior finishes fall into two categories:

  • Clear finishes that allow the wood’s natural grain, texture, and color to show
  • Lightly-pigmented color stains which enhance or contrast the natural colors

Learn more about interior finish options and application guidelines in the California Redwood Associations Interior Finishes guide.

Redwood Grades

Redwood is available in over 30 different general and special use grades – there is a grade of redwood for almost any application of wood. Redwood is graded on appearance and durability based on criteria defined by the Redwood Inspection Service.

There are two primary groups of redwood grades:

  • Architectural grades for the finest interior and exterior applications
  • Garden grades that are often specified for decks, fences, and garden structures where the presence of knots and other natural characteristics will have little or no effect

The California Redwood Association’s Redwood Lumber Grades and Uses guide illustrates and explains the various grades of redwood. Humboldt Redwood offers lumber in a number of Redwood Heartwood and Redwood Sapwood grades.


contact US

Humboldt Redwood Company 125 Main Street
P.O. Box 565
Scotia, CA 95565

(707) 764-4472 – Main Number
(707) 764-4444 – Fax

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