Redwood is a popular building material, valued for its appearance and resistance to the elements. Its hardness is a key factor in determining its suitability for various projects. Understanding wood hardness helps in selecting the right material for specific applications, ensuring longevity and good performance.
How Wood Hardness is Measured
Wood hardness is primarily assessed using the Janka hardness test, an industry standard for determining a wood’s resistance to denting and wear. This test measures the force required to embed an 11.28-millimeter steel ball halfway into a wood sample. The Janka rating is typically expressed in pounds-force (lbf) in the United States, though other units like kilonewtons (kN) or kilograms-force (kgf) are used elsewhere. A higher Janka number indicates greater resistance to denting and wear, making the wood more durable for applications like flooring. The test is usually performed on wood from the heartwood, taken at a 12% moisture content, and free of knots.
Redwood’s Specific Hardness
Redwood is classified as a softwood. Its Janka hardness rating typically ranges from 420 to 480 lbf, placing it lower than many hardwoods, such as red oak (1290 lbf). The specific hardness of redwood can vary depending on its origin. Old-growth redwood generally exhibits a higher Janka rating of around 480 lbf due to its denser wood and tighter growth rings. In contrast, second-growth redwood typically has a lower rating of about 420 lbf. Despite being a softwood, redwood offers notable durability and resistance to warping.
Hardness and Redwood’s Common Uses
Redwood’s relative softness influences its suitability for various applications. While not ideal for high-impact uses like flooring, its other properties make it a preferred choice for many outdoor projects. Redwood is frequently used for decking, siding, fencing, and outdoor furniture. Its natural resistance to decay, insects, and moisture, due to tannins and oils in its heartwood, contributes to its longevity in exterior settings. Redwood also boasts good dimensional stability, meaning it is less prone to shrinking, warping, or checking, and its lightweight nature and appealing reddish-brown hues make it a versatile material.
Working with Redwood
Redwood’s relative softness makes it notably easy to work with using both hand and power tools. It cuts, nails, glues, and sands well. When nailing or screwing, its softer nature means it is less likely to split. Due to its open-celled structure and low resin content, redwood readily absorbs and retains finishes, contributing to its aesthetic appeal and long-term protection. This ease of manipulation makes redwood a favored material for projects where precise shaping and finishing are desired.