Unit 5 Softwood and Hardwood Softwood and Hardwood Trees • Softwood Lumber • Softwood Lumber Standards • Softwood Grading Systems • Grade Marks • Hardwood Lumber • Hardwood Grading System

Softwood lumber comes from evergreen trees, which bear cones and have needle‑shaped leaves. Softwood trees are called conifers. Conifers have thin needles and bear cones from which seeds germinate and grow. See Figure 5‑1. Conifers are commonly referred to as evergreens since they bear green needles throughout the year. Over 75% of the wood used for construction applications is softwood.

Hardwood lumber comes from broad‑leaved, deciduous trees, which lose their leaves in the fall. Most hardwood trees in North America are broad-leaved, deciduous trees, which lose their leaves in the autumn. See Figure 5‑2. Hardwood lumber is typically used for furniture and cabinetry where attractive grain patterns are desired.

Redwood is commonly used for exterior applications, such as fences and siding, since it is decay-resistant. Many softwood species have similar strength and stress characteristics and are used for general applications. However, redwood and western red cedar are more decay-resistant than other species and are rec-ommended for exterior trim, siding, decks, and fences. See Figure 5-3.

Dimension lumber is used for studs, plates, trusses, and other components that form the framework of a building. The Dimension lumber classification includes products that are 2″ to 4″ thick by 2″ and wider and includes studs, joists, planks, roof rafters, trusses, and other components that form the framework of a building. See Figure 5-4. …see complete list of Dimension lumber classifications on page 33.

Timbers are heavy structural members and are commonly used for posts, beams, and stringers. The Posts and Timbers grade group includes lumber that is 5″ × 5″ and larger, with the width not more than 2″ greater than the thickness. Nominal 6 × 6s and 6 × 8s are included in this grade group. See Figure 5-5. Post and Timbers grades include Dense Select Structural, Dense No. 1, Dense No. 2, Select Structural, No. 1, and No. 2.

Appearance grade lumber is used to make interior molding. In most cases, appearance grades apply to lumber 1″ and thicker by 2″ and wider. The highest grades are clear (without knots or other defects) or nearly clear and are used where the beauty of exposed lumber is the primary consideration. Appearance grade lumber is typically used for applications such as moldings, window and door frames, interior paneling, exterior siding, and floor decking. See Figures 5-6.

Appearance grade lumber, including redwood, is used for siding. Appearance grade lumber is typically used for appli-cations such as moldings, window and door frames, interior paneling, exterior siding, and floor decking. See Figures 5-7. Appearance grades range from clear lumber to rustic blue-stained boards that contain knotholes.

Finish appearance grades of redwood lumber may be used for interior paneling. Lumber graded as B & BTR contains very few defects, and is very limited in availability. B & BTR lumber is used for fine furniture, exposed cabinetry, trim, and flooring. See Figure 5-8.

Concrete forms are commonly braced with 4 Common grade lumber. Lumber with the 4 Common grade is the most commonly used grade for bracing members of concrete forms, economical fencing, and crating. See Figure 5-9.

Grade marks stamped on lumber provide grading and other relevant information. Grade marks are stamped on lumber to provide grading information for end users. A typical grade mark includes the official certification mark of the grading association, such as the Western Wood Products Association or Southern Pine Inspection Bureau, lumber grade, mill identification number, wood species, and surfacing and moisture designations. See Figure 5‑10.

Hardwood lumber has an attractive grain pattern and is commonly used for high-quality furniture and cabinets. Hardwood accounts for approximately 25% of total lumber production. Most hardwood species suitable for lumber are grown in the eastern United States. Hard-wood lumber is typically more expensive than softwood. Hardwood lumber is used for moldings, stair treads, outside veneers of doors and wall paneling, and flooring. High-quality furniture and kitchen cabinets are often constructed from hardwood. See Figure 5-11.