How Thick is 8/4 Lumber in Construction in USA

In U.S. construction, 8/4 lumber is a standard term used in the hardwood industry, representing a nominal thickness of 2 inches. This specific size of lumber is highly regarded for its structural integrity, dimensional stability, and versatility across various residential, commercial, and custom woodworking applications. Understanding the exact thickness, real-world use, and processing implications of 8/4 lumber is essential for builders, architects, and craftsmen.

Actual Thickness of 8/4 Lumber

The designation 8/4 refers to eight quarters of an inch, meaning the nominal thickness is 2 inches. However, the actual thickness can differ depending on the stage of processing:

• Rough Sawn Thickness: 2.00 inches
• After Surfacing (S2S or S4S): 1.75 inches to 1.8125 inches

This difference is due to planing, which smooths the surfaces for precision use in fine construction and cabinetry.

Lumber Thickness Conversion: Imperial to Metric

For international and metric-based construction, the thickness of 8/4 lumber translates as follows:

• 2.00 inches = 50.8 mm
• 1.75 inches (surfaced) = 44.45 mm

Builders often refer to 50 mm hardwood stock as a metric counterpart to 8/4, especially when sourcing imported or specialty materials.

Applications of 8/4 Lumber in Construction

Furniture Making and Cabinetry

8/4 hardwood boards are preferred for solid wood tabletops, benches, legs, and stiles. Their thickness provides the structural heft and grain visibility needed for high-end furniture.

• Used in dining tables, kitchen islands, and bookcases
• Enables joinery techniques such as mortise and tenon
• Offers a premium grain finish for aesthetic appeal

Architectural Millwork and Trim

Builders incorporate 8/4 stock into crown molding, window sills, mantels, and coffered ceilings where substantial dimensional lumber is required.

• Provides depth and shadow lines in interior designs
• Easily customized with routering and CNC milling
• Ensures durability in high-traffic or decorative features

Stair Components and Rail Systems

Due to its strength, 8/4 material is suitable for constructing newel posts, handrails, and tread supports.

• Supports weight without warping
• Allows for precision shaping and detailing
• Offers superior support over thinner cuts

Solid Wood Countertops and Bar Tops

8/4 slabs are frequently used in the fabrication of butcher block tops, live edge counters, and commercial bars.

• Can be laminated for added width
• Durable against impact and wear
• Compatible with food-safe finishing products

Common Wood Species in 8/4 Lumber

In the U.S., 8/4 lumber is predominantly available in hardwood species. These include:

• Hard Maple – High density, pale color, excellent for furniture
• Black Walnut – Rich brown tones, luxurious appearance
• White Oak – Durable, moisture-resistant, good for interiors and exteriors
• Cherry – Smooth grain, deepens in color with age
• Ash – Strong, shock-resistant, easy to work with

These species influence the cost, workability, and finishing characteristics of the lumber.

Surfacing Options for 8/4 Lumber

Rough Sawn

• Full 2-inch thickness
• Allows for custom milling
• Ideal for joinery where precise fit is essential

S2S (Surfaced Two Sides)

• Planed on face surfaces only
• Edges left rough for trimming
• Suitable for projects requiring minimal finishing

S4S (Surfaced Four Sides)

• Ready-to-use finish
• Exact dimensioning for precision installations
• Preferred in commercial millwork or retail-ready applications

Moisture Content and Shrinkage

8/4 lumber is particularly sensitive to moisture due to its thickness. Lumber is typically kiln-dried to 6%–8% moisture content before shipping. Without proper seasoning:

• Warping, cupping, or checking may occur
• Thickness can shrink by up to 3%
• Wood becomes unstable for precision applications

To mitigate these effects:

• Store indoors in a controlled humidity environment
• Acclimate lumber to the installation site before use
• Apply sealers or stabilizers for outdoor applications

Weight and Handling of 8/4 Lumber

Due to its thickness and density, 8/4 boards are significantly heavier than thinner stock.

For example, a 10-foot 8/4 oak board measuring 10 inches wide could weigh over 35 pounds, requiring special care in transport and installation.

Dimensional Tolerances and Grading

Lumber graded as FAS (First and Seconds) in 8/4 offers the highest yield of clear wood. Other common grades include:

• Select: Slightly more defects than FAS
• #1 Common: Economical, with limited clear area
• #2 Common: Suitable for rustic or utility applications

Each board must meet NHLA (National Hardwood Lumber Association) standards for thickness, width, length, and defect limitations.

Cutting and Milling Considerations

Thicker boards like 8/4 require:

• Sharp, high-torque saw blades to reduce burning
• Slower feed rates during planing and routing
• Robust clamping systems for edge-gluing

Milling techniques such as resawing, ripping, and laminating are often used to transform 8/4 into smaller dimensional parts or wide panels.

Cost Analysis of 8/4 Lumber

Pricing varies based on:

• Species
• Grade
• Finish (rough vs. surfaced)
• Market availability

As a rough estimate:

• Hard Maple 8/4: $6.00 – $9.00 per board foot
• Walnut 8/4: $10.00 – $14.00 per board foot
• Cherry 8/4: $7.00 – $11.00 per board foot

Specialty cuts such as live edge slabs or wide boards may command significantly higher prices.

Where to Source 8/4 Lumber in the USA

8/4 lumber is widely available at:

• Hardwood lumber yards
• Specialty woodworking retailers
• Online suppliers offering nationwide delivery
• Mills that cater to architectural and custom builds

Always verify moisture content, surfacing level, and grading before purchase.

Conclusion

8/4 lumber in U.S. construction plays a vital role where strength, thickness, and visual appeal are required. Its actual thickness of 2 inches (rough) or approximately 1.75 inches (surfaced) makes it the preferred choice for furniture makers, architects, craftsmen, and contractors alike. With its ability to be crafted, shaped, and finished into lasting, high-value components, 8/4 hardwood continues to serve as a foundational element in premium construction and woodworking projects.