6 x 6 Nominal Size in Construction in the USA

Understanding the Nominal vs. Actual Size of 6×6 Lumber

In construction, understanding the difference between nominal and actual sizes of lumber is crucial. The term 6×6 nominal size refers to a piece of wood that, in theory, measures 6 inches by 6 inches. However, due to the drying, planing, and smoothing process that occurs in milling, the actual dimensions of a 6×6 board are typically smaller. The standard actual size of a 6×6 is 5½ inches by 5½ inches.

This difference is a common occurrence in most dimensional lumber in the United States. The nominal size is used for simplicity in classification, while the actual size reflects the true measurements of the wood after it has been processed.

What Are the Common Uses of 6×6 Lumber in Construction?

Structural Support in Heavy Construction

One of the primary uses of 6×6 lumber in construction is for structural support in heavy-duty applications. Because of its larger size and superior strength, a 6×6 board is ideal for projects that require additional load-bearing capacity. Common structural uses include:

• Supporting beams in large buildings
• Posts for fences and retaining walls
• Vertical support posts in decks and outdoor structures
• Heavy framing members for commercial construction projects

These applications take advantage of the robust nature of a 6×6 piece of lumber, ensuring that the structure remains stable even under significant weight or pressure.

Outdoor Applications

The 6×6 nominal size is particularly common in outdoor construction due to its durability and ability to withstand the elements. Pressure-treated 6×6 lumber is frequently used for:

• Deck posts and railings
• Pergolas and gazebos
• Playground equipment
• Dock posts and marine structures

These applications benefit from the strength and weather-resistant qualities of 6×6 treated lumber, which can withstand moisture, insects, and rot much better than smaller dimensions.

Timber Framing

In timber framing, 6x6s are often used for major load-bearing components like:

• Beams in the roof structure
• Columns in large homes or commercial buildings
• Cross members that support rafters or trusses

These boards provide exceptional strength, which is essential for maintaining the integrity of larger structures and ensuring they stand the test of time.

Pressure-Treated 6×6 Lumber

For outdoor applications, pressure-treated 6×6 lumber is a standard choice. Pressure treatment involves infusing the wood with chemicals that help protect it from environmental hazards, such as:

• Wood rot
• Pests, including termites
• Fungi and mildew

When 6×6 lumber is pressure-treated, it is infused with preservative chemicals under high pressure, which forces the chemicals deep into the wood fibers. This process allows the lumber to withstand moisture exposure and be used in environments where untreated wood would quickly deteriorate.

Common uses for pressure-treated 6×6 lumber include:

• Outdoor decks where durability is critical
• Fencing posts, which are buried in the ground
• Support posts in areas with high moisture, like near pools or ponds

The lifespan of pressure-treated 6×6 lumber can range from 20 to 40 years depending on the type of preservative used and the environmental conditions.

Weight and Handling of 6×6 Lumber

Due to its size and strength, 6×6 lumber is relatively heavy, which can impact how it is handled on the job site. The weight of a 6×6 board will depend on the wood species, moisture content, and whether it is pressure-treated. On average:

• Dry 6×6 lumber weighs around 10 to 12 lbs per foot
• Pressure-treated 6x6s can weigh 12 to 16 lbs per foot or more

Given the weight, proper handling techniques, such as using lifting equipment or teamwork, are essential to ensure safety and prevent damage to the wood.

Dimensional Tolerances in 6×6 Lumber

When working with 6×6 boards, it’s important to be aware of the dimensional tolerances. Due to natural variations in wood, the actual dimensions of 6×6 lumber can vary slightly:

• Actual dimensions typically measure 5½ inches by 5½ inches
• Tolerances for this dimensional lumber are usually within 1/16 to 1/8 inch depending on milling standards and wood species

These slight variances mean that 6×6 lumber must be carefully inspected during construction, especially when precise dimensions are critical to the project’s overall performance.

Wood Species for 6×6 Lumber

The species of wood chosen for 6×6 lumber plays a significant role in determining the board’s strength, durability, and suitability for various applications. Common wood species used for 6×6 lumber include:

Southern Yellow Pine

• Known for its strength and resilience under heavy loads.
• Pressure-treated Southern Yellow Pine is commonly used for outdoor construction, such as deck posts and fence posts.

Douglas Fir

• Offers good dimensional stability and is often used in structural framing and timber framing for both residential and commercial buildings.
• Particularly known for its strength-to-weight ratio, making it ideal for load-bearing applications.

Redwood and Cedar

• Typically used for aesthetic purposes, these species are resistant to rot and insects and are ideal for outdoor applications where appearance is important, such as in landscape framing or decking.

Cost of 6×6 Lumber

The cost of 6×6 lumber varies depending on factors such as:

• Wood species
• Pressure treatment
• Length of the board
• Local supply and demand

On average, 6×6 lumber can cost anywhere from $3 to $10 per linear foot for common species like pine. The price increases significantly for premium woods like redwood or cedar, or for pressure-treated lumber, which can add $2 to $4 per foot to the cost.

For large-scale construction, purchasing 6×6 lumber in bulk often results in a discount per unit, helping to reduce overall project costs.

Safety Considerations When Using 6×6 Lumber

When handling and working with 6×6 lumber, safety is a primary concern. Due to its size and weight, the risk of injury is higher if proper techniques are not followed. Key safety tips include:

• Use proper lifting techniques or equipment to avoid strain or injury
• Wear protective gloves to prevent splinters and cuts
• Use eye protection when cutting or sanding the lumber
• Ensure ventilation when working with pressure-treated lumber to avoid inhaling chemicals

Additionally, it is essential to properly store 6×6 lumber to prevent damage, such as warping or cracking. Store the lumber off the ground in a dry, well-ventilated area.

Conclusion

The 6×6 nominal size in construction offers a robust and versatile solution for a wide range of building projects. Whether used for structural support, decking posts, or outdoor structures, the strength and durability of 6×6 lumber are crucial in ensuring long-lasting, safe, and stable construction. From pressure-treated lumber used in outdoor environments to timber framing that supports heavy loads, 6×6 boards are a go-to choice for many contractors and builders. Proper handling, understanding of the actual dimensions, and attention to the wood species and treatment will ensure that 6×6 lumber performs optimally in every application.